1
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Liu FM, Wang C, Chen MC, Chen H, Li SW, Shang ZX, Ying C, Wang JW, Huo YH, Peng CZ, Zhu X, Lu CY, Pan JW. Quantum computer-aided design for advanced superconducting qubit: Plasmonium. Sci Bull (Beijing) 2023; 68:1625-1631. [PMID: 37453825 DOI: 10.1016/j.scib.2023.06.030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2023] [Revised: 05/14/2023] [Accepted: 06/25/2023] [Indexed: 07/18/2023]
Abstract
Complex quantum electronic circuits can be used to design noise-protected qubits, but their complexity may exceed the capabilities of classical simulation. In such cases, quantum computers are necessary for efficient simulation. In this work, we demonstrate the use of variational quantum computing on a transmon-based quantum processor to simulate a superconducting quantum electronic circuit and design a new type of qubit called "Plasmonium", which operates in the plasmon-transition regime. The fabricated Plasmonium qubits show a high two-qubit gate fidelity of 99.58(3)%, as well as a smaller physical size and larger anharmonicity compared to transmon qubits. These properties make Plasmonium a promising candidate for scaling up multi-qubit devices. Our results demonstrate the potential of using quantum computers to aid in the design of advanced quantum processors.
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Affiliation(s)
- Feng-Ming Liu
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China; Shanghai Branch CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Can Wang
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China; Shanghai Branch CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Ming-Cheng Chen
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China; Shanghai Branch CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China.
| | - He Chen
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China; Shanghai Branch CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Shao-Wei Li
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China; Shanghai Branch CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Zhong-Xia Shang
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China; Shanghai Branch CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Chong Ying
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China; Shanghai Branch CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Jian-Wen Wang
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China; Shanghai Branch CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Yong-Heng Huo
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China; Shanghai Branch CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Cheng-Zhi Peng
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China; Shanghai Branch CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Xiaobo Zhu
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China; Shanghai Branch CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Chao-Yang Lu
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China; Shanghai Branch CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China.
| | - Jian-Wei Pan
- Hefei National Research Center for Physical Sciences at the Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China; Shanghai Branch CAS Centre for Excellence and Synergetic Innovation Centre in Quantum Information and Quantum Physics, University of Science and Technology of China, Shanghai 201315, China; Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
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2
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Shirai S, Okubo Y, Matsuura K, Osada A, Nakamura Y, Noguchi A. All-Microwave Manipulation of Superconducting Qubits with a Fixed-Frequency Transmon Coupler. PHYSICAL REVIEW LETTERS 2023; 130:260601. [PMID: 37450826 DOI: 10.1103/physrevlett.130.260601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 06/01/2023] [Indexed: 07/18/2023]
Abstract
All-microwave control of fixed-frequency superconducting quantum computing circuits is advantageous for minimizing the noise channels and wiring costs. Here we introduce a swap interaction between two data transmons assisted by the third-order nonlinearity of a coupler transmon under a microwave drive. We model the interaction analytically and numerically and use it to implement an all-microwave controlled-Z gate. The gate based on the coupler-assisted swap transition maintains high drive efficiency and small residual interaction over a wide range of detuning between the data transmons.
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Affiliation(s)
- Shotaro Shirai
- Komaba Institute for Science (KIS), The University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan
| | - Yuta Okubo
- Komaba Institute for Science (KIS), The University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan
| | - Kohei Matsuura
- Department of Applied Physics, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Alto Osada
- Komaba Institute for Science (KIS), The University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan
- PRESTO, Japan Science and Technology Agency, Kawaguchi-shi, Saitama 332-0012, Japan
| | - Yasunobu Nakamura
- Department of Applied Physics, Graduate School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan
- RIKEN Center for Quantum Computing (RQC), Wako, Saitama 351-0198, Japan
| | - Atsushi Noguchi
- Komaba Institute for Science (KIS), The University of Tokyo, Meguro-ku, Tokyo 153-8902, Japan
- RIKEN Center for Quantum Computing (RQC), Wako, Saitama 351-0198, Japan
- Inamori Research Institute for Science (InaRIS), Kyoto-shi, Kyoto 600-8411, Japan
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3
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Kim Y, Eddins A, Anand S, Wei KX, van den Berg E, Rosenblatt S, Nayfeh H, Wu Y, Zaletel M, Temme K, Kandala A. Evidence for the utility of quantum computing before fault tolerance. Nature 2023; 618:500-505. [PMID: 37316724 PMCID: PMC10266970 DOI: 10.1038/s41586-023-06096-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 46.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Accepted: 04/18/2023] [Indexed: 06/16/2023]
Abstract
Quantum computing promises to offer substantial speed-ups over its classical counterpart for certain problems. However, the greatest impediment to realizing its full potential is noise that is inherent to these systems. The widely accepted solution to this challenge is the implementation of fault-tolerant quantum circuits, which is out of reach for current processors. Here we report experiments on a noisy 127-qubit processor and demonstrate the measurement of accurate expectation values for circuit volumes at a scale beyond brute-force classical computation. We argue that this represents evidence for the utility of quantum computing in a pre-fault-tolerant era. These experimental results are enabled by advances in the coherence and calibration of a superconducting processor at this scale and the ability to characterize1 and controllably manipulate noise across such a large device. We establish the accuracy of the measured expectation values by comparing them with the output of exactly verifiable circuits. In the regime of strong entanglement, the quantum computer provides correct results for which leading classical approximations such as pure-state-based 1D (matrix product states, MPS) and 2D (isometric tensor network states, isoTNS) tensor network methods2,3 break down. These experiments demonstrate a foundational tool for the realization of near-term quantum applications4,5.
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Affiliation(s)
- Youngseok Kim
- IBM Quantum, IBM Thomas J. Watson Research Center, Yorktown Heights, NY, USA.
| | - Andrew Eddins
- IBM Quantum, IBM Research - Cambridge, Cambridge, MA, USA.
| | - Sajant Anand
- Department of Physics, University of California, Berkeley, Berkeley, CA, USA
| | - Ken Xuan Wei
- IBM Quantum, IBM Thomas J. Watson Research Center, Yorktown Heights, NY, USA
| | - Ewout van den Berg
- IBM Quantum, IBM Thomas J. Watson Research Center, Yorktown Heights, NY, USA
| | - Sami Rosenblatt
- IBM Quantum, IBM Thomas J. Watson Research Center, Yorktown Heights, NY, USA
| | - Hasan Nayfeh
- IBM Quantum, IBM Thomas J. Watson Research Center, Yorktown Heights, NY, USA
| | - Yantao Wu
- Department of Physics, University of California, Berkeley, Berkeley, CA, USA
- RIKEN iTHEMS, Wako, Japan
| | - Michael Zaletel
- Department of Physics, University of California, Berkeley, Berkeley, CA, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Kristan Temme
- IBM Quantum, IBM Thomas J. Watson Research Center, Yorktown Heights, NY, USA
| | - Abhinav Kandala
- IBM Quantum, IBM Thomas J. Watson Research Center, Yorktown Heights, NY, USA.
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4
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Grossi M, Kiss O, De Luca F, Zollo C, Gremese I, Mandarino A. Finite-size criticality in fully connected spin models on superconducting quantum hardware. Phys Rev E 2023; 107:024113. [PMID: 36932510 DOI: 10.1103/physreve.107.024113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 01/17/2023] [Indexed: 02/12/2023]
Abstract
The emergence of a collective behavior in a many-body system is responsible for the quantum criticality separating different phases of matter. Interacting spin systems in a magnetic field offer a tantalizing opportunity to test different approaches to study quantum phase transitions. In this work, we exploit the new resources offered by quantum algorithms to detect the quantum critical behavior of fully connected spin-1/2 models. We define a suitable Hamiltonian depending on an internal anisotropy parameter γ that allows us to examine three paradigmatic examples of spin models, whose lattice is a fully connected graph. We propose a method based on variational algorithms run on superconducting transmon qubits to detect the critical behavior for systems of finite size. We evaluate the energy gap between the first excited state and the ground state, the magnetization along the easy axis of the system, and the spin-spin correlations. We finally report a discussion about the feasibility of scaling such approach on a real quantum device for a system having a dimension such that classical simulations start requiring significant resources.
