1
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Arias D, Rodríguez de Guzmán IG, Rodríguez M, Terres EB, Sanz B, de la Puerta JG, Pastor I, Zubillaga A, Bringas PG. Let’s Do it Right the First Time: Survey on Security Concerns in the Way to Quantum Software Engineering. Neurocomputing 2023. [DOI: 10.1016/j.neucom.2023.03.060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
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2
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Salari V, Paneru D, Saglamyurek E, Ghadimi M, Abdar M, Rezaee M, Aslani M, Barzanjeh S, Karimi E. Quantum face recognition protocol with ghost imaging. Sci Rep 2023; 13:2401. [PMID: 36765078 PMCID: PMC9918728 DOI: 10.1038/s41598-022-25280-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 11/28/2022] [Indexed: 02/12/2023] Open
Abstract
Face recognition is one of the most ubiquitous examples of pattern recognition in machine learning, with numerous applications in security, access control, and law enforcement, among many others. Pattern recognition with classical algorithms requires significant computational resources, especially when dealing with high-resolution images in an extensive database. Quantum algorithms have been shown to improve the efficiency and speed of many computational tasks, and as such, they could also potentially improve the complexity of the face recognition process. Here, we propose a quantum machine learning algorithm for pattern recognition based on quantum principal component analysis, and quantum independent component analysis. A novel quantum algorithm for finding dissimilarity in the faces based on the computation of trace and determinant of a matrix (image) is also proposed. The overall complexity of our pattern recognition algorithm is [Formula: see text]-N is the image dimension. As an input to these pattern recognition algorithms, we consider experimental images obtained from quantum imaging techniques with correlated photons, e.g. "interaction-free" imaging or "ghost" imaging. Interfacing these imaging techniques with our quantum pattern recognition processor provides input images that possess a better signal-to-noise ratio, lower exposures, and higher resolution, thus speeding up the machine learning process further. Our fully quantum pattern recognition system with quantum algorithm and quantum inputs promises a much-improved image acquisition and identification system with potential applications extending beyond face recognition, e.g., in medical imaging for diagnosing sensitive tissues or biology for protein identification.
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Affiliation(s)
- Vahid Salari
- grid.22072.350000 0004 1936 7697Department of Physics and Astronomy, Institute for Quantum Science and Technology, University of Calgary, Calgary, AB T2N 1N4 Canada ,grid.462072.50000 0004 0467 2410BCAM - Basque Center for Applied Mathematics, Alameda de Mazarredo 14, 48009 Bilbao, Basque Country Spain
| | - Dilip Paneru
- grid.28046.380000 0001 2182 2255Nexus for Quantum Technologies, University of Ottawa, 25 Templeton Street, Ottawa, ON K1N 6N5 Canada
| | - Erhan Saglamyurek
- grid.22072.350000 0004 1936 7697Department of Physics and Astronomy, Institute for Quantum Science and Technology, University of Calgary, Calgary, AB T2N 1N4 Canada ,grid.17089.370000 0001 2190 316XDepartment of Physics, University of Alberta, Edmonton, AB T6G 2E1 Canada
| | - Milad Ghadimi
- grid.411751.70000 0000 9908 3264Department of Physics, Isfahan University of Technology, Isfahan, 8415683111 Iran
| | - Moloud Abdar
- grid.1021.20000 0001 0526 7079Institute for Intelligent Systems Research and Innovation (IISRI), Deakin University, Geelong, Australia
| | - Mohammadreza Rezaee
- grid.28046.380000 0001 2182 2255Nexus for Quantum Technologies, University of Ottawa, 25 Templeton Street, Ottawa, ON K1N 6N5 Canada
| | - Mehdi Aslani
- grid.411751.70000 0000 9908 3264Department of Physics, Isfahan University of Technology, Isfahan, 8415683111 Iran
| | - Shabir Barzanjeh
- grid.22072.350000 0004 1936 7697Department of Physics and Astronomy, Institute for Quantum Science and Technology, University of Calgary, Calgary, AB T2N 1N4 Canada
| | - Ebrahim Karimi
- Nexus for Quantum Technologies, University of Ottawa, 25 Templeton Street, Ottawa, ON, K1N 6N5, Canada. .,National Research Council of Canada, 100 Sussex Drive, Ottawa, ON, K1A 0R6, Canada.
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3
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Ivanov SS, Torosov BT, Vitanov NV. High-Fidelity Quantum Control by Polychromatic Pulse Trains. PHYSICAL REVIEW LETTERS 2022; 129:240505. [PMID: 36563260 DOI: 10.1103/physrevlett.129.240505] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 11/08/2022] [Indexed: 06/17/2023]
Abstract
We introduce a quantum control technique using polychromatic pulse trains, consisting of pulses with different carrier frequencies, i.e., different detunings with respect to the qubit transition frequency. We derive numerous polychromatic pulse trains, which generate broadband, narrowband, and passband excitation profiles for different target transition probabilities. This makes it possible to create high-fidelity excitation profiles which are either (i) robust to deviations in the experimental parameters, which is attractive for quantum computing, or (ii) more sensitive to such variations, which is attractive for crosstalk elimination and quantum sensing. The method is demonstrated experimentally using one of IBM's superconducting quantum processors, in a very good agreement between theory and experiment. These results demonstrate both the excellent coherence properties of the IBM qubits and the accuracy, robustness, and flexibility of the proposed quantum control technique. They also show that the detuning is a control parameter which is as efficient as the pulse phase that is commonly used in composite pulses. Hence the method opens a variety of perspectives for quantum control in areas where phase manipulation is difficult or inaccurate.
