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Sun J, Endo S, Lin H, Hayden P, Vedral V, Yuan X. Perturbative Quantum Simulation. Phys Rev Lett 2022; 129:120505. [PMID: 36179156 DOI: 10.1103/physrevlett.129.120505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Revised: 01/27/2022] [Accepted: 08/17/2022] [Indexed: 06/16/2023]
Abstract
Approximation based on perturbation theory is the foundation for most of the quantitative predictions of quantum mechanics, whether in quantum many-body physics, chemistry, quantum field theory, or other domains. Quantum computing provides an alternative to the perturbation paradigm, yet state-of-the-art quantum processors with tens of noisy qubits are of limited practical utility. Here, we introduce perturbative quantum simulation, which combines the complementary strengths of the two approaches, enabling the solution of large practical quantum problems using limited noisy intermediate-scale quantum hardware. The use of a quantum processor eliminates the need to identify a solvable unperturbed Hamiltonian, while the introduction of perturbative coupling permits the quantum processor to simulate systems larger than the available number of physical qubits. We present an explicit perturbative expansion that mimics the Dyson series expansion and involves only local unitary operations, and show its optimality over other expansions under certain conditions. We numerically benchmark the method for interacting bosons, fermions, and quantum spins in different topologies, and study different physical phenomena, such as information propagation, charge-spin separation, and magnetism, on systems of up to 48 qubits only using an 8+1 qubit quantum hardware. We demonstrate our scheme on the IBM quantum cloud, verifying its noise robustness and illustrating its potential for benchmarking large quantum processors with smaller ones.
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Affiliation(s)
- Jinzhao Sun
- Center on Frontiers of Computing Studies, Peking University, Beijing 100871, China
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
- Quantum Advantage Research, Beijing 100080, China
| | - Suguru Endo
- NTT Computer & Data Science Laboratories, NTT corporation, Musashino, Tokyo 180-8585, Japan
| | - Huiping Lin
- Center on Frontiers of Computing Studies, Peking University, Beijing 100871, China
- School of Computer Science, Peking University, Beijing 100871, China
| | - Patrick Hayden
- Stanford Institute for Theoretical Physics, Stanford University, Stanford, California 94305, USA
| | - Vlatko Vedral
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
- Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore
| | - Xiao Yuan
- Center on Frontiers of Computing Studies, Peking University, Beijing 100871, China
- School of Computer Science, Peking University, Beijing 100871, China
- Stanford Institute for Theoretical Physics, Stanford University, Stanford, California 94305, USA
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2
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Marletto C, Vedral V, Knoll LT, Piacentini F, Bernardi E, Rebufello E, Avella A, Gramegna M, Degiovanni IP, Genovese M. Emergence of Constructor-Based Irreversibility in Quantum Systems: Theory and Experiment. Phys Rev Lett 2022; 128:080401. [PMID: 35275647 DOI: 10.1103/physrevlett.128.080401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2021] [Accepted: 01/14/2022] [Indexed: 06/14/2023]
Abstract
How irreversibility arises in a universe with time-reversal symmetric laws is a central problem in physics. In this Letter, we discuss a radically different take on the emergence of irreversibility, adopting the recently proposed constructor theory framework. Irreversibility is expressed as the requirement that a task is possible, while its inverse is not. We prove the compatibility of such irreversibility with quantum theory's time-reversal symmetric laws, using a dynamical model based on the universal quantum homogenizer. We also test the physical realizability of this model by means of an experimental demonstration with high-quality single-photon qubits.
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Affiliation(s)
- Chiara Marletto
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom and Fondazione ISI, Via Chisola 5, Torino, Italy and Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 and Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
| | - Vlatko Vedral
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom and Fondazione ISI, Via Chisola 5, Torino, Italy and Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 and Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
| | - Laura T Knoll
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy
| | - Fabrizio Piacentini
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy
| | - Ettore Bernardi
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy
| | - Enrico Rebufello
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy
| | - Alessio Avella
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy
| | - Marco Gramegna
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy
| | - Ivo Pietro Degiovanni
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy and INFN, sezione di Torino, via P. Giuria 1, 10125 Torino, Italy
| | - Marco Genovese
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy and INFN, sezione di Torino, via P. Giuria 1, 10125 Torino, Italy
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Marletto C, Vedral V, Virzì S, Avella A, Piacentini F, Gramegna M, Degiovanni IP, Genovese M. Temporal teleportation with pseudo-density operators: How dynamics emerges from temporal entanglement. Sci Adv 2021; 7:eabe4742. [PMID: 34524847 PMCID: PMC8443168 DOI: 10.1126/sciadv.abe4742] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 07/23/2021] [Indexed: 06/13/2023]
Abstract
We show that, by using temporal quantum correlations as expressed by pseudo-density operators (PDOs), it is possible to recover formally the standard quantum dynamical evolution as a sequence of teleportations in time. We demonstrate that any completely positive evolution can be formally reconstructed by teleportation with different temporally correlated states. This provides a different interpretation of maximally correlated PDOs, as resources to induce quantum time evolution. Furthermore, we note that the possibility of this protocol stems from the strict formal correspondence between spatial and temporal entanglement in quantum theory. We proceed to demonstrate experimentally this correspondence, by showing a multipartite violation of generalized temporal and spatial Bell inequalities and verifying agreement with theoretical predictions to a high degree of accuracy, in high-quality photon qubits.
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Affiliation(s)
- Chiara Marletto
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543
- ISI Foundation, Via Chisola 5, I-10126 Torino, Italy
| | - Vlatko Vedral
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543
- ISI Foundation, Via Chisola 5, I-10126 Torino, Italy
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
| | | | | | | | | | - Ivo Pietro Degiovanni
- INRIM, Strada Delle Cacce 91, I-10135 Torino, Italy
- INFN, via P. Giuria 1, I-10125 Torino, Italy
| | - Marco Genovese
- INRIM, Strada Delle Cacce 91, I-10135 Torino, Italy
- INFN, via P. Giuria 1, I-10125 Torino, Italy
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5
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Chia A, Hajdušek M, Nair R, Fazio R, Kwek LC, Vedral V. Phase-Preserving Linear Amplifiers Not Simulable by the Parametric Amplifier. Phys Rev Lett 2020; 125:163603. [PMID: 33124847 DOI: 10.1103/physrevlett.125.163603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 04/26/2019] [Accepted: 09/18/2020] [Indexed: 06/11/2023]
Abstract
It is commonly accepted that a parametric amplifier can simulate a phase-preserving linear amplifier regardless of how the latter is realized [C. M. Caves et al., Phys. Rev. A 86, 063802 (2012)PLRAAN1050-294710.1103/PhysRevA.86.063802]. If true, this reduces all phase-preserving linear amplifiers to a single familiar model. Here we disprove this claim by constructing two counterexamples. A detailed discussion of the physics of our counterexamples is provided. It is shown that a Heisenberg-picture analysis facilitates a microscopic explanation of the physics. This also resolves a question about the nature of amplifier-added noise in degenerate two-photon amplification.
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Affiliation(s)
- A Chia
- Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore
| | - M Hajdušek
- Keio University Shonan-Fujisawa Campus, Fujisawa, Kanagawa 252-0882, Japan
| | - R Nair
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
- Complexity Institute, Nanyang Technological University, Singapore 637460, Singapore
| | - R Fazio
- Abdus Salam ICTP, Trieste 34151, Italy
- Dipartimento di Fisica, Università di Napoli Federico II, Complesso di Monte S. Angelo, Napoli 80126, Italy
| | - L C Kwek
- Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore
- National Institute of Education, Nanyang Technological University, Singapore 637616, Singapore
| | - V Vedral
- Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore
- Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, United Kingdom
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Abstract
We propose a thermodynamic refrigeration cycle which uses indefinite causal orders to achieve nonclassical cooling. The cycle cools a cold reservoir while consuming purity in a control qubit. We first show that the application to an input state of two identical thermalizing channels of temperature T in an indefinite causal order can result in an output state with a temperature not equal to T. We investigate the properties of the refrigeration cycle and show that thermodynamically, the result is compatible with unitary quantum mechanics in the circuit model but could not be achieved classically. We believe that this cycle could be implemented experimentally using tabletop photonics. Our result suggests the development of a new class of thermodynamic resource theories in which operations are allowed to be performed in an indefinite causal order.
