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Lin MC, Lo PY, Nori F, Chen HB. Precession-induced nonclassicality of the free induction decay of NV centers by a dynamical polarized nuclear spin bath. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:505701. [PMID: 36261040 DOI: 10.1088/1361-648x/ac9bbe] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 10/19/2022] [Indexed: 06/16/2023]
Abstract
The ongoing exploration of the ambiguous boundary between the quantum and the classical worlds has spurred substantial developments in quantum science and technology. Recently, the nonclassicality of dynamical processes has been proposed from a quantum-information-theoretic perspective, in terms of witnessing nonclassical correlations with Hamiltonian ensemble simulations. To acquire insights into the quantum-dynamical mechanism of the process nonclassicality, here we propose to investigate the nonclassicality of the electron spin free-induction-decay process associated with an NV-center. By controlling the nuclear spin precession dynamics via an external magnetic field and nuclear spin polarization, it is possible to manipulate the dynamical behavior of the electron spin, showing a transition between classicality and nonclassicality. We propose an explanation of the classicality-nonclassicality transition in terms of the nuclear spin precession axis orientation and dynamics. We have also performed a series of numerical simulations supporting our findings. Consequently, we can attribute the nonclassical trait of the electron spin dynamics to the behavior of nuclear spin precession dynamics.
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Affiliation(s)
- Mu-Che Lin
- Department of Engineering Science, National Cheng Kung University, Tainan 701401, Taiwan
| | - Ping-Yuan Lo
- Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 300093, Taiwan
| | - Franco Nori
- Quantum Computing Center, and Theoretical Quantum Physics Laboratory, Cluster for Pioneering Research, RIKEN, Wakoshi, Saitama 351-0198, Japan
- Physics Department, University of Michigan, Ann Arbor, MI 48109-1040, United States of America
| | - Hong-Bin Chen
- Department of Engineering Science, National Cheng Kung University, Tainan 701401, Taiwan
- Center for Quantum Frontiers of Research & Technology, NCKU, Tainan 701401, Taiwan
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Biagi N, Francesconi S, Zavatta A, Bellini M. Coherent Superpositions of Photon Creation Operations and Their Application to Multimode States of Light. ENTROPY 2021; 23:e23080999. [PMID: 34441139 PMCID: PMC8391713 DOI: 10.3390/e23080999] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Revised: 07/28/2021] [Accepted: 07/28/2021] [Indexed: 12/03/2022]
Abstract
We present a concise review of recent experimental results concerning the conditional implementation of coherent superpositions of single-photon additions onto distinct field modes. Such a basic operation is seen to give rise to a wealth of interesting and useful effects, from the generation of a tunable degree of entanglement to the birth of peculiar correlations in the photon numbers and the quadratures of multimode, multiphoton, states of light. The experimental investigation of these properties will have an impact both on fundamental studies concerning, for example, the quantumness and entanglement of macroscopic states, and for possible applications in the realm of quantum-enhanced technologies.
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Affiliation(s)
- Nicola Biagi
- Istituto Nazionale di Ottica (CNR-INO), L.go E. Fermi 6, 50125 Firenze, Italy; (N.B.); (S.F.); (A.Z.)
- LENS and Department of Physics & Astronomy, University of Firenze, 50019 Sesto Fiorentino, Italy
| | - Saverio Francesconi
- Istituto Nazionale di Ottica (CNR-INO), L.go E. Fermi 6, 50125 Firenze, Italy; (N.B.); (S.F.); (A.Z.)
- LENS and Department of Physics & Astronomy, University of Firenze, 50019 Sesto Fiorentino, Italy
| | - Alessandro Zavatta
- Istituto Nazionale di Ottica (CNR-INO), L.go E. Fermi 6, 50125 Firenze, Italy; (N.B.); (S.F.); (A.Z.)
- LENS and Department of Physics & Astronomy, University of Firenze, 50019 Sesto Fiorentino, Italy
| | - Marco Bellini
- Istituto Nazionale di Ottica (CNR-INO), L.go E. Fermi 6, 50125 Firenze, Italy; (N.B.); (S.F.); (A.Z.)
