1
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Tobar G, Manikandan SK, Beitel T, Pikovski I. Detecting single gravitons with quantum sensing. Nat Commun 2024; 15:7229. [PMID: 39174544 PMCID: PMC11341900 DOI: 10.1038/s41467-024-51420-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Accepted: 08/07/2024] [Indexed: 08/24/2024] Open
Abstract
The quantization of gravity is widely believed to result in gravitons - particles of discrete energy that form gravitational waves. But their detection has so far been considered impossible. Here we show that signatures of single graviton exchange can be observed in laboratory experiments. We show that stimulated and spontaneous single-graviton processes can become relevant for massive quantum acoustic resonators and that stimulated absorption can be resolved through continuous sensing of quantum jumps. We analyze the feasibility of observing the exchange of single energy quanta between matter and gravitational waves. Our results show that single graviton signatures are within reach of experiments. In analogy to the discovery of the photo-electric effect for photons, such signatures can provide the first experimental clue of the quantization of gravity.
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Affiliation(s)
- Germain Tobar
- Department of Physics, Stockholm University, SE-106 91, Stockholm, Sweden
- Okinawa Institute of Science and Technology, 1919-1 Tancha, Onna-son, Kunigami-gun, Okinawa, 904-0495, Japan
| | - Sreenath K Manikandan
- Nordita, KTH Royal Institute of Technology and Stockholm University, SE-106 91, Stockholm, Sweden
| | - Thomas Beitel
- Department of Physics, Stevens Institute of Technology, Hoboken, NJ, 07030, USA
| | - Igor Pikovski
- Department of Physics, Stockholm University, SE-106 91, Stockholm, Sweden.
- Department of Physics, Stevens Institute of Technology, Hoboken, NJ, 07030, USA.
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2
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Paulino PJ, Lesanovsky I, Carollo F. Large Deviation Full Counting Statistics in Adiabatic Open Quantum Dynamics. PHYSICAL REVIEW LETTERS 2024; 132:260402. [PMID: 38996317 DOI: 10.1103/physrevlett.132.260402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 05/21/2024] [Indexed: 07/14/2024]
Abstract
The state of an open quantum system undergoing an adiabatic process evolves by following the instantaneous stationary state of its time-dependent generator. This observation allows one to characterize, for a generic adiabatic evolution, the average dynamics of the open system. However, information about fluctuations of dynamical observables, such as the number of photons emitted or the time-integrated stochastic entropy production in single experimental runs, requires controlling the whole spectrum of the generator and not only the stationary state. Here, we show how such information can be obtained in adiabatic open quantum dynamics by exploiting tools from large deviation theory. We prove an adiabatic theorem for deformed generators, which allows us to encode, in a biased quantum state, the full counting statistics of generic time-integrated dynamical observables. We further compute the probability associated with an arbitrary "rare" time history of the observable and derive a dynamics which realizes it in its typical behavior. Our results provide a way to characterize and engineer adiabatic open quantum dynamics and to control their fluctuations.
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3
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Thorbeck T, Xiao Z, Kamal A, Govia LCG. Readout-Induced Suppression and Enhancement of Superconducting Qubit Lifetimes. PHYSICAL REVIEW LETTERS 2024; 132:090602. [PMID: 38489646 DOI: 10.1103/physrevlett.132.090602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2023] [Accepted: 01/23/2024] [Indexed: 03/17/2024]
Abstract
It has long been known that the lifetimes of superconducting qubits suffer during readout, increasing readout errors. We show that this degradation is due to the anti-Zeno effect, as readout-induced dephasing broadens the qubit so that it overlaps "hot spots" of strong dissipation, likely due to two-level systems in the qubit's bath. Using a flux-tunable qubit to probe the qubit's frequency-dependent loss, we accurately predict the change in lifetime during readout with a new self-consistent master equation that incorporates the modification to qubit relaxation due to measurement-induced dephasing. Moreover, we controllably demonstrate both the Zeno and anti-Zeno effects, which can explain both suppression and the rarer enhancement of qubit lifetimes during readout.
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Affiliation(s)
- Ted Thorbeck
- IBM Quantum, IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Zhihao Xiao
- Department of Physics and Applied Physics, University of Massachusetts, Lowell, Massachusetts 01854, USA
| | - Archana Kamal
- Department of Physics and Applied Physics, University of Massachusetts, Lowell, Massachusetts 01854, USA
| | - Luke C G Govia
- IBM Quantum, IBM Almaden Research Center, San Jose, California 95120, USA
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4
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Becker T, Netzer C, Eckardt A. Quantum Trajectories for Time-Local Non-Lindblad Master Equations. PHYSICAL REVIEW LETTERS 2023; 131:160401. [PMID: 37925713 DOI: 10.1103/physrevlett.131.160401] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2023] [Revised: 08/30/2023] [Accepted: 09/20/2023] [Indexed: 11/07/2023]
Abstract
For the efficient simulation of open quantum systems, we often use quantum jump trajectories given by pure states that evolve stochastically to unravel the dynamics of the underlying master equation. In the Markovian regime, when the dynamics is described by a Gorini-Kossakowski-Sudarshan-Lindblad (GKSL) master equation, this procedure is known as Monte Carlo wave function approach. However, beyond ultraweak system-bath coupling, the dynamics of the system is not described by an equation of GKSL type, but rather by the Redfield equation, which can be brought into pseudo-Lindblad form. Here, negative dissipation strengths prohibit the conventional approach. To overcome this problem, we propose a pseudo-Lindblad quantum trajectory (PLQT) unraveling. It does not require an effective extension of the state space, like other approaches, except for the addition of a single classical bit. We test the PLQT for the eternal non-Markovian master equation for a single qubit and an interacting Fermi-Hubbard chain coupled to a thermal bath and discuss its computational effort compared to solving the full master equation.
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Affiliation(s)
- Tobias Becker
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany
| | - Ché Netzer
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany
| | - André Eckardt
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstrasse 36, 10623 Berlin, Germany
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5
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Lledó C, Dassonneville R, Moulinas A, Cohen J, Shillito R, Bienfait A, Huard B, Blais A. Cloaking a qubit in a cavity. Nat Commun 2023; 14:6313. [PMID: 37813905 PMCID: PMC10562410 DOI: 10.1038/s41467-023-42060-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Accepted: 09/28/2023] [Indexed: 10/11/2023] Open
Abstract
Cavity quantum electrodynamics (QED) uses a cavity to engineer the mode structure of the vacuum electromagnetic field such as to enhance the interaction between light and matter. Exploiting these ideas in solid-state systems has lead to circuit QED which has emerged as a valuable tool to explore the rich physics of quantum optics and as a platform for quantum computation. Here we introduce a simple approach to further engineer the light-matter interaction in a driven cavity by controllably decoupling a qubit from the cavity's photon population, effectively cloaking the qubit from the cavity. This is realized by driving the qubit with an external tone tailored to destructively interfere with the cavity field, leaving the qubit to interact with a cavity which appears to be in the vacuum state. Our experiment demonstrates how qubit cloaking can be exploited to cancel the ac-Stark shift and measurement-induced dephasing, and to accelerate qubit readout. In addition to qubit readout, applications of this method include qubit logical operations and the preparation of non-classical cavity states in circuit QED and other cavity-based setups.
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Affiliation(s)
- Cristóbal Lledó
- Institut Quantique and Département de Physique, Université de Sherbrooke, Sherbrooke, J1K 2R1 QC, Canada.
| | - Rémy Dassonneville
- Ecole Normale Supérieure de Lyon, CNRS, Laboratoire de Physique, F-69342, Lyon, France
| | - Adrien Moulinas
- Institut Quantique and Département de Physique, Université de Sherbrooke, Sherbrooke, J1K 2R1 QC, Canada
| | - Joachim Cohen
- Institut Quantique and Département de Physique, Université de Sherbrooke, Sherbrooke, J1K 2R1 QC, Canada
| | - Ross Shillito
- Institut Quantique and Département de Physique, Université de Sherbrooke, Sherbrooke, J1K 2R1 QC, Canada
| | - Audrey Bienfait
- Ecole Normale Supérieure de Lyon, CNRS, Laboratoire de Physique, F-69342, Lyon, France
| | - Benjamin Huard
- Ecole Normale Supérieure de Lyon, CNRS, Laboratoire de Physique, F-69342, Lyon, France
| | - Alexandre Blais
- Institut Quantique and Département de Physique, Université de Sherbrooke, Sherbrooke, J1K 2R1 QC, Canada
- Canadian Institute for Advanced Research, Toronto, ON, M5G1M1, Canada
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6
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Cook RL, Ko L, Whaley KB. A quantum trajectory picture of single photon absorption and energy transport in photosystem II. J Chem Phys 2023; 159:134108. [PMID: 37795784 DOI: 10.1063/5.0168631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 09/12/2023] [Indexed: 10/06/2023] Open
Abstract
We use quantum trajectory theory to study the dynamics of the first step in photosynthesis for a single photon interacting with photosystem II (PSII). By considering individual trajectories we are able to look beyond the ensemble average dynamics to compute the PSII system evolution conditioned upon individual photon counting measurements. Measurements of the transmitted photon beam strongly affects the system state, since detection of an outgoing photon confirms that the PSII must be in the electronic ground state, while a null measurement implies it is in an excited electronic state. We show that under ideal conditions, observing the null result transforms a state with a low excited state population to a state with nearly all population contained in the excited states. We study the PSII dynamics conditioned on such photon counting for both a pure excitonic model of PSII and a more realistic model with exciton-phonon coupling to a dissipative phononic environment. In the absence of such coupling, we show that the measured fluorescence rates show oscillations constituting a photon-counting witness of excitonic coherence. Excitonic coupling to the phonon environment has a strong effect on the observed rates of fluorescence, damping the oscillations. Addition of non-radiative decay and incoherent transitions to radical pair states in the reaction center to the phononic model allows extraction of a quantum efficiency of 92.5% from the long-time evolution, consistent with bulk experimental measurements.