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Affiliation(s)
- Michele Grossi
- European Organization for Nuclear Research (CERN), 1211 Geneva, Switzerland
| | - Oriel Kiss
- European Organization for Nuclear Research (CERN), 1211 Geneva, Switzerland.,Department of Particle and Nuclear Physics, University of Geneva, 1211 Geneva, Switzerland
| | | | - Carlo Zollo
- Department of Physics, University of Trieste, 34127 Trieste, Italy
| | - Ian Gremese
- Department of Physics, University of Trieste, 34127 Trieste, Italy
| | - Antonio Mandarino
- International Centre for Theory of Quantum Technologies, University of Gdańsk, 80-309 Gdańsk, Poland
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5
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Tang S, Yang C, Li D, Shao X. Implementation of Quantum Algorithms via Fast Three-Rydberg-Atom CCZ Gates. ENTROPY (BASEL, SWITZERLAND) 2022; 24:1371. [PMID: 37420391 DOI: 10.3390/e24101371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 09/20/2022] [Accepted: 09/21/2022] [Indexed: 07/09/2023]
Abstract
Multiqubit CCZ gates form one of the building blocks of quantum algorithms and have been involved in achieving many theoretical and experimental triumphs. Designing a simple and efficient multiqubit gate for quantum algorithms is still by no means trivial as the number of qubits increases. Here, by virtue of the Rydberg blockade effect, we propose a scheme to rapidly implement a three-Rydberg-atom CCZ gate via a single Rydberg pulse, and successfully apply the gate to realize the three-qubit refined Deutsch-Jozsa algorithm and three-qubit Grover search. The logical states of the three-qubit gate are encoded to the same ground states to avoid an adverse effect of the atomic spontaneous emission. Furthermore, there is no requirement for individual addressing of atoms in our protocol.
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Affiliation(s)
- Shiqing Tang
- College of Physics and Electronic Engineering, Hengyang Normal University, Hengyang 421002, China
| | - Chong Yang
- College of Physics Science and Technology, Shenyang Normal University, Shenyang 110034, China
| | - Dongxiao Li
- College of Physics Science and Technology, Shenyang Normal University, Shenyang 110034, China
| | - Xiaoqiang Shao
- Center for Quantum Sciences and School of Physics, Northeast Normal University, Changchun 130024, China
- Center for Advanced Optoelectronic Functional Materials Research, and Key Laboratory for UV Light-Emitting Materials and Technology of Ministry of Education, Northeast Normal University, Changchun 130024, China
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6
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McGinley M, Roy S, Parameswaran SA. Absolutely Stable Spatiotemporal Order in Noisy Quantum Systems. PHYSICAL REVIEW LETTERS 2022; 129:090404. [PMID: 36083640 DOI: 10.1103/physrevlett.129.090404] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 06/28/2022] [Indexed: 06/15/2023]
Abstract
We introduce a model of nonunitary quantum dynamics that exhibits infinitely long-lived discrete spatiotemporal order robust against any unitary or dissipative perturbation. Ergodicity is evaded by combining a sequence of projective measurements with a local feedback rule that is inspired by Toom's "north-east-center" classical cellular automaton. The measurements in question only partially collapse the wave function of the system, allowing some quantum coherence to persist. We demonstrate our claims using numerical simulations of a Clifford circuit in two spatial dimensions which allows access to large system sizes, and also present results for more generic dynamics on modest system sizes. We also devise explicit experimental protocols realizing this dynamics using one- and two-qubit gates that are available on present-day quantum computing platforms.
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Affiliation(s)
- Max McGinley
- Rudolf Peierls Centre for Theoretical Physics, Clarendon Laboratory, Oxford University, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Sthitadhi Roy
- Rudolf Peierls Centre for Theoretical Physics, Clarendon Laboratory, Oxford University, Parks Road, Oxford OX1 3PU, United Kingdom
- Physical and Theoretical Chemistry, Oxford University, South Parks Road, Oxford OX1 3QZ, United Kingdom
- International Centre for Theoretical Sciences, Tata Institute of Fundamental Research, Bengaluru 560089, India
| | - S A Parameswaran
- Rudolf Peierls Centre for Theoretical Physics, Clarendon Laboratory, Oxford University, Parks Road, Oxford OX1 3PU, United Kingdom
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7
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Wei KX, Magesan E, Lauer I, Srinivasan S, Bogorin DF, Carnevale S, Keefe GA, Kim Y, Klaus D, Landers W, Sundaresan N, Wang C, Zhang EJ, Steffen M, Dial OE, McKay DC, Kandala A. Hamiltonian Engineering with Multicolor Drives for Fast Entangling Gates and Quantum Crosstalk Cancellation. PHYSICAL REVIEW LETTERS 2022; 129:060501. [PMID: 36018659 DOI: 10.1103/physrevlett.129.060501] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Accepted: 06/14/2022] [Indexed: 06/15/2023]
Abstract
Quantum computers built with superconducting artificial atoms already stretch the limits of their classical counterparts. While the lowest energy states of these artificial atoms serve as the qubit basis, the higher levels are responsible for both a host of attractive gate schemes as well as generating undesired interactions. In particular, when coupling these atoms to generate entanglement, the higher levels cause shifts in the computational levels that lead to unwanted ZZ quantum crosstalk. Here, we present a novel technique to manipulate the energy levels and mitigate this crosstalk with simultaneous off-resonant drives on coupled qubits. This breaks a fundamental deadlock between qubit-qubit coupling and crosstalk. In a fixed-frequency transmon architecture with strong coupling and crosstalk cancellation, additional cross-resonance drives enable a 90 ns CNOT with a gate error of (0.19±0.02)%, while a second set of off-resonant drives enables a novel CZ gate. Furthermore, we show a definitive improvement in circuit performance with crosstalk cancellation over seven qubits, demonstrating the scalability of the technique. This Letter paves the way for superconducting hardware with faster gates and greatly improved multiqubit circuit fidelities.
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Affiliation(s)
- K X Wei
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - E Magesan
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - I Lauer
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - S Srinivasan
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - D F Bogorin
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - S Carnevale
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - G A Keefe
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Y Kim
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - D Klaus
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - W Landers
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - N Sundaresan
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - C Wang
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - E J Zhang
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - M Steffen
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - O E Dial
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - D C McKay
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - A Kandala
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
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8
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Motta M, Rice JE. Emerging quantum computing algorithms for quantum chemistry. WIRES COMPUTATIONAL MOLECULAR SCIENCE 2022. [DOI: 10.1002/wcms.1580] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Mario Motta
- IBM Quantum, IBM Research‐Almaden San Jose California USA
| | - Julia E. Rice
- IBM Quantum, IBM Research‐Almaden San Jose California USA
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9
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Schlimgen AW, Head-Marsden K, Sager LM, Narang P, Mazziotti DA. Quantum Simulation of Open Quantum Systems Using a Unitary Decomposition of Operators. PHYSICAL REVIEW LETTERS 2021; 127:270503. [PMID: 35061424 DOI: 10.1103/physrevlett.127.270503] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Accepted: 12/03/2021] [Indexed: 06/14/2023]
Abstract
Electron transport in realistic physical and chemical systems often involves the nontrivial exchange of energy with a large environment, requiring the definition and treatment of open quantum systems. Because the time evolution of an open quantum system employs a nonunitary operator, the simulation of open quantum systems presents a challenge for universal quantum computers constructed from only unitary operators or gates. Here, we present a general algorithm for implementing the action of any nonunitary operator on an arbitrary state on a quantum device. We show that any quantum operator can be exactly decomposed as a linear combination of at most four unitary operators. We demonstrate this method on a two-level system in both zero and finite temperature amplitude damping channels. The results are in agreement with classical calculations, showing promise in simulating nonunitary operations on intermediate-term and future quantum devices.
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Affiliation(s)
- Anthony W Schlimgen
- Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
| | - Kade Head-Marsden
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - LeeAnn M Sager
- Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
| | - Prineha Narang
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA
| | - David A Mazziotti
- Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
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10
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Kandala A, Wei KX, Srinivasan S, Magesan E, Carnevale S, Keefe GA, Klaus D, Dial O, McKay DC. Demonstration of a High-Fidelity cnot Gate for Fixed-Frequency Transmons with Engineered ZZ Suppression. PHYSICAL REVIEW LETTERS 2021; 127:130501. [PMID: 34623861 DOI: 10.1103/physrevlett.127.130501] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 07/28/2021] [Indexed: 06/13/2023]
Abstract
Improving two-qubit gate performance and suppressing cross talk are major, but often competing, challenges to achieving scalable quantum computation. In particular, increasing the coupling to realize faster gates has been intrinsically linked to enhanced cross talk due to unwanted two-qubit terms in the Hamiltonian. Here, we demonstrate a novel coupling architecture for transmon qubits that circumvents the standard relationship between desired and undesired interaction rates. Using two fixed frequency coupling elements to tune the dressed level spacings, we demonstrate an intrinsic suppression of the static ZZ while maintaining large effective coupling rates. Our architecture reveals no observable degradation of qubit coherence (T_{1},T_{2}>100 μs) and, over a factor of 6 improvement in the ratio of desired to undesired coupling. Using the cross-resonance interaction, we demonstrate a 180 ns single-pulse controlled not (cnot) gate, and measure a cnot fidelity of 99.77(2)% from interleaved randomized benchmarking.