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Affiliation(s)
- David Felce
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, OX1 3PU, England
| | - Vlatko Vedral
- Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, OX1 3PU, England
- Centre for Quantum Technologies, National University of Singapore, Block S15, 3 Science Drive 2, 117543, Singapore
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Marletto C, Vedral V. Aharonov-Bohm Phase is Locally Generated Like All Other Quantum Phases. Phys Rev Lett 2020; 125:040401. [PMID: 32794810 DOI: 10.1103/physrevlett.125.040401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Accepted: 06/30/2020] [Indexed: 06/11/2023]
Abstract
In the Aharonov-Bohm (AB) effect, a superposed charge acquires a detectable phase by enclosing an infinite solenoid, in a region where the solenoid's electric and magnetic fields are zero. Its generation seems therefore explainable only by the local action of gauge-dependent potentials, not of gauge-independent fields. This was recently challenged by Vaidman, who explained the phase by the solenoid's current interacting with the electron's field (at the solenoid). Still, his model has a residual nonlocality: it does not explain how the phase, generated at the solenoid, is detectable on the charge. In this Letter, we solve this nonlocality explicitly by quantizing the field. We show that the AB phase is mediated locally by the entanglement between the charge and the photons, like all electromagnetic phases. We also predict a gauge-invariant value for the phase difference at each point along the charge's path. We propose a realistic experiment to measure this phase difference locally, by partial quantum state tomography on the charge, without closing the interference loop.
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Affiliation(s)
- Chiara Marletto
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom; Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543, Singapore; Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
- ISI Foundation, Via Chisola, 5, 10126 Torino TO, Italy
| | - Vlatko Vedral
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom; Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543, Singapore; Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
- ISI Foundation, Via Chisola, 5, 10126 Torino TO, Italy
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Park JJ, Nha H, Kim SW, Vedral V. Information fluctuation theorem for an open quantum bipartite system. Phys Rev E 2020; 101:052128. [PMID: 32575248 DOI: 10.1103/physreve.101.052128] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 04/28/2020] [Indexed: 11/07/2022]
Abstract
We study an arbitrary nonequilibrium dynamics of a quantum bipartite system coupled to a reservoir. For its characterization, we present a fluctuation theorem (FT) that explicitly addresses the quantum correlation of subsystems during the thermodynamic evolution. To our aim, we designate the local and the global states altogether in the time-forward and the time-reversed transition probabilities. In view of the two-point measurement scheme, only the global states are subject to measurements whereas the local states are used only as an augmented information on the composite system. We specifically derive a FT in such a form that relates the entropy production of local systems in the time-forward transition to the change of quantum correlation in the time-reversed transition. This also leads to a useful thermodynamic inequality and we illustrate its advantage by an example of an isothermal process on Werner states.
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Affiliation(s)
- Jung Jun Park
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543, Singapore.,Department of Physics, Texas A&M University at Qatar, P.O. Box 23874, Doha, Qatar.,Korea Institute for Advanced Study, Seoul 02455, Korea
| | - Hyunchul Nha
- Department of Physics, Texas A&M University at Qatar, P.O. Box 23874, Doha, Qatar
| | - Sang Wook Kim
- Department of Physics, Kyung Hee University, Seoul 02447, Republic of Korea
| | - Vlatko Vedral
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543, Singapore.,Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX13PU, United Kingdom
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Mack K, Kruszelnicki K, Randall L, Wade J, Al-Khalili J, Vedral V. Reaching out. Nat Rev Phys 2020; 2:282-284. [PMID: 38624338 PMCID: PMC7233191 DOI: 10.1038/s42254-020-0185-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 04/24/2020] [Indexed: 05/05/2023]
Abstract
In the midst of the COVID-19 pandemic, science is crucial to inform public policy. At the same time, mistrust of scientists and misinformation about scientific facts are rampant. Six scientists, actively involved in outreach, reflect on how to build a better understanding and trust of science.
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Affiliation(s)
- Katherine Mack
- Department of Physics, North Carolina State University, Raleigh, NC USA
| | | | - Lisa Randall
- Department of Physics, Harvard University, Cambridge, MA USA
| | - Jessica Wade
- Department of Chemistry, Imperial College London, London, UK
| | - Jim Al-Khalili
- Department of Physics, University of Surrey, Guildford, UK
| | - Vlatko Vedral
- Department of Physics, University of Oxford, Oxford, UK
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11
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Marletto C, Vedral V, Virzì S, Rebufello E, Avella A, Piacentini F, Gramegna M, Degiovanni IP, Genovese M. Non-Monogamy of Spatio-Temporal Correlations and the Black Hole Information Loss Paradox. Entropy (Basel) 2020; 22:e22020228. [PMID: 33286002 PMCID: PMC7516659 DOI: 10.3390/e22020228] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 02/16/2020] [Accepted: 02/17/2020] [Indexed: 11/16/2022]
Abstract
Pseudo-density matrices are a generalisation of quantum states and do not obey monogamy of quantum correlations. Could this be the solution to the paradox of information loss during the evaporation of a black hole? In this paper we discuss this possibility, providing a theoretical proposal to extend quantum theory with these pseudo-states to describe the statistics arising in black-hole evaporation. We also provide an experimental demonstration of this theoretical proposal, using a simulation in optical regime, that tomographically reproduces the correlations of the pseudo-density matrix describing this physical phenomenon.
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Affiliation(s)
- Chiara Marletto
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK;
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
- Correspondence:
| | - Vlatko Vedral
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK;
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore
| | - Salvatore Virzì
- Dipartimento di Fisica, Università di Torino, via P. Giuria 1, 10125 Torino, Italy;
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy; (E.R.); (A.A.); (F.P.); (M.G.); (I.P.D.); (M.G.)
| | - Enrico Rebufello
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy; (E.R.); (A.A.); (F.P.); (M.G.); (I.P.D.); (M.G.)
- Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy
| | - Alessio Avella
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy; (E.R.); (A.A.); (F.P.); (M.G.); (I.P.D.); (M.G.)
| | - Fabrizio Piacentini
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy; (E.R.); (A.A.); (F.P.); (M.G.); (I.P.D.); (M.G.)
| | - Marco Gramegna
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy; (E.R.); (A.A.); (F.P.); (M.G.); (I.P.D.); (M.G.)
| | - Ivo Pietro Degiovanni
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy; (E.R.); (A.A.); (F.P.); (M.G.); (I.P.D.); (M.G.)
| | - Marco Genovese
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135 Torino, Italy; (E.R.); (A.A.); (F.P.); (M.G.); (I.P.D.); (M.G.)
- INFN, sezione di Torino, via P. Giuria 1, 10125 Torino, Italy
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Jaseem N, Hajdušek M, Vedral V, Fazio R, Kwek LC, Vinjanampathy S. Quantum synchronization in nanoscale heat engines. Phys Rev E 2020; 101:020201. [PMID: 32168700 DOI: 10.1103/physreve.101.020201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Accepted: 01/02/2020] [Indexed: 06/10/2023]
Abstract
Owing to the ubiquity of synchronization in the classical world, it is interesting to study its behavior in quantum systems. Though quantum synchronization has been investigated in many systems, a clear connection to quantum technology applications is lacking. We bridge this gap and show that nanoscale heat engines are a natural platform to study quantum synchronization and always possess a stable limit cycle. Furthermore, we demonstrate an intimate relationship between the power of a coherently driven heat engine and its phase-locking properties by proving that synchronization places an upper bound on the achievable steady-state power of the engine. We also demonstrate that such an engine exhibits finite steady-state power if and only if its synchronization measure is nonzero. Finally, we show that the efficiency of the engine sets a point in terms of the bath temperatures where synchronization vanishes. We link the physical phenomenon of synchronization with the emerging field of quantum thermodynamics by establishing quantum synchronization as a mechanism of stable phase coherence.