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Affiliation(s)
- Svetoslav S Ivanov
- Department of Physics, St Kliment Ohridski University of Sofia, 5 James Bourchier Boulevard, 1164 Sofia, Bulgaria
| | - Boyan T Torosov
- Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko chaussée, 1784 Sofia, Bulgaria
| | - Nikolay V Vitanov
- Department of Physics, St Kliment Ohridski University of Sofia, 5 James Bourchier Boulevard, 1164 Sofia, Bulgaria
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4
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Jheng SD, Chen TW, Cheng SC. Spontaneous giant vortices and circular supercurrents in a trapped exciton-polariton condensate. OPTICS EXPRESS 2022; 30:35325-35337. [PMID: 36258486 DOI: 10.1364/oe.468330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 08/23/2022] [Indexed: 06/16/2023]
Abstract
We theoretically study an exciton-polariton condensate trapped in a harmonic potential with an annular pump. With a circular pump, predictions were made for a spontaneous rotating vortex lattice packed by singly quantized vortices. If the circular pump is replaced by an annular pump, singly quantized vortices are absorbed into the central hole and form a multiply quantized vortex. For a sufficiently narrow annular width, all vortices are absorbed into the central hole, ultimately forming a giant vortex with supersonic circular supercurrents flowing around it. Vortex-antivortex pairs can be generated if a defect is present in these supersonic circular supercurrents. We further discover that the motion of the vortex-antivortex pairs depends on the position at which they were generated. We suggest that this property can be used to control whether the velocity of the circular supercurrents is above or below the sound velocity.
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5
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Verification of Information Thermodynamics in a Trapped Ion System. ENTROPY 2022; 24:e24060813. [PMID: 35741534 PMCID: PMC9222944 DOI: 10.3390/e24060813] [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: 04/22/2022] [Revised: 06/07/2022] [Accepted: 06/08/2022] [Indexed: 02/05/2023]
Abstract
Information thermodynamics has developed rapidly over past years, and the trapped ions, as a controllable quantum system, have demonstrated feasibility to experimentally verify the theoretical predictions in the information thermodynamics. Here, we address some representative theories of information thermodynamics, such as the quantum Landauer principle, information equality based on the two-point measurement, information-theoretical bound of irreversibility, and speed limit restrained by the entropy production of system, and review their experimental demonstration in the trapped ion system. In these schemes, the typical physical processes, such as the entropy flow, energy transfer, and information flow, build the connection between thermodynamic processes and information variation. We then elucidate the concrete quantum control strategies to simulate these processes by using quantum operators and the decay paths in the trapped-ion system. Based on them, some significantly dynamical processes in the trapped ion system to realize the newly proposed information-thermodynamic models is reviewed. Although only some latest experimental results of information thermodynamics with a single trapped-ion quantum system are reviewed here, we expect to find more exploration in the future with more ions involved in the experimental systems.
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6
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Kukita S, Kiya H, Kondo Y. Geometric property of off resonance error robust composite pulse. Sci Rep 2022; 12:9574. [PMID: 35688848 PMCID: PMC9187774 DOI: 10.1038/s41598-022-13207-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Accepted: 05/23/2022] [Indexed: 11/23/2022] Open
Abstract
The precision of quantum operations is affected by unavoidable systematic errors. A composite pulse (CP), which has been well investigated in nuclear magnetic resonance (NMR), is a technique that suppresses the influence of systematic errors by replacing a single operation with a sequence of operations. In one-qubit operations, there are two typical systematic errors, Pulse Length Error (PLE) and Off Resonance Error (ORE). Recently, it was found that PLE robust CPs have a clear geometric property. In this study, we show that ORE robust CPs also have a simple geometric property, which is associated with trajectories on the Bloch sphere of the corresponding operations. We discuss the geometric property of ORE robust CPs using two examples.
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Affiliation(s)
- Shingo Kukita
- Department of Physics, Kindai University, Higashi, Osaka, 577-8502, Japan.
| | - Haruki Kiya
- Department of Physics, Kindai University, Higashi, Osaka, 577-8502, Japan
| | - Yasushi Kondo
- Department of Physics, Kindai University, Higashi, Osaka, 577-8502, Japan
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7
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Castellanos MA, Willard AP. Designing excitonic circuits for the Deutsch-Jozsa algorithm: mitigating fidelity loss by merging gate operations. Phys Chem Chem Phys 2021; 23:15196-15208. [PMID: 34231586 DOI: 10.1039/d1cp01643a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this manuscript, we examine design strategies for the development of excitonic circuits that are capable of performing simple 2-qubit multi-step quantum algorithms. Specifically, we compare two different strategies for designing dye-based systems that prescribe exciton evolution encoding a particular quantum algorithm. A serial strategy implements the computation as a step-by-step series of circuits, with each carrying out a single operation of the quantum algorithm, and a combined strategy implements the entire computation in a single circuit. We apply these two approaches to the well-studied Deutsch-Jozsa algorithm and evaluate circuit fidelity in an idealized system under a model harmonic bath, and also for a bath that is parameterized to reflect the thermal fluctuations of an explicit molecular environment. We find that the combined strategy tends to yield higher fidelity and that the harmonic bath approximation leads to lower fidelity than a model molecular bath. These results imply that the programming of excitonic circuits for quantum computation should favor hard-coded modules that incorporate multiple algorithmic steps and should represent the molecular nature of the circuit environment.
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Affiliation(s)
- Maria A Castellanos
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA.
| | - Adam P Willard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA.
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8
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Hayes D, Stack D, Bjork B, Potter AC, Baldwin CH, Stutz RP. Eliminating Leakage Errors in Hyperfine Qubits. PHYSICAL REVIEW LETTERS 2020; 124:170501. [PMID: 32412273 DOI: 10.1103/physrevlett.124.170501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 04/13/2020] [Indexed: 06/11/2023]
Abstract
Population leakage outside the qubit subspace presents a particularly harmful source of error that cannot be handled by standard error correction methods. Using a trapped ^{171}Yb^{+} ion, we demonstrate an optical pumping scheme to suppress leakage errors in atomic hyperfine qubits. The selection rules and narrow linewidth of a quadrupole transition are used to selectively pump population out of leakage states and back into the qubit subspace. Each pumping cycle reduces the leakage population by a factor of ∼3, allowing for an exponential suppression in the number of cycles. We use interleaved randomized benchmarking on the qubit subspace to show that this pumping procedure has negligible side effects on the qubit subspace, bounding the induced qubit memory error by ≤2.0(8)×10^{-5} per cycle, and qubit population decay to ≤1.4(3)×10^{-7} per cycle. These results clear a major obstacle for implementations of quantum error correction and error mitigation protocols.