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Affiliation(s)
- A Kandala
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - K X Wei
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - S Srinivasan
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - E Magesan
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - S Carnevale
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - G A Keefe
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - D Klaus
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - O Dial
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - D C McKay
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
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11
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Córcoles AD, Takita M, Inoue K, Lekuch S, Minev ZK, Chow JM, Gambetta JM. Exploiting Dynamic Quantum Circuits in a Quantum Algorithm with Superconducting Qubits. PHYSICAL REVIEW LETTERS 2021; 127:100501. [PMID: 34533358 DOI: 10.1103/physrevlett.127.100501] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2021] [Accepted: 08/06/2021] [Indexed: 06/13/2023]
Abstract
To date, quantum computation on real, physical devices has largely been limited to simple, time-ordered sequences of unitary operations followed by a final projective measurement. As hardware platforms for quantum computing continue to mature in size and capability, it is imperative to enable quantum circuits beyond their conventional construction. Here we break into the realm of dynamic quantum circuits on a superconducting-based quantum system. Dynamic quantum circuits not only involve the evolution of the quantum state throughout the computation but also periodic measurements of qubits midcircuit and concurrent processing of the resulting classical information on timescales shorter than the execution times of the circuits. Using noisy quantum hardware, we explore one of the most fundamental quantum algorithms, quantum phase estimation, in its adaptive version, which exploits dynamic circuits, and compare the results to a nonadaptive implementation of the same algorithm. We demonstrate that the version of real-time quantum computing with dynamic circuits can yield results comparable to an approach involving classical asynchronous postprocessing, thus opening the door to a new realm of available algorithms on real quantum systems.
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Affiliation(s)
- A D Córcoles
- IBM Quantum, IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Maika Takita
- IBM Quantum, IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Ken Inoue
- IBM Quantum, IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Scott Lekuch
- IBM Quantum, IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Zlatko K Minev
- IBM Quantum, IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Jerry M Chow
- IBM Quantum, IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Jay M Gambetta
- IBM Quantum, IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
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12
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Simulating Static and Dynamic Properties of Magnetic Molecules with Prototype Quantum Computers. MAGNETOCHEMISTRY 2021. [DOI: 10.3390/magnetochemistry7080117] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Magnetic molecules are prototypical systems to investigate peculiar quantum mechanical phenomena. As such, simulating their static and dynamical behavior is intrinsically difficult for a classical computer, due to the exponential increase of required resources with the system size. Quantum computers solve this issue by providing an inherently quantum platform, suited to describe these magnetic systems. Here, we show that both the ground state properties and the spin dynamics of magnetic molecules can be simulated on prototype quantum computers, based on superconducting qubits. In particular, we study small-size anti-ferromagnetic spin chains and rings, which are ideal test-beds for these pioneering devices. We use the variational quantum eigensolver algorithm to determine the ground state wave-function with targeted ansatzes fulfilling the spin symmetries of the investigated models. The coherent spin dynamics are simulated by computing dynamical correlation functions, an essential ingredient to extract many experimentally accessible properties, such as the inelastic neutron cross-section.
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13
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Cai TQ, Han XY, Wu YK, Ma YL, Wang JH, Wang ZL, Zhang HY, Wang HY, Song YP, Duan LM. Impact of Spectators on a Two-Qubit Gate in a Tunable Coupling Superconducting Circuit. PHYSICAL REVIEW LETTERS 2021; 127:060505. [PMID: 34420337 DOI: 10.1103/physrevlett.127.060505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Accepted: 07/06/2021] [Indexed: 06/13/2023]
Abstract
Cross-resonance (CR) gates have emerged as a promising scheme for fault-tolerant quantum computation with fixed-frequency qubits. We experimentally implement an entangling CR gate by using a microwave-only control in a tunable coupling superconducting circuit, where the tunable coupler provides extra degrees of freedom to verify optimal conditions for constructing a CR gate. By developing a three-qubit Hamiltonian tomography protocol, we systematically investigate the dependency of gate fidelities on spurious qubit interactions and present the first experimental approach to the evaluation of the perturbation impact arising from spectator qubits. Our results reveal that the spectator qubits lead to reductions in CR gate fidelity dependent on ZZ interactions and particular frequency detunings between spectator and gate qubits. The target spectator demonstrates a more serious impact than the control spectator under a standard echo pulse scheme, whereas the degradation of gate fidelity is observed up to 22.5% as both the spectators are present with a modest ZZ coupling to the computational qubits. Our experiments uncover an optimal CR operation regime, and the method we develop here can readily be applied to improving other kinds of two-qubit gates in large-scale quantum circuits.
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Affiliation(s)
- T-Q Cai
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - X-Y Han
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - Y-K Wu
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - Y-L Ma
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - J-H Wang
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - Z-L Wang
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - H-Y Zhang
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - H-Y Wang
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - Y-P Song
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - L-M Duan
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
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14
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Militello B, Napoli A. Synchronizing Two Superconducting Qubits through a Dissipating Resonator. ENTROPY 2021; 23:e23080998. [PMID: 34441137 PMCID: PMC8392702 DOI: 10.3390/e23080998] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Revised: 07/28/2021] [Accepted: 07/29/2021] [Indexed: 11/16/2022]
Abstract
A system consisting of two qubits and a resonator is considered in the presence of different sources of noise, bringing to light the possibility of making the two qubits evolve in a synchronized way. A direct qubit–qubit interaction turns out to be a crucial ingredient, as well as the dissipation processes involving the resonator. The detrimental role of the local dephasing of the qubits is also taken into account.
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Affiliation(s)
- Benedetto Militello
- Dipartimento di Fisica e Chimica—Emilio Segrè, Universitá degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy;
- INFN Sezione di Catania, Via Santa Sofia 64, 95123 Catania, Italy
- Correspondence:
| | - Anna Napoli
- Dipartimento di Fisica e Chimica—Emilio Segrè, Universitá degli Studi di Palermo, Via Archirafi 36, 90123 Palermo, Italy;
- INFN Sezione di Catania, Via Santa Sofia 64, 95123 Catania, Italy
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15
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Winick A, Wallman JJ, Emerson J. Simulating and Mitigating Crosstalk. PHYSICAL REVIEW LETTERS 2021; 126:230502. [PMID: 34170151 DOI: 10.1103/physrevlett.126.230502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Accepted: 05/04/2021] [Indexed: 06/13/2023]
Abstract
We describe an efficient and scalable framework for modeling crosstalk effects on quantum information processors. By applying optimal control techniques, we show how to tune-up arbitrary high-fidelity parallel operations on systems with substantial local and nonlocal crosstalk. As an example, we simulate a 2D square array of 100 superconducting transmon qubits. These results suggest that rather than striving to engineer away undesirable interactions during fabrication, we can largely mitigate such effects with software through careful characterization and control optimization.
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Affiliation(s)
- Adam Winick
- Quantum Benchmark Inc., 51 Breithaupt Street Suite 100, Kitchener, Ontario N2H 4C3, Canada
- Institute for Quantum Computing, University of Waterloo, 200 University Avenue West Waterloo, Ontario N2L 3G1, Canada
| | - Joel J Wallman
- Quantum Benchmark Inc., 51 Breithaupt Street Suite 100, Kitchener, Ontario N2H 4C3, Canada
- Institute for Quantum Computing, University of Waterloo, 200 University Avenue West Waterloo, Ontario N2L 3G1, Canada
| | - Joseph Emerson
- Quantum Benchmark Inc., 51 Breithaupt Street Suite 100, Kitchener, Ontario N2H 4C3, Canada
- Institute for Quantum Computing, University of Waterloo, 200 University Avenue West Waterloo, Ontario N2L 3G1, Canada
- Canadian Institute for Advanced Research, MaRS Centre, West Tower 661 University Ave., Suite 505 Toronto, Ontario M5G 1M1, Canada
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16
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Smart SE, Mazziotti DA. Quantum Solver of Contracted Eigenvalue Equations for Scalable Molecular Simulations on Quantum Computing Devices. PHYSICAL REVIEW LETTERS 2021; 126:070504. [PMID: 33666467 DOI: 10.1103/physrevlett.126.070504] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 10/02/2020] [Accepted: 01/05/2021] [Indexed: 06/12/2023]
Abstract
The accurate computation of ground and excited states of many-fermion quantum systems is one of the most consequential, contemporary challenges in the physical and computational sciences whose solution stands to benefit significantly from the advent of quantum computing devices. Existing methodologies using phase estimation or variational algorithms have potential drawbacks such as deep circuits requiring substantial error correction or nontrivial high-dimensional classical optimization. Here, we introduce a quantum solver of contracted eigenvalue equations, the quantum analog of classical methods for the energies and reduced density matrices of ground and excited states. The solver does not require deep circuits or difficult classical optimization and achieves an exponential speed-up over its classical counterpart. We demonstrate the algorithm though computations on both a quantum simulator and two IBM quantum processing units.