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Affiliation(s)
- Robert L Cook
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Liwen Ko
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - K Birgitta Whaley
- Department of Chemistry, University of California, Berkeley, California 94720, USA
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7
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Ostrowski LA, Baker TJ, Saadatmand SN, Wiseman HM. No Tradeoff between Coherence and Sub-Poissonianity for Heisenberg-Limited Lasers. PHYSICAL REVIEW LETTERS 2023; 130:183602. [PMID: 37204878 DOI: 10.1103/physrevlett.130.183602] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 03/27/2023] [Indexed: 05/21/2023]
Abstract
The Heisenberg limit to laser coherence C-the number of photons in the maximally populated mode of the laser beam-is the fourth power of the number of excitations inside the laser. We generalize the previous proof of this upper bound scaling by dropping the requirement that the beam photon statistics be Poissonian (i.e., Mandel's Q=0). We then show that the relation between C and sub-Poissonianity (Q<0) is win-win, not a tradeoff. For both regular (non-Markovian) pumping with semiunitary gain (which allows Q→-1), and random (Markovian) pumping with optimized gain, C is maximized when Q is minimized.
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Affiliation(s)
- L A Ostrowski
- Centre for Quantum Dynamics, Griffith University, Yuggera Country, Brisbane, Queensland 4111, Australia
| | - T J Baker
- Centre for Quantum Dynamics, Griffith University, Yuggera Country, Brisbane, Queensland 4111, Australia
| | - S N Saadatmand
- Centre for Quantum Dynamics, Griffith University, Yuggera Country, Brisbane, Queensland 4111, Australia
| | - H M Wiseman
- Centre for Quantum Dynamics, Griffith University, Yuggera Country, Brisbane, Queensland 4111, Australia
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8
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Jin T, Martin DG. Kardar-Parisi-Zhang Physics and Phase Transition in a Classical Single Random Walker under Continuous Measurement. PHYSICAL REVIEW LETTERS 2022; 129:260603. [PMID: 36608188 DOI: 10.1103/physrevlett.129.260603] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 11/28/2022] [Indexed: 06/17/2023]
Abstract
We introduce and study a new model consisting of a single classical random walker undergoing continuous monitoring at rate γ on a discrete lattice. Although such a continuous measurement cannot affect physical observables, it has a nontrivial effect on the probability distribution of the random walker. At small γ, we show analytically that the time evolution of the latter can be mapped to the stochastic heat equation. In this limit, the width of the log-probability thus follows a Family-Vicsek scaling law, N^{α}f(t/N^{α/β}), with roughness and growth exponents corresponding to the Kardar-Parisi-Zhang (KPZ) universality class, i.e., α_{KPZ}^{1D}=1/2 and β_{KPZ}^{1D}=1/3, respectively. When γ is increased outside this regime, we find numerically in 1D a crossover from the KPZ class to a new universality class characterized by exponents α_{M}^{1D}≈1 and β_{M}^{1D}≈1.4. In 3D, varying γ beyond a critical value γ_{M}^{c} leads to a phase transition from a smooth phase that we identify as the Edwards-Wilkinson class to a new universality class with α_{M}^{3D}≈1.
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Affiliation(s)
- Tony Jin
- DQMP, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland
| | - David G Martin
- Enrico Fermi Institute, The University of Chicago, 933 East 56th Street, Chicago, Illinois 60637, USA
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9
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Liu F. Semi-Markov processes in open quantum systems: Connections and applications in counting statistics. Phys Rev E 2022; 106:054152. [PMID: 36559413 DOI: 10.1103/physreve.106.054152] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Accepted: 11/02/2022] [Indexed: 06/17/2023]
Abstract
Using the age-structure formalism, we definitely establish connections between semi-Markov processes and the dynamics of open quantum systems that satisfy the Markov quantum master equations. A generalized Feynman-Kac formula of the semi-Markov processes is also proposed. In addition to inheriting all statistical properties possessed by the piecewise deterministic processes of wave functions, the semi-Markov processes show their unique advantages in quantum counting statistics. Compared with the conventional method of the tilted quantum master equation, they can be applied to more general counting quantities. In particular, the terms involved in the method have precise probability meanings. We use a driven two-level quantum system to exemplify these results.
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Affiliation(s)
- Fei Liu
- School of Physics, Beihang University, Beijing 100191, China
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10
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Anderson MC, Schile AJ, Limmer DT. Nonadiabatic transition paths from quantum jump trajectories. J Chem Phys 2022; 157:164105. [DOI: 10.1063/5.0102891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a means of studying rare reactive pathways in open quantum systems using transition path theory and ensembles of quantum jump trajectories. This approach allows for the elucidation of reactive paths for dissipative, nonadiabatic dynamics when the system is embedded in a Markovian environment. We detail the dominant pathways and rates of thermally activated processes and the relaxation pathways and photoyields following vertical excitation in a minimal model of a conical intersection. We find that the geometry of the conical intersection affects the electronic character of the transition state as defined through a generalization of a committor function for a thermal barrier crossing event. Similarly, the geometry changes the mechanism of relaxation following a vertical excitation. Relaxation in models resulting from small diabatic coupling proceeds through pathways dominated by pure dephasing, while those with large diabatic coupling proceed through pathways limited by dissipation. The perspective introduced here for the nonadiabatic dynamics of open quantum systems generalizes classical notions of reactive paths to fundamentally quantum mechanical processes.
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Affiliation(s)
- Michelle C. Anderson
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - Addison J. Schile
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | - David T. Limmer
- Department of Chemistry, University of California, Berkeley, California 94720, USA
- Kavli Energy NanoSciences Institute, University of California, Berkeley, California 94720, USA
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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11
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Andersen AL, Mølmer K. Quantum Nondemolition Measurements of Moving Target States. PHYSICAL REVIEW LETTERS 2022; 129:120402. [PMID: 36179166 DOI: 10.1103/physrevlett.129.120402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Accepted: 08/26/2022] [Indexed: 06/16/2023]
Abstract
We present a protocol for probing the state of a quantum system by its resonant coupling and entanglement with a meter system. By continuous measurement of a time evolving meter observable, we infer the evolution of the entangled systems and, ultimately, the state and dynamics of the system of interest. The photon number in a cavity field is thus resolved by simulated monitoring of the Rabi oscillations of a resonantly coupled two-level system, and we propose to regard this as a practical extension of quantum nondemolition measurements with applications in quantum metrology and quantum computing.
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Affiliation(s)
- Anton L Andersen
- Center for Complex Quantum Systems, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
| | - Klaus Mølmer
- Aarhus Institute of Advanced Studies, Aarhus University, Høegh-Guldbergs Gade 6B, DK-8000 Aarhus C, Denmark and Center for Complex Quantum Systems, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
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12
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Kato Y, Nakao H. Turing instability in quantum activator–inhibitor systems. Sci Rep 2022; 12:15573. [PMID: 36114210 PMCID: PMC9481611 DOI: 10.1038/s41598-022-19010-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 08/23/2022] [Indexed: 11/26/2022] Open
Abstract
Turing instability is a fundamental mechanism of nonequilibrium self-organization. However, despite the universality of its essential mechanism, Turing instability has thus far been investigated mostly in classical systems. In this study, we show that Turing instability can occur in a quantum dissipative system and analyze its quantum features such as entanglement and the effect of measurement. We propose a degenerate parametric oscillator with nonlinear damping in quantum optics as a quantum activator–inhibitor unit and demonstrate that a system of two such units can undergo Turing instability when diffusively coupled with each other. The Turing instability induces nonuniformity and entanglement between the two units and gives rise to a pair of nonuniform states that are mixed due to quantum noise. Further performing continuous measurement on the coupled system reveals the nonuniformity caused by the Turing instability. Our results extend the universality of the Turing mechanism to the quantum realm and may provide a novel perspective on the possibility of quantum nonequilibrium self-organization and its application in quantum technologies.
