Extracting Information from a Qubit by Multiple Observers: Toward a Theory of Sequential State Discrimination

Bergou, János A.; Feldman, Edgar; Hillery, Mark

doi:10.1103/physrevlett.111.100501

Cited by 68 publications

(156 citation statements)

References 14 publications

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“…One also can obtain these results by calculating the limits of (15) and (17). In the limit of θ 0 = θ 1 → 0,…”

Section: Lf Xu Et Almentioning

confidence: 99%

“…Since the solution of |η i for the absence of entanglement in state ρ SA is not unique, we choose the ones satisfying the equations (17)(18)(19)(20), which provides a uniform treatment to the four cases of priori probabilities and overlap. Since the GMQD is not normalized to one and its value for maximally entangled qutrit-qubit states is 0.5, we plot the quantity 2D G (ρ SA ) for the case with equal a priori overlaps in Fig.…”

Section: Lf Xu Et Almentioning

confidence: 99%

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Assisted optimal state discrimination without entanglement

Zhang

Liang

et al. 2014

EPL

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PACS 03.65.Ta -Foundations of quantum mechanics; measurement theory PACS 03.67.Mn -Entanglement measures, witnesses, and other characterizations PACS 42.50.Dv -Quantum state engineering and measurements Abstract -A fundamental problem in quantum information is to explore the roles of different quantum correlations in a quantum information procedure. Recent work [Phys. Rev. Lett., 107 (2011) 080401] shows that the protocol for assisted optimal state discrimination (AOSD) may be implemented successfully without entanglement, but with another correlation, quantum dissonance. However, both the original work and the extension to discrimination of d states [Phys. Rev. A, 85 (2012) 022328] have only proved that entanglement can be absent in the case with equal a priori probabilities. By improving the protocol in [Sci. Rep., 3 (2013) 2134], we investigate this topic in a simple case to discriminate three nonorthogonal states of a qutrit, with positive real overlaps. In our procedure, the entanglement between the qutrit and an auxiliary qubit is found to be completely unnecessary. This result shows that the quantum dissonance may play as a key role in optimal state discrimination assisted by a qubit for more general cases.Introduction. -Quantum correlations contained in composite quantum states play important roles in quantum information processing and have been widely studied from various perspectives. Many concepts have been presented to reflect these correlations, such as quantum entanglement [1], Bell nonlocality [2], and quantum discord [3,4]. Entanglement had been regarded as the only resource for demonstrating the superiority of quantum information processing [1,5]. However, recent studies [6,7] show that the algorithm for deterministic quantum computation with one qubit (DQC1) can surpass the performance of the corresponding classical algorithm in the absence of entanglement between the control qubit and a completely mixed state. The quantum discord, which measures the nonclassical correlations and can exist in a separable state, is regarded to be the key resource in this quantum algorithm and has gained wide attention in recent years. Based on a unified view [8] of quantum and classical correlations, another type of quantum correlations called dissonance was put forward. Quantum dissonance measures the nonclassical correlations with entanglement being completely excluded. For a separable state, its dissonance is exactly

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“…One also can obtain these results by calculating the limits of (15) and (17). In the limit of θ 0 = θ 1 → 0,…”

Section: Lf Xu Et Almentioning

confidence: 99%

Section: Lf Xu Et Almentioning

confidence: 99%

Assisted optimal state discrimination without entanglement

Zhang

Liang

et al. 2014

EPL

View full text Add to dashboard Cite

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“…The problem studied here is closely related to that of sequential measurements on the same quantum system [6][7][8]. Rather surprisingly, it has been shown that one can gain information about the initial state of a system even though a measurement has intervened and changed the state of the system [6,7].…”

Section: Introductionmentioning

confidence: 99%

Retrodiction of a sequence of measurement results in qubit interferometers

Hillery

Koch

2016

Phys. Rev. A

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We study how well we can retrodict results of measurements made on a quantum system if we can make measurements on its final state. We know what measurements were made, but not their results. An initial examination shows that we can gain anywhere from no information to perfect information about the results of previous measurements, depending on the measurements and the initial state of the system. The case of two two-outcome measurements, the second of which is a projective measurement, is examined in some detail. We then look at a model of a qubit interferometer in which measurements are made in order to determine the path the qubit followed. The measurement made on the final state of the qubit depends on the information about previous measurement results that we are trying to determine. One can attempt to find the result of just one of the measurements, all of them, or find a measurement sequence that was not realized. We study all three possibilities.