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Affiliation(s)
- Scott E Smart
- Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
| | - David A Mazziotti
- Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago, Illinois 60637, USA
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17
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Collodo MC, Herrmann J, Lacroix N, Andersen CK, Remm A, Lazar S, Besse JC, Walter T, Wallraff A, Eichler C. Implementation of Conditional Phase Gates Based on Tunable ZZ Interactions. PHYSICAL REVIEW LETTERS 2020; 125:240502. [PMID: 33412023 DOI: 10.1103/physrevlett.125.240502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 10/12/2020] [Indexed: 06/12/2023]
Abstract
High fidelity two-qubit gates exhibiting low cross talk are essential building blocks for gate-based quantum information processing. In superconducting circuits, two-qubit gates are typically based either on rf-controlled interactions or on the in situ tunability of qubit frequencies. Here, we present an alternative approach using a tunable cross-Kerr-type ZZ interaction between two qubits, which we realize with a flux-tunable coupler element. We control the ZZ-coupling rate over 3 orders of magnitude to perform a rapid (38 ns), high-contrast, low leakage (0.14±0.24%) conditional phase CZ gate with a fidelity of 97.9±0.7% as measured in interleaved randomized benchmarking without relying on the resonant interaction with a noncomputational state. Furthermore, by exploiting the direct nature of the ZZ coupling, we easily access the entire conditional phase gate family by adjusting only a single control parameter.
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Affiliation(s)
| | | | - Nathan Lacroix
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | | | - Ants Remm
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Stefania Lazar
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | | | - Theo Walter
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
| | - Andreas Wallraff
- Department of Physics, ETH Zurich, CH-8093 Zurich, Switzerland
- Quantum Center, ETH Zurich, CH-8093 Zurich, Switzerland
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18
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Xu Y, Chu J, Yuan J, Qiu J, Zhou Y, Zhang L, Tan X, Yu Y, Liu S, Li J, Yan F, Yu D. High-Fidelity, High-Scalability Two-Qubit Gate Scheme for Superconducting Qubits. PHYSICAL REVIEW LETTERS 2020; 125:240503. [PMID: 33412065 DOI: 10.1103/physrevlett.125.240503] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Accepted: 10/12/2020] [Indexed: 06/12/2023]
Abstract
High-quality two-qubit gate operations are crucial for scalable quantum information processing. Often, the gate fidelity is compromised when the system becomes more integrated. Therefore, a low-error-rate, easy-to-scale two-qubit gate scheme is highly desirable. Here, we experimentally demonstrate a new two-qubit gate scheme that exploits fixed-frequency qubits and a tunable coupler in a superconducting quantum circuit. The scheme requires less control lines, reduces cross talk effect, and simplifies calibration procedures, yet produces a controlled-Z gate in 30 ns with a high fidelity of 99.5%, derived from the interleaved randomized benchmarking method. Error analysis shows that gate errors are mostly coherence limited. Our demonstration paves the way for large-scale implementation of high-fidelity quantum operations.
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Affiliation(s)
- Yuan Xu
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
- Guangdong Provincial Key Laboratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
- Shenzhen Key Laboratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
| | - Ji Chu
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing, Jiangsu, 210093, China
| | - Jiahao Yuan
- Institute for Quantum Science and Engineering and Department of Physics, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
| | - Jiawei Qiu
- Institute for Quantum Science and Engineering and Department of Physics, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
| | - Yuxuan Zhou
- Institute for Quantum Science and Engineering and Department of Physics, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
| | - Libo Zhang
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
- Guangdong Provincial Key Laboratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
- Shenzhen Key Laboratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
| | - Xinsheng Tan
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing, Jiangsu, 210093, China
| | - Yang Yu
- National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing, Jiangsu, 210093, China
| | - Song Liu
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
- Guangdong Provincial Key Laboratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
- Shenzhen Key Laboratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
| | - Jian Li
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
- Guangdong Provincial Key Laboratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
- Shenzhen Key Laboratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
| | - Fei Yan
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
- Guangdong Provincial Key Laboratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
- Shenzhen Key Laboratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
| | - Dapeng Yu
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
- Guangdong Provincial Key Laboratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
- Shenzhen Key Laboratory of Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, 518055, China
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19
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Ku J, Xu X, Brink M, McKay DC, Hertzberg JB, Ansari MH, Plourde BLT. Suppression of Unwanted ZZ Interactions in a Hybrid Two-Qubit System. PHYSICAL REVIEW LETTERS 2020; 125:200504. [PMID: 33258640 DOI: 10.1103/physrevlett.125.200504] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 09/02/2020] [Indexed: 06/12/2023]
Abstract
Mitigating crosstalk errors, whether classical or quantum mechanical, is critically important for achieving high-fidelity entangling gates in multiqubit circuits. For weakly anharmonic superconducting qubits, unwanted ZZ interactions can be suppressed by combining qubits with opposite anharmonicity. We present experimental measurements and theoretical modeling of two-qubit gate error for gates based on the cross resonance interaction between a capacitively shunted flux qubit and a transmon, and demonstrate the elimination of the ZZ interaction.
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Affiliation(s)
- Jaseung Ku
- Department of Physics, Syracuse University, Syracuse, New York 13244, USA
| | - Xuexin Xu
- Peter Grünberg Institute, Forschungszentrum Jülich, Jülich 52428, Germany
- Jülich-Aachen Research Alliance (JARA), Fundamentals of Future Information Technologies, Jülich 52428, Germany
| | - Markus Brink
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - David C McKay
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Jared B Hertzberg
- IBM Quantum, IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Mohammad H Ansari
- Peter Grünberg Institute, Forschungszentrum Jülich, Jülich 52428, Germany
- Jülich-Aachen Research Alliance (JARA), Fundamentals of Future Information Technologies, Jülich 52428, Germany
| | - B L T Plourde
- Department of Physics, Syracuse University, Syracuse, New York 13244, USA
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20
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Zhao P, Xu P, Lan D, Chu J, Tan X, Yu H, Yu Y. High-Contrast ZZ Interaction Using Superconducting Qubits with Opposite-Sign Anharmonicity. PHYSICAL REVIEW LETTERS 2020; 125:200503. [PMID: 33258656 DOI: 10.1103/physrevlett.125.200503] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Accepted: 08/11/2020] [Indexed: 06/12/2023]
Abstract
For building a scalable quantum processor with superconducting qubits, ZZ interaction is of great concern because its residual has a crucial impact to two-qubit gate fidelity. Two-qubit gates with fidelity meeting the criterion of fault-tolerant quantum computation have been demonstrated using ZZ interaction. However, as the performance of quantum processors improves, the residual static ZZ can become a performance-limiting factor for quantum gate operation and quantum error correction. Here, we introduce a superconducting architecture using qubits with opposite-sign anharmonicity, a transmon qubit, and a C-shunt flux qubit, to address this issue. We theoretically demonstrate that by coupling the two types of qubits, the high-contrast ZZ interaction can be realized. Thus, we can control the interaction with a high on-off ratio to implement two-qubit controlled-Z gates, or suppress it during two-qubit gate operation using XY interaction (e.g., an iSWAP gate). The proposed architecture can also be scaled up to multiqubit cases. In a fixed coupled system, ZZ crosstalk related to neighboring spectator qubits could also be heavily suppressed.
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Affiliation(s)
- Peng Zhao
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 230039, China
| | - Peng Xu
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 230039, China
- Institute of Quantum Information and Technology, Nanjing University of Posts and Telecommunications, Nanjing 210003, China
- State Key Laboratory of Quantum Optics and Devices, Shanxi University, Taiyuan 030006, China
| | - Dong Lan
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 230039, China
| | - Ji Chu
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 230039, China
| | - Xinsheng Tan
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 230039, China
| | - Haifeng Yu
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 230039, China
| | - Yang Yu
- National Laboratory of Solid State Microstructures, School of Physics, Nanjing University, Nanjing 230039, China
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21
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Bootstrapping quantum process tomography via a perturbative ansatz. Nat Commun 2020; 11:1084. [PMID: 32107382 PMCID: PMC7046656 DOI: 10.1038/s41467-020-14873-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Accepted: 02/06/2020] [Indexed: 11/23/2022] Open
Abstract
Quantum process tomography has become increasingly critical as the need grows for robust verification and validation of candidate quantum processors, since it plays a key role in both performance assessment and debugging. However, as these processors grow in size, standard process tomography becomes an almost impossible task. Here, we present an approach for efficient quantum process tomography that uses a physically motivated ansatz for an unknown quantum process. Our ansatz bootstraps to an effective description for an unknown process on a multi-qubit processor from pairwise two-qubit tomographic data. Further, our approach can inherit insensitivity to system preparation and measurement error from the two-qubit tomography scheme. We benchmark our approach using numerical simulation of noisy three-qubit gates, and show that it produces highly accurate characterizations of quantum processes. Further, we demonstrate our approach experimentally on a superconducting quantum processor, building three-qubit gate reconstructions from two-qubit tomographic data. Quantum process tomography represents one of the workhorses of quantum information processing, but suffers from exponential resource scaling. Here, the authors propose to efficiently infer general processes by approximating them through a sequence of two-qubit processes, and demonstrate it on a three-qubit case.