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Affiliation(s)
- Noufal Jaseem
- Department of Physics, Indian Institute of Technology-Bombay, Powai, Mumbai 400076, India
| | - Michal Hajdušek
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543
- Keio University Shonan Fujisawa Campus, 5322 Endo, Fujisawa, Kanagawa 252-0882, Japan
| | - Vlatko Vedral
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543
- Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, United Kingdom
| | - Rosario Fazio
- Abdus Salam ICTP, Strada Costiera 11, I-34151 Trieste, Italy
- Dipartimento di Fisica, Università di Napoli Federico II, Complesso di Monte S. Angelo, 80126 Napoli, Italy
| | - Leong-Chuan Kwek
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543
- Institute of Advanced Studies, Nanyang Technological University, Singapore 639673
- National Institute of Education, Nanyang Technological University, Singapore 637616
| | - Sai Vinjanampathy
- Department of Physics, Indian Institute of Technology-Bombay, Powai, Mumbai 400076, India
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543
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Zhang A, Xie J, Xu H, Zheng K, Zhang H, Poon YT, Vedral V, Zhang L. Experimental Self-Characterization of Quantum Measurements. Phys Rev Lett 2020; 124:040402. [PMID: 32058739 DOI: 10.1103/physrevlett.124.040402] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Indexed: 06/10/2023]
Abstract
The accurate and reliable description of measurement devices is a central problem in both observing uniquely nonclassical behaviors and realizing quantum technologies from powerful computing to precision metrology. To date quantum tomography is the prevalent tool to characterize quantum detectors. However, such a characterization relies on accurately characterized probe states, rendering reliability of the characterization lost in circular argument. Here we report a self-characterization method of quantum measurements based on reconstructing the response range-the entirety of attainable measurement outcomes, eliminating the reliance on known states. We characterize two representative measurements implemented with photonic setups and obtain fidelities above 99.99% with the conventional tomographic reconstructions. This initiates range-based techniques in characterizing quantum systems and foreshadows novel device-independent protocols of quantum information applications.
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Affiliation(s)
- Aonan Zhang
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Manipulation (Ministry of Education), College of Engineering and Applied Sciences and School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jie Xie
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Manipulation (Ministry of Education), College of Engineering and Applied Sciences and School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Huichao Xu
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Manipulation (Ministry of Education), College of Engineering and Applied Sciences and School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Kaimin Zheng
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Manipulation (Ministry of Education), College of Engineering and Applied Sciences and School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Han Zhang
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Manipulation (Ministry of Education), College of Engineering and Applied Sciences and School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yiu-Tung Poon
- Department of Mathematics, Iowa State University, Ames, Iowa 50011, USA
- Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China
- Center for Quantum Computing, Peng Cheng Laboratory, Shenzhen, 518055, China
| | - Vlatko Vedral
- Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX13PU, United Kingdom
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543, Singapore
| | - Lijian Zhang
- National Laboratory of Solid State Microstructures, Key Laboratory of Intelligent Optical Sensing and Manipulation (Ministry of Education), College of Engineering and Applied Sciences and School of Physics, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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14
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Zhang K, Thompson J, Zhang X, Shen Y, Lu Y, Zhang S, Ma J, Vedral V, Gu M, Kim K. Modular quantum computation in a trapped ion system. Nat Commun 2019; 10:4692. [PMID: 31619670 PMCID: PMC6795904 DOI: 10.1038/s41467-019-12643-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 09/17/2019] [Indexed: 11/09/2022] Open
Abstract
Modern computation relies crucially on modular architectures, breaking a complex algorithm into self-contained subroutines. A client can then call upon a remote server to implement parts of the computation independently via an application programming interface (API). Present APIs relay only classical information. Here we implement a quantum API that enables a client to estimate the absolute value of the trace of a server-provided unitary operation [Formula: see text]. We demonstrate that the algorithm functions correctly irrespective of what unitary [Formula: see text] the server implements or how the server specifically realizes [Formula: see text]. Our experiment involves pioneering techniques to coherently swap qubits encoded within the motional states of a trapped [Formula: see text] ion, controlled on its hyperfine state. This constitutes the first demonstration of modular computation in the quantum regime, providing a step towards scalable, parallelization of quantum computation.
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Affiliation(s)
- Kuan Zhang
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China.
- MOE Key Laboratory of Fundamental Physical Quantities Measurement & Hubei Key Laboratory of Gravitation and Quantum Physics, PGMF and School of Physics, Huazhong University of Science and Technology, 430074, Wuhan, China.
| | - Jayne Thompson
- Centre for Quantum Technologies, National University of Singapore, Singapore, 117543, Singapore.
| | - Xiang Zhang
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China
- Department of Physics, Renmin University of China, 100872, Beijing, China
| | - Yangchao Shen
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China
| | - Yao Lu
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China
| | - Shuaining Zhang
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China
| | - Jiajun Ma
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China
- Department of Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU, UK
| | - Vlatko Vedral
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China
- Centre for Quantum Technologies, National University of Singapore, Singapore, 117543, Singapore
- Department of Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Oxford, OX1 3PU, UK
- Department of Physics, National University of Singapore, Singapore, 117551, Singapore
| | - Mile Gu
- Centre for Quantum Technologies, National University of Singapore, Singapore, 117543, Singapore.
- School of Mathematical and Physical Sciences, Nanyang Technological University, Singapore, 637371, Singapore.
- Complexity Institute, Nanyang Technological University, Singapore, 637335, Singapore.
| | - Kihwan Kim
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China.
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15
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Pisarczyk R, Zhao Z, Ouyang Y, Vedral V, Fitzsimons JF. Causal Limit on Quantum Communication. Phys Rev Lett 2019; 123:150502. [PMID: 31702284 DOI: 10.1103/physrevlett.123.150502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Indexed: 06/10/2023]
Abstract
The capacity of a channel is known to be equivalent to the highest rate at which it can generate entanglement. Analogous to entanglement, the notion of a causality measure characterizes the temporal aspect of quantum correlations. Despite holding an equally fundamental role in physics, temporal quantum correlations have yet to find their operational significance in quantum communication. Here we uncover a connection between quantum causality and channel capacity. We show the amount of temporal correlations between two ends of the noisy quantum channel, as quantified by a causality measure, implies a general upper bound on its channel capacity. The expression of this new bound is simpler to evaluate than most previously known bounds. We demonstrate the utility of this bound by applying it to a class of shifted depolarizing channels, which results in improvement over previously known bounds for this class of channels.
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Affiliation(s)
- Robert Pisarczyk
- Mathematical Institute, University of Oxford, Woodstock Road, Oxford OX2 6GG, United Kingdom
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543, Singapore
| | - Zhikuan Zhao
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543, Singapore
- Department of Computer Science, ETH Zürich, Universitätstrasse 6, 8092 Zürich
- Singapore University of Technology and Design, 8 Somapah Road, 487372, Singapore
| | - Yingkai Ouyang
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543, Singapore
- Singapore University of Technology and Design, 8 Somapah Road, 487372, Singapore
- University of Sheffield, Department of Physics and Astronomy, 226 Hounsfield Rd, Sheffield S3 7RH, United Kingdom
| | - Vlatko Vedral
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543, Singapore
- Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117542, Singapore
| | - Joseph F Fitzsimons
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543, Singapore
- Singapore University of Technology and Design, 8 Somapah Road, 487372, Singapore
- Horizon Quantum Computing, 79 Ayer Rajah Crescent, Singapore 139955
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16
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Pusuluk O, Farrow T, Deliduman C, Vedral V. Emergence of correlated proton tunnelling in water ice. Proc Math Phys Eng Sci 2019; 475:20180867. [PMID: 31236049 DOI: 10.1098/rspa.2018.0867] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Accepted: 02/12/2019] [Indexed: 11/12/2022] Open
Abstract
Several experimental and theoretical studies report instances of concerted or correlated multiple proton tunnelling in solid phases of water. Here, we construct a pseudo-spin model for the quantum motion of protons in a hexameric H2O ring and extend it to open system dynamics that takes environmental effects into account in the form of O-H stretch vibrations. We approach the problem of correlations in tunnelling using quantum information theory in a departure from previous studies. Our formalism enables us to quantify the coherent proton mobility around the hexagonal ring by one of the principal measures of coherence, the l 1 norm of coherence. The nature of the pairwise pseudo-spin correlations underlying the overall mobility is further investigated within this formalism. We show that the classical correlations of the individual quantum tunnelling events in long-time limit is sufficient to capture the behaviour of coherent proton mobility observed in low-temperature experiments. We conclude that long-range intra-ring interactions do not appear to be a necessary condition for correlated proton tunnelling in water ice.
