Programmable discriminator of coherent states: Experimental realization

Bartůšková, Lucie; Cernoch, A; Soubusta, Jan; Dušek, Miloslav

doi:10.1103/physreva.77.034306

Cited by 31 publications

(31 citation statements)

References 23 publications

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“…While the viability of unambiguous state discrimination has been demonstrated in many experiments (see e.g. [62][63][64][65]), the experimental realization of gate discrimination strategies is a rather unexplored territory. A recent experiment demonstrating unambiguous discrimination of two non-orthogonal gates was reported in [66] in the single-query scenario.…”

Section: Resultsmentioning

confidence: 99%

Identification of a reversible quantum gate: assessing the resources

2013

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We assess the resources needed to identify a reversible quantum gate among a finite set of alternatives, including in our analysis both deterministic and probabilistic strategies. Among the probabilistic strategies, we consider unambiguous gate discrimination-where errors are not tolerated but inconclusive outcomes are allowed-and we prove that parallel strategies are sufficient to unambiguously identify the unknown gate with minimum number of queries. This result is used to provide upper and lower bounds on the query complexity and on the minimum ancilla dimension. In addition, we introduce the notion of generalized t-designs, which includes unitary t-designs and group representations as special cases. For gates forming a generalized t-design we give an explicit expression for the maximum probability of correct gate identification and we prove that there is no gap between the performances of deterministic strategies and those of probabilistic strategies. Hence, evaluating of the query complexity of perfect deterministic discrimination is reduced to the easier problem of evaluating the query complexity of unambiguous 4 Identifying an unknown unitary evolution, available as a black box, is a fundamental problem in quantum theory [1][2][3][4][5][6][7][8][9], with a wide range of applications in quantum information and computation. In quantum computation, the problem is known as oracle identification [10][11][12][13][14] and is the core of paradigmatic quantum algorithms such as Grover's [15] and . In quantum information processing, the identification of an unknown unitary gate plays a key role in the stabilizer formalism of quantum error correction [17,18] and in its generalization to unitary error bases [19][20][21][22][23], in the security analysis of quantum cryptographic protocols that encode secret data into unitary gates [24][25][26][27][28][29], New Journal of Physics 15 (2013) 103019 (http://www.njp.org/)

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Section: Resultsmentioning

confidence: 99%

Identification of a reversible quantum gate: assessing the resources

2013

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“…Our receiver cannot reach the