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13
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Shirts RB, Welch JS. Quantum Interstate Phase Differences and Multiphoton Processes: Quantum Jumps or Dynamic Beats? ACS OMEGA 2022; 7:30632-30641. [PMID: 36061689 PMCID: PMC9434749 DOI: 10.1021/acsomega.2c04554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2022] [Accepted: 07/28/2022] [Indexed: 06/15/2023]
Abstract
Whether quantum state transitions occur by instantaneous jumps (a la Bohr) or deterministic dynamics (Schrödinger's preference) has been intensely debated. Recent experimental measurements of shelved electrons have reignited the debate. We examine aspects of the time-dependent numerical solutions of the Schrödinger equation in quantum systems with two and three levels perturbed by a sinusoidal field. A geometrical construction involving quantum state phase differences illuminates the role of interstate phase differences in a deterministic, rather than random, process of multiphoton absorption. Alternate halves of the Rabi cycle exhibit phase reversals much like the classical beats of coupled oscillators. For non-zero detuning, population inversion does not occur because the exciting field drifts out of the proper phase before inversion is complete. A close correspondence with classical, coupled oscillator beats offers insights for interpretation of deterministic quantum dynamics and suggests an experimental test for the correctness of this picture depending on the long-time phase stability of exciting fields.
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14
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Stefanov VP, Shatokhin VN, Mogilevtsev DS, Kilin SY. Key for a Hidden Quantum State. PHYSICAL REVIEW LETTERS 2022; 129:083603. [PMID: 36053688 DOI: 10.1103/physrevlett.129.083603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 03/05/2022] [Accepted: 07/27/2022] [Indexed: 06/15/2023]
Abstract
Quantum trajectories are crucial to understanding the evolution of open systems. We consider an open cavity mode undergoing up and down multistate quantum jumps due to the emission and absorption of photons. We prove that among all subtrajectories, starting simultaneously from different photon number states, only one survives a long single-run evolution. A random Fock state terminating the subtrajectory becomes known for the ergodic case via the key-the processed record of the input and output photocounts, and the trajectory duration. Based on this result, we propose a robust protocol to infer the Fock state, a valuable resource for quantum applications.
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Affiliation(s)
- V P Stefanov
- B.I.Stepanov Institute of Physics of NAS of Belarus, Nezavisimosti Ave. 68, 220072, Minsk, Belarus
| | - V N Shatokhin
- Physikalisches Institut and EUCOR Centre for Quantum Science and Quantum Computing, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Str. 3, D-79104 Freiburg, Germany
| | - D S Mogilevtsev
- B.I.Stepanov Institute of Physics of NAS of Belarus, Nezavisimosti Ave. 68, 220072, Minsk, Belarus
| | - S Ya Kilin
- B.I.Stepanov Institute of Physics of NAS of Belarus, Nezavisimosti Ave. 68, 220072, Minsk, Belarus
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15
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Deliyannis P, Sud J, Chamaki D, Webb-Mack Z, Bauer CW, Nachman B. Improving quantum simulation efficiency of final state radiation with dynamic quantum circuits. Int J Clin Exp Med 2022. [DOI: 10.1103/physrevd.106.036007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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16
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Annby-Andersson B, Bakhshinezhad F, Bhattacharyya D, De Sousa G, Jarzynski C, Samuelsson P, Potts PP. Quantum Fokker-Planck Master Equation for Continuous Feedback Control. PHYSICAL REVIEW LETTERS 2022; 129:050401. [PMID: 35960579 DOI: 10.1103/physrevlett.129.050401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Accepted: 06/24/2022] [Indexed: 06/15/2023]
Abstract
Measurement and feedback control are essential features of quantum science, with applications ranging from quantum technology protocols to information-to-work conversion in quantum thermodynamics. Theoretical descriptions of feedback control are typically given in terms of stochastic equations requiring numerical solutions, or are limited to linear feedback protocols. Here we present a formalism for continuous quantum measurement and feedback, both linear and nonlinear. Our main result is a quantum Fokker-Planck master equation describing the joint dynamics of a quantum system and a detector with finite bandwidth. For fast measurements, we derive a Markovian master equation for the system alone, amenable to analytical treatment. We illustrate our formalism by investigating two basic information engines, one quantum and one classical.
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Affiliation(s)
| | - Faraj Bakhshinezhad
- Physics Department and NanoLund, Lund University, Box 118, 22100 Lund, Sweden
| | - Debankur Bhattacharyya
- Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
| | - Guilherme De Sousa
- Department of Physics, University of Maryland, College Park, Maryland 20742, USA
| | - Christopher Jarzynski
- Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
| | - Peter Samuelsson
- Physics Department and NanoLund, Lund University, Box 118, 22100 Lund, Sweden
| | - Patrick P Potts
- Physics Department and NanoLund, Lund University, Box 118, 22100 Lund, Sweden
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
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17
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Donvil B, Muratore-Ginanneschi P. Quantum trajectory framework for general time-local master equations. Nat Commun 2022; 13:4140. [PMID: 35842427 PMCID: PMC9288492 DOI: 10.1038/s41467-022-31533-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 06/10/2022] [Indexed: 11/09/2022] Open
Abstract
Master equations are one of the main avenues to study open quantum systems. When the master equation is of the Lindblad-Gorini-Kossakowski-Sudarshan form, its solution can be "unraveled in quantum trajectories" i.e., represented as an average over the realizations of a Markov process in the Hilbert space of the system. Quantum trajectories of this type are both an element of quantum measurement theory as well as a numerical tool for systems in large Hilbert spaces. We prove that general time-local and trace-preserving master equations also admit an unraveling in terms of a Markov process in the Hilbert space of the system. The crucial ingredient is to weigh averages by a probability pseudo-measure which we call the "influence martingale". The influence martingale satisfies a 1d stochastic differential equation enslaved to the ones governing the quantum trajectories. We thus extend the existing theory without increasing the computational complexity.
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Affiliation(s)
- Brecht Donvil
- University of Helsinki, Department of Mathematics and Statistics, P.O. Box 68, FIN-00014, Helsinki, Finland.
- Institute for Complex Quantum Systems and IQST, Ulm University, Albert-Einstein-Allee 11, D-89069, Ulm, Germany.
| | - Paolo Muratore-Ginanneschi
- University of Helsinki, Department of Mathematics and Statistics, P.O. Box 68, FIN-00014, Helsinki, Finland.
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18
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Wang HY, Zhao XM, Zhuang L, Liu WM. Non-Floquet engineering in periodically driven dissipative open quantum systems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:365402. [PMID: 35760065 DOI: 10.1088/1361-648x/ac7c4e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Accepted: 06/27/2022] [Indexed: 06/15/2023]
Abstract
Floquet engineering plays a key role in realizing novel dynamical topological states. The conventional Floquet engineering, however, only applies to time-periodic non-dissipative Hermitian systems, and for the open quantum systems, non-Hermitian processes usually occur. So far, it remains unclear how to characterize the topological phases of time-periodic open quantum systems via the frequency space Floquet Hamiltonian. Here, we propose the non-Floquet theory to solve the problem and illustrate it by a continuously time-periodic non-Hermitian bipartite chain. In non-Floquet theory, a temporal non-unitary transformation is exercised on the Floquet states, and the transformed Floquet spectrum restores the form of the Wannier-Stark ladder. Besides, we also show that different choices of the starting points of the driving period can result in different localization behavior, effects of which can reversely be utilized to design quantum detectors of phases in dissipative oscillating fields. Our methods are capable of describing topological features in dynamical open quantum systems with various driving types and can find its applications to construct new types of dynamical topological materials.
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Affiliation(s)
- Huan-Yu Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Xiao-Ming Zhao
- Department of Physics, Institute of Theoretical physics, University of Science and Technology Beijing, Beijing, 100083, People's Republic of China
| | - Lin Zhuang
- School of Physics, Sun Yat-Sen University, Guangzhou 510275, People's Republic of China
| | - Wu-Ming Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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19
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Meng C, Brawley GA, Khademi S, Bridge EM, Bennett JS, Bowen WP. Measurement-based preparation of multimode mechanical states. SCIENCE ADVANCES 2022; 8:eabm7585. [PMID: 35622924 PMCID: PMC9140969 DOI: 10.1126/sciadv.abm7585] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 04/13/2022] [Indexed: 06/15/2023]
Abstract
Nanomechanical resonators are a key tool for future quantum technologies, such as quantum force sensors and interfaces, and for studies of macroscopic quantum physics. The ability to prepare room temperature nonclassical states is a major outstanding challenge. It has been suggested that this could be achieved using a fast continuous measurement to break the usual symmetry between position and momentum. Here, we demonstrate this symmetry breaking and use it to prepare a thermally squeezed mechanical state. Our experiments take advantage of collective measurements on multiple mechanical modes, which we show can increase the measurement speed and improve state preparation. Theoretically, we show that this result extends to the quantum regime, relaxing the requirements to generate nonclassical states. We predict that multimode conditioning can enable room temperature quantum squeezing with existing technology. Our work paves the way toward room temperature quantum nanomechanical devices and toward their application in quantum technology and fundamental science.