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“…Quantum entanglement and hyperentanglement are highly important, fundamental, and indefeasible features of quantum mechanics. Entangled states have numerous applications in emerging technologies such as quantum computing [1], quantum cryptography [2,3], quantum teleportation [4][5][6], and quantum algorithms [7,8]. The highly attractive hyperentangled states extend possibilities of quantum technologies, allowing new quantum communication protocols, superdense teleportation [10], and objects with higher dimensionality [9].…”

mentioning

confidence: 99%

“…The considered system should be realizable on a single chip using current waveguide technology in the LiN bO3 platform. [4][5][6], and quantum algorithms [7,8]. The highly attractive hyperentangled states extend possibilities of quantum technologies, allowing new quantum communication protocols, superdense teleportation [10], and objects with higher dimensionality [9].…”

mentioning

confidence: 99%

Modified two-photon interference achieved by the manipulation of entanglement

et al. 2017

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In this theoretical study we demonstrate that entangled states are able to significantly extend the functionality of Hong-Ou-Mandel (HOM) interferometers. By generating a coherent superposition of parametric-down-conversion photons and spatial entanglement in the input channel, the coincidence probability measured at the output changes from a typical HOM-type dip (photon bunching) into much richer patterns including an anti-bunching peak and rapid oscillation fringes with twice the optical frequency. The considered system should be realizable on a single chip using current waveguide technology in the LiN bO3 platform. [4][5][6], and quantum algorithms [7,8]. The highly attractive hyperentangled states extend possibilities of quantum technologies, allowing new quantum communication protocols, superdense teleportation [10], and objects with higher dimensionality [9]. Therefore the generation and application of photon states with a high degree of entanglement and hyperentangled states is an intensely studied topic in quantum optics.An important element in a computational infrastructure based on photons are quantum interferometers which allow to measure the degree of indistinguishability of photons. Such interferometers can be realized using the well-known two-photon Hong-Ou-Mandel (HOM) interference, which was demonstrated in several systems [11][12][13][14][15][16][17].For practical large-scale applications in quantum information processing free-space set-ups are not very reliable because of the experimental complexity that is required to achieve and maintain a precise and stable adjustment between the elements and due to the significant size of such systems. However, due to their small size and high stability integrated quantum optical systems [18] are very promising in this direction. Furthermore, they provide an attractive platform for the realization of a wide range of functionalities including quantum simulations [19,20], boson sampling [21-23], quantum computation, and quantum communication processing [24].In this paper, we propose and analyze a device which can be realized on a single integrated platform and is able to manipulate the two-photon coincidence probability by interference and to create hyperentanglement. The photon pair generation is incorporated into the system using an on-chip parametric-down-conversion (PDC) [25][26][27][28] source. We theoretically show that the creation of spatially-entangled photons in a singlet Bell state is possible in such a device and that the entanglement leads to novel features in the coincidence probability. In particular, different regimes of bunching (HOM-type dips) and anti-bunching (singlet Bell state) and rapid interference fringes corresponding to twice the optical frequency are predicted. Simultaneously, frequency correlations are preserved in the system which leads to the creation a hyperentanglement, see Fig. 1. FIG. 1. Two photons generated in a PDC process have frequency correlations. The creation of spatial entanglement between the photons leads to a hy...

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Extracting Information from a Qubit by Multiple Observers: Toward a Theory of Sequential State Discrimination

Cited by 68 publications

References 14 publications

Assisted optimal state discrimination without entanglement

Assisted optimal state discrimination without entanglement

Retrodiction of a sequence of measurement results in qubit interferometers

Modified two-photon interference achieved by the manipulation of entanglement

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