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Affiliation(s)
- Onur Pusuluk
- Department of Physics, Koç University, Sarıyer, İstanbul 34450, Turkey.,Department of Physics, İstanbul Technical University, Maslak, İstanbul 34469, Turkey
| | - Tristan Farrow
- Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK.,Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543, Singapore
| | - Cemsinan Deliduman
- Department of Physics, Mimar Sinan Fine Arts University, Bomonti, İstanbul 34380, Turkey
| | - Vlatko Vedral
- Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK.,Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543, Singapore
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17
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Marletto C, Vedral V, Virzì S, Rebufello E, Avella A, Piacentini F, Gramegna M, Degiovanni IP, Genovese M. Theoretical description and experimental simulation of quantum entanglement near open time-like curves via pseudo-density operators. Nat Commun 2019; 10:182. [PMID: 30643140 PMCID: PMC6331626 DOI: 10.1038/s41467-018-08100-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Accepted: 12/07/2018] [Indexed: 12/05/2022] Open
Abstract
Closed timelike curves are striking predictions of general relativity allowing for time-travel. They are afflicted by notorious causality issues (e.g. grandfather’s paradox). Quantum models where a qubit travels back in time solve these problems, at the cost of violating quantum theory’s linearity—leading e.g. to universal quantum cloning. Interestingly, linearity is violated even by open timelike curves (OTCs), where the qubit does not interact with its past copy, but is initially entangled with another qubit. Non-linear dynamics is needed to avoid violating entanglement monogamy. Here we propose an alternative approach to OTCs, allowing for monogamy violations. Specifically, we describe the qubit in the OTC via a pseudo-density operator—a unified descriptor of both temporal and spatial correlations. We also simulate the monogamy violation with polarization-entangled photons, providing a pseudo-density operator quantum tomography. Remarkably, our proposal applies to any space-time correlations violating entanglement monogamy, such as those arising in black holes. Description of a qubit following an open time-like curve usually incurs into conceptual problems such as violation of entanglement monogamy. Here, the authors show how to use the formalism of pseudo-density operators to describe such a process, showing a proof-of-principle experimental simulation.
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Affiliation(s)
- Chiara Marletto
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, UK. .,Fondazione ISI, Via Chisola 5, Torino, 10126, Italy. .,Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore, 117543, Singapore.
| | - Vlatko Vedral
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, UK.,Fondazione ISI, Via Chisola 5, Torino, 10126, Italy.,Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore, 117543, Singapore.,Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore, 117542, Singapore
| | - Salvatore Virzì
- Università di Torino, via P. Giuria 1, 10125, Torino, Italy.,Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135, Torino, Italy
| | - Enrico Rebufello
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135, Torino, Italy.,Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129, Torino, Italy
| | - Alessio Avella
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135, Torino, Italy
| | - Fabrizio Piacentini
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135, Torino, Italy
| | - Marco Gramegna
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135, Torino, Italy
| | - Ivo Pietro Degiovanni
- Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, 10135, Torino, Italy
| | - Marco Genovese
- INFN - sezione di Torino, Via P. Giuria, 110125, Torino, Italy
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18
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Pusuluk O, Farrow T, Deliduman C, Burnett K, Vedral V. Proton tunnelling in hydrogen bonds and its implications in an induced-fit model of enzyme catalysis. Proc Math Phys Eng Sci 2018. [DOI: 10.1098/rspa.2018.0037] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The role of proton tunnelling in biological catalysis is investigated here within the frameworks of quantum information theory and thermodynamics. We consider the quantum correlations generated through two hydrogen bonds between a substrate and a prototypical enzyme that first catalyses the tautomerization of the substrate to move on to a subsequent catalysis, and discuss how the enzyme can derive its catalytic potency from these correlations. In particular, we show that classical changes induced in the binding site of the enzyme spreads the quantum correlations among all of the four hydrogen-bonded atoms thanks to the directionality of hydrogen bonds. If the enzyme rapidly returns to its initial state after the binding stage, the substrate ends in a new transition state corresponding to a quantum superposition. Open quantum system dynamics can then naturally drive the reaction in the forward direction from the major tautomeric form to the minor tautomeric form without needing any additional catalytic activity. We find that in this scenario the enzyme lowers the activation energy so much that there is no energy barrier left in the tautomerization, even if the quantum correlations quickly decay.
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Affiliation(s)
- Onur Pusuluk
- Department of Physics, İstanbul Technical University, Maslak, Istanbul 34469, Turkey
| | - Tristan Farrow
- Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543, Singapore
| | - Cemsinan Deliduman
- Department of Physics, Mimar Sinan Fine Arts University, Bomonti, Istanbul 34380, Turkey
| | - Keith Burnett
- University of Sheffield, Western Bank, Sheffield S10 2TN, UK
| | - Vlatko Vedral
- Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543, Singapore
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19
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Zhang K, Ma J, Zhang X, Thompson J, Vedral V, Kim K, Gu M. Operational effects of the UNOT gate on classical and quantum correlations. Sci Bull (Beijing) 2018; 63:765-770. [PMID: 36658950 DOI: 10.1016/j.scib.2018.05.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 05/03/2018] [Accepted: 05/08/2018] [Indexed: 01/21/2023]
Abstract
The NOT gate that flips a classical bit is ubiquitous in classical information processing. However its quantum analogue, the universal NOT (UNOT) gate that flips a quantum spin in any alignment into its antipodal counterpart is strictly forbidden. Here we explore the connection between this discrepancy and how UNOT gates affect classical and quantum correlations. We show that while a UNOT gate always preserves classical correlations between two spins, it can non-locally increase or decrease their shared discord in ways that allow violation of the data processing inequality. We experimentally illustrate this using a multi-level trapped 171Yb+ ion that allows simulation of anti-unitary operations.
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Affiliation(s)
- Kuan Zhang
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China.
| | - Jiajun Ma
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China; Department of Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, UK
| | - Xiang Zhang
- Department of Physics, Renmin University of China, Beijing 100872, China; Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - Jayne Thompson
- Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore
| | - Vlatko Vedral
- Department of Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, UK; Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore; Department of Physics, National University of Singapore, Singapore 117551, Singapore; Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - Kihwan Kim
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China.
| | - Mile Gu
- School of Mathematical and Physical Sciences, Nanyang Technological University, Singapore 637371, Singapore; Complexity Institute, Nanyang Technological University, Singapore 637335, Singapore; Centre for Quantum Technologies, National University of Singapore, Singapore 117543, Singapore; Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China.
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20
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Yunger Halpern N, Garner AJP, Dahlsten OCO, Vedral V. Maximum one-shot dissipated work from Rényi divergences. Phys Rev E 2018; 97:052135. [PMID: 29906852 DOI: 10.1103/physreve.97.052135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2017] [Indexed: 06/08/2023]
Abstract
Thermodynamics describes large-scale, slowly evolving systems. Two modern approaches generalize thermodynamics: fluctuation theorems, which concern finite-time nonequilibrium processes, and one-shot statistical mechanics, which concerns small scales and finite numbers of trials. Combining these approaches, we calculate a one-shot analog of the average dissipated work defined in fluctuation contexts: the cost of performing a protocol in finite time instead of quasistatically. The average dissipated work has been shown to be proportional to a relative entropy between phase-space densities, to a relative entropy between quantum states, and to a relative entropy between probability distributions over possible values of work. We derive one-shot analogs of all three equations, demonstrating that the order-infinity Rényi divergence is proportional to the maximum possible dissipated work in each case. These one-shot analogs of fluctuation-theorem results contribute to the unification of these two toolkits for small-scale, nonequilibrium statistical physics.
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Affiliation(s)
- Nicole Yunger Halpern
- Institute for Quantum Information and Matter, Caltech, Pasadena, California 91125, USA
| | - Andrew J P Garner
- Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
- Center for Quantum Technologies, National University of Singapore 117543, Republic of Singapore
| | - Oscar C O Dahlsten
- Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
- Institute for Quantum Science and Engineering, and Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
- London Institute for Mathematical Sciences, 35a South Street, Mayfair, London W1K 2XF, United Kingdom
| | - Vlatko Vedral
- Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
- Center for Quantum Technologies, National University of Singapore 117543, Republic of Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542
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21
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Sonar S, Hajdušek M, Mukherjee M, Fazio R, Vedral V, Vinjanampathy S, Kwek LC. Squeezing Enhances Quantum Synchronization. Phys Rev Lett 2018; 120:163601. [PMID: 29756922 DOI: 10.1103/physrevlett.120.163601] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Indexed: 06/08/2023]
Abstract
It is desirable to observe synchronization of quantum systems in the quantum regime, defined by the low number of excitations and a highly nonclassical steady state of the self-sustained oscillator. Several existing proposals of observing synchronization in the quantum regime suffer from the fact that the noise statistics overwhelm synchronization in this regime. Here, we resolve this issue by driving a self-sustained oscillator with a squeezing Hamiltonian instead of a harmonic drive and analyze this system in the classical and quantum regime. We demonstrate that strong entrainment is possible for small values of squeezing, and in this regime, the states are nonclassical. Furthermore, we show that the quality of synchronization measured by the FWHM of the power spectrum is enhanced with squeezing.