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Affiliation(s)
- Chao Meng
- Australian Research Council Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - George A. Brawley
- Australian Research Council Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland 4072, Australia
- Terra15 Technologies Pty Ltd., Level 9/256 Adelaide Terrace, Perth, Western Australia 6000, Australia
| | - Soroush Khademi
- Australian Research Council Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Elizabeth M. Bridge
- Australian Research Council Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - James S. Bennett
- Australian Research Council Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland 4072, Australia
| | - Warwick P. Bowen
- Australian Research Council Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, The University of Queensland, St Lucia, Queensland 4072, Australia
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20
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Yada T, Yoshioka N, Sagawa T. Quantum Fluctuation Theorem under Quantum Jumps with Continuous Measurement and Feedback. PHYSICAL REVIEW LETTERS 2022; 128:170601. [PMID: 35570443 DOI: 10.1103/physrevlett.128.170601] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Revised: 03/17/2022] [Accepted: 03/23/2022] [Indexed: 06/15/2023]
Abstract
While the fluctuation theorem in classical systems has been thoroughly generalized under various feedback control setups, an intriguing situation in quantum systems, namely under continuous feedback, remains to be investigated. In this work, we derive the generalized fluctuation theorem under quantum jumps with continuous measurement and feedback. The essence for the derivation is to newly introduce the operationally meaningful information, which we call quantum-classical-transfer (QC-transfer) entropy. QC-transfer entropy can be naturally interpreted as the quantum counterpart of transfer entropy that is commonly used in classical time series analysis. We also verify our theoretical results by numerical simulation and propose an experiment-numerics hybrid verification method. Our work reveals a fundamental connection between quantum thermodynamics and quantum information, which can be experimentally tested with artificial quantum systems such as circuit quantum electrodynamics.
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Affiliation(s)
- Toshihiro Yada
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Nobuyuki Yoshioka
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Takahiro Sagawa
- Department of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- Quantum-Phase Electronics Center (QPEC), The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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21
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Livingston WP, Blok MS, Flurin E, Dressel J, Jordan AN, Siddiqi I. Experimental demonstration of continuous quantum error correction. Nat Commun 2022; 13:2307. [PMID: 35484135 DOI: 10.1038/s41467-022-29906-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 04/06/2022] [Indexed: 11/09/2022] Open
Abstract
The storage and processing of quantum information are susceptible to external noise, resulting in computational errors. A powerful method to suppress these effects is quantum error correction. Typically, quantum error correction is executed in discrete rounds, using entangling gates and projective measurement on ancillary qubits to complete each round of error correction. Here we use direct parity measurements to implement a continuous quantum bit-flip correction code in a resource-efficient manner, eliminating entangling gates, ancillary qubits, and their associated errors. An FPGA controller actively corrects errors as they are detected, achieving an average bit-flip detection efficiency of up to 91%. Furthermore, the protocol increases the relaxation time of the protected logical qubit by a factor of 2.7 over the relaxation times of the bare comprising qubits. Our results showcase resource-efficient stabilizer measurements in a multi-qubit architecture and demonstrate how continuous error correction codes can address challenges in realizing a fault-tolerant system.
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Affiliation(s)
- William P Livingston
- Department of Physics, University of California, Berkeley, CA, 94720, USA. .,Center for Quantum Coherent Science, University of California, Berkeley, CA, 94720, USA.
| | - Machiel S Blok
- Department of Physics, University of California, Berkeley, CA, 94720, USA.,Center for Quantum Coherent Science, University of California, Berkeley, CA, 94720, USA.,Department of Physics and Astronomy, University of Rochester, Rochester, NY, 14627, USA
| | - Emmanuel Flurin
- Université Paris-Saclay, CEA, CNRS, SPEC, 91191, Gif-sur-Yvette Cedex, France
| | - Justin Dressel
- Institute for Quantum Studies, Chapman University, Orange, CA, 92866, USA.,Schmid College of Science and Technology, Chapman University, Orange, CA, 92866, USA
| | - Andrew N Jordan
- Department of Physics and Astronomy, University of Rochester, Rochester, NY, 14627, USA.,Institute for Quantum Studies, Chapman University, Orange, CA, 92866, USA
| | - Irfan Siddiqi
- Department of Physics, University of California, Berkeley, CA, 94720, USA.,Center for Quantum Coherent Science, University of California, Berkeley, CA, 94720, USA
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22
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Abbasi M, Chen W, Naghiloo M, Joglekar YN, Murch KW. Topological Quantum State Control through Exceptional-Point Proximity. PHYSICAL REVIEW LETTERS 2022; 128:160401. [PMID: 35522514 DOI: 10.1103/physrevlett.128.160401] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Revised: 01/12/2022] [Accepted: 03/22/2022] [Indexed: 06/14/2023]
Abstract
We study the quantum evolution of a non-Hermitian qubit realized as a submanifold of a dissipative superconducting transmon circuit. Real-time tuning of the system parameters to encircle an exceptional point results in nonreciprocal quantum state transfer. We further observe chiral geometric phases accumulated under state transport, verifying the quantum coherent nature of the evolution in the complex energy landscape and distinguishing between coherent and incoherent effects associated with exceptional point encircling. Our work demonstrates an entirely new method for control over quantum state vectors, highlighting new facets of quantum bath engineering enabled through dynamical non-Hermitian control.
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Affiliation(s)
- Maryam Abbasi
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
| | - Weijian Chen
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
- Center for Quantum Sensors, Washington University, St. Louis, Missouri 63130, USA
| | - Mahdi Naghiloo
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
- Research Laboratory of Electronics, MIT, Cambridge, Massachusetts 02139, USA
| | - Yogesh N Joglekar
- Department of Physics, Indiana University Purdue University Indianapolis (IUPUI), Indianapolis, Indiana 46202, USA
| | - Kater W Murch
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
- Center for Quantum Sensors, Washington University, St. Louis, Missouri 63130, USA
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23
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Kong OCW. Towards noncommutative quantum reality. STUDIES IN HISTORY AND PHILOSOPHY OF SCIENCE 2022; 92:186-195. [PMID: 35219869 DOI: 10.1016/j.shpsa.2022.02.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 02/08/2022] [Accepted: 02/09/2022] [Indexed: 06/14/2023]
Abstract
The implications of the physical theory of quantum mechanics on the question of realism is much a subject of sustaining interest, while the background questions among physicists on how to think about all the theoretical notion and 'interpretation' of the theory remains controversial. Through a careful analysis of the theoretical notions with the help of modern mathematical perspectives, we give here a picture of quantum mechanics, as the basic theory for 'nonrelativistic' particle dynamics, that can be seen as being as much about the physical reality as classical mechanics itself. The key is to fully embrace the noncommutativity of the theory and see it as a notion about the reality of physical quantities. Quantum reality is then just a noncommutative version of the classical reality.
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Affiliation(s)
- Otto C W Kong
- Department of Physics and Center for High Energy and High Field Physics, National Central University, Chung-li 32054, Taiwan.
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24
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Sierant P, Turkeshi X. Universal Behavior beyond Multifractality of Wave Functions at Measurement-Induced Phase Transitions. PHYSICAL REVIEW LETTERS 2022; 128:130605. [PMID: 35426694 DOI: 10.1103/physrevlett.128.130605] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 01/26/2022] [Accepted: 03/15/2022] [Indexed: 06/14/2023]
Abstract
We investigate the structure of many-body wave functions of 1D quantum circuits with local measurements employing the participation entropies. The leading term in system size dependence of participation entropy indicates a model-dependent multifractal scaling of the wave functions at any nonzero measurement rate. The subleading term contains universal information about measurement-induced phase transitions and plays the role of an order parameter, being constant nonzero in the error-correcting phase and vanishing in the quantum Zeno phase. We provide robust numerical evidence investigating a variety of quantum many-body systems and provide an analytical interpretation of this behavior expressing the participation entropy in terms of partition functions of classical statistical models in 2D.