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Affiliation(s)
- D Hayes
- Honeywell Quantum Solutions, 303 S. Technology Ct. 80021 Broomfield, Colorado, USA
| | - D Stack
- Honeywell Quantum Solutions, 303 S. Technology Ct. 80021 Broomfield, Colorado, USA
| | - B Bjork
- Honeywell Quantum Solutions, 303 S. Technology Ct. 80021 Broomfield, Colorado, USA
| | - A C Potter
- Honeywell Quantum Solutions, 303 S. Technology Ct. 80021 Broomfield, Colorado, USA
| | - C H Baldwin
- Honeywell Quantum Solutions, 303 S. Technology Ct. 80021 Broomfield, Colorado, USA
| | - R P Stutz
- Honeywell Quantum Solutions, 303 S. Technology Ct. 80021 Broomfield, Colorado, USA
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9
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Zhang K, Thompson J, Zhang X, Shen Y, Lu Y, Zhang S, Ma J, Vedral V, Gu M, Kim K. Modular quantum computation in a trapped ion system. Nat Commun 2019; 10:4692. [PMID: 31619670 PMCID: PMC6795904 DOI: 10.1038/s41467-019-12643-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 09/17/2019] [Indexed: 11/09/2022] Open
Abstract
Modern computation relies crucially on modular architectures, breaking a complex algorithm into self-contained subroutines. A client can then call upon a remote server to implement parts of the computation independently via an application programming interface (API). Present APIs relay only classical information. Here we implement a quantum API that enables a client to estimate the absolute value of the trace of a server-provided unitary operation [Formula: see text]. We demonstrate that the algorithm functions correctly irrespective of what unitary [Formula: see text] the server implements or how the server specifically realizes [Formula: see text]. Our experiment involves pioneering techniques to coherently swap qubits encoded within the motional states of a trapped [Formula: see text] ion, controlled on its hyperfine state. This constitutes the first demonstration of modular computation in the quantum regime, providing a step towards scalable, parallelization of quantum computation.
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Affiliation(s)
- Kuan Zhang
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China.
- MOE Key Laboratory of Fundamental Physical Quantities Measurement & Hubei Key Laboratory of Gravitation and Quantum Physics, PGMF and School of Physics, Huazhong University of Science and Technology, 430074, Wuhan, China.
| | - Jayne Thompson
- Centre for Quantum Technologies, National University of Singapore, Singapore, 117543, Singapore.
| | - Xiang Zhang
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China
- Department of Physics, Renmin University of China, 100872, Beijing, China
| | - Yangchao Shen
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China
| | - Yao Lu
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China
| | - Shuaining Zhang
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China
| | - Jiajun Ma
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China
- Department of Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU, UK
| | - Vlatko Vedral
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China
- Centre for Quantum Technologies, National University of Singapore, Singapore, 117543, Singapore
- Department of Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU, UK
- Department of Physics, National University of Singapore, Singapore, 117551, Singapore
| | - Mile Gu
- Centre for Quantum Technologies, National University of Singapore, Singapore, 117543, Singapore.
- School of Mathematical and Physical Sciences, Nanyang Technological University, Singapore, 637371, Singapore.
- Complexity Institute, Nanyang Technological University, Singapore, 637335, Singapore.
| | - Kihwan Kim
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China.
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10
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Heo J, Won K, Yang HJ, Hong JP, Choi SG. Photonic scheme of discrete quantum Fourier transform for quantum algorithms via quantum dots. Sci Rep 2019; 9:12440. [PMID: 31455794 PMCID: PMC6712008 DOI: 10.1038/s41598-019-48695-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2019] [Accepted: 08/07/2019] [Indexed: 11/24/2022] Open
Abstract
We propose an optical scheme of discrete quantum Fourier transform (DQFT) via ancillary systems using quantum dots (QDs) confined in single-sided cavities (QD-cavity systems). In our DQFT scheme, the main component is a controlled-rotation k (CRk) gate, which utilizes the interactions between photons and QDs, consisting of two QD-cavity systems. Since the proposed CRk gate can be experimentally implemented with high efficiency and reliable performance, the scalability of multi-qubit DQFT scheme can also be realized through the simple composition of the proposed CRk gates via the QD-cavity systems. Subsequently, in order to demonstrate the performance of the CRk gate, we analyze the interaction between a photon and a QD-cavity system, and then indicate the condition to be efficient CRk gate with feasibility under vacuum noise and sideband leakage.
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Affiliation(s)
- Jino Heo
- College of Electrical and Computer Engineering, Chungbuk National University, Chungdae-ro 1, Seowon-Gu, Cheongju, Republic of Korea
| | - Kitak Won
- Program in Bio-medical Science, Korea University, Sejong, 30019, Republic of Korea.,Department of Natural Science, Republic of Korea Air-Force Academy, Cheongju, 28187, Republic of Korea
| | - Hyung-Jin Yang
- Program in Bio-medical Science, Korea University, Sejong, 30019, Republic of Korea.,Department of Physics, Korea University, Sejong, 339-700, Republic of Korea
| | - Jong-Phil Hong
- College of Electrical and Computer Engineering, Chungbuk National University, Chungdae-ro 1, Seowon-Gu, Cheongju, Republic of Korea
| | - Seong-Gon Choi
- College of Electrical and Computer Engineering, Chungbuk National University, Chungdae-ro 1, Seowon-Gu, Cheongju, Republic of Korea.
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11
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Shyshlov D, Babikov D. Computational study of cold ions trapped in a double-well potential. Mol Phys 2018. [DOI: 10.1080/00268976.2018.1559956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
| | - Dmitri Babikov
- Chemistry Department, Marquette University, Milwaukee, USA
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12
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Abstract
Recent years have seen an emergence of network modeling applied to moods, attitudes, and problems in the realm of psychology. In this framework, psychological variables are understood to directly affect each other rather than being caused by an unobserved latent entity. In this tutorial, we introduce the reader to estimating the most popular network model for psychological data: the partial correlation network. We describe how regularization techniques can be used to efficiently estimate a parsimonious and interpretable network structure in psychological data. We show how to perform these analyses in R and demonstrate the method in an empirical example on posttraumatic stress disorder data. In addition, we discuss the effect of the hyperparameter that needs to be manually set by the researcher, how to handle non-normal data, how to determine the required sample size for a network analysis, and provide a checklist with potential solutions for problems that can arise when estimating regularized partial correlation networks. (PsycINFO Database Record (c) 2018 APA, all rights reserved).
