Experimental investigation of the no-signalling principle in parity–time symmetric theory using an open quantum system

Tang, Jian; Wang, Yi Tao; Yu, Shang; He, De Yong; Xu, Jiankuan; Liu, Bi-Heng; Chen, Geng; Sun, Yong; Sun, Kai; Han, Yong Jian; Li, Chuan Feng; Guo, Guanhua

doi:10.1038/nphoton.2016.144

Cited by 91 publications

(63 citation statements)

References 33 publications

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“…we adopt a Naimark dilation approach [20,22,52] using an extended Hermitian system. The evolution of the total system (including the system s and the ancilla qubit a) |Ψ(t) = |0 a ⊗ |ψ(t) s + |1 a ⊗ |χ(t) s follows a dilated Hamiltonian H [58].…”

Section: Initializationmentioning

confidence: 99%

“…ηH = H † η with a Hermitian invertible linear operator η) [6][7][8][9] can have real spectrum. The discovery has opened a new avenue to intriguing non-Hermitian physics in both classical and quantum systems [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. In particular, the concepts of exceptional point [25][26][27] and PT -phase transition [28,29] lead to important experimental observations such as single-mode lasers [30,31], non-reciprocal light transport [32,33], non-Hermitian topological light steering [34], asymmetric mode switching [35] and topological energy transfer [36] when encircling an exceptional point.…”

mentioning

confidence: 99%

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Quantum Sensing with a Single-Qubit Pseudo-Hermitian System

Chu

Liu

et al. 2020

Phys. Rev. Lett.

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Quantum sensing exploits fundamental features of quantum system to achieve highly efficient measurement of physical quantities. Here, we propose a strategy to realize a single-qubit pseudo-Hermitian sensor from a dilated two-qubit Hermitian system. The pseudo-Hermitian sensor exhibits divergent susceptibility in dynamical evolution that does not necessarily involve exceptional point. We demonstrate its potential advantages to overcome noises that cannot be averaged out by repetitive measurements. The proposal is feasible with the state-of-art experimental capability in a variety of qubit systems, and represents a step towards the application of non-Hermitian physics in quantum sensing.Introduction.-Non-Hermitian Hamiltonians usually have complex energy eigenvalues and do not conserve probabilities, thus presumably only serve as phenomenological descriptions of open quantum system [1,2]. Remarkably, a non-Hermitian Hamiltonian H with an exact PT -symmetry [3-5] and more general pseudo-Hermiticity (i.e. ηH = H † η with a Hermitian invertible linear operator η) [6-9] can have real spectrum. The discovery has opened a new avenue to intriguing non-Hermitian physics in both classical and quantum systems [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. In particular, the concepts of exceptional point [25][26][27] and PT -phase transition [28,29] lead to important experimental observations such as single-mode lasers [30, 31], non-reciprocal light transport [32, 33], non-Hermitian topological light steering [34], asymmetric mode switching [35] and topological energy transfer [36] when encircling an exceptional point.Among a number of important applications, enhancing the sensitivity of energy splitting detection by using exceptional points attracts increasingly intensive theoretical interest [37][38][39][40][41][42]. The unique feature of exceptional point based sensing is the divergent eigenvalue susceptibility arising from the square-root frequency topology around exceptional points [27]. Exceptional point based sensing has been demonstrated in PT -symmetric linear coupled-mode optic systems, with potential applications for single-particle detection [43,44] and optical gyroscope [45]. Nevertheless, the singular behavior of the energy splitting is counteracted by the eigenstate coalescence [46][47][48]. Quantum sensing based on non-Hermitian qubit system without involving exceptional points and its potential advantages remain largely unexplored.In this work, we propose a novel strategy to harness a qubit probe with pseudo-Hermiticity as a resource for quantum sensing by introducing an additional qubit ancilla [49][50][51][52]. The dilated two-qubit Hermitian system, when exposed to a parameter-dependent weak field, reproduces an effective pseudo-Hermitian qubit sensor by postselection, inheriting the influence of the parameter. The eigenstate coalescence without involving exceptional point induces divergent susceptibility in the normalized

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Section: Initializationmentioning

confidence: 99%

mentioning

confidence: 99%

Quantum Sensing with a Single-Qubit Pseudo-Hermitian System

Chu

Liu

et al. 2020

Phys. Rev. Lett.