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Affiliation(s)
- Sameer Sonar
- Department of Physics, Indian Institute of Technology-Bombay, Powai, Mumbai 400076, India
| | - Michal Hajdušek
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore, Singapore
| | - Manas Mukherjee
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore, Singapore
- Department of Physics, National University Singapore, Singapore 117551, Singapore
- MajuLab, CNRS-UNS-NUS-NTU International Joint Research Unit, Singapore UMI 3654, Singapore
| | - Rosario Fazio
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore, Singapore
- ICTP, Strada Costiera 11, 34151 Trieste, Italy
- NEST, Scuola Normale Superiore and Instituto Nanoscienze-CNR, I-56126 Pisa, Italy
| | - Vlatko Vedral
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore, Singapore
- Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Sai Vinjanampathy
- Department of Physics, Indian Institute of Technology-Bombay, Powai, Mumbai 400076, India
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore, Singapore
| | - Leong-Chuan Kwek
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore, Singapore
- MajuLab, CNRS-UNS-NUS-NTU International Joint Research Unit, Singapore UMI 3654, Singapore
- Institute of Advanced Studies, Nanyang Technological University, Singapore 639673, Singapore
- National Institute of Education, Nanyang Technological University, Singapore 637616, Singapore
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22
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23
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Xiong TP, Yan LL, Zhou F, Rehan K, Liang DF, Chen L, Yang WL, Ma ZH, Feng M, Vedral V. Experimental Verification of a Jarzynski-Related Information-Theoretic Equality by a Single Trapped Ion. Phys Rev Lett 2018; 120:010601. [PMID: 29350940 DOI: 10.1103/physrevlett.120.010601] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2017] [Revised: 11/13/2017] [Indexed: 06/07/2023]
Abstract
Most nonequilibrium processes in thermodynamics are quantified only by inequalities; however, the Jarzynski relation presents a remarkably simple and general equality relating nonequilibrium quantities with the equilibrium free energy, and this equality holds in both the classical and quantum regimes. We report a single-spin test and confirmation of the Jarzynski relation in the quantum regime using a single ultracold ^{40}Ca^{+} ion trapped in a harmonic potential, based on a general information-theoretic equality for a temporal evolution of the system sandwiched between two projective measurements. By considering both initially pure and mixed states, respectively, we verify, in an exact and fundamental fashion, the nonequilibrium quantum thermodynamics relevant to the mutual information and Jarzynski equality.
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Affiliation(s)
- T P Xiong
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
- School of Physics, University of the Chinese Academy of Sciences, Beijing 100049, China
| | - L L Yan
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
| | - F Zhou
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
| | - K Rehan
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
- School of Physics, University of the Chinese Academy of Sciences, Beijing 100049, China
| | - D F Liang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
- Synergetic Innovation Center for Quantum Effects and Applications (SICQEA), Hunan Normal University, Changsha 410081, China
| | - L Chen
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
| | - W L Yang
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
| | - Z H Ma
- Department of Mathematics, Shanghai Jiaotong University, Shanghai 200240, China
| | - M Feng
- State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China
- Synergetic Innovation Center for Quantum Effects and Applications (SICQEA), Hunan Normal University, Changsha 410081, China
- Center for Cold Atom Physics, Chinese Academy of Sciences, Wuhan 430071, China
- Department of Physics, Zhejiang Normal University, Jinhua 321004, China
| | - V Vedral
- Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
- Centre for Quantum Technologies, National University of Singapore, 117543 Singapore, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 Singapore, Singapore
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24
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Marletto C, Vedral V. Gravitationally Induced Entanglement between Two Massive Particles is Sufficient Evidence of Quantum Effects in Gravity. Phys Rev Lett 2017; 119:240402. [PMID: 29286752 DOI: 10.1103/physrevlett.119.240402] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Indexed: 06/07/2023]
Abstract
All existing quantum-gravity proposals are extremely hard to test in practice. Quantum effects in the gravitational field are exceptionally small, unlike those in the electromagnetic field. The fundamental reason is that the gravitational coupling constant is about 43 orders of magnitude smaller than the fine structure constant, which governs light-matter interactions. For example, detecting gravitons-the hypothetical quanta of the gravitational field predicted by certain quantum-gravity proposals-is deemed to be practically impossible. Here we adopt a radically different, quantum-information-theoretic approach to testing quantum gravity. We propose witnessing quantumlike features in the gravitational field, by probing it with two masses each in a superposition of two locations. First, we prove that any system (e.g., a field) mediating entanglement between two quantum systems must be quantum. This argument is general and does not rely on any specific dynamics. Then, we propose an experiment to detect the entanglement generated between two masses via gravitational interaction. By our argument, the degree of entanglement between the masses is a witness of the field quantization. This experiment does not require any quantum control over gravity. It is also closer to realization than detecting gravitons or detecting quantum gravitational vacuum fluctuations.
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Affiliation(s)
- C Marletto
- Clarendon Laboratory, Department of Physics, University of Oxford, England
| | - V Vedral
- Clarendon Laboratory, Department of Physics, University of Oxford, England
- Centre for Quantum Technologies, National University of Singapore, Block S15, 3 Science Drive 2, Singapore
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25
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Coles D, Flatten LC, Sydney T, Hounslow E, Saikin SK, Aspuru-Guzik A, Vedral V, Tang JKH, Taylor RA, Smith JM, Lidzey DG. A Nanophotonic Structure Containing Living Photosynthetic Bacteria. Small 2017; 13:1701777. [PMID: 28809455 DOI: 10.1002/smll.201701777] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2017] [Revised: 07/08/2017] [Indexed: 06/07/2023]
Abstract
Photosynthetic organisms rely on a series of self-assembled nanostructures with tuned electronic energy levels in order to transport energy from where it is collected by photon absorption, to reaction centers where the energy is used to drive chemical reactions. In the photosynthetic bacteria Chlorobaculum tepidum, a member of the green sulfur bacteria family, light is absorbed by large antenna complexes called chlorosomes to create an exciton. The exciton is transferred to a protein baseplate attached to the chlorosome, before migrating through the Fenna-Matthews-Olson complex to the reaction center. Here, it is shown that by placing living Chlorobaculum tepidum bacteria within a photonic microcavity, the strong exciton-photon coupling regime between a confined cavity mode and exciton states of the chlorosome can be accessed, whereby a coherent exchange of energy between the bacteria and cavity mode results in the formation of polariton states. The polaritons have energy distinct from that of the exciton which can be tuned by modifying the energy of the optical modes of the microcavity. It is believed that this is the first demonstration of the modification of energy levels within living biological systems using a photonic structure.
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Affiliation(s)
- David Coles
- Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK
| | - Lucas C Flatten
- Department of Materials, University of Oxford, Sheffield, OX1 3PH, UK
| | - Thomas Sydney
- Department of Chemistry, University of Sheffield, Sheffield, S3 7HF, UK
| | - Emily Hounslow
- Department of Chemical and Biological Engineering, University of Sheffield, Sheffield, S1 3JD, UK
| | - Semion K Saikin
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138, USA
- Institute of Physics, Kazan Federal University, Kazan, 420008, Russian Federation
| | - Alán Aspuru-Guzik
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA, 02138, USA
| | - Vlatko Vedral
- Department of Physics, University of Oxford, Oxford, OX1 3PU, UK
| | - Joseph Kuo-Hsiang Tang
- Department of Chemistry and Biochemistry, Clark University, Worcester, MA, 01610-1477, USA
| | - Robert A Taylor
- Department of Physics, University of Oxford, Oxford, OX1 3PU, UK
| | - Jason M Smith
- Department of Materials, University of Oxford, Sheffield, OX1 3PH, UK
| | - David G Lidzey
- Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK
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26
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27
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Dall'Arno M, Brandsen S, Tosini A, Buscemi F, Vedral V. No-Hypersignaling Principle. Phys Rev Lett 2017; 119:020401. [PMID: 28753334 DOI: 10.1103/physrevlett.119.020401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Indexed: 06/07/2023]
Abstract
A paramount topic in quantum foundations, rooted in the study of the Einstein-Podolsky-Rosen (EPR) paradox and Bell inequalities, is that of characterizing quantum theory in terms of the spacelike correlations it allows. Here, we show that to focus only on spacelike correlations is not enough: we explicitly construct a toy model theory that, while not contradicting classical and quantum theories at the level of spacelike correlations, still displays an anomalous behavior in its timelike correlations. We call this anomaly, quantified in terms of a specific communication game, the "hypersignaling" phenomena. We hence conclude that the "principle of quantumness," if it exists, cannot be found in spacelike correlations alone: nontrivial constraints need to be imposed also on timelike correlations, in order to exclude hypersignaling theories.