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Affiliation(s)
- Sacha Epskamp
- Department of Psychological Methods, University of Amsterdam
| | - Eiko I Fried
- Department of Psychological Methods, University of Amsterdam
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13
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Zhang K, Ma J, Zhang X, Thompson J, Vedral V, Kim K, Gu M. Operational effects of the UNOT gate on classical and quantum correlations. Sci Bull (Beijing) 2018; 63:765-770. [PMID: 36658950 DOI: 10.1016/j.scib.2018.05.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 05/03/2018] [Accepted: 05/08/2018] [Indexed: 01/21/2023]
Abstract
The NOT gate that flips a classical bit is ubiquitous in classical information processing. However its quantum analogue, the universal NOT (UNOT) gate that flips a quantum spin in any alignment into its antipodal counterpart is strictly forbidden. Here we explore the connection between this discrepancy and how UNOT gates affect classical and quantum correlations. We show that while a UNOT gate always preserves classical correlations between two spins, it can non-locally increase or decrease their shared discord in ways that allow violation of the data processing inequality. We experimentally illustrate this using a multi-level trapped 171Yb+ ion that allows simulation of anti-unitary operations.
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Affiliation(s)
- Kuan Zhang
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China.
| | - Jiajun Ma
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China; Department of Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, UK
| | - Xiang Zhang
- Department of Physics, Renmin University of China, Beijing 100872, China; Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - Jayne Thompson
- Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore
| | - Vlatko Vedral
- Department of Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, UK; Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore; Department of Physics, National University of Singapore, Singapore 117551, Singapore; Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - Kihwan Kim
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China.
| | - Mile Gu
- School of Mathematical and Physical Sciences, Nanyang Technological University, Singapore 637371, Singapore; Complexity Institute, Nanyang Technological University, Singapore 637335, Singapore; Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore; Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China.
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14
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Watson TF, Philips SGJ, Kawakami E, Ward DR, Scarlino P, Veldhorst M, Savage DE, Lagally MG, Friesen M, Coppersmith SN, Eriksson MA, Vandersypen LMK. A programmable two-qubit quantum processor in silicon. Nature 2018; 555:633-637. [PMID: 29443962 DOI: 10.1038/nature25766] [Citation(s) in RCA: 138] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2017] [Accepted: 01/16/2018] [Indexed: 12/18/2022]
Abstract
Now that it is possible to achieve measurement and control fidelities for individual quantum bits (qubits) above the threshold for fault tolerance, attention is moving towards the difficult task of scaling up the number of physical qubits to the large numbers that are needed for fault-tolerant quantum computing. In this context, quantum-dot-based spin qubits could have substantial advantages over other types of qubit owing to their potential for all-electrical operation and ability to be integrated at high density onto an industrial platform. Initialization, readout and single- and two-qubit gates have been demonstrated in various quantum-dot-based qubit representations. However, as seen with small-scale demonstrations of quantum computers using other types of qubit, combining these elements leads to challenges related to qubit crosstalk, state leakage, calibration and control hardware. Here we overcome these challenges by using carefully designed control techniques to demonstrate a programmable two-qubit quantum processor in a silicon device that can perform the Deutsch-Josza algorithm and the Grover search algorithm-canonical examples of quantum algorithms that outperform their classical analogues. We characterize the entanglement in our processor by using quantum-state tomography of Bell states, measuring state fidelities of 85-89 per cent and concurrences of 73-82 per cent. These results pave the way for larger-scale quantum computers that use spins confined to quantum dots.
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Affiliation(s)
- T F Watson
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
| | - S G J Philips
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
| | - E Kawakami
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
| | - D R Ward
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - P Scarlino
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
| | - M Veldhorst
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
| | - D E Savage
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M G Lagally
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - Mark Friesen
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - S N Coppersmith
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - M A Eriksson
- University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
| | - L M K Vandersypen
- QuTech and the Kavli Institute of Nanoscience, Delft University of Technology, 2600 GA Delft, The Netherlands
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15
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Riofrío CA, Gross D, Flammia ST, Monz T, Nigg D, Blatt R, Eisert J. Experimental quantum compressed sensing for a seven-qubit system. Nat Commun 2017; 8:15305. [PMID: 28513587 PMCID: PMC5442320 DOI: 10.1038/ncomms15305] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 03/20/2017] [Indexed: 11/20/2022] Open
Abstract
Well-controlled quantum devices with their increasing system size face a new roadblock hindering further development of quantum technologies. The effort of quantum tomography—the reconstruction of states and processes of a quantum device—scales unfavourably: state-of-the-art systems can no longer be characterized. Quantum compressed sensing mitigates this problem by reconstructing states from incomplete data. Here we present an experimental implementation of compressed tomography of a seven-qubit system—a topological colour code prepared in a trapped ion architecture. We are in the highly incomplete—127 Pauli basis measurement settings—and highly noisy—100 repetitions each—regime. Originally, compressed sensing was advocated for states with few non-zero eigenvalues. We argue that low-rank estimates are appropriate in general since statistical noise enables reliable reconstruction of only the leading eigenvectors. The remaining eigenvectors behave consistently with a random-matrix model that carries no information about the true state. Quantum compressed sensing can provide a scalable way to characterize quantum states and devices, but has been so far limited to states with quickly decaying eigenvalues. Here the authors show that it can be appropriate even in the general case, demonstrating reconstruction the state of a seven-qubit system.