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“…We note that the evolution = U U for unitary evolution U and = U aU for non-unitary evolution U. Thus, the POVM device can realize unitary evolution and efficiently simulate non-unitary evolution with loss rate a, which is used in many experiments simulating non-unitary systems [7,8]. In application, applying gain operations to the initial system to compensate the loss inŪ can make it an efficient realization of U [7].…”

Section: Implementation Of Quantum Evolution Via Povmmentioning

confidence: 99%

“…Therefore, how to realize quantum evolution is a question with long-standing interests, and the solutions cover from mathematical decomposition and machine learning [1][2][3]. Recently, the rapid development of non-unitary physics initiates new requests for the method to realize non-unitary quantum evolution [4][5][6][7][8][9][10][11][12][13][14]. In experiments, non-unitarity of quantum evolution is always realized via introducing specific loss to the system [7,8].…”

Section: Introductionmentioning

confidence: 99%

“…Recently, the rapid development of non-unitary physics initiates new requests for the method to realize non-unitary quantum evolution [4][5][6][7][8][9][10][11][12][13][14]. In experiments, non-unitarity of quantum evolution is always realized via introducing specific loss to the system [7,8]. However, a universal method to realize arbitrary non-unitary evolution, i.e., when and how to introduce loss, is imperative for studying non-unitary physics.…”

Section: Introductionmentioning

confidence: 99%

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Quantum walk as generalized evolution and measurement device

Zhan

2019

J. Phys. Commun.

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We show that arbitrary quantum evolution, both unitary and non-unitary ones, can be efficiently realized via one-dimensional quantum walk. This is done based on the equivalence between quantum evolution and positive-operated valued measurements, and an algorithm of properly controlling onedimensional discrete-time quantum walk to realize arbitrary positive-operated valued measurements. Furthermore, our method based on one-dimensional quantum walk can be easily generalized to other platforms Our method enriches technics for quantum information processes, and the applications of quantum walk.

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Parity‐Time Symmetry in Non‐Hermitian Complex Optical Media

et al. 2019

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The explorations of the quantum-inspired symmetries in optical and photonic systems have witnessed immense research interests both fundamentally and technologically in a wide range of subjects of physics and engineering. One of the principal emerging fields in this context is non-Hermitian physics based on parity-time symmetry, originally proposed in the studies pertaining to quantum mechanics and quantum field theory, recently ramified into diverse set of areas, particularly in optics and photonics. The intriguing physical effects enabled by non-Hermitian physics and PT symmetry have enhanced significant applications prospects and engineering of novel materials. In addition, it has observed increasing research interests in many emerging directions beyond optics and photonics. This Review paper attempts to bring together the state of the art developments in the field of complex non-Hermitian physics based on PT symmetry in various physical settings along with elucidating key concepts and background and a detailed perspective on new emerging directions. It can be anticipated that this trendy field of interest can be indispensable in providing new perspectives in maneuvering the flow of light in the diverse physical platforms in optics, photonics, condensed matter, opto-electronics and beyond, and offer distinctive applications prospects in novel functional materials.

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Experimental investigation of the no-signalling principle in parity–time symmetric theory using an open quantum system

Cited by 91 publications

References 33 publications

Quantum Sensing with a Single-Qubit Pseudo-Hermitian System

Quantum Sensing with a Single-Qubit Pseudo-Hermitian System

Quantum walk as generalized evolution and measurement device

Parity‐Time Symmetry in Non‐Hermitian Complex Optical Media

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