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22
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Rol MA, Battistel F, Malinowski FK, Bultink CC, Tarasinski BM, Vollmer R, Haider N, Muthusubramanian N, Bruno A, Terhal BM, DiCarlo L. Fast, High-Fidelity Conditional-Phase Gate Exploiting Leakage Interference in Weakly Anharmonic Superconducting Qubits. PHYSICAL REVIEW LETTERS 2019; 123:120502. [PMID: 31633950 DOI: 10.1103/physrevlett.123.120502] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Indexed: 06/10/2023]
Abstract
Conditional-phase (cz) gates in transmons can be realized by flux pulsing computational states towards resonance with noncomputational ones. We present a 40 ns cz gate based on a bipolar flux pulse suppressing leakage (0.1%) by interference and approaching the speed limit set by exchange coupling. This pulse harnesses a built-in echo to enhance fidelity (99.1%) and is robust to long-timescale distortion in the flux-control line, ensuring repeatability. Numerical simulations matching experiment show that fidelity is limited by high-frequency dephasing and leakage by short-timescale distortion.
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Affiliation(s)
- M A Rol
- QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
| | - F Battistel
- QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
| | - F K Malinowski
- QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
| | - C C Bultink
- QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
| | - B M Tarasinski
- QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
| | - R Vollmer
- QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
| | - N Haider
- QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
- Netherlands Organisation for Applied Scientic Research (TNO), P.O. Box 96864, 2509 JG The Hague, The Netherlands
| | - N Muthusubramanian
- QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
| | - A Bruno
- QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
| | - B M Terhal
- QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
- JARA Institute for Quantum Information, Forschungszentrum Juelich, D-52425 Juelich, Germany
| | - L DiCarlo
- QuTech, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
- Kavli Institute of Nanoscience, Delft University of Technology, P.O. Box 5046, 2600 GA Delft, The Netherlands
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23
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Kaur E, Das S, Wilde MM, Winter A. Extendibility Limits the Performance of Quantum Processors. PHYSICAL REVIEW LETTERS 2019; 123:070502. [PMID: 31491098 DOI: 10.1103/physrevlett.123.070502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Indexed: 06/10/2023]
Abstract
Resource theories in quantum information science are helpful for the study and quantification of the performance of information-processing tasks that involve quantum systems. These resource theories also find applications in other areas of study; e.g., the resource theories of entanglement and coherence have found use and implications in the study of quantum thermodynamics and memory effects in quantum dynamics. In this paper, we introduce the resource theory of unextendibility, which is associated with the inability of extending quantum entanglement in a given quantum state to multiple parties. The free states in this resource theory are the k-extendible states, and the free channels are k-extendible channels, which preserve the class of k-extendible states. We make use of this resource theory to derive nonasymptotic, upper bounds on the rate at which quantum communication or entanglement preservation is possible by utilizing an arbitrary quantum channel a finite number of times, along with the assistance of k-extendible channels at no cost. We then show that the bounds obtained are significantly tighter than previously known bounds for quantum communication over both the depolarizing and erasure channels.
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Affiliation(s)
- Eneet Kaur
- Hearne Institute for Theoretical Physics, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Siddhartha Das
- Hearne Institute for Theoretical Physics, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
- Centre for Quantum Information & Communication (QuIC), École polytechnique de Bruxelles, Université libre de Bruxelles, Brussels, B-1050, Belgium
| | - Mark M Wilde
- Hearne Institute for Theoretical Physics, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
- Center for Computation and Technology, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Andreas Winter
- ICREA & Física Teòrica: Informació i Fenòmens Quàntics, Departament de Física, Universitat Autònoma de Barcelona, ES-08193 Bellaterra (Barcelona), Spain
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24
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Kandala A, Temme K, Córcoles AD, Mezzacapo A, Chow JM, Gambetta JM. Error mitigation extends the computational reach of a noisy quantum processor. Nature 2019; 567:491-495. [DOI: 10.1038/s41586-019-1040-7] [Citation(s) in RCA: 304] [Impact Index Per Article: 60.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 01/04/2019] [Indexed: 11/09/2022]
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25
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Lee Y, Joo J, Lee S. Hybrid quantum linear equation algorithm and its experimental test on IBM Quantum Experience. Sci Rep 2019; 9:4778. [PMID: 30886316 PMCID: PMC6423050 DOI: 10.1038/s41598-019-41324-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 02/25/2019] [Indexed: 11/26/2022] Open
Abstract
We propose a hybrid quantum algorithm based on the Harrow-Hassidim-Lloyd (HHL) algorithm for solving a system of linear equations. In this paper, we show that our hybrid algorithm can reduce a circuit depth from the original HHL algorithm by means of a classical information feed-forward after the quantum phase estimation algorithm, and the results of the hybrid algorithm are identical to those of the HHL algorithm. In addition, it is experimentally examined with four qubits in the IBM Quantum Experience setups, and the experimental results of our algorithm show higher accurate performance on specific systems of linear equations than that of the HHL algorithm.
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Affiliation(s)
- Yonghae Lee
- Department of Mathematics and Research Institute for Basic Sciences, Kyung Hee University, Seoul, 02447, Korea
| | - Jaewoo Joo
- School of Computational Sciences, Korea Institute for Advanced Study, Seoul, 02455, Korea.,Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom
| | - Soojoon Lee
- Department of Mathematics and Research Institute for Basic Sciences, Kyung Hee University, Seoul, 02447, Korea. .,School of Computational Sciences, Korea Institute for Advanced Study, Seoul, 02455, Korea. .,School of Mathematical Sciences and Centre for the Mathematics and Theoretical Physics of Quantum Non-Equilibrium Systems, University of Nottingham, University Park, Nottingham, NG7 2RD, United Kingdom.
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26
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Noh T, Park G, Lee SG, Song W, Chong Y. Construction of controlled-NOT gate based on microwave-activated phase (MAP) gate in two transmon system. Sci Rep 2018; 8:13598. [PMID: 30206262 PMCID: PMC6134032 DOI: 10.1038/s41598-018-31896-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Accepted: 08/29/2018] [Indexed: 11/09/2022] Open
Abstract
We experimentally constructed an all-microwave scheme for the controlled-NOT (cNOT) gate between two superconducting transmon qubits in a three dimensional cavity. Our cNOT gate is based on the microwave-activated phase (MAP) gate, which requires an additional procedure to compensate the accumulated phases during the operation of the MAP gate. We applied Z-axis phase gates using microwave hyperbolic secant pulse on both qubits with adequate rotation angles systematically calibrated by separate measurements. We evaluated the gate performance of the constructed cNOT gate by performing two-qubit quantum process tomography (QPT). Finally, we present the experimental implementation of the Deutsch-Jozsa algorithm using the cNOT gate.
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Affiliation(s)
- Taewan Noh
- Korea Research Institute of Standards and Science, Daejeon, 34113, Republic of Korea
| | - Gwanyeol Park
- Korea Research Institute of Standards and Science, Daejeon, 34113, Republic of Korea.,Korea University Sejong Campus, Sejong, 30019, Republic of Korea
| | - Soon-Gul Lee
- Korea University Sejong Campus, Sejong, 30019, Republic of Korea
| | - Woon Song
- Korea Research Institute of Standards and Science, Daejeon, 34113, Republic of Korea
| | - Yonuk Chong
- Korea Research Institute of Standards and Science, Daejeon, 34113, Republic of Korea. .,University of Science and Technology, Daejeon, 34113, Republic of Korea.
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27
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Eichler C, Petta JR. Realizing a Circuit Analog of an Optomechanical System with Longitudinally Coupled Superconducting Resonators. PHYSICAL REVIEW LETTERS 2018; 120:227702. [PMID: 29906158 DOI: 10.1103/physrevlett.120.227702] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2017] [Indexed: 06/08/2023]
Abstract
We realize a superconducting circuit analog of the generic cavity-optomechanical Hamiltonian by longitudinally coupling two superconducting resonators, which are an order of magnitude different in frequency. We achieve longitudinal coupling by embedding a superconducting quantum interference device into a high frequency resonator, making its resonance frequency depend on the zero point current fluctuations of a nearby low frequency LC resonator. By applying sideband drive fields we enhance the intrinsic coupling strength of about 15 kHz up to 280 kHz by controlling the amplitude of the drive field. Our results pave the way towards the exploration of optomechanical effects in a fully superconducting platform and could enable quantum optics experiments with photons in the yet unexplored radio frequency band.
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Affiliation(s)
- C Eichler
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
| | - J R Petta
- Department of Physics, Princeton University, Princeton, New Jersey 08544, USA
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28
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Bronn NT, Adiga VP, Olivadese SB, Wu X, Chow JM, Pappas DP. High coherence plane breaking packaging for superconducting qubits. QUANTUM SCIENCE AND TECHNOLOGY 2018; 3:024007. [PMID: 29726551 PMCID: PMC5927379 DOI: 10.1088/2058-9565/aaa645] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We demonstrate a pogo pin package for a superconducting quantum processor specifically designed with a nontrivial layout topology (e.g., a center qubit that cannot be accessed from the sides of the chip). Two experiments on two nominally identical superconducting quantum processors in pogo packages, which use commercially available parts and require modest machining tolerances, are performed at low temperature (10 mK) in a dilution refrigerator and both found to behave comparably to processors in standard planar packages with wirebonds where control and readout signals come in from the edges. Single- and two-qubit gate errors are also characterized via randomized benchmarking, exhibiting similar error rates as in standard packages, opening the possibility of integrating pogo pin packaging with extensible qubit architectures.
