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- PublicationOpen AccessAll-versus-nothing proof of Einstein-Podolsky-Rosen steering(Springer, 2013)
;Chen, Jing-Ling ;Ye, Xiang-Jun ;Wu, Chunfeng ;Su, Hong-Yi ;Cabello, Adan; Oh, Choo HiapShow more Einstein-Podolsky-Rosen steering is a form of quantum nonlocality intermediate between entanglement and Bell nonlocality. Although Schro¨dinger already mooted the idea in 1935, steering still defies a complete understanding. In analogy to ‘‘all-versus-nothing’’ proofs of Bell nonlocality, here we present a proof of steering without inequalities rendering the detection of correlations leading to a violation of steering inequalities unnecessary. We show that, given any two-qubit entangled state, the existence of certain projective measurement by Alice so that Bob’s normalized conditional states can be regarded as two different pure states provides a criterion for Alice-to-Bob steerability. Asteering inequality equivalent to the all-versus-nothing proof is also obtained. Our result clearly demonstrates that there exist many quantum states which do not violate any previously known steering inequality but are indeed steerable. Our method offers advantages over the existing methods for experimentally testing steerability, and sheds new light on the asymmetric steering problem.Show more WOS© Citations 65Scopus© Citations 66 371 162 - PublicationOpen AccessAsymmetric multipartite Greenberger-Horne-Zeilinger states and Bell inequalities(2004)
;Gosal, Darwin ;Kaszlikowski, Dagomir; ;Zukowski, MarekOh, Choo HiapShow more We study the multiparticle generalized GHZ states. It has been shown that for an odd number of qubits and for a specific range of parameters, they do not violate any Bell inequality for correlation functions. We show here both analytically and numerically that, nevertheless, such states violate local realism, once a more detailed analysis of the correlations is made than the one allowed by correlation functions. The results imply that multiparticle Clauser-Horne-type inequalities involving probabilities are stronger tools for analyzing violations of local realism in multiparticle systems than inequalities involving the correlation functions.Show more WOS© Citations 2Scopus© Citations 2 161 159 - PublicationOpen AccessBell inequalities for three particles
Show more We present tight Bell inequalities expressed by probabilities for three four- and five-dimensional systems. A tight structure of Bell inequalities for three d-dimensional systems (qudits) is proposed. Some interesting Bell inequalities of three qubits reduced from those of three qudits are also studied.Show more WOS© Citations 16Scopus© Citations 16 366 152 - PublicationOpen AccessBures fidelity of displaced squeezed thermal states
Show more Fidelity has always been an important concept in quantum optics. Recently, it was found that fidelity can also play a key role in quantum information and communication theory. Fidelity can be interpreted as the probability that a decoded message possesses the same information content as the message prior to coding and transmission. In this paper, we give a formula of Bures fidelity for displaced squeezed thermal states directly by the displacement and squeezing parameters and briefly discuss how the results can apply to quantum information theory.Show more WOS© Citations 14Scopus© Citations 18 158 192 - PublicationOpen AccessClauser-Horne inequality for three-state systems(2002)
;Kaszlikowski, Dagomir; ;Chen, Jing-Ling ;Zukowski, MarekOh, Choo HiapShow more We show a new Bell-Clauser-Horne inequality for two entangled three-dimensional quantum systems (so-called qutrits). This inequality is not violated by a maximally entangled state of two qutrits observed through a symmetric three-input- and three-output-port beam splitter only if the amount of noise in the system is greater than (11−63 √ )/2≈0.308. This result is in a perfect agreement with the previous numerical calculations presented in Kaszlikowski et al. [Phys. Rev. Lett. 85, 4418 (2000)]. Moreover, we prove that for noiseless case, the necessary and sufficient condition for the threshold quantum efficiency of detectors below which there is no violation of local realism for the optimal choice of observables is equal to 6(15−43 √ )/59≈0.821. This efficiency result again agrees with the numerical predictions.Show more WOS© Citations 97Scopus© Citations 104 321 256 - PublicationOpen AccessCoincidence Bell inequality for three three-dimensional systems(American Physical Society, 2004)
;Acin, A. ;Chen, Jing-Ling ;Gisin, N. ;Kaszlikowski, Dagomir; ;Oh, Choo HiapZukowski, MarekShow more We construct a Bell inequality for coincidence probabilities on a three three-dimensional (qutrit) system. We show that this inequality is violated when each observer measures two noncommuting observables, defined by the so-called unbiased six-port beam splitter, on a maximally entangled state of two qutrits. The strength of the violation agrees with the numerical results presented by Kaszlikowski et al. , quant-ph/0202019. It is proven that the inequality defines facets of the polytope of local variable models.Show more WOS© Citations 37Scopus© Citations 36 346 173 - PublicationOpen AccessContinuous multipartite entangled state in Wigner representation and violation of the Zukowski-Brukner inequality(American Physical Society, 2005)