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Affiliation(s)
- Piotr Sierant
- ICTP-The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
- Institute of Theoretical Physics, Jagiellonian University in Krakow, Łojasiewicza 11, 30-348 Kraków, Poland
| | - Xhek Turkeshi
- ICTP-The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy
- SISSA-International School of Advanced Studies, via Bonomea 265, 34136 Trieste, Italy
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25
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Deist E, Gerber JA, Lu YH, Zeiher J, Stamper-Kurn DM. Superresolution Microscopy of Optical Fields Using Tweezer-Trapped Single Atoms. PHYSICAL REVIEW LETTERS 2022; 128:083201. [PMID: 35275676 DOI: 10.1103/physrevlett.128.083201] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 12/11/2021] [Accepted: 01/05/2022] [Indexed: 06/14/2023]
Abstract
We realize a scanning probe microscope using single trapped ^{87}Rb atoms to measure optical fields with subwavelength spatial resolution. Our microscope operates by detecting fluorescence from a single atom driven by near-resonant light and determining the ac Stark shift of an atomic transition from other local optical fields via the change in the fluorescence rate. We benchmark the microscope by measuring two standing-wave Gaussian modes of a Fabry-Pérot resonator with optical wavelengths of 1560 and 781 nm. We attain a spatial resolution of 300 nm, which is superresolving compared to the limit set by the 780 nm wavelength of the detected light. Sensitivity to short length scale features is enhanced by adapting the sensor to characterize an optical field via the force it exerts on the atom.
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Affiliation(s)
- Emma Deist
- Department of Physics, University of California, Berkeley, California 94720, USA
- Challenge Institute for Quantum Computation, University of California, Berkeley, California 94720, USA
| | - Justin A Gerber
- Department of Physics, University of California, Berkeley, California 94720, USA
- Challenge Institute for Quantum Computation, University of California, Berkeley, California 94720, USA
| | - Yue-Hui Lu
- Department of Physics, University of California, Berkeley, California 94720, USA
- Challenge Institute for Quantum Computation, University of California, Berkeley, California 94720, USA
| | - Johannes Zeiher
- Department of Physics, University of California, Berkeley, California 94720, USA
- Max-Planck-Institut für Quantenoptik, 85748 Garching, Germany
- Munich Center for Quantum Science and Technology (MCQST), 80799 Munich, Germany
| | - Dan M Stamper-Kurn
- Department of Physics, University of California, Berkeley, California 94720, USA
- Challenge Institute for Quantum Computation, University of California, Berkeley, California 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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26
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Abstract
Interfacing long-lived qubits with propagating photons is a fundamental challenge in quantum technology. Cavity and circuit quantum electrodynamics (cQED) architectures rely on an off-resonant cavity, which blocks the qubit emission and enables a quantum non-demolition (QND) dispersive readout. However, no such buffer mode is necessary for controlling a large class of three-level systems that combine a metastable qubit transition with a bright cycling transition, using the electron shelving effect. Here we demonstrate shelving of a circuit atom, fluxonium, placed inside a microwave waveguide. With no cavity modes in the setup, the qubit coherence time exceeds 50 μs, and the cycling transition’s radiative lifetime is under 100 ns. By detecting a homodyne fluorescence signal from the cycling transition, we implement a QND readout of the qubit and account for readout errors using a minimal optical pumping model. Our result establishes a resource-efficient (cavityless) alternative to cQED for controlling superconducting qubits. Existing schemes for coherent control and measurements in superconducting circuits rely on the coupling between superconducting qubits and cavity photons. Here the authors implement conditional fluorescence readout of a fluxonium qubit placed inside an open waveguide, with no coupling to cavity modes.
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27
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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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28
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Xu W, Venkatramani AV, Cantú SH, Šumarac T, Klüsener V, Lukin MD, Vuletić V. Fast Preparation and Detection of a Rydberg Qubit Using Atomic Ensembles. PHYSICAL REVIEW LETTERS 2021; 127:050501. [PMID: 34397223 DOI: 10.1103/physrevlett.127.050501] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 05/15/2021] [Accepted: 06/29/2021] [Indexed: 06/13/2023]
Abstract
We demonstrate a new approach for fast preparation, manipulation, and collective readout of an atomic Rydberg-state qubit. By making use of Rydberg blockade inside a small atomic ensemble, we prepare a single qubit within 3 μs with a success probability of F_{p}=0.93±0.02, rotate it, and read out its state in 6 μs with a single-shot fidelity of F_{d}=0.92±0.04. The ensemble-assisted detection is 10^{3} times faster than imaging of a single atom with the same optical resolution, and enables fast repeated nondestructive measurement. We observe qubit coherence times of 15 μs, much longer than the π rotation time of 90 ns. Potential applications ranging from faster quantum information processing in atom arrays to efficient implementation of quantum error correction are discussed.
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Affiliation(s)
- Wenchao Xu
- Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Aditya V Venkatramani
- Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Sergio H Cantú
- Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Tamara Šumarac
- Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Valentin Klüsener
- Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- University of Erlangen-Nuremberg, Erlangen 91054, Germany
| | - Mikhail D Lukin
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Vladan Vuletić
- Department of Physics and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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29
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Thomsen K. Timelessness Strictly inside the Quantum Realm. ENTROPY (BASEL, SWITZERLAND) 2021; 23:772. [PMID: 34207444 PMCID: PMC8235759 DOI: 10.3390/e23060772] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Revised: 05/28/2021] [Accepted: 06/15/2021] [Indexed: 11/17/2022]
Abstract
Time is one of the undisputed foundations of our life in the real world. Here it is argued that inside small isolated quantum systems, time does not pass as we are used to, and it is primarily in this sense that quantum objects enjoy only limited reality. Quantum systems, which we know, are embedded in the everyday classical world. Their preparation as well as their measurement-phases leave durable records and traces in the entropy of the environment. The Landauer Principle then gives a quantitative threshold for irreversibility. With double slit experiments and tunneling as paradigmatic examples, it is proposed that a label of timelessness offers clues for rendering a Copenhagen-type interpretation of quantum physics more "realistic" and acceptable by providing a coarse but viable link from the fundamental quantum realm to the classical world which humans directly experience.
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Affiliation(s)
- Knud Thomsen
- Paul Scherrer Institute (PSI), 5232 Villigen, Switzerland
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30
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Abstract
A rise in fragility as a system approaches a tipping point may be sometimes estimated using dynamical indicators of resilience (DIORs) that measure the characteristic slowing down of recovery rates before a tipping point. A change in DIORs could be interpreted as an early warning signal for an upcoming critical transition. However, in order to be able to estimate the DIORs, observational records need to be long enough to capture the response rate of the system. As we show here, the required length of the time series depends on the response rates of the system. For instance, the current rate of anthropogenic climate forcing is fast relative to the response rate of some parts of the climate system. Therefore, we may expect difficulties estimating the resilience from modern time series. So far, there have been no systematic studies of the effects of the response rates of the dynamical systems and the rates of forcing on the detectability trends in the DIORs prior to critical transitions. Here, we quantify the performance of the resilience indicators variance and temporal autocorrelation, in systems with different response rates and for different rates of forcing. Our results show that the rapid rise of anthropogenic forcing to the Earth may make it difficult to detect changes in the resilience of ecosystems and climate elements from time series. These findings suggest that in order to determine with models whether the use of the DIORs is appropriate, we need to use realistic models that incorporate the key processes with the appropriate time constants.
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Affiliation(s)
- Bregje van der Bolt
- Department of Environmental Sciences, Wageningen University, Wageningen, The Netherlands
| | - Egbert H van Nes
- Department of Environmental Sciences, Wageningen University, Wageningen, The Netherlands
| | - Marten Scheffer
- Department of Environmental Sciences, Wageningen University, Wageningen, The Netherlands
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31
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Van Regemortel M, Cian ZP, Seif A, Dehghani H, Hafezi M. Entanglement Entropy Scaling Transition under Competing Monitoring Protocols. PHYSICAL REVIEW LETTERS 2021; 126:123604. [PMID: 33834828 DOI: 10.1103/physrevlett.126.123604] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Revised: 01/05/2021] [Accepted: 03/01/2021] [Indexed: 06/12/2023]
Abstract
Dissipation generally leads to the decoherence of a quantum state. In contrast, numerous recent proposals have illustrated that dissipation can also be tailored to stabilize many-body entangled quantum states. While the focus of these works has been primarily on engineering the nonequilibrium steady state, we investigate the buildup of entanglement in the quantum trajectories. Specifically, we analyze the competition between two different dissipation channels arising from two incompatible continuous monitoring protocols. The first protocol locks the phase of neighboring sites upon registering a quantum jump, thereby generating a long-range entanglement through the system, while the second destroys the coherence via a dephasing mechanism. By studying the unraveling of stochastic quantum trajectories associated with the continuous monitoring protocols, we present a transition for the scaling of the averaged trajectory entanglement entropies, from critical scaling to area-law behavior. Our work provides an alternative perspective on the measurement-induced phase transition: the measurement can be viewed as monitoring and registering quantum jumps, offering an intriguing extension of these phase transitions through the long-established realm of quantum optics.