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Affiliation(s)
- Nicholas T Bronn
- IBM T.J. Watson Research Center, Yorktown Heights, NY 10598, United States of America
| | - Vivekananda P Adiga
- IBM T.J. Watson Research Center, Yorktown Heights, NY 10598, United States of America
| | - Salvatore B Olivadese
- IBM T.J. Watson Research Center, Yorktown Heights, NY 10598, United States of America
| | - Xian Wu
- National Institute of Standards and Technology, Boulder, CO 80305, United States of America
| | - Jerry M Chow
- IBM T.J. Watson Research Center, Yorktown Heights, NY 10598, United States of America
| | - David P Pappas
- National Institute of Standards and Technology, Boulder, CO 80305, United States of America
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29
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Takita M, Cross AW, Córcoles AD, Chow JM, Gambetta JM. Experimental Demonstration of Fault-Tolerant State Preparation with Superconducting Qubits. PHYSICAL REVIEW LETTERS 2017; 119:180501. [PMID: 29219563 DOI: 10.1103/physrevlett.119.180501] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Indexed: 06/07/2023]
Abstract
Robust quantum computation requires encoding delicate quantum information into degrees of freedom that are hard for the environment to change. Quantum encodings have been demonstrated in many physical systems by observing and correcting storage errors, but applications require not just storing information; we must accurately compute even with faulty operations. The theory of fault-tolerant quantum computing illuminates a way forward by providing a foundation and collection of techniques for limiting the spread of errors. Here we implement one of the smallest quantum codes in a five-qubit superconducting transmon device and demonstrate fault-tolerant state preparation. We characterize the resulting code words through quantum process tomography and study the free evolution of the logical observables. Our results are consistent with fault-tolerant state preparation in a protected qubit subspace.
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Affiliation(s)
- Maika Takita
- IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Andrew W Cross
- IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - A D Córcoles
- IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Jerry M Chow
- IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Jay M Gambetta
- IBM T.J. Watson Research Center, Yorktown Heights, New York 10598, USA
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30
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Song C, Xu K, Liu W, Yang CP, Zheng SB, Deng H, Xie Q, Huang K, Guo Q, Zhang L, Zhang P, Xu D, Zheng D, Zhu X, Wang H, Chen YA, Lu CY, Han S, Pan JW. 10-Qubit Entanglement and Parallel Logic Operations with a Superconducting Circuit. PHYSICAL REVIEW LETTERS 2017; 119:180511. [PMID: 29219550 DOI: 10.1103/physrevlett.119.180511] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2017] [Indexed: 06/07/2023]
Abstract
Here we report on the production and tomography of genuinely entangled Greenberger-Horne-Zeilinger states with up to ten qubits connecting to a bus resonator in a superconducting circuit, where the resonator-mediated qubit-qubit interactions are used to controllably entangle multiple qubits and to operate on different pairs of qubits in parallel. The resulting 10-qubit density matrix is probed by quantum state tomography, with a fidelity of 0.668±0.025. Our results demonstrate the largest entanglement created so far in solid-state architectures and pave the way to large-scale quantum computation.
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Affiliation(s)
- Chao Song
- Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Kai Xu
- Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Wuxin Liu
- Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Chui-Ping Yang
- Department of Physics, Hangzhou Normal University, Hangzhou, Zhejiang 310036, China
| | - Shi-Biao Zheng
- Fujian Key Laboratory of Quantum Information and Quantum Optics, College of Physics and Information Engineering, Fuzhou University, Fuzhou, Fujian 350116, China
| | - Hui Deng
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Qiwei Xie
- Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China
| | - Keqiang Huang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qiujiang Guo
- Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Libo Zhang
- Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Pengfei Zhang
- Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Da Xu
- Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, China
| | - Dongning Zheng
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xiaobo Zhu
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Shanghai 201315, China
| | - H Wang
- Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310027, China
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Y-A Chen
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Shanghai 201315, China
| | - C-Y Lu
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Shanghai 201315, China
| | - Siyuan Han
- Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA
| | - Jian-Wei Pan
- CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China
- Shanghai Branch, National Laboratory for Physical Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Shanghai 201315, China
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31
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Wendin G. Quantum information processing with superconducting circuits: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:106001. [PMID: 28682303 DOI: 10.1088/1361-6633/aa7e1a] [Citation(s) in RCA: 107] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
During the last ten years, superconducting circuits have passed from being interesting physical devices to becoming contenders for near-future useful and scalable quantum information processing (QIP). Advanced quantum simulation experiments have been shown with up to nine qubits, while a demonstration of quantum supremacy with fifty qubits is anticipated in just a few years. Quantum supremacy means that the quantum system can no longer be simulated by the most powerful classical supercomputers. Integrated classical-quantum computing systems are already emerging that can be used for software development and experimentation, even via web interfaces. Therefore, the time is ripe for describing some of the recent development of superconducting devices, systems and applications. As such, the discussion of superconducting qubits and circuits is limited to devices that are proven useful for current or near future applications. Consequently, the centre of interest is the practical applications of QIP, such as computation and simulation in Physics and Chemistry.
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Affiliation(s)
- G Wendin
- Department of Microtechnology and Nanoscience-MC2, Chalmers University of Technology, SE-41296 Gothenburg, Sweden
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32
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Transferring arbitrary d-dimensional quantum states of a superconducting transmon qudit in circuit QED. Sci Rep 2017; 7:7039. [PMID: 28765631 PMCID: PMC5539217 DOI: 10.1038/s41598-017-07225-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 06/26/2017] [Indexed: 11/08/2022] Open
Abstract
A qudit (d-level quantum system) has a large Hilbert space and thus can be used to achieve many quantum information and communication tasks. Here, we propose a method to transfer arbitrary d-dimensional quantum states (known or unknown) between two superconducting transmon qudits coupled to a single cavity. The state transfer can be performed by employing resonant interactions only. In addition, quantum states can be deterministically transferred without measurement. Numerical simulations show that high-fidelity transfer of quantum states between two superconducting transmon qudits (d ≤ 5) is feasible with current circuit QED technology. This proposal is quite general and can be applied to accomplish the same task with natural or artificial atoms of a ladder-type level structure coupled to a cavity or resonator.
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33
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Lillie SE, Broadway DA, Wood JDA, Simpson DA, Stacey A, Tetienne JP, Hollenberg LCL. Environmentally Mediated Coherent Control of a Spin Qubit in Diamond. PHYSICAL REVIEW LETTERS 2017; 118:167204. [PMID: 28474945 DOI: 10.1103/physrevlett.118.167204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Indexed: 06/07/2023]
Abstract
The coherent control of spin qubits forms the basis of many applications in quantum information processing and nanoscale sensing, imaging, and spectroscopy. Such control is conventionally achieved by direct driving of the qubit transition with a resonant global field, typically at microwave frequencies. Here we introduce an approach that relies on the resonant driving of nearby environment spins, whose localized magnetic field in turn drives the qubit when the environmental spin Rabi frequency matches the qubit resonance. This concept of environmentally mediated resonance (EMR) is explored experimentally using a qubit based on a single nitrogen-vacancy (NV) center in diamond, with nearby electronic spins serving as the environmental mediators. We demonstrate EMR driven coherent control of the NV spin state, including the observation of Rabi oscillations, free induction decay, and spin echo. This technique also provides a way to probe the nanoscale environment of spin qubits, which we illustrate by acquisition of electron spin resonance spectra from single NV centers in various settings.
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Affiliation(s)
- Scott E Lillie
- Centre for Quantum Computation and Communication Technology, School of Physics, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - David A Broadway
- Centre for Quantum Computation and Communication Technology, School of Physics, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - James D A Wood
- Centre for Quantum Computation and Communication Technology, School of Physics, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - David A Simpson
- School of Physics, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - Alastair Stacey
- Centre for Quantum Computation and Communication Technology, School of Physics, The University of Melbourne, Melbourne, VIC 3010, Australia
- Melbourne Centre for Nanofabrication, 151 Wellington Road, Clayton, VIC 3168, Australia
| | - Jean-Philippe Tetienne
- Centre for Quantum Computation and Communication Technology, School of Physics, The University of Melbourne, Melbourne, VIC 3010, Australia
- School of Physics, The University of Melbourne, Melbourne, VIC 3010, Australia
| | - Lloyd C L Hollenberg
- Centre for Quantum Computation and Communication Technology, School of Physics, The University of Melbourne, Melbourne, VIC 3010, Australia
- School of Physics, The University of Melbourne, Melbourne, VIC 3010, Australia
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34
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Abstract
We run a selection of algorithms on two state-of-the-art 5-qubit quantum computers that are based on different technology platforms. One is a publicly accessible superconducting transmon device (www. RESEARCH ibm.com/ibm-q) with limited connectivity, and the other is a fully connected trapped-ion system. Even though the two systems have different native quantum interactions, both can be programed in a way that is blind to the underlying hardware, thus allowing a comparison of identical quantum algorithms between different physical systems. We show that quantum algorithms and circuits that use more connectivity clearly benefit from a better-connected system of qubits. Although the quantum systems here are not yet large enough to eclipse classical computers, this experiment exposes critical factors of scaling quantum computers, such as qubit connectivity and gate expressivity. In addition, the results suggest that codesigning particular quantum applications with the hardware itself will be paramount in successfully using quantum computers in the future.