- LENS and Department of Physics & Astronomy, University of Firenze, 50019 Sesto Fiorentino, Italy
- Correspondence:
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Canonical Hamiltonian ensemble representation of dephasing dynamics and the impact of thermal fluctuations on quantum-to-classical transition. Sci Rep 2021; 11:10046. [PMID: 33976361 PMCID: PMC8113319 DOI: 10.1038/s41598-021-89400-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Accepted: 04/26/2021] [Indexed: 12/02/2022] Open
Abstract
An important mathematical tool for studying open quantum system theory, which studies the dynamics of a reduced system, is the completely positive and trace-preserving dynamical linear map parameterized by a special parameter-time. Counter-intuitively, akin to the Fourier transform of a signal in time-sequence to its frequency distribution, the time evolution of a reduced system can also be studied in the frequency domain. A recent proposed idea which studies the representation of dynamical processes in the frequency domain, referred to as canonical Hamiltonian ensemble representation (CHER), proved its capability of characterizing the noncalssical traits of the dynamics. Here we elaborate in detail the theoretical foundation within a unified framework and demonstrate several examples for further studies of its properties. In particular, we find that the thermal fluctuations are clearly manifested in the manner of broadening CHER, and consequently rendering the CHER less nonclassical. We also point out the discrepancy between the notions of nonclassicality and non-Markovianity, show multiple CHERs beyond pure dephasing, and, finally, to support the practical viability, propose an experimental realization based upon the free induction decay measurement of nitrogen-vacancy center in diamond.
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Regula B, Lami L, Ferrari G, Takagi R. Operational Quantification of Continuous-Variable Quantum Resources. PHYSICAL REVIEW LETTERS 2021; 126:110403. [PMID: 33798371 DOI: 10.1103/physrevlett.126.110403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2020] [Accepted: 02/08/2021] [Indexed: 06/12/2023]
Abstract
The diverse range of resources which underlie the utility of quantum states in practical tasks motivates the development of universally applicable methods to measure and compare resources of different types. However, many of such approaches were hitherto limited to the finite-dimensional setting or were not connected with operational tasks. We overcome this by introducing a general method of quantifying resources for continuous-variable quantum systems based on the robustness measure, applicable to a plethora of physically relevant resources such as optical nonclassicality, entanglement, genuine non-Gaussianity, and coherence. We demonstrate in particular that the measure has a direct operational interpretation as the advantage enabled by a given state in a class of channel discrimination tasks. We show that the robustness constitutes a well-behaved, bona fide resource quantifier in any convex resource theory, contrary to a related negativity-based measure known as the standard robustness. Furthermore, we show the robustness to be directly observable-it can be computed as the expectation value of a single witness operator-and establish general methods for evaluating the measure. Explicitly applying our results to the relevant resources, we demonstrate the exact computability of the robustness for several classes of states.
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Affiliation(s)
- Bartosz Regula
- School of Physical and Mathematical Sciences, Nanyang Technological University, 637371, Singapore
| | - Ludovico Lami
- Institut für Theoretische Physik und IQST, Universität Ulm, Albert-Einstein-Allee 11, D-89069 Ulm, Germany
| | - Giovanni Ferrari
- Institut für Theoretische Physik und IQST, Universität Ulm, Albert-Einstein-Allee 11, D-89069 Ulm, Germany
- Dipartimento di Fisica e Astronomia Galileo Galilei, Università degli studi di Padova, via Marzolo 8, 35131 Padova, Italy
| | - Ryuji Takagi
- School of Physical and Mathematical Sciences, Nanyang Technological University, 637371, Singapore
- Center for Theoretical Physics and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Biagi N, Costanzo LS, Bellini M, Zavatta A. Entangling Macroscopic Light States by Delocalized Photon Addition. PHYSICAL REVIEW LETTERS 2020; 124:033604. [PMID: 32031852 DOI: 10.1103/physrevlett.124.033604] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Indexed: 06/10/2023]
Abstract
We present a scheme, based on the delocalized heralded addition of a single photon, to entangle two or more distinct field modes, each containing arbitrary light states. A high degree of entanglement can in principle endure light states of macroscopic intensities and is expected to be particularly robust against losses. We experimentally establish and measure significant entanglement between two identical weak laser pulses containing up to 60 photons each.