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Affiliation(s)
- Mathias Van Regemortel
- Joint Quantum Institute, College Park, 20742 Maryland, USA and The Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, 20742 Maryland, USA
| | - Ze-Pei Cian
- Joint Quantum Institute, College Park, 20742 Maryland, USA and The Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, 20742 Maryland, USA
| | - Alireza Seif
- Joint Quantum Institute, College Park, 20742 Maryland, USA and The Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, 20742 Maryland, USA
| | - Hossein Dehghani
- Joint Quantum Institute, College Park, 20742 Maryland, USA and The Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, 20742 Maryland, USA
| | - Mohammad Hafezi
- Joint Quantum Institute, College Park, 20742 Maryland, USA and The Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, 20742 Maryland, USA
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32
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Quantum measurement arrow of time and fluctuation relations for measuring spin of ultracold atoms. Nat Commun 2021; 12:1847. [PMID: 33758199 PMCID: PMC7988044 DOI: 10.1038/s41467-021-22094-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 02/19/2021] [Indexed: 11/09/2022] Open
Abstract
The origin of macroscopic irreversibility from microscopically time-reversible dynamical laws—often called the arrow-of-time problem—is of fundamental interest in both science and philosophy. Experimentally probing such questions in quantum theory requires systems with near-perfect isolation from the environment and long coherence times. Ultracold atoms are uniquely suited to this task. We experimentally demonstrate a striking parallel between the statistical irreversibility of wavefunction collapse and the arrow of time problem in the weak measurement of the quantum spin of an atomic cloud. Our experiments include statistically rare events where the arrow of time is inferred backward; nevertheless we provide evidence for absolute irreversibility and a strictly positive average arrow of time for the measurement process, captured by a fluctuation theorem. We further demonstrate absolute irreversibility for measurements performed on a quantum many-body entangled wavefunction—a unique opportunity afforded by our platform—with implications for studying quantum many-body dynamics and quantum thermodynamics. Irreversibility in quantum measurements shares conceptual links with statistical and thermodynamical irreversibility. Here, the authors are able to operationally associate an "arrow of time” to quantum weak measurements, testing it experimentally on a cloud of ultracold atoms.
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33
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Monroe JT, Yunger Halpern N, Lee T, Murch KW. Weak Measurement of a Superconducting Qubit Reconciles Incompatible Operators. PHYSICAL REVIEW LETTERS 2021; 126:100403. [PMID: 33784149 DOI: 10.1103/physrevlett.126.100403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Revised: 11/19/2020] [Accepted: 01/29/2021] [Indexed: 06/12/2023]
Abstract
Traditional uncertainty relations dictate a minimal amount of noise in incompatible projective quantum measurements. However, not all measurements are projective. Weak measurements are minimally invasive methods for obtaining partial state information without projection. Recently, weak measurements were shown to obey an uncertainty relation cast in terms of entropies. We experimentally test this entropic uncertainty relation with strong and weak measurements of a superconducting transmon qubit. A weak measurement, we find, can reconcile two strong measurements' incompatibility, via backaction on the state. Mathematically, a weak value-a preselected and postselected expectation value-lowers the uncertainty bound. Hence we provide experimental support for the physical interpretation of the weak value as a determinant of a weak measurement's ability to reconcile incompatible operations.
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Affiliation(s)
- Jonathan T Monroe
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
| | - Nicole Yunger Halpern
- ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138, USA
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
- Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- Joint Center for Quantum Information and Computer Science, NIST and University of Maryland, College Park, Maryland 20742, USA
- Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA
- Institute for Quantum Information and Matter, California Institute of Technology, Pasadena, California 91125, USA
| | - Taeho Lee
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
| | - Kater W Murch
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
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34
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Manzano G, Subero D, Maillet O, Fazio R, Pekola JP, Roldán É. Thermodynamics of Gambling Demons. PHYSICAL REVIEW LETTERS 2021; 126:080603. [PMID: 33709732 DOI: 10.1103/physrevlett.126.080603] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 11/23/2020] [Accepted: 01/28/2021] [Indexed: 06/12/2023]
Abstract
We introduce and realize demons that follow a customary gambling strategy to stop a nonequilibrium process at stochastic times. We derive second-law-like inequalities for the average work done in the presence of gambling, and universal stopping-time fluctuation relations for classical and quantum nonstationary stochastic processes. We test experimentally our results in a single-electron box, where an electrostatic potential drives the dynamics of individual electrons tunneling into a metallic island. We also discuss the role of coherence in gambling demons measuring quantum jump trajectories.
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Affiliation(s)
- Gonzalo Manzano
- International Centre for Theoretical Physics ICTP, Strada Costiera 11, I-34151 Trieste, Italy
- Institute for Quantum Optics and Quantum Information (IQOQI), Austrian Academy of Sciences, Boltzmanngasse 3, 1090 Vienna, Austria
| | - Diego Subero
- PICO group, QTF Centre of Excellence, Department of Applied Physics, Aalto University, 00076 Aalto, Finland
| | - Olivier Maillet
- PICO group, QTF Centre of Excellence, Department of Applied Physics, Aalto University, 00076 Aalto, Finland
| | - Rosario Fazio
- International Centre for Theoretical Physics ICTP, Strada Costiera 11, I-34151 Trieste, Italy
- Dipartimento di Fisica, Università di Napoli "Federico II," Monte S. Angelo, I-80126 Napoli, Italy
| | - Jukka P Pekola
- PICO group, QTF Centre of Excellence, Department of Applied Physics, Aalto University, 00076 Aalto, Finland
| | - Édgar Roldán
- International Centre for Theoretical Physics ICTP, Strada Costiera 11, I-34151 Trieste, Italy
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35
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A Quantum Time Coordinate. Symmetry (Basel) 2021. [DOI: 10.3390/sym13020306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
We discuss quantum time states formed with a finite number of energy eigenstates with the purpose of obtaining a time coordinate. These time states are eigenstates of the recently introduced discrete time operator. The coordinate and momentum representations of these time eigenstates resemble classical time curves and become classical at high energies. To illustrate this behavior, we consider the simple example of the particle-in-a-box model. We can follow the quantum-classical transition of the system. Among the many existing solutions for the particle in a box, we use a set which leads to time eigenstates for use as a coordinate system.
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36
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Tacchino F, Santos TFF, Gerace D, Campisi M, Santos MF. Charging a quantum battery via nonequilibrium heat current. Phys Rev E 2021; 102:062133. [PMID: 33466004 DOI: 10.1103/physreve.102.062133] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Accepted: 11/24/2020] [Indexed: 11/07/2022]
Abstract
When a quantum system is subject to a thermal gradient it may sustain a steady nonequilibrium heat current by entering into a so-called nonequilibrium steady state (NESS). Here we show that NESS constitute a thermodynamic resource that can be exploited to charge a quantum battery. This adds to the list of recently reported sources available at the nanoscale, such as coherence, entanglement, and quantum measurements. We elucidate this concept by showing analytic and numerical studies of a two-qubit quantum battery that is alternatively charged by an incoherent heat flow and discharged by application of a properly chosen unitary gate. The presence of a NESS for the charging step guarantees steady operation with positive power output. Decreasing the duration of the charging step results in a time-periodic steady state accompanied by increased efficiency and output power. The device is amenable to implementation with different nanotechnology platforms.
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Affiliation(s)
| | - Tiago F F Santos
- Instituto de Física, Universidade Federal do Rio de Janeiro, CP68528, Rio de Janeiro, Rio de Janeiro 21941-972, Brazil
| | - Dario Gerace
- Dipartimento di Fisica, Università di Pavia, I-27100, Pavia, Italy
| | - Michele Campisi
- NEST, Istituto Nanoscienze-CNR and Scuola Normale Superiore I-56127 Pisa, Italy.,Dipartmento di Fisica e Astronomia, Università di Firenze, I-50019, Sesto Fiorentino (FI), Italy.,INFN-Sezione di Pisa, I-56127 Pisa, Italy
| | - Marcelo F Santos
- Instituto de Física, Universidade Federal do Rio de Janeiro, CP68528, Rio de Janeiro, Rio de Janeiro 21941-972, Brazil
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37
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Porrati M, Putterman S. Prediction of Short Time Qubit Readout via Measurement of the Next Quantum Jump of a Coupled Damped Driven Harmonic Oscillator. PHYSICAL REVIEW LETTERS 2020; 125:260403. [PMID: 33449707 DOI: 10.1103/physrevlett.125.260403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 11/30/2020] [Indexed: 06/12/2023]
Abstract
The dynamics of the next quantum jump for a qubit [two level system] coupled to a readout resonator [damped driven harmonic oscillator] is calculated. A quantum mechanical treatment of readout resonator reveals nonexponential short time behavior which could facilitate detection of the state of the qubit faster than the resonator lifetime.