;Wu, Chunfeng ;Chen, Jing-Ling; ;Oh, Choo HiapXue, KangShow more We construct an explicit Wigner function for the N-mode squeezed state. Based on a previous observation that the Wigner function describes correlations in the joint measurement of the phase-space displaced parity operator, we investigate the nonlocality of the multipartite entangled state by the violation of the Żukowski-Brukner N-qubit Bell inequality. We find that quantum predictions for such a squeezed state violate these inequalities by an amount that grows with the number N.Show more WOS© Citations 9Scopus© Citations 9 327 178 - PublicationOpen AccessCorrelation-function Bell inequality with improved visibility for three qubits
Show more We construct a Bell inequality in terms of correlation functions for three qubits. The inequality is violated by quantum mechanics for all pure entangled states of three qubits. The strength of the violation for the GHZ state is stronger than the result given by Chen et al. [ Phys. Rev. Lett. 93, 140407 (2004)] , indicating that our three-qubit Bell inequality is more resistant to noise than those presented in the literature and hence is more useful in its practical applications.Show more WOS© Citations 9Scopus© Citations 9 158 159 - PublicationOpen AccessEffective Hamiltonian approach to adiabatic approximation in open systems
Show more The adiabatic approximation in open systems is formulated through the effective Hamiltonian approach. By introducing an ancilla, we embed the open system dynamics into a non-Hermitian quantum dynamics of a composite system, the adiabatic evolution of the open system is then defined as the adiabatic dynamics of the composite system. Validity and invalidity conditions for this approximation are established and discussed. A High-order adiabatic approximation for open systems is introduced. As an example, the adiabatic condition for an open spin- 1 2 particle in time-dependent magnetic fields is analyzed.Show more WOS© Citations 33Scopus© Citations 34 137 110 - PublicationOpen AccessElectronic entanglement purification scheme enhanced by charge detections
Show more We present an entanglement purification scheme for the mixed entangled states of electrons with the aid of charge detections. Our scheme adopts the electronic polarizing beam splitters rather than the controlled-NOT (CNOT) operations, but the total successful probability of our scheme can reach the quantity as large as that of the CNOT-operation-based protocol and twice as large as that of linear-optics-based protocol for the purification of photonic entangled states. Thus our scheme can achieve a high successful prabability without the usage of CNOT operations.Show more WOS© Citations 39Scopus© Citations 41 125 108 - PublicationOpen AccessEntangled three-state systems violate local realism more strongly than qubits: An analytical proof(American Physical Society, 2001)
;Chen, Jing-Ling ;Kaszlikowski, Dagomir; ;Oh, Choo HiapZukowski, MarekShow more In Kaszlikowski et al. [Phys. Rev. Lett. 85, 4418 (2000), it has been shown numerically that the violation of local realism for two maximally entangled N-dimensional (3≤N) quantum objects is stronger than for two maximally entangled qubits and grows with N. In this paper, we present the analytical proof of this fact for N=3.Show more WOS© Citations 55Scopus© Citations 60 126 120 - PublicationOpen AccessAn experimental observation of geometric phases for mixed states using NMR interferometry(2003)
;Du, Jiangfeng ;Zou, Ping ;Shi, Mingjun; ;Pan, Jian-Wei ;Oh, Choo Hiap ;Ekert, Artur K. ;Oi, Daniel K. L.Ericsson, MarieShow more Examples of geometric phases abound in many areas of physics. They offer both fundamental insights into many physical phenomena and lead to interesting practical implementations. One of them, as indicated recently, might be an inherently fault-tolerant quantum computation. This, however, requires to deal with geometric phases in the presence of noise and interactions between different physical subsystems. Despite the wealth of literature on the subject of geometric phases very little is known about this very important case. Here we report the first experimental study of geometric phases for mixed quantum states. We show how different they are from the well understood, noiseless, pure-state case.Show more WOS© Citations 129Scopus© Citations 129 169 127 - PublicationOpen AccessExperimental quantum cloning with prior partial information(2005)
;Du, Jiangfeng ;Durt, Thomas ;Zou, Ping ;Li, Hui; ;Lai, C. H. ;Oh, Choo HiapEkert, Artur K.Show more When prior partial information about a state to be cloned is available, it can be cloned with a fidelity higher than that of universal quantum cloning. We experimentally verify this intriguing relationship between the cloning fidelity and the prior information by reporting the first experimental optimal quantum state-dependent cloning, using nuclear magnetic resonance techniques. Our experiments may further have important implications into many quantum information processing protocols.Show more WOS© Citations 111Scopus© Citations 110 315 122 - PublicationOpen AccessExperimental quantum multimeter and one-qubit fingerprinting(2006)