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Affiliation(s)
- C A Riofrío
- Dahlem Center for Complex Quantum Systems, Freie Universität Berlin, D-14195 Berlin, Germany
| | - D Gross
- Institute for Theoretical Physics, University of Cologne, D-50937 Cologne, Germany.,Centre for Engineered Quantum Systems, School of Physics, The University of Sydney, Sydney, New South Wales, Australia
| | - S T Flammia
- Centre for Engineered Quantum Systems, School of Physics, The University of Sydney, Sydney, New South Wales, Australia
| | - T Monz
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - D Nigg
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria
| | - R Blatt
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.,Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstraße 21a, A-6020 Innsbruck, Austria
| | - J Eisert
- Dahlem Center for Complex Quantum Systems, Freie Universität Berlin, D-14195 Berlin, Germany
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17
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Demonstration of a small programmable quantum computer with atomic qubits. Nature 2016; 536:63-6. [DOI: 10.1038/nature18648] [Citation(s) in RCA: 435] [Impact Index Per Article: 54.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Accepted: 06/01/2016] [Indexed: 11/08/2022]
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18
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Theis T, Feng Y, Wu T, Warren WS. Composite and shaped pulses for efficient and robust pumping of disconnected eigenstates in magnetic resonance. J Chem Phys 2014; 140:014201. [DOI: 10.1063/1.4851337] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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19
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Thom J, Wilpers G, Riis E, Sinclair AG. Accurate and agile digital control of optical phase, amplitude and frequency for coherent atomic manipulation of atomic systems. OPTICS EXPRESS 2013; 21:18712-18723. [PMID: 23938787 DOI: 10.1364/oe.21.018712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We demonstrate a system for fast and agile digital control of laser phase, amplitude and frequency for applications in coherent atomic systems. The full versatility of a direct digital synthesis radiofrequency source is faithfully transferred to laser radiation via acousto-optic modulation. Optical beatnotes are used to measure phase steps up to 2π, which are accurately implemented with a resolution of ≤ 10 mrad. By linearizing the optical modulation process, amplitude-shaped pulses of durations ranging from 500 ns to 500 ms, in excellent agreement with the programmed functional form, are demonstrated. Pulse durations are limited only by the 30 ns rise time of the modulation process, and a measured extinction ratio of > 5 × 10(11) is achieved. The system presented here was developed specifically for controlling the quantum state of trapped ions with sequences of multiple laser pulses, including composite and bichromatic pulses. The demonstrated techniques are widely applicable to other atomic systems ranging across quantum information processing, frequency metrology, atom interferometry, and single-photon generation.
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Affiliation(s)
- Joseph Thom
- National Physical Laboratory, Teddington, Middlesex, TW11 0LW, UK
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20
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Mizrahi J, Senko C, Neyenhuis B, Johnson KG, Campbell WC, Conover CWS, Monroe C. Ultrafast spin-motion entanglement and interferometry with a single atom. PHYSICAL REVIEW LETTERS 2013; 110:203001. [PMID: 25167401 DOI: 10.1103/physrevlett.110.203001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Indexed: 06/03/2023]
Abstract
We report entanglement of a single atom's hyperfine spin state with its motional state in a time scale of less than 3 ns. We engineer a short train of intense laser pulses to impart a spin-dependent momentum transfer of ± 2 ħk. Using pairs of momentum kicks, we create an atomic interferometer and demonstrate collapse and revival of spin coherence as the motional wave packet is split and recombined. The revival after a pair of kicks occurs only when the second kick is delayed by an integer multiple of the harmonic trap period, a signature of entanglement and disentanglement of the spin with the motion. Such quantum control opens a new regime of ultrafast entanglement in atomic qubits.
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Affiliation(s)
- J Mizrahi
- Joint Quantum Institute, University of Maryland Department of Physics and National Institute of Standards and Technology, College Park, Maryland 20742, USA
| | - C Senko
- Joint Quantum Institute, University of Maryland Department of Physics and National Institute of Standards and Technology, College Park, Maryland 20742, USA
| | - B Neyenhuis
- Joint Quantum Institute, University of Maryland Department of Physics and National Institute of Standards and Technology, College Park, Maryland 20742, USA
| | - K G Johnson
- Joint Quantum Institute, University of Maryland Department of Physics and National Institute of Standards and Technology, College Park, Maryland 20742, USA
| | - W C Campbell
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095, USA
| | - C W S Conover
- Physics Department, Colby College, Waterville, Maine 04901, USA
| | - C Monroe
- Joint Quantum Institute, University of Maryland Department of Physics and National Institute of Standards and Technology, College Park, Maryland 20742, USA
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21
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Husain S, Kawamura M, Jones JA. Further analysis of some symmetric and antisymmetric composite pulses for tackling pulse strength errors. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 230:145-154. [PMID: 23500528 DOI: 10.1016/j.jmr.2013.02.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2012] [Revised: 01/30/2013] [Accepted: 02/03/2013] [Indexed: 06/01/2023]
Abstract
Composite pulses have found widespread use in both conventional Nuclear Magnetic Resonance experiments and in experimental quantum information processing to reduce the effects of systematic errors. Here we describe several families of time symmetric and antisymmetric fully compensating composite pulses, inspired by the previous Fn, Gn and BB1 families family developed by Wimperis. We describe families of composite 180° pulses (not gates) which exhibit unprecedented tolerance of pulse strength errors without unreasonable sensitivity to off-resonance errors, and related families with more exotic tailored responses. Next we address the problem of extending these methods to other rotation angles, and discuss numerical results for 90° pulses. Finally we demonstrate the performance of some 90° and 180° pulses in NMR experiments.
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Affiliation(s)
- Sami Husain
- Centre for Quantum Computation, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
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22
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Zaari RR, Brown A. Effect of laser pulse shaping parameters on the fidelity of quantum logic gates. J Chem Phys 2012; 137:104306. [PMID: 22979858 DOI: 10.1063/1.4747703] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The effect of varying parameters specific to laser pulse shaping instruments on resulting fidelities for the ACNOT(1), NOT(2), and Hadamard(2) quantum logic gates are studied for the diatomic molecule (12)C(16)O. These parameters include varying the frequency resolution, adjusting the number of frequency components and also varying the amplitude and phase at each frequency component. A time domain analytic form of the original discretized frequency domain laser pulse function is derived, providing a useful means to infer the resulting pulse shape through variations to the aforementioned parameters. We show that amplitude variation at each frequency component is a crucial requirement for optimal laser pulse shaping, whereas phase variation provides minimal contribution. We also show that high fidelity laser pulses are dependent upon the frequency resolution and increasing the number of frequency components provides only a small incremental improvement to quantum gate fidelity. Analysis through use of the pulse area theorem confirms the resulting population dynamics for one or two frequency high fidelity laser pulses and implies similar dynamics for more complex laser pulse shapes. The ability to produce high fidelity laser pulses that provide both population control and global phase alignment is attributed greatly to the natural evolution phase alignment of the qubits involved within the quantum logic gate operation.