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Affiliation(s)
- Massimo Porrati
- Center for Cosmology and Particle Physics, Department of Physics, New York University, 726 Broadway, New York, New York 10003, USA
| | - Seth Putterman
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095-1547, USA
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38
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Magnard P, Storz S, Kurpiers P, Schär J, Marxer F, Lütolf J, Walter T, Besse JC, Gabureac M, Reuer K, Akin A, Royer B, Blais A, Wallraff A. Microwave Quantum Link between Superconducting Circuits Housed in Spatially Separated Cryogenic Systems. PHYSICAL REVIEW LETTERS 2020; 125:260502. [PMID: 33449744 DOI: 10.1103/physrevlett.125.260502] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Accepted: 11/16/2020] [Indexed: 05/26/2023]
Abstract
Superconducting circuits are a strong contender for realizing quantum computing systems and are also successfully used to study quantum optics and hybrid quantum systems. However, their cryogenic operation temperatures and the current lack of coherence-preserving microwave-to-optical conversion solutions have hindered the realization of superconducting quantum networks spanning different cryogenic systems or larger distances. Here, we report the successful operation of a cryogenic waveguide coherently linking transmon qubits located in two dilution refrigerators separated by a physical distance of five meters. We transfer qubit states and generate entanglement on demand with average transfer and target state fidelities of 85.8% and 79.5%, respectively, between the two nodes of this elementary network. Cryogenic microwave links provide an opportunity to scale up systems for quantum computing and create local area superconducting quantum communication networks over length scales of at least tens of meters.
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Affiliation(s)
- P Magnard
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - S Storz
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - P Kurpiers
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - J Schär
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - F Marxer
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - J Lütolf
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - T Walter
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - J-C Besse
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - M Gabureac
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - K Reuer
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - A Akin
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
| | - B Royer
- Institut Quantique and Département de Physique, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
| | - A Blais
- Institut Quantique and Département de Physique, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
- Canadian Institute for Advanced Research, Toronto, Ontario M5G 1Z8, Canada
| | - A Wallraff
- Department of Physics, ETH Zürich, CH-8093 Zürich, Switzerland
- Quantum Center, ETH Zürich, 8093 Zürich, Switzerland
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39
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Rossi MAC, Albarelli F, Tamascelli D, Genoni MG. Noisy Quantum Metrology Enhanced by Continuous Nondemolition Measurement. PHYSICAL REVIEW LETTERS 2020; 125:200505. [PMID: 33258625 DOI: 10.1103/physrevlett.125.200505] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Accepted: 10/19/2020] [Indexed: 06/12/2023]
Abstract
We show that continuous quantum nondemolition (QND) measurement of an atomic ensemble is able to improve the precision of frequency estimation even in the presence of independent dephasing acting on each atom. We numerically simulate the dynamics of an ensemble with up to N=150 atoms initially prepared in a (classical) spin coherent state, and we show that, thanks to the spin squeezing dynamically generated by the measurement, the information obtainable from the continuous photocurrent scales superclassically with respect to the number of atoms N. We provide evidence that such superclassical scaling holds for different values of dephasing and monitoring efficiency. We moreover calculate the extra information obtainable via a final strong measurement on the conditional states generated during the dynamics and show that the corresponding ultimate limit is nearly achieved via a projective measurement of the spin-squeezed collective spin operator. We also briefly discuss the difference between our protocol and standard estimation schemes, where the state preparation time is neglected.
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Affiliation(s)
- Matteo A C Rossi
- QTF Centre of Excellence, Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, FI-20014 Turun Yliopisto, Finland
| | - Francesco Albarelli
- Faculty of Physics, University of Warsaw, Pasteura 5, 02-093 Warszawa, Poland
| | - Dario Tamascelli
- Dipartimento di Fisica "Aldo Pontremoli," Università degli Studi di Milano, I-20133 Milano, Italy
| | - Marco G Genoni
- Dipartimento di Fisica "Aldo Pontremoli," Università degli Studi di Milano, I-20133 Milano, Italy
- INFN - Sezione di Milano, I-20133 Milano, Italy
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40
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Meng C, Brawley GA, Bennett JS, Vanner MR, Bowen WP. Mechanical Squeezing via Fast Continuous Measurement. PHYSICAL REVIEW LETTERS 2020; 125:043604. [PMID: 32794807 DOI: 10.1103/physrevlett.125.043604] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 06/25/2020] [Indexed: 06/11/2023]
Abstract
We revisit quantum state preparation of an oscillator by continuous linear position measurement. Quite general analytical expressions are derived for the conditioned state of the oscillator. Remarkably, we predict that quantum squeezing is possible outside of both the backaction dominated and quantum coherent oscillation regimes, relaxing experimental requirements even compared to ground-state cooling. This provides a new way to generate nonclassical states of macroscopic mechanical oscillators, and opens the door to quantum sensing and tests of quantum macroscopicity at room temperature.
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Affiliation(s)
- Chao Meng
- Australian Research Council Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, University of Queensland, St Lucia, Queensland 4072, Australia
| | - George A Brawley
- Australian Research Council Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, University of Queensland, St Lucia, Queensland 4072, Australia
| | - James S Bennett
- Australian Research Council Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Michael R Vanner
- Australian Research Council Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, University of Queensland, St Lucia, Queensland 4072, Australia
- QOLS, Blackett Laboratory, Imperial College London, London SW7 2BW, United Kingdom
| | - Warwick P Bowen
- Australian Research Council Centre of Excellence for Engineered Quantum Systems, School of Mathematics and Physics, University of Queensland, St Lucia, Queensland 4072, Australia
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41
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Abstract
This article develops a view of consciousness in the context of a new philosophical approach that invokes the concept of emergence, through which the operative principles of each level of organization of physical energy flow are functionally dissociated from those of the levels below it, despite the continuity of the physical laws that govern them. The particular form of emergence that is the focus of the present analysis is the emergence of conscious mental processing from neural activity carried by the underlying biochemical principles of brain organization. Within this framework, a process model of consciousness is developed to account for many of the experienced aspects of consciousness, many that are rarely considered in the philosophical discourse. Each of these aspects is rigorously specified in terms of its definable properties. It is then analyzed in terms of specific empirical tests that can be used to determine its neural substrate and relevant data that implement such tests. The article concludes with an analysis of the evolutionary function of consciousness, and a critique of the Integrated Information Theory approach to defining its properties.
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42
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Smirne A, Caiaffa M, Piilo J. Rate Operator Unraveling for Open Quantum System Dynamics. PHYSICAL REVIEW LETTERS 2020; 124:190402. [PMID: 32469534 DOI: 10.1103/physrevlett.124.190402] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 04/20/2020] [Indexed: 06/11/2023]
Abstract
Stochastic methods with quantum jumps are often used to solve open quantum system dynamics. Moreover, they provide insight into fundamental topics, such as the role of measurements in quantum mechanics and the description of non-Markovian memory effects. However, there is no unified framework to use quantum jumps to describe open-system dynamics in any regime. We solve this issue by developing the rate operator quantum jump (ROQJ) approach. The method not only applies to both Markovian and non-Markovian evolutions, but also allows us to unravel master equations for which previous methods do not work. In addition, ROQJ yields a rigorous measurement-scheme interpretation for a wide class of dynamics, including a set of master equations with negative decay rates, and sheds light on different types of memory effects which arise when using stochastic quantum jump methods.
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Affiliation(s)
- Andrea Smirne
- Dipartimento di Fisica "Aldo Pontremoli," Università degli Studi di Milano, and Istituto Nazionale di Fisica Nucleare, Sezione di Milano, via Celoria 16, I-20133 Milan, Italy
- Institute of Theoretical Physics, Universität Ulm, Albert-Einstein-Allee 11D-89069 Ulm, Germany
| | - Matteo Caiaffa
- SUPA and Department of Physics, University of Strathclyde, Glasgow G4 0NG, United Kingdom
| | - Jyrki Piilo
- QTF Centre of Excellence, Turku Centre for Quantum Physics, Department of Physics and Astronomy, University of Turku, FI-20014, Turun Yliopisto, Finland
- Laboratory of Quantum Optics, Department of Physics and Astronomy, University of Turku, FI-20014, Turun yliopisto, Finland
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43
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Karimi B, Pekola JP. Quantum Trajectory Analysis of Single Microwave Photon Detection by Nanocalorimetry. PHYSICAL REVIEW LETTERS 2020; 124:170601. [PMID: 32412284 DOI: 10.1103/physrevlett.124.170601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 04/09/2020] [Indexed: 06/11/2023]
Abstract
We apply quantum trajectory techniques to analyze a realistic setup of a superconducting qubit coupled to a heat bath formed by a resistor, a system that yields explicit expressions of the relevant transition rates to be used in the analysis. We discuss the main characteristics of the jump trajectories and relate them to the expected outcomes ("clicks") of a fluorescence measurement using the resistor as a nanocalorimeter. As the main practical outcome, we present a model that predicts the time-domain response of a realistic calorimeter subject to single microwave photons, incorporating the intrinsic noise due to the fundamental thermal fluctuations of the absorber and finite bandwidth of a thermometer.