;Du, Jiangfeng ;Zou, Ping ;Peng, Xinhua ;Oi, Daniel K. L.; ;Oh, Choo HiapEkert, Artur K.Show more There has been much recent effort to realize quantum devices in many different physical systems. Among them, nuclear magnetic resonance (NMR) has been the first to demonstrate nontrivial quantum algorithms with small numbers of qubits and hence is a prototype for the key ingredients needed to build quantum computers. An important building block in many quantum applications is the scattering circuit, which can be used as a quantum multimeter to perform various quantum information processing tasks directly without recourse to quantum tomography. We implement in NMR a three-qubit version of the multimeter and also demonstrate a single-qubit fingerprinting.Show more WOS© Citations 22Scopus© Citations 23 339 239 - PublicationOpen AccessFractional spin Hall effect in atomic Bose gases(2009)
;Liu, Xiong-Jun ;Liu, Xin; Oh, Choo HiapShow more We propose fractional spin Hall effect (FSHE) by coupling pseudospin states of cold bosonic atoms to optical fields. The present scheme is an extension to interacting bosonic system of the recent work [X.-J. Liu, X. Liu, L. C. Kwek, and C. H. Oh, Phys. Rev. Lett. 98, 026602 (2007) and S.-L. Zhu, H. Fu, C.-J. Wu, S.-C. Zhang, and L.-M. Duan, Phys. Rev. Lett. 97, 240401 (2006)] on optically induced spin Hall effect in noninteracting atomic system. The system has two different types of ground states. The first type of ground state is a 1/3-factor Laughlin function and has the property of chiral-antichiral interchange antisymmetry, while the second type is shown to be a 1/4-factor wave function with chiral-antichiral symmetry. The fractional statistics corresponding to the fractional spin Hall states are studied in detail and are discovered to be different from that corresponding to the fractional quantum Hall (FQH) states. Therefore the present FSHE can be distinguished from FQH regime in the measurement.Show more WOS© Citations 10Scopus© Citations 10 122 107 - PublicationOpen AccessGeneral formalism of Hamiltonians for realizing a prescribed evolution of a qubit(2003)
;Tong, Dianmin ;Chen, Jing-Ling; ;Lai, C. H.Oh, Choo HiapShow more We investigate the inverse problem concerning the evolution of a qubit system, specifically we consider how one can establish the Hamiltonians that account for the evolution of a qubit along a prescribed path in the projected Hilbert space. For a given path, there are infinite Hamiltonians which can realize the same evolution. A general form of the Hamiltonians is constructed in which one may select the desired one for implementing a prescribed evolution. This scheme can be generalized to higher dimensional systems.Show more WOS© Citations 3 116 66 - PublicationOpen AccessGeometric phase in open systems: Beyond the Markov approximation and weak coupling limit(American Physical Society, 2006)
;Yi, X. X. ;Tong, Dianmin ;Wang, L. C.; Oh, Choo HiapShow more Beyond the quantum Markov approximation and the weak-coupling limit, we present a general theory to calculate the geometric phase for open systems with and without conserved energy. As an example, the geometric phase for a two-level system coupling both dephasingly and dissipatively to its environment is calculated. Comparison with the results from quantum trajectory analysis is presented and discussed.Show more WOS© Citations 40Scopus© Citations 40 228 135 - PublicationOpen AccessGisin’s theorem for three qubits(2004)
;Chen, Jing-Ling ;Wu, Chunfeng; Oh, Choo HiapShow more We present a Theorem that all generalized Greenberger-Horne-Zeilinger states of a three-qubit system violate a Bell inequality in terms of probabilities. All pure entangled states of a three-qubit system are shown to violate a Bell inequality for probabilities; thus, one has Gisin’s theorem for three qubits.Show more WOS© Citations 74Scopus© Citations 74 151 143 - PublicationOpen AccessKinematic approach to off-diagonal geometric phases of nondegenerate and degenerate mixed states(2005)
;Tong, Dianmin ;Sjöqvist, Erik ;Filipp, Stefan; Oh, Choo HiapShow more Off-diagonal geometric phases have been developed in order to provide information of the geometry of paths that connect noninterfering quantal states. We propose a kinematic approach to off-diagonal geometric phases for pure and mixed states. We further extend the mixed-state concept proposed in [Phys. Rev. Lett. 90, 050403 (2003)] to degenerate density operators. The first- and second-order off-diagonal geometric phases are analyzed for unitarily evolving pairs of pseudopure states.Show more WOS© Citations 13Scopus© Citations 13 324 132 - PublicationOpen AccessKinematic approach to the mixed state geometric phase in nonunitary evolution
Show more A kinematic approach to the geometric phase for mixed quantal states in nonunitary evolution is proposed. This phase is manifestly gauge invariant and can be experimentally tested in interferometry. It leads to well-known results when the evolution is unitary.Show more WOS© Citations 272Scopus© Citations 280 324 132

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