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Affiliation(s)
- Michele Dall'Arno
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore
| | - Sarah Brandsen
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore
| | - Alessandro Tosini
- QUIT group, Physics Department, Pavia University, and INFN Sezione di Pavia, via Bassi 6, 27100 Pavia, Italy
| | - Francesco Buscemi
- Graduate School of Informatics, Nagoya University, Chikusa-ku, 464-8601 Nagoya, Japan
| | - Vlatko Vedral
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore
- Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX13PU, United Kingdom
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Abstract
We consider the problem of characterizing the set of input-output correlations that can be generated by an arbitrarily given quantum measurement. Our main result is to provide a closed-form, full characterization of such a set for any qubit measurement, and to discuss its geometrical interpretation. As applications, we further specify our results to the cases of real and complex symmetric, informationally complete measurements and mutually unbiased bases of a qubit, in the presence of isotropic noise. Our results provide the optimal device-independent tests of quantum measurements.
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Affiliation(s)
- Michele Dall'Arno
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2 117543, Singapore
| | - Sarah Brandsen
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2 117543, Singapore
- California Institute of Technology, 1200 E. California Blvd, Pasadena, California 91125, USA
| | - Francesco Buscemi
- Graduate School of Informatics, Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan
| | - Vlatko Vedral
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2 117543, Singapore
- Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX13PU, United Kingdom
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30
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Abstract
Many organisms capitalize on their ability to predict the environment to maximize available free energy and reinvest this energy to create new complex structures. This functionality relies on the manipulation of patterns-temporally ordered sequences of data. Here, we propose a framework to describe pattern manipulators-devices that convert thermodynamic work to patterns or vice versa-and use them to build a "pattern engine" that facilitates a thermodynamic cycle of pattern creation and consumption. We show that the least heat dissipation is achieved by the provably simplest devices, the ones that exhibit desired operational behavior while maintaining the least internal memory. We derive the ultimate limits of this heat dissipation and show that it is generally nonzero and connected with the pattern's intrinsic crypticity-a complexity theoretic quantity that captures the puzzling difference between the amount of information the pattern's past behavior reveals about its future and the amount one needs to communicate about this past to optimally predict the future.
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Affiliation(s)
- Andrew J P Garner
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543, Singapore
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
| | - Jayne Thompson
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543, Singapore
| | - Vlatko Vedral
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543, Singapore
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
- Atomic and Laser Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford OX1 3PU, United Kingdom
- Department of Physics, National University of Singapore, 3 Science Drive 2, Singapore 117543
| | - Mile Gu
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543, Singapore
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084, China
- School of Physical and Mathematical Sciences, Nanyang Technological University, 639673, Singapore
- Complexity Institute, Nanyang Technological University, 639673, Singapore
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31
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Abstract
A crucial point in statistical mechanics is the definition of the notion of thermal equilibrium, which can be given as the state that maximises the von Neumann entropy, under the validity of some constraints. Arguing that such a notion can never be experimentally probed, in this paper we propose a new notion of thermal equilibrium, focused on observables rather than on the full state of the quantum system. We characterise such notion of thermal equilibrium for an arbitrary observable via the maximisation of its Shannon entropy and we bring to light the thermal properties that it heralds. The relation with Gibbs ensembles is studied and understood. We apply such a notion of equilibrium to a closed quantum system and show that there is always a class of observables which exhibits thermal equilibrium properties and we give a recipe to explicitly construct them. Eventually, an intimate connection with the Eigenstate Thermalisation Hypothesis is brought to light.
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Affiliation(s)
- F. Anzà
- Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, UK
| | - V. Vedral
- Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford, OX1 3PU, UK
- Centre for Quantum Technologies, National University of Singapore, 117543, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551, Singapore
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084, Beijing, China
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32
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Zhou F, Yan L, Gong S, Ma Z, He J, Xiong T, Chen L, Yang W, Feng M, Vedral V. Verifying Heisenberg's error-disturbance relation using a single trapped ion. Sci Adv 2016; 2:e1600578. [PMID: 28861461 PMCID: PMC5566201 DOI: 10.1126/sciadv.1600578] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Accepted: 09/20/2016] [Indexed: 06/07/2023]
Abstract
Heisenberg's uncertainty relations have played an essential role in quantum physics since its very beginning. The uncertainty relations in the modern quantum formalism have become a fundamental limitation on the joint measurements of general quantum mechanical observables, going much beyond the original discussion of the trade-off between knowing a particle's position and momentum. Recently, the uncertainty relations have generated a considerable amount of lively debate as a result of the new inequalities proposed as extensions of the original uncertainty relations. We report an experimental test of one of the new Heisenberg's uncertainty relations using a single 40Ca+ ion trapped in a harmonic potential. By performing unitary operations under carrier transitions, we verify the uncertainty relation proposed by Busch, Lahti, and Werner (BLW) based on a general error-trade-off relation for joint measurements on two compatible observables. The positive operator-valued measure, required by the compatible observables, is constructed by single-qubit operations, and the lower bound of the uncertainty, as observed, is satisfied in a state-independent manner. Our results provide the first evidence confirming the BLW-formulated uncertainty at a single-spin level and will stimulate broad interests in various fields associated with quantum mechanics.
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Affiliation(s)
- Fei Zhou
- State Key Laboratory of Magnetic Resonance and Atomic and
Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of
Sciences, Wuhan 430071, China
| | - Leilei Yan
- State Key Laboratory of Magnetic Resonance and Atomic and
Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of
Sciences, Wuhan 430071, China
- University of the Chinese Academy of Sciences, Beijing
100049, China
| | - Shijie Gong
- State Key Laboratory of Magnetic Resonance and Atomic and
Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of
Sciences, Wuhan 430071, China
- University of the Chinese Academy of Sciences, Beijing
100049, China
| | - Zhihao Ma
- Department of Mathematics, Shanghai Jiaotong University,
Shanghai 200240, China
| | - Jiuzhou He
- State Key Laboratory of Magnetic Resonance and Atomic and
Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of
Sciences, Wuhan 430071, China
- University of the Chinese Academy of Sciences, Beijing
100049, China
| | - Taiping Xiong
- State Key Laboratory of Magnetic Resonance and Atomic and
Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of
Sciences, Wuhan 430071, China
- University of the Chinese Academy of Sciences, Beijing
100049, China
| | - Liang Chen
- State Key Laboratory of Magnetic Resonance and Atomic and
Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of
Sciences, Wuhan 430071, China
| | - Wanli Yang
- State Key Laboratory of Magnetic Resonance and Atomic and
Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of
Sciences, Wuhan 430071, China
| | - Mang Feng
- State Key Laboratory of Magnetic Resonance and Atomic and
Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of
Sciences, Wuhan 430071, China
- Synergetic Innovation Center for Quantum Effects and
Applications, Hunan Normal University, Changsha 410081, China
| | - Vlatko Vedral
- Department of Physics, Clarendon Laboratory, University
of Oxford, Parks Road, Oxford OX1 3PU, U.K
- Centre for Quantum Technologies, National University of
Singapore, Singapore 117543, Singapore
- Department of Physics, National University of Singapore,
2 Science Drive 3, Singapore 117551, Singapore
- Center for Quantum Information, Institute for
Interdisciplinary Information Sciences, Tsinghua University, Beijing 100084,
China
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33
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Abstract
Recent results in quantum information theory characterize quantum coherence in the context of resource theories. Here, we study the relation between quantum coherence and quantum discord, a kind of quantum correlation which appears even in nonentangled states. We prove that the creation of quantum discord with multipartite incoherent operations is bounded by the amount of quantum coherence consumed in its subsystems during the process. We show how the interplay between quantum coherence consumption and creation of quantum discord works in the preparation of multipartite quantum correlated states and in the model of deterministic quantum computation with one qubit.
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Affiliation(s)
- Jiajun Ma
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084 Beijing, China
- Department of Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Benjamin Yadin
- Department of Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Davide Girolami
- Department of Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Vlatko Vedral
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084 Beijing, China
- Department of Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
- Centre for Quantum Technologies, National University of Singapore, 117543 Singapore, Singapore
- Department of Physics, National University of Singapore, 2 Science Drive 3, 117551 Singapore, Singapore
| | - Mile Gu
- Center for Quantum Information, Institute for Interdisciplinary Information Sciences, Tsinghua University, 100084 Beijing, China
- Centre for Quantum Technologies, National University of Singapore, 117543 Singapore, Singapore
- School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, 637371 Singapore, Singapore
- Complexity Institute, Nanyang Technological University, 18 Nanyang Drive, 637723 Singapore, Singapore
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34
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Abstract
We report an experimental realization of Maxwell's demon in a photonic setup. We show that a measurement at the few-photons level followed by a feed-forward operation allows the extraction of work from intense thermal light into an electric circuit. The interpretation of the experiment stimulates the derivation of an equality relating work extraction to information acquired by measurement. We derive a bound using this relation and show that it is in agreement with the experimental results. Our work puts forward photonic systems as a platform for experiments related to information in thermodynamics.