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Affiliation(s)
- Ryan R Zaari
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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23
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Gandolfi D, Niedermayr M, Kumph M, Brownnutt M, Blatt R. Compact radio-frequency resonator for cryogenic ion traps. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2012; 83:084705. [PMID: 22938322 DOI: 10.1063/1.4737889] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report on the investigation and implementation of a lumped-component, radio-frequency resonator used in a cryogenic vacuum environment to drive an ion trap. The resonator was required to achieve the voltages necessary to trap (~100 V), while dissipating very little power. Ultimately, for an input voltage of 1.35 V, a voltage gain of 100 was measured at 5.7 K, using a design which dissipated only 18 mW. The resonator operated at a frequency of 7.64 MHz and had a Q of 700. Single (40)Ca(+) ions were confined in a trap driven by this device, providing proof of successful resonator operation at low temperature.
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Affiliation(s)
- D Gandolfi
- Dipartimento di Fisica, Università degli Studi di Trento, I 38123 Trento, Italy
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24
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MISHIMA K, YAMASHITA K. Decoherence of Entanglement in Markov Approximation in Terms of Rotating Wave Approximation. JOURNAL OF COMPUTER CHEMISTRY-JAPAN 2012. [DOI: 10.2477/jccj.2011-0016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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25
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Jones JA. Quantum computing with NMR. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2011; 59:91-120. [PMID: 21742157 DOI: 10.1016/j.pnmrs.2010.11.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2010] [Accepted: 11/02/2010] [Indexed: 05/31/2023]
Affiliation(s)
- Jonathan A Jones
- Centre for Quantum Computation, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK.
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26
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Zaari RR, Brown A. Effect of diatomic molecular properties on binary laser pulse optimizations of quantum gate operations. J Chem Phys 2011; 135:044317. [DOI: 10.1063/1.3617248] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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27
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Torosov BT, Guérin S, Vitanov NV. High-fidelity adiabatic passage by composite sequences of chirped pulses. PHYSICAL REVIEW LETTERS 2011; 106:233001. [PMID: 21770500 DOI: 10.1103/physrevlett.106.233001] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Indexed: 05/31/2023]
Abstract
We present a method for optimization of the technique of adiabatic passage between two quantum states by composite sequences of frequency-chirped pulses with specific relative phases: composite adiabatic passage (CAP). By choosing the composite phases appropriately the nonadiabatic losses can be canceled to any desired order with sufficiently long sequences, regardless of the nonadiabatic coupling. The values of the composite phases are universal for they do not depend on the pulse shapes and the chirp. The accuracy of the CAP technique and its robustness against parameter variations make CAP suitable for high-fidelity quantum information processing.
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28
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Ivanov SS, Vitanov NV. High-fidelity local addressing of trapped ions and atoms by composite sequences of laser pulses. OPTICS LETTERS 2011; 36:1275-1277. [PMID: 21479056 DOI: 10.1364/ol.36.001275] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A vital requirement for a quantum computer is the ability to locally address, with high fidelity, any of its qubits without affecting their neighbors. We propose an addressing method using composite sequences of laser pulses that dramatically reduces the addressing error in a lattice of closely spaced atoms or ions and at the same time significantly enhances the robustness of qubit manipulations. To this end, we design novel (to our knowledge) high-fidelity composite pulses for the most important single-qubit operations. In principle, this method allows one to beat the diffraction limit, for only atoms situated in a small spatial region around the center of the laser beam are excited, well within the laser beam waist.
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Affiliation(s)
- Svetoslav S Ivanov
- Department of Physics, Sofia University, 5 James Bourchier Boulevard, 1164 Sofia, Bulgaria. ‐sofia.bg
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29
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A cloud of laser cooled 40Ca+ in a linear ion trap. CHINESE SCIENCE BULLETIN-CHINESE 2010. [DOI: 10.1007/s11434-010-4072-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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30
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Shi F, Rong X, Xu N, Wang Y, Wu J, Chong B, Peng X, Kniepert J, Schoenfeld RS, Harneit W, Feng M, Du J. Room-temperature implementation of the Deutsch-Jozsa algorithm with a single electronic spin in diamond. PHYSICAL REVIEW LETTERS 2010; 105:040504. [PMID: 20867828 DOI: 10.1103/physrevlett.105.040504] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Revised: 04/30/2010] [Indexed: 05/29/2023]
Abstract
The nitrogen-vacancy defect center (N-V center) is a promising candidate for quantum information processing due to the possibility of coherent manipulation of individual spins in the absence of the cryogenic requirement. We report a room-temperature implementation of the Deutsch-Jozsa algorithm by encoding both a qubit and an auxiliary state in the electron spin of a single N-V center. By thus exploiting the specific S=1 character of the spin system, we demonstrate how even scarce quantum resources can be used for test-bed experiments on the way towards a large-scale quantum computing architecture.
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Affiliation(s)
- Fazhan Shi
- Hefei National Laboratory for Physics Sciences at Microscale and Department of Modern Physics, University of Science and Technology of China, Hefei, 230026, China
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31
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Zaari RR, Brown A. Quantum gate operations using midinfrared binary shaped pulses on the rovibrational states of carbon monoxide. J Chem Phys 2010; 132:014307. [PMID: 20078161 DOI: 10.1063/1.3290957] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Frequency domain shaped binary laser pulses were optimized to perform 2 qubit quantum gate operations in (12)C(16)O. The qubit rovibrational state representation was chosen so that all gate operations consisted of one-photon transitions. The amplitude and phase varied binary pulses were determined using a genetic algorithm optimization routine. Binary pulses have two possible amplitudes, 0 or 1, and two phases, 0 or pi, for each frequency component of the pulse. Binary pulses are the simplest to shape experimentally and provide a minimum fidelity limit for amplitude and phase shaped pulses. With the current choice of qubit representation and using optimized binary pulses, fidelities of 0.80 and as high as 0.97 were achieved for the controlled-NOT and alternative controlled-NOT quantum gates. This indicates that with a judicious choice of qubits, most of the required control can be obtained with a binary pulse. Limited control was observed for 2 qubit NOT and Hadamard gates due to the need to control multiple excitations. The current choice of qubit representation produces pulses with decreased energies and superior fidelities when compared with rovibrational qubit representations consisting of two-photon transitions. The choice of input pulse energy is important and applying pulses of increased energy does not necessarily lead to a better fidelity.