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35
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Paik H, Mezzacapo A, Sandberg M, McClure DT, Abdo B, Córcoles AD, Dial O, Bogorin DF, Plourde BLT, Steffen M, Cross AW, Gambetta JM, Chow JM. Experimental Demonstration of a Resonator-Induced Phase Gate in a Multiqubit Circuit-QED System. PHYSICAL REVIEW LETTERS 2016; 117:250502. [PMID: 28036205 DOI: 10.1103/physrevlett.117.250502] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Indexed: 06/06/2023]
Abstract
The resonator-induced phase (RIP) gate is an all-microwave multiqubit entangling gate that allows a high degree of flexibility in qubit frequencies, making it attractive for quantum operations in large-scale architectures. We experimentally realize the RIP gate with four superconducting qubits in a three-dimensional circuit-QED architecture, demonstrating high-fidelity controlled-z (cz) gates between all possible pairs of qubits from two different 4-qubit devices in pair subspaces. These qubits are arranged within a wide range of frequency detunings, up to as large as 1.8 GHz. We further show a dynamical multiqubit refocusing scheme in order to isolate out 2-qubit interactions, and combine them to generate a 4-qubit Greenberger-Horne-Zeilinger state.
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Affiliation(s)
- Hanhee Paik
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598-0218, USA
| | - A Mezzacapo
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598-0218, USA
| | - Martin Sandberg
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598-0218, USA
| | - D T McClure
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598-0218, USA
| | - B Abdo
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598-0218, USA
| | - A D Córcoles
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598-0218, USA
| | - O Dial
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598-0218, USA
| | - D F Bogorin
- Department of Physics, Syracuse University, Syracuse, New York 13244-1130, USA
| | - B L T Plourde
- Department of Physics, Syracuse University, Syracuse, New York 13244-1130, USA
| | - M Steffen
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598-0218, USA
| | - A W Cross
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598-0218, USA
| | - J M Gambetta
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598-0218, USA
| | - Jerry M Chow
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598-0218, USA
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36
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Takita M, Córcoles AD, Magesan E, Abdo B, Brink M, Cross A, Chow JM, Gambetta JM. Demonstration of Weight-Four Parity Measurements in the Surface Code Architecture. PHYSICAL REVIEW LETTERS 2016; 117:210505. [PMID: 27911561 DOI: 10.1103/physrevlett.117.210505] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Indexed: 06/06/2023]
Abstract
We present parity measurements on a five-qubit lattice with connectivity amenable to the surface code quantum error correction architecture. Using all-microwave controls of superconducting qubits coupled via resonators, we encode the parities of four data qubit states in either the X or the Z basis. Given the connectivity of the lattice, we perform a full characterization of the static Z interactions within the set of five qubits, as well as dynamical Z interactions brought along by single- and two-qubit microwave drives. The parity measurements are significantly improved by modifying the microwave two-qubit gates to dynamically remove nonideal Z errors.
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Affiliation(s)
- Maika Takita
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - A D Córcoles
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Easwar Magesan
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Baleegh Abdo
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Markus Brink
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Andrew Cross
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Jerry M Chow
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Jay M Gambetta
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
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37
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Beaudoin F, Lachance-Quirion D, Coish WA, Pioro-Ladrière M. Coupling a single electron spin to a microwave resonator: controlling transverse and longitudinal couplings. NANOTECHNOLOGY 2016; 27:464003. [PMID: 27749276 DOI: 10.1088/0957-4484/27/46/464003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Microwave-frequency superconducting resonators are ideally suited to perform dispersive qubit readout, to mediate two-qubit gates, and to shuttle states between distant quantum systems. A prerequisite for these applications is a strong qubit-resonator coupling. Strong coupling between an electron-spin qubit and a microwave resonator can be achieved by correlating spin- and orbital degrees of freedom. This correlation can be achieved through the Zeeman coupling of a single electron in a double quantum dot to a spatially inhomogeneous magnetic field generated by a nearby nanomagnet. In this paper, we consider such a device and estimate spin-resonator couplings of order ∼1 MHz with realistic parameters. Further, through realistic simulations, we show that precise placement of the double-dot relative to the nanomagnet allows to select between a purely longitudinal coupling (commuting with the bare spin Hamiltonian) and a purely transverse (spin non-conserving) coupling. Additionally, we suggest methods to mitigate dephasing and relaxation channels that are introduced in this coupling scheme. This analysis gives a clear route toward the realization of coherent state transfer between a microwave resonator and a single electron spin in a GaAs double quantum dot with a fidelity above 90%. Improved dynamical decoupling sequences, low-noise environments, and longer-lived microwave cavity modes may lead to substantially higher fidelities in the near future.
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Affiliation(s)
- Félix Beaudoin
- Department of Physics, McGill University, Montréal, Québec H3A 2T8, Canada
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38
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Puri S, Blais A. High-Fidelity Resonator-Induced Phase Gate with Single-Mode Squeezing. PHYSICAL REVIEW LETTERS 2016; 116:180501. [PMID: 27203311 DOI: 10.1103/physrevlett.116.180501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Indexed: 06/05/2023]
Abstract
We propose to increase the fidelity of two-qubit resonator-induced phase gates in circuit QED by the use of narrow-band single-mode squeezing. We show that there exists an optimal squeezing angle and strength that erases qubit "which-path" information leaking out of the cavity and thereby minimizes qubit dephasing during these gates. Our analytical results for the gate fidelity are in excellent agreement with numerical simulations of a cascaded master equation that takes into account the dynamics of the source of squeezed radiation. With realistic parameters, we find that it is possible to realize a controlled-phase gate with a gate time of 200 ns and average infidelity of 10^{-5}.
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Affiliation(s)
- Shruti Puri
- Départment de Physique, Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1
| | - Alexandre Blais
- Départment de Physique, Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1
- Canadian Institute for Advanced Research, Toronto, Canada
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39
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D'Anjou B, Coish WA. Soft decoding of a qubit readout apparatus. PHYSICAL REVIEW LETTERS 2014; 113:230402. [PMID: 25526105 DOI: 10.1103/physrevlett.113.230402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Indexed: 06/04/2023]
Abstract
Qubit readout is commonly performed by thresholding a collection of analog detector signals to obtain a sequence of single-shot bit values. The intrinsic irreversibility of the mapping from analog to digital signals discards soft information associated with an a posteriori confidence that can be assigned to each bit value when a detector is well characterized. Accounting for soft information, we show significant improvements in enhanced state detection with the quantum repetition code as well as quantum state or parameter estimation. These advantages persist in spite of non-Gaussian features of realistic readout models, experimentally relevant small numbers of qubits, and finite encoding errors. These results show useful and achievable advantages for a wide range of current experiments on quantum state tomography, parameter estimation, and qubit readout.
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Affiliation(s)
- B D'Anjou
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada
| | - W A Coish
- Department of Physics, McGill University, Montreal, Quebec H3A 2T8, Canada and Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8, Canada
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40
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Allman MS, Whittaker JD, Castellanos-Beltran M, Cicak K, da Silva F, DeFeo MP, Lecocq F, Sirois A, Teufel JD, Aumentado J, Simmonds RW. Tunable resonant and nonresonant interactions between a phase qubit and LC resonator. PHYSICAL REVIEW LETTERS 2014; 112:123601. [PMID: 24724648 DOI: 10.1103/physrevlett.112.123601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Indexed: 06/03/2023]
Abstract
We use a flux-biased radio frequency superconducting quantum interference device (rf SQUID) with an embedded flux-biased direct current SQUID to generate strong resonant and nonresonant tunable interactions between a phase qubit and a lumped-element resonator. The rf SQUID creates a tunable magnetic susceptibility between the qubit and resonator providing resonant coupling strengths from zero to near the ultrastrong coupling regime. By modulating the magnetic susceptibility, nonresonant parametric coupling achieves rates >100 MHz. Nonlinearity of the magnetic susceptibility also leads to parametric coupling at the subharmonics of the qubit-resonator detuning.