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Affiliation(s)
- Mihai D Vidrighin
- QOLS, Blackett Laboratory, Imperial College London, London SW7 2BW, United Kingdom
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - Oscar Dahlsten
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
- London Institute for Mathematical Sciences, 35a South Street, Mayfair WIK 2XF, United Kingdom
| | - Marco Barbieri
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
- Dipartimento di Scienze, Università degli Studi Roma Tre, Via della Vasca Navale 84, 00146 Rome, Italy
| | - M S Kim
- QOLS, Blackett Laboratory, Imperial College London, London SW7 2BW, United Kingdom
| | - Vlatko Vedral
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore, Republic of Singapore
| | - Ian A Walmsley
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
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35
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Abstract
Whether many-body objects like organic molecules can exhibit full quantum behaviour, including entanglement, is an open fundamental question. We present a generic theoretical protocol for entangling two organic molecules, such as dibenzoterrylene in anthracene. The availability of organic dye molecules with two-level energy structures characterised by sharp and intense emission lines are characteristics that position them favourably as candidates for quantum information processing technologies involving single-photons. Quantum entanglement can in principle be generated between several organic molecules by carefully interfering their photoluminescence spectra. Major milestones have been achieved in the last 10 years showcasing entanglement in diverse systems including ions, cold atoms, superconductors, photons, quantum dots and NV-centres in diamond, but not yet in molecules.
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Affiliation(s)
- T Farrow
- Atomic & Laser Physics, Clarendon Laboratory, University of Oxford, OX1 3PU, UK.
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36
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You JB, Shao XQ, Tong QJ, Chan AH, Oh CH, Vedral V. Majorana transport in superconducting nanowire with Rashba and Dresselhaus spin-orbit couplings. J Phys Condens Matter 2015; 27:225302. [PMID: 25984649 DOI: 10.1088/0953-8984/27/22/225302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
The tunneling experiment is a key technique for detecting Majorana fermion (MF) in solid state systems. We use Keldysh non-equilibrium Green function method to study two-lead tunneling in superconducting nanowire with Rashba and Dresselhaus spin-orbit couplings. A zero-bias dc conductance peak appears in our setup which signifies the existence of MF and is in accordance with previous experimental results on InSb nanowire. Interestingly, due to the exotic property of MF, there exists a hole transmission channel which makes the currents asymmetric at the left and right leads. The ac current response mediated by MF is also studied here. To discuss the impacts of Coulomb interaction and disorder on the transport property of Majorana nanowire, we use the renormalization group method to study the phase diagram of the wire. It is found that there is a topological phase transition under the interplay of superconductivity and disorder. We find that the Majorana transport is preserved in the superconducting-dominated topological phase and destroyed in the disorder-dominated non-topological insulator phase.
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Affiliation(s)
- Jia-Bin You
- Centre for Quantum Technologies, National University of Singapore, 117543, Singapore
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37
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Orrit M, Evans G, Cordes T, Kratochvilova I, Moerner W, Needham LM, Sekatskii S, Vainer Y, Faez S, Vedral V, Prabal Goswami H, Clark A, Meixner AJ, Piatkowski L, Birkedal V, Sandoghdar V, Skinner GM, Langbein W, Du J, Koberling F, Michaelis J, Shi F, Taylor R, Chowdhury A, Lounis B, van Hulst N, El-Khoury P, Novotny L, Wrachtrup J, Farrow T, Naumov A, Gladush M, Hanson R. Quantum optics, molecular spectroscopy and low-temperature spectroscopy: general discussion. Faraday Discuss 2015; 184:275-303. [DOI: 10.1039/c5fd90088c] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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38
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Abstract
Maxwell's daemon is a popular personification of a principle connecting information gain and extractable work in thermodynamics. A Szilard Engine is a particular hypothetical realization of Maxwell's daemon, which is able to extract work from a single thermal reservoir by measuring the position of particle(s) within the system. Here we investigate the role of particle statistics in the whole process; namely, how the extractable work changes if instead of classical particles fermions or bosons are used as the working medium. We give a unifying argument for the optimal work in the different cases: the extractable work is determined solely by the information gain of the initial measurement, as measured by the mutual information, regardless of the number and type of particles which constitute the working substance.
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Affiliation(s)
- Martin Plesch
- 1] Institute of Physics, Slovak Academy of Sciences, Bratislava, Slovakia [2] Faculty of Informatics, Masaryk University, Brno, Czech Republic [3] Department of Physics, University of Oxford, Clarendon Laboratory, Oxford, OX1 3PU, UK
| | - Oscar Dahlsten
- Department of Physics, University of Oxford, Clarendon Laboratory, Oxford, OX1 3PU, UK
| | - John Goold
- 1] Department of Physics, University of Oxford, Clarendon Laboratory, Oxford, OX1 3PU, UK [2] The Abdus Salam International Centre for Theoretical Physics, 34014 Trieste, Italy
| | - Vlatko Vedral
- 1] Department of Physics, University of Oxford, Clarendon Laboratory, Oxford, OX1 3PU, UK [2] Center for Quantum Technology, National University of Singapore, Singapore
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39
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Gu M, Vedral V. Zen and the art of quantum complexity. New Sci 2014. [DOI: 10.1016/s0262-4079(14)62192-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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40
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Abstract
Landauer's principle states that it costs at least kBTln2 of work to reset one bit in the presence of a heat bath at temperature T. The bound of kBTln2 is achieved in the unphysical infinite-time limit. Here we ask what is possible if one is restricted to finite-time protocols. We prove analytically that it is possible to reset a bit with a work cost close to kBTln2 in a finite time. We construct an explicit protocol that achieves this, which involves thermalizing and changing the system's Hamiltonian so as to avoid quantum coherences. Using concepts and techniques pertaining to single-shot statistical mechanics, we furthermore prove that the heat dissipated is exponentially close to the minimal amount possible not just on average, but guaranteed with high confidence in every run. Moreover, we exploit the protocol to design a quantum heat engine that works near the Carnot efficiency in finite time.
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Affiliation(s)
- Cormac Browne
- Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX13PU, United Kingdom
| | - Andrew J P Garner
- Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX13PU, United Kingdom
| | - Oscar C O Dahlsten
- Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX13PU, United Kingdom and Center for Quantum Technologies, National University of Singapore, Singapore 117543, Republic of Singapore
| | - Vlatko Vedral
- Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX13PU, United Kingdom and Center for Quantum Technologies, National University of Singapore, Singapore 117543, Republic of Singapore
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41
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Dahlsten OCO, Garner AJP, Vedral V. The uncertainty principle enables non-classical dynamics in an interferometer. Nat Commun 2014; 5:4592. [PMID: 25105741 DOI: 10.1038/ncomms5592] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 07/04/2014] [Indexed: 11/09/2022] Open
Abstract
The quantum uncertainty principle stipulates that when one observable is predictable there must be some other observables that are unpredictable. The principle is viewed as holding the key to many quantum phenomena and understanding it deeper is of great interest in the study of the foundations of quantum theory. Here we show that apart from being restrictive, the principle also plays a positive role as the enabler of non-classical dynamics in an interferometer. First we note that instantaneous action at a distance should not be possible. We show that for general probabilistic theories this heavily curtails the non-classical dynamics. We prove that there is a trade-off with the uncertainty principle that allows theories to evade this restriction. On one extreme, non-classical theories with maximal certainty have their non-classical dynamics absolutely restricted to only the identity operation. On the other extreme, quantum theory minimizes certainty in return for maximal non-classical dynamics.