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Affiliation(s)
- Ryan R Zaari
- Department of Chemistry, University of Alberta, Edmonton, Alberta T6G 2G2, Canada
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32
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33
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Simmonds RW, Strauch FW. Circuits that process with magic. Nature 2009; 460:187-8. [DOI: 10.1038/460187a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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34
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Demonstration of two-qubit algorithms with a superconducting quantum processor. Nature 2009; 460:240-4. [PMID: 19561592 DOI: 10.1038/nature08121] [Citation(s) in RCA: 206] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Accepted: 05/05/2009] [Indexed: 11/08/2022]
Abstract
Quantum computers, which harness the superposition and entanglement of physical states, could outperform their classical counterparts in solving problems with technological impact-such as factoring large numbers and searching databases. A quantum processor executes algorithms by applying a programmable sequence of gates to an initialized register of qubits, which coherently evolves into a final state containing the result of the computation. Building a quantum processor is challenging because of the need to meet simultaneously requirements that are in conflict: state preparation, long coherence times, universal gate operations and qubit readout. Processors based on a few qubits have been demonstrated using nuclear magnetic resonance, cold ion trap and optical systems, but a solid-state realization has remained an outstanding challenge. Here we demonstrate a two-qubit superconducting processor and the implementation of the Grover search and Deutsch-Jozsa quantum algorithms. We use a two-qubit interaction, tunable in strength by two orders of magnitude on nanosecond timescales, which is mediated by a cavity bus in a circuit quantum electrodynamics architecture. This interaction allows the generation of highly entangled states with concurrence up to 94 per cent. Although this processor constitutes an important step in quantum computing with integrated circuits, continuing efforts to increase qubit coherence times, gate performance and register size will be required to fulfil the promise of a scalable technology.
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Abstract
To process information using quantum-mechanical principles, the states of individual particles need to be entangled and manipulated. One way to do this is to use trapped, laser-cooled atomic ions. Attaining a general-purpose quantum computer is, however, a distant goal, but recent experiments show that just a few entangled trapped ions can be used to improve the precision of measurements. If the entanglement in such systems can be scaled up to larger numbers of ions, simulations that are intractable on a classical computer might become possible.
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37
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Silicon as a model ion trap: Time domain measurements of donor Rydberg states. Proc Natl Acad Sci U S A 2008. [DOI: 10.1073/pnas.0802721105] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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38
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Crick DR, Ohadi H, Bhatti I, Thompson RC, Segal DM. Two-ion Coulomb crystals of Ca + in a Penning trap. OPTICS EXPRESS 2008; 16:2351-2362. [PMID: 18542313 DOI: 10.1364/oe.16.002351] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Results demonstrating laser cooling and observation of individual calcium ions in a Penning trap are presented. We show that we are able to trap, cool, image and manipulate the shape of very small ensembles of ions sufficiently well to produce two-ion 'Coulomb crystals' aligned along the magnetic field of a Penning trap. Images are presented which show the individual ions to be resolved in a two-ion crystal. A distinct change in the configuration of such a crystal is observed as the experimental parameters are changed. These structures could eventually be used as building blocks in a Penning trap based quantum computer.
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Affiliation(s)
- D R Crick
- Imperial College of Science, Technology and Medicine, Prince Consort Rd., London SW7 2AZ, UK
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39
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Suter D, Mahesh TS. Spins as qubits: Quantum information processing by nuclear magnetic resonance. J Chem Phys 2008; 128:052206. [DOI: 10.1063/1.2838166] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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40
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Hill CD. Robust controlled-NOT gates from almost any interaction. PHYSICAL REVIEW LETTERS 2007; 98:180501. [PMID: 17501549 DOI: 10.1103/physrevlett.98.180501] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/17/2005] [Revised: 10/16/2006] [Indexed: 05/15/2023]
Abstract
There are many cases where the interaction between two qubits is not precisely known, but single-qubit operations are available. In this Letter we show how, regardless of an incomplete knowledge of the strength or form of the interaction between two qubits, it is often possible to construct a controlled-NOT gate which has arbitrarily high fidelity. In particular, we show that oscillations in the strength of the exchange interaction in solid state Si and Ge structures are correctable.
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Affiliation(s)
- Charles D Hill
- Centre for Quantum Computer Technology, and Department of Physics, The University of Queensland, St Lucia, QLD 4072, Australia.
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41
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Zhu SL, Monroe C, Duan LM. Trapped ion quantum computation with transverse phonon modes. PHYSICAL REVIEW LETTERS 2006; 97:050505. [PMID: 17026088 DOI: 10.1103/physrevlett.97.050505] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2006] [Indexed: 05/12/2023]
Abstract
We propose a scheme to implement quantum gates on any pair of trapped ions immersed in a large linear crystal, using interaction mediated by the transverse phonon modes. Compared with the conventional approaches based on the longitudinal phonon modes, this scheme is much less sensitive to ion heating and thermal motion outside of the Lamb-Dicke limit thanks to the stronger confinement in the transverse direction. The cost for such a gain is only a moderate increase of the laser power to achieve the same gate speed. We also show how to realize arbitrary-speed quantum gates with transverse phonon modes based on simple shaping of the laser pulses.
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Affiliation(s)
- Shi-Liang Zhu
- FOCUS Center and MCTP, Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA
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42
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Scholz M, Aichele T, Ramelow S, Benson O. Deutsch-jozsa algorithm using triggered single photons from a single quantum dot. PHYSICAL REVIEW LETTERS 2006; 96:180501. [PMID: 16712351 DOI: 10.1103/physrevlett.96.180501] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Indexed: 05/09/2023]
Abstract
We demonstrate a two-qubit Deutsch-Jozsa algorithm with single photons from a single InP quantum dot. The qubits are implemented via the spatial mode and the polarization of a single photon. Our photon source is operated both under continuous and pulsed excitation, the latter allowing deterministic quantum logic by generating photons on demand with a strong suppression of two-photon events. The computation reached a success probability of up to 79%. We also exploit the concept of decoherence-free subspaces that helps to make our experimental setup robust against sources of phase noise.
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Affiliation(s)
- M Scholz
- Physics Department, Nano-Optics, Humboldt-University Berlin, Hausvogteiplatz 5-7, D-10117 Berlin, Germany
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43
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Teranishi Y, Ohtsuki Y, Hosaka K, Chiba H, Katsuki H, Ohmori K. Implementation of quantum gate operations in molecules with weak laser fields. J Chem Phys 2006; 124:114110. [PMID: 16555877 DOI: 10.1063/1.2172605] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
We numerically propose a way to perform quantum computations by combining an ensemble of molecular states and weak laser pulses. A logical input state is expressed as a superposition state (a wave packet) of molecular states, which is initially prepared by a designed femtosecond laser pulse. The free propagation of the wave packet for a specified time interval leads to the specified change in the relative phases among the molecular basis states, which corresponds to a computational result. The computational results are retrieved by means of quantum interferometry. Numerical tests are implemented in the vibrational states of the B state of I2 employing controlled-NOT gate, and 2 and 3 qubits Fourier transforms. All the steps involved in the computational scheme, i.e., the initial preparation, gate operation, and detection steps, are achieved with extremely high precision.