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Affiliation(s)
- Bayan Karimi
- QTF Centre of Excellence, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, 00076 Aalto, Finland
| | - Jukka P Pekola
- QTF Centre of Excellence, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, 00076 Aalto, Finland
- Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Russia
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44
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Gebhart V, Snizhko K, Wellens T, Buchleitner A, Romito A, Gefen Y. Topological transition in measurement-induced geometric phases. Proc Natl Acad Sci U S A 2020; 117:5706-5713. [PMID: 32123099 PMCID: PMC7084105 DOI: 10.1073/pnas.1911620117] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The state of a quantum system, adiabatically driven in a cycle, may acquire a measurable phase depending only on the closed trajectory in parameter space. Such geometric phases are ubiquitous and also underline the physics of robust topological phenomena such as the quantum Hall effect. Equivalently, a geometric phase may be induced through a cyclic sequence of quantum measurements. We show that the application of a sequence of weak measurements renders the closed trajectories, hence the geometric phase, stochastic. We study the concomitant probability distribution and show that, when varying the measurement strength, the mapping between the measurement sequence and the geometric phase undergoes a topological transition. Our finding may impact measurement-induced control and manipulation of quantum states-a promising approach to quantum information processing. It also has repercussions on understanding the foundations of quantum measurement.
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Affiliation(s)
- Valentin Gebhart
- Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Kyrylo Snizhko
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Thomas Wellens
- Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany
| | - Andreas Buchleitner
- Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany
| | - Alessandro Romito
- Department of Physics, Lancaster University, Lancaster LA1 4YB, United Kingdom
| | - Yuval Gefen
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel;
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45
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Pokorny F, Zhang C, Higgins G, Cabello A, Kleinmann M, Hennrich M. Tracking the Dynamics of an Ideal Quantum Measurement. PHYSICAL REVIEW LETTERS 2020; 124:080401. [PMID: 32167322 DOI: 10.1103/physrevlett.124.080401] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 09/04/2019] [Accepted: 01/24/2020] [Indexed: 06/10/2023]
Abstract
The existence of ideal quantum measurements is one of the fundamental predictions of quantum mechanics. In theory, an ideal measurement projects a quantum state onto the eigenbasis of the measurement observable, while preserving coherences between eigenstates that have the same eigenvalue. The question arises whether there are processes in nature that correspond to such ideal quantum measurements and how such processes are dynamically implemented in nature. Here we address this question and present experimental results monitoring the dynamics of a naturally occurring measurement process: the coupling of a trapped ion qutrit to the photon environment. By taking tomographic snapshots during the detection process, we show that the process develops in agreement with the model of an ideal quantum measurement with an average fidelity of 94%.
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Affiliation(s)
- Fabian Pokorny
- Department of Physics, Stockholm University, 10691 Stockholm, Sweden
| | - Chi Zhang
- Department of Physics, Stockholm University, 10691 Stockholm, Sweden
| | - Gerard Higgins
- Department of Physics, Stockholm University, 10691 Stockholm, Sweden
| | - Adán Cabello
- Departamento de Física Aplicada II, Universidad de Sevilla, E-41012 Sevilla, Spain
- Instituto Carlos I de Física Teórica y Computacional, Universidad de Sevilla, E-41012 Sevilla, Spain
| | - Matthias Kleinmann
- Department of Theoretical Physics, University of the Basque Country UPV/EHU, E-48080 Bilbao, Spain
- Naturwissenschaftlich-Technische Fakultät, Universität Siegen, 57068 Siegen, Germany
| | - Markus Hennrich
- Department of Physics, Stockholm University, 10691 Stockholm, Sweden
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46
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Szombati D, Gomez Frieiro A, Müller C, Jones T, Jerger M, Fedorov A. Quantum Rifling: Protecting a Qubit from Measurement Back Action. PHYSICAL REVIEW LETTERS 2020; 124:070401. [PMID: 32142306 DOI: 10.1103/physrevlett.124.070401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2019] [Accepted: 01/27/2020] [Indexed: 06/10/2023]
Abstract
Quantum mechanics postulates that measuring the qubit's wave function results in its collapse, with the recorded discrete outcome designating the particular eigenstate that the qubit collapsed into. We show that this picture breaks down when the qubit is strongly driven during measurement. More specifically, for a fast evolving qubit the measurement returns the time-averaged expectation value of the measurement operator, erasing information about the initial state of the qubit while completely suppressing the measurement backaction. We call this regime quantum rifling, as the fast spinning of the Bloch vector protects it from deflection into either of its eigenstates. We study this phenomenon with two superconducting qubits coupled to the same probe field and demonstrate that quantum rifling allows us to measure either one of the qubits on demand while protecting the state of the other from measurement backaction. Our results allow for the implementation of selective readout multiplexing of several qubits, contributing to the efficient scaling up of quantum processors for future quantum technologies.
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Affiliation(s)
- Daniel Szombati
- ARC Centre of Excellence for Engineered Quantum Systems, St Lucia, Queensland 4072, Australia
- School of Mathematics and Physics, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Alejandro Gomez Frieiro
- ARC Centre of Excellence for Engineered Quantum Systems, St Lucia, Queensland 4072, Australia
- School of Mathematics and Physics, University of Queensland, St Lucia, Queensland 4072, Australia
| | | | - Tyler Jones
- ARC Centre of Excellence for Engineered Quantum Systems, St Lucia, Queensland 4072, Australia
- School of Mathematics and Physics, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Markus Jerger
- ARC Centre of Excellence for Engineered Quantum Systems, St Lucia, Queensland 4072, Australia
- School of Mathematics and Physics, University of Queensland, St Lucia, Queensland 4072, Australia
| | - Arkady Fedorov
- ARC Centre of Excellence for Engineered Quantum Systems, St Lucia, Queensland 4072, Australia
- School of Mathematics and Physics, University of Queensland, St Lucia, Queensland 4072, Australia
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47
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Karimi B, Brange F, Samuelsson P, Pekola JP. Reaching the ultimate energy resolution of a quantum detector. Nat Commun 2020; 11:367. [PMID: 31953442 PMCID: PMC6969185 DOI: 10.1038/s41467-019-14247-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 12/16/2019] [Indexed: 11/20/2022] Open
Abstract
Quantum calorimetry, the thermal measurement of quanta, is a method of choice for ultrasensitive radiation detection ranging from microwaves to gamma rays. The fundamental temperature fluctuations of the calorimeter, dictated by the coupling of it to the heat bath, set the ultimate lower bound of its energy resolution. Here we reach this limit of fundamental equilibrium fluctuations of temperature in a nanoscale electron calorimeter, exchanging energy with the phonon bath at very low temperatures. The approach allows noninvasive measurement of energy transport in superconducting quantum circuits in the microwave regime with high efficiency, opening the way, for instance, to observe quantum jumps, detecting their energy to tackle central questions in quantum thermodynamics.
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Affiliation(s)
- Bayan Karimi
- QTF Centre of Excellence, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, FI-00076, Aalto, Finland.
| | - Fredrik Brange
- Department of Physics and NanoLund, Lund University, Box 188, SE-221 00, Lund, Sweden
| | - Peter Samuelsson
- Department of Physics and NanoLund, Lund University, Box 188, SE-221 00, Lund, Sweden
| | - Jukka P Pekola
- QTF Centre of Excellence, Department of Applied Physics, Aalto University School of Science, P.O. Box 13500, FI-00076, Aalto, Finland.
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48
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Reflexivity, coding and quantum biology. Biosystems 2019; 185:104027. [PMID: 31494127 DOI: 10.1016/j.biosystems.2019.104027] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2019] [Revised: 08/29/2019] [Accepted: 08/31/2019] [Indexed: 12/31/2022]
Abstract
Biological systems are fundamentally computational in that they process information in an apparently purposeful fashion rather than just transferring bits of it in a purely syntactical manner. Biological information, such has genetic information stored in DNA sequences, has semantic content. It carries meaning that is defined by the molecular context of its cellular environment. Information processing in biological systems displays an inherent reflexivity, a tendency for the computational information-processing to be "about" the behaviour of the molecules that participate in the computational process. This is most evident in the operation of the genetic code, where the specificity of the reactions catalysed by the aminoacyl-tRNA synthetase (aaRS) enzymes is required to be self-sustaining. A cell's suite of aaRS enzymes completes a reflexively autocatalytic set of molecular components capable of making themselves through the operation of the code. This set requires the existence of a body of reflexive information to be stored in an organism's genome. The genetic code is a reflexively self-organised mapping of the chemical properties of amino acid sidechains onto codon "tokens". It is a highly evolved symbolic system of chemical self-description. Although molecular biological coding is generally portrayed in terms of classical bit-transfer events, various biochemical events explicitly require quantum coherence for their occurrence. Whether the implicit transfer of quantum information, qbits, is indicative of wide-ranging quantum computation in living systems is currently the subject of extensive investigation and speculation in the field of Quantum Biology.
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