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Affiliation(s)
- Oscar C O Dahlsten
- 1] Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX13PU, UK [2] Center for Quantum Technologies, National University of Singapore, Singapore 117543, Republic of Singapore
| | - Andrew J P Garner
- Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX13PU, UK
| | - Vlatko Vedral
- 1] Atomic and Laser Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX13PU, UK [2] Center for Quantum Technologies, National University of Singapore, Singapore 117543, Republic of Singapore
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42
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Abstract
A generic and intuitive model for coherent energy transport in multiple minima systems coupled to a quantum mechanical bath is shown. Using a simple spin-boson system, we illustrate how a generic donor-acceptor system can be brought into resonance using a narrow band of vibrational modes, such that the transfer efficiency of an electron-hole pair (exciton) is made arbitrarily high. Coherent transport phenomena in nature are of renewed interest since the discovery that a photon captured by the light-harvesting complex (LHC) in photosynthetic organisms can be conveyed to a chemical reaction centre with near-perfect efficiency. Classical explanations of the transfer use stochastic diffusion to model the hopping motion of a photo-excited exciton. This accounts inadequately for the speed and efficiency of the energy transfer measured in a series of recent landmark experiments. Taking a quantum mechanical perspective can help capture the salient features of the efficient part of that transfer. To show the versatility of the model, we extend it to a multiple minima system comprising seven-sites, reminiscent of the widely studied Fenna-Matthews-Olson (FMO) light-harvesting complex. We show that an idealised transport model for multiple minima coupled to a narrow-band phonon can transport energy with arbitrarily high efficiency.
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Affiliation(s)
- Tristan Farrow
- 1] Atomic & Laser Physics, Clarendon Laboratory, University of Oxford, OX1 3PU, UK [2] Centre for Quantum Technologies, National University of Singapore, Singapore 117543 [3] Oxford Martin School, Old Indian Institute, University of Oxford, OX1 3BD, UK
| | - Vlatko Vedral
- 1] Atomic & Laser Physics, Clarendon Laboratory, University of Oxford, OX1 3PU, UK [2] Centre for Quantum Technologies, National University of Singapore, Singapore 117543 [3] Oxford Martin School, Old Indian Institute, University of Oxford, OX1 3BD, UK
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43
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Mascarenhas E, Bragança H, Dorner R, França Santos M, Vedral V, Modi K, Goold J. Work and quantum phase transitions: quantum latency. Phys Rev E Stat Nonlin Soft Matter Phys 2014; 89:062103. [PMID: 25019721 DOI: 10.1103/physreve.89.062103] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Indexed: 06/03/2023]
Abstract
We study the physics of quantum phase transitions from the perspective of nonequilibrium thermodynamics. For first-order quantum phase transitions, we find that the average work done per quench in crossing the critical point is discontinuous. This leads us to introduce the quantum latent work in analogy with the classical latent heat of first order classical phase transitions. For second order quantum phase transitions the irreversible work is closely related to the fidelity susceptibility for weak sudden quenches of the system Hamiltonian. We demonstrate our ideas with numerical simulations of first, second, and infinite order phase transitions in various spin chain models.
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Affiliation(s)
- E Mascarenhas
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - H Bragança
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - R Dorner
- Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom and Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - M França Santos
- Departamento de Física, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - V Vedral
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom and Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 and Department of Physics, National University of Singapore, 2 Science Drive 2, Singapore 117543
| | - K Modi
- School of Physics, Monash University, VIC 3800, Australia
| | - J Goold
- The Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, Italy
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44
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Abstract
A Comment on the Letter by S. W. Kim et al., Phys. Rev. Lett. 106, 070401 (2011). The authors of the Letter offer a Reply.
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Affiliation(s)
- Martin Plesch
- Faculty of Informatics, Masaryk University, Brno 602 00, Czech Republic and Institute of Physics, Slovak Academy of Sciences, Bratislava 845 11, Slovakia
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45
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Lanyon BP, Jurcevic P, Hempel C, Gessner M, Vedral V, Blatt R, Roos CF. Experimental generation of quantum discord via noisy processes. Phys Rev Lett 2013; 111:100504. [PMID: 25166643 DOI: 10.1103/physrevlett.111.100504] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Revised: 08/21/2013] [Indexed: 06/03/2023]
Abstract
Quantum systems in mixed states can be unentangled and yet still nonclassically correlated. These correlations can be quantified by the quantum discord and might provide a resource for quantum information processing tasks. By precisely controlling the interaction of two ionic qubits with their environment, we investigate the capability of noise to generate discord. Firstly, we show that noise acting on only one quantum system can generate discord between two. States generated in this way are restricted in terms of the rank of their correlation matrix. Secondly, we show that classically correlated noise processes are capable of generating a much broader range of discordant states with correlation matrices of any rank. Our results show that noise processes prevalent in many physical systems can automatically generate nonclassical correlations and highlight fundamental differences between discord and entanglement.
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Affiliation(s)
- B P Lanyon
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstrasse 21A, 6020 Innsbruck, Austria and Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
| | - P Jurcevic
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstrasse 21A, 6020 Innsbruck, Austria and Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
| | - C Hempel
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstrasse 21A, 6020 Innsbruck, Austria and Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
| | - M Gessner
- Department of Physics, University of California, Berkeley, California 94720, USA and Physikalisches Institut, Universität Freiburg, Hermann-Herder-Strasse 3, D-79104 Freiburg, Germany
| | - V Vedral
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, 117543 Singapore, Singapore and Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom and Department of Physics, National University of Singapore, 2 Science Drive 3, 117542 Singapore, Singapore
| | - R Blatt
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstrasse 21A, 6020 Innsbruck, Austria and Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
| | - C F Roos
- Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstrasse 21A, 6020 Innsbruck, Austria and Institut für Experimentalphysik, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
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46
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Zhang FL, Chen JL, Kwek LC, Vedral V. Requirement of dissonance in assisted optimal state discrimination. Sci Rep 2013; 3:2134. [PMID: 23823646 PMCID: PMC3701169 DOI: 10.1038/srep02134] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Accepted: 06/13/2013] [Indexed: 11/09/2022] Open
Abstract
A fundamental problem in quantum information is to explore what kind of quantum correlations is responsible for successful completion of a quantum information procedure. Here we study the roles of entanglement, discord, and dissonance needed for optimal quantum state discrimination when the latter is assisted with an auxiliary system. In such process, we present a more general joint unitary transformation than the existing results. The quantum entanglement between a principal qubit and an ancilla is found to be completely unnecessary, as it can be set to zero in the arbitrary case by adjusting the parameters in the general unitary without affecting the success probability. This result also shows that it is quantum dissonance that plays as a key role in assisted optimal state discrimination and not quantum entanglement. A necessary criterion for the necessity of quantum dissonance based on the linear entropy is also presented. PACS numbers: 03.65.Ta, 03.67.Mn, 42.50.Dv.
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Affiliation(s)
- Fu-Lin Zhang
- Physics Department, School of Science, Tianjin University, Tianjin 300072, China.
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Vedral V. Quantum information: Are we nearly there yet? New Sci 2013. [DOI: 10.1016/s0262-4079(13)61639-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Vedral V. Quantum information: Killer apps. New Sci 2013. [DOI: 10.1016/s0262-4079(13)61638-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Dorner R, Clark SR, Heaney L, Fazio R, Goold J, Vedral V. Extracting quantum work statistics and fluctuation theorems by single-qubit interferometry. Phys Rev Lett 2013; 110:230601. [PMID: 25167476 DOI: 10.1103/physrevlett.110.230601] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2013] [Revised: 04/29/2013] [Indexed: 06/03/2023]
Abstract
We propose an experimental scheme to verify the quantum nonequilibrium fluctuation relations using current technology. Specifically, we show that the characteristic function of the work distribution for a nonequilibrium quench of a general quantum system can be extracted by Ramsey interferometry of a single probe qubit. Our scheme paves the way for the full characterization of nonequilibrium processes in a variety of quantum systems, ranging from single particles to many-body atomic systems and spin chains. We demonstrate our idea using a time-dependent quench of the motional state of a trapped ion, where the internal pseudospin provides a convenient probe qubit.
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Affiliation(s)
- R Dorner
- Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, United Kingdom and Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom
| | - S R Clark
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom and Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543
| | - L Heaney
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543
| | - R Fazio
- Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543 and NEST, Scuola Normale Superiore and Istituto Nanoscienze-CNR, I-56126 Pisa, Italy
| | - J Goold
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom and Department of Physics, University College Cork, Cork, Ireland
| | - V Vedral
- Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom and Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543
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Dorner R, Goold J, Cormick C, Paternostro M, Vedral V. Emergent thermodynamics in a quenched quantum many-body system. Phys Rev Lett 2012; 109:160601. [PMID: 23215064 DOI: 10.1103/physrevlett.109.160601] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Indexed: 05/25/2023]
Abstract
We study the statistics of the work done, fluctuation relations, and irreversible entropy production in a quantum many-body system subject to the sudden quench of a control parameter. By treating the quench as a thermodynamic transformation we show that the emergence of irreversibility in the nonequilibrium dynamics of closed many-body quantum systems can be accurately characterized. We demonstrate our ideas by considering a transverse quantum Ising model that is taken out of equilibrium by an instantaneous change of the transverse field.
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Affiliation(s)
- R Dorner
- Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ, United Kingdom
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