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Affiliation(s)
- Yoshiaki Teranishi
- Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan.
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44
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Häffner H, Hänsel W, Roos CF, Benhelm J, Chek-al-Kar D, Chwalla M, Körber T, Rapol UD, Riebe M, Schmidt PO, Becher C, Gühne O, Dür W, Blatt R. Scalable multiparticle entanglement of trapped ions. Nature 2005; 438:643-6. [PMID: 16319886 DOI: 10.1038/nature04279] [Citation(s) in RCA: 180] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2005] [Accepted: 10/03/2005] [Indexed: 11/08/2022]
Abstract
The generation, manipulation and fundamental understanding of entanglement lies at the very heart of quantum mechanics. Entangled particles are non-interacting but are described by a common wavefunction; consequently, individual particles are not independent of each other and their quantum properties are inextricably interwoven. The intriguing features of entanglement become particularly evident if the particles can be individually controlled and physically separated. However, both the experimental realization and characterization of entanglement become exceedingly difficult for systems with many particles. The main difficulty is to manipulate and detect the quantum state of individual particles as well as to control the interaction between them. So far, entanglement of four ions or five photons has been demonstrated experimentally. The creation of scalable multiparticle entanglement demands a non-exponential scaling of resources with particle number. Among the various kinds of entangled states, the 'W state' plays an important role as its entanglement is maximally persistent and robust even under particle loss. Such states are central as a resource in quantum information processing and multiparty quantum communication. Here we report the scalable and deterministic generation of four-, five-, six-, seven- and eight-particle entangled states of the W type with trapped ions. We obtain the maximum possible information on these states by performing full characterization via state tomography, using individual control and detection of the ions. A detailed analysis proves that the entanglement is genuine. The availability of such multiparticle entangled states, together with full information in the form of their density matrices, creates a test-bed for theoretical studies of multiparticle entanglement. Independently, 'Greenberger-Horne-Zeilinger' entangled states with up to six ions have been created and analysed in Boulder.
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Affiliation(s)
- H Häffner
- Institut für Experimentalphysik, Universität Innsbruck, Technikerstrae 25, A-6020 Innsbruck, Austria.
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45
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Schön C, Solano E, Verstraete F, Cirac JI, Wolf MM. Sequential generation of entangled multiqubit states. PHYSICAL REVIEW LETTERS 2005; 95:110503. [PMID: 16196992 DOI: 10.1103/physrevlett.95.110503] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2005] [Indexed: 05/04/2023]
Abstract
We consider the deterministic generation of entangled multiqubit states by the sequential coupling of an ancillary system to initially uncorrelated qubits. We characterize all achievable states in terms of classes of matrix-product states and give a recipe for the generation on demand of any multiqubit state. The proposed methods are suitable for any sequential generation scheme, though we focus on streams of single-photon time-bin qubits emitted by an atom coupled to an optical cavity. We show, in particular, how to generate familiar quantum information states such as W, Greenberger-Horne-Zeilinger, and cluster states within such a framework.
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Affiliation(s)
- C Schön
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching, Germany
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46
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Oliveira AND, Walborn SP, Monken CH. Implementing the Deutsch algorithm with polarization and transverse spatial modes. ACTA ACUST UNITED AC 2005. [DOI: 10.1088/1464-4266/7/9/009] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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47
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Ohtsuki Y. Simulating the Deutsch–Jozsa algorithm using vibrational states of I2 excited by optimally designed gate pulses. Chem Phys Lett 2005. [DOI: 10.1016/j.cplett.2005.01.080] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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48
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Porras D, Cirac JI. Bose-Einstein condensation and strong-correlation behavior of phonons in ion traps. PHYSICAL REVIEW LETTERS 2004; 93:263602. [PMID: 15697979 DOI: 10.1103/physrevlett.93.263602] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2004] [Indexed: 05/24/2023]
Abstract
We show that the dynamics of phonons in a set of trapped ions interacting with lasers is described by a Bose-Hubbard model whose parameters can be externally adjusted. We investigate the possibility of observing several quantum many-body phenomena, including Bose-Einstein condensation as well as a superfluid-Mott insulator quantum phase transition.
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Affiliation(s)
- D Porras
- Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, Garching, D-85748, Germany.
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Duan LM. Scaling ion trap quantum computation through fast quantum gates. PHYSICAL REVIEW LETTERS 2004; 93:100502. [PMID: 15447393 DOI: 10.1103/physrevlett.93.100502] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2004] [Indexed: 05/24/2023]
Abstract
We propose a method to achieve scalable quantum computation based on fast quantum gates on an array of trapped ions, without the requirement of ion shuttling. Conditional quantum gates are obtained for any neighboring ions through spin-dependent acceleration of the ions from periodic photon kicks. The gates are shown to be robust to influence all the other ions in the array and insensitive to the ions' temperature.
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Affiliation(s)
- L-M Duan
- FOCUS Center and MCTP, Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA
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Krojanski HG, Suter D. Scaling of decoherence in wide NMR quantum registers. PHYSICAL REVIEW LETTERS 2004; 93:090501. [PMID: 15447087 DOI: 10.1103/physrevlett.93.090501] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2004] [Indexed: 05/24/2023]
Abstract
Among the most important parameters for the usefulness of quantum computers are the size of the quantum register and the decoherence time for the quantum information. The decoherence time is expected to get shorter with the number of correlated qubits, but experimental data are only available for small numbers of qubits. Solid-state nuclear magnetic resonance allows one to correlate large numbers of qubits (several hundred) and measure their decoherence rates. We use a modified magnetic dipole-dipole interaction to correlate the proton spins in a solid sample and observe the decay of the resulting highly correlated states. By systematically varying the number of correlated spins, we measure the increase of the decoherence rate with the size of the quantum register.
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