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Affiliation(s)
- M S Allman
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - J D Whittaker
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - M Castellanos-Beltran
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - K Cicak
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - F da Silva
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - M P DeFeo
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - F Lecocq
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - A Sirois
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - J D Teufel
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - J Aumentado
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
| | - R W Simmonds
- National Institute of Standards and Technology, 325 Broadway Street, Boulder, Colorado 80305-3328, USA
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41
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Albert F, Sivalertporn K, Kasprzak J, Strauß M, Schneider C, Höfling S, Kamp M, Forchel A, Reitzenstein S, Muljarov EA, Langbein W. Microcavity controlled coupling of excitonic qubits. Nat Commun 2013; 4:1747. [PMID: 23612288 PMCID: PMC3644086 DOI: 10.1038/ncomms2764] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 03/19/2013] [Indexed: 11/27/2022] Open
Abstract
Controlled non-local energy and coherence transfer enables light harvesting in photosynthesis and non-local logical operations in quantum computing. This process is intuitively pictured by a pair of mechanical oscillators, coupled by a spring, allowing for a reversible exchange of excitation. On a microscopic level, the most relevant mechanism of coherent coupling of distant quantum bits—like trapped ions, superconducting qubits or excitons confined in semiconductor quantum dots—is coupling via the electromagnetic field. Here we demonstrate the controlled coherent coupling of spatially separated quantum dots via the photon mode of a solid state microresonator using the strong exciton–photon coupling regime. This is enabled by two-dimensional spectroscopy of the sample’s coherent response, a sensitive probe of the coherent coupling. The results are quantitatively understood in a rigorous description of the cavity-mediated coupling of the quantum dot excitons. This mechanism can be used, for instance in photonic crystal cavity networks, to enable a long-range, non-local coherent coupling. Controlling coupling between distant quantum objects is important for implementation of quantum technologies. Providing an important step towards using semiconductor structures for hosting optically controlled qubits, this work shows coherent coupling between three quantum dot excitons via a cavity.
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Affiliation(s)
- F Albert
- Technische Physik, Physikalisches Institut, and Wilhelm Conrad Röntgen Research Center for Complex Material Systems, Universität Würzburg, Am Hubland, Würzburg D-97074, Germany
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42
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Gustavsson S, Zwier O, Bylander J, Yan F, Yoshihara F, Nakamura Y, Orlando TP, Oliver WD. Improving quantum gate fidelities by using a qubit to measure microwave pulse distortions. PHYSICAL REVIEW LETTERS 2013; 110:040502. [PMID: 25166145 DOI: 10.1103/physrevlett.110.040502] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2012] [Indexed: 06/03/2023]
Abstract
We present a new method for determining pulse imperfections and improving the single-gate fidelity in a superconducting qubit. By applying consecutive positive and negative π pulses, we amplify the qubit evolution due to microwave pulse distortions, which causes the qubit state to rotate around an axis perpendicular to the intended rotation axis. Measuring these rotations as a function of pulse period allows us to reconstruct the shape of the microwave pulse arriving at the sample. Using the extracted response to predistort the input signal, we are able to reduce the average error per gate by 37%, which enables us to reach an average single-qubit gate fidelity higher than 0.998.
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Affiliation(s)
- Simon Gustavsson
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Olger Zwier
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA and Zernike Institute for Advanced Materials, University of Groningen, 9747AG Groningen, The Netherlands
| | - Jonas Bylander
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Fei Yan
- Department of Nuclear Science and Engineering, MIT, Cambridge, Massachusetts 02139, USA
| | - Fumiki Yoshihara
- The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan
| | - Yasunobu Nakamura
- The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan and Research Center for Advanced Science and Technology (RCAST), The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8904, Japan
| | - Terry P Orlando
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - William D Oliver
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA and MIT Lincoln Laboratory, 244 Wood Street, Lexington, Massachusetts 02420, USA
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43
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Poletto S, Gambetta JM, Merkel ST, Smolin JA, Chow JM, Córcoles AD, Keefe GA, Rothwell MB, Rozen JR, Abraham DW, Rigetti C, Steffen M. Entanglement of two superconducting qubits in a waveguide cavity via monochromatic two-photon excitation. PHYSICAL REVIEW LETTERS 2012; 109:240505. [PMID: 23368296 DOI: 10.1103/physrevlett.109.240505] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2012] [Indexed: 06/01/2023]
Abstract
We report a system where fixed interactions between noncomputational levels make bright the otherwise forbidden two-photon |00}→|11} transition. The system is formed by hand selection and assembly of two discrete component transmon-style superconducting qubits inside a rectangular microwave cavity. The application of a monochromatic drive tuned to this transition induces two-photon Rabi-like oscillations between the ground and doubly excited states via the Bell basis. The system therefore allows all-microwave two-qubit universal control with the same techniques and hardware required for single qubit control. We report Ramsey-like and spin echo sequences with the generated Bell states, and measure a two-qubit gate fidelity of F(g)=90% (unconstrained) and 86% (maximum likelihood estimator).
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Affiliation(s)
- S Poletto
- IBM TJ Watson Research Center, Yorktown Heights, New York 10598, USA
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44
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Chow JM, Gambetta JM, Córcoles AD, Merkel ST, Smolin JA, Rigetti C, Poletto S, Keefe GA, Rothwell MB, Rozen JR, Ketchen MB, Steffen M. Universal quantum gate set approaching fault-tolerant thresholds with superconducting qubits. PHYSICAL REVIEW LETTERS 2012; 109:060501. [PMID: 23006254 DOI: 10.1103/physrevlett.109.060501] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Indexed: 06/01/2023]
Abstract
We use quantum process tomography to characterize a full universal set of all-microwave gates on two superconducting single-frequency single-junction transmon qubits. All extracted gate fidelities, including those for Clifford group generators, single-qubit π/4 and π/8 rotations, and a two-qubit controlled-not, exceed 95% (98%), without (with) subtracting state preparation and measurement errors. Furthermore, we introduce a process map representation in the Pauli basis which is visually efficient and informative. This high-fidelity gate set serves as a critical building block towards scalable architectures of superconducting qubits for error correction schemes and pushes up on the known limits of quantum gate characterization.
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Affiliation(s)
- Jerry M Chow
- IBM TJ Watson Research Center, Yorktown Heights, New York 10598, USA
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45
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Gustavsson S, Yan F, Bylander J, Yoshihara F, Nakamura Y, Orlando TP, Oliver WD. Dynamical decoupling and dephasing in interacting two-level systems. PHYSICAL REVIEW LETTERS 2012; 109:010502. [PMID: 23031094 DOI: 10.1103/physrevlett.109.010502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2012] [Indexed: 06/01/2023]
Abstract
We implement dynamical decoupling techniques to mitigate noise and enhance the lifetime of an entangled state that is formed in a superconducting flux qubit coupled to a microscopic two-level system. By rapidly changing the qubit's transition frequency relative to the two-level system, we realize a refocusing pulse that reduces dephasing due to fluctuations in the transition frequencies, thereby improving the coherence time of the entangled state. The coupling coherence is further enhanced when applying multiple refocusing pulses, in agreement with our 1/f noise model. The results are applicable to any two-qubit system with transverse coupling and they highlight the potential of decoupling techniques for improving two-qubit gate fidelities, an essential prerequisite for implementing fault-tolerant quantum computing.
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Affiliation(s)
- Simon Gustavsson
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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46
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Smolin JA, Gambetta JM, Smith G. Efficient method for computing the maximum-likelihood quantum state from measurements with additive Gaussian noise. PHYSICAL REVIEW LETTERS 2012; 108:070502. [PMID: 22401185 DOI: 10.1103/physrevlett.108.070502] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Revised: 09/27/2011] [Indexed: 05/31/2023]
Abstract
We provide an efficient method for computing the maximum-likelihood mixed quantum state (with density matrix ρ) given a set of measurement outcomes in a complete orthonormal operator basis subject to Gaussian noise. Our method works by first changing basis yielding a candidate density matrix μ which may have nonphysical (negative) eigenvalues, and then finding the nearest physical state under the 2-norm. Our algorithm takes at worst O(d(4)) for the basis change plus O(d(3)) for finding ρ where d is the dimension of the quantum state. In the special case where the measurement basis is strings of Pauli operators, the basis change takes only O(d(3)) as well. The workhorse of the algorithm is a new linear-time method for finding the closest probability distribution (in Euclidean distance) to a set of real numbers summing to one.
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Affiliation(s)
- John A Smolin
- IBM TJ Watson Research Center, Yorktown Heights, New York 10598, USA.
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47
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Dewes A, Ong FR, Schmitt V, Lauro R, Boulant N, Bertet P, Vion D, Esteve D. Characterization of a two-transmon processor with individual single-shot qubit readout. PHYSICAL REVIEW LETTERS 2012; 108:057002. [PMID: 22400953 DOI: 10.1103/physrevlett.108.057002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Indexed: 05/31/2023]
Abstract
We report the characterization of a two-qubit processor implemented with two capacitively coupled tunable superconducting qubits of the transmon type, each qubit having its own nondestructive single-shot readout. The fixed capacitive coupling yields the sqrt[iSWAP] two-qubit gate for a suitable interaction time. We reconstruct by state tomography the coherent dynamics of the two-bit register as a function of the interaction time, observe a violation of the Bell inequality by 22 standard deviations after correcting readout errors, and measure by quantum process tomography a gate fidelity of 90%.
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Affiliation(s)
- A Dewes
- Quantronics group, Service de Physique de l'État Condensé (CNRS URA 2464), IRAMIS, DSM, CEA-Saclay, 91191 Gif-sur-Yvette, France
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