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Affiliation(s)
- Nicola Biagi
- Istituto Nazionale di Ottica (CNR-INO), L.go E. Fermi 6, 50125 Florence, Italy and LENS and Department of Physics & Astronomy, University of Firenze, 50019 Sesto Fiorentino, Florence, Italy
| | - Luca S Costanzo
- Istituto Nazionale di Ottica (CNR-INO), L.go E. Fermi 6, 50125 Florence, Italy and LENS and Department of Physics & Astronomy, University of Firenze, 50019 Sesto Fiorentino, Florence, Italy
| | - Marco Bellini
- Istituto Nazionale di Ottica (CNR-INO), L.go E. Fermi 6, 50125 Florence, Italy and LENS and Department of Physics & Astronomy, University of Firenze, 50019 Sesto Fiorentino, Florence, Italy
| | - Alessandro Zavatta
- Istituto Nazionale di Ottica (CNR-INO), L.go E. Fermi 6, 50125 Florence, Italy and LENS and Department of Physics & Astronomy, University of Firenze, 50019 Sesto Fiorentino, Florence, Italy
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Abstract
One of the central problems in quantum theory is to characterize, detect, and quantify quantumness in terms of classical strategies. Dephasing processes, caused by non-dissipative information exchange between quantum systems and environments, provides a natural platform for this purpose, as they control the quantum-to-classical transition. Recently, it has been shown that dephasing dynamics itself can exhibit (non)classical traits, depending on the nature of the system-environment correlations and the related (im)possibility to simulate these dynamics with Hamiltonian ensembles–the classical strategy. Here we establish the framework of detecting and quantifying the nonclassicality for pure dephasing dynamics. The uniqueness of the canonical representation of Hamiltonian ensembles is shown, and a constructive method to determine the latter is presented. We illustrate our method for qubit, qutrit, and qubit-pair pure dephasing and describe how to implement our approach with quantum process tomography experiments. Our work is readily applicable to present-day quantum experiments. The presence of processes that cannot be simulated classically in open quantum system dynamics is acknowledged, but an exact quantifier for this non-classical character is still missing. Here, the authors provide a quantitative measure of non-classicality for purely dephasing evolutions.
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Chen HB, Gneiting C, Lo PY, Chen YN, Nori F. Simulating Open Quantum Systems with Hamiltonian Ensembles and the Nonclassicality of the Dynamics. PHYSICAL REVIEW LETTERS 2018; 120:030403. [PMID: 29400538 DOI: 10.1103/physrevlett.120.030403] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2017] [Indexed: 06/07/2023]
Abstract
The incoherent dynamical properties of open quantum systems are generically attributed to an ongoing correlation between the system and its environment. Here, we propose a novel way to assess the nature of these system-environment correlations by examining the system dynamics alone. Our approach is based on the possibility or impossibility to simulate open-system dynamics with Hamiltonian ensembles. As we show, such (im)possibility to simulate is closely linked to the system-environment correlations. We thus define the nonclassicality of open-system dynamics in terms of the nonexistence of a Hamiltonian-ensemble simulation. This classifies any nonunital open-system dynamics as nonclassical. We give examples for open-system dynamics that are unital and classical, as well as unital and nonclassical.
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Affiliation(s)
- Hong-Bin Chen
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
| | - Clemens Gneiting
- Quantum Condensed Matter Research Group, RIKEN, Wako-shi, Saitama 351-0198, Japan
| | - Ping-Yuan Lo
- Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan
| | - Yueh-Nan Chen
- Department of Physics, National Cheng Kung University, Tainan 70101, Taiwan
- Physics Division, National Center for Theoretical Sciences, Hsinchu 30013, Taiwan
| | - Franco Nori
- Quantum Condensed Matter Research Group, RIKEN, Wako-shi, Saitama 351-0198, Japan
- Physics Department, University of Michigan, Ann Arbor, Michigan 48109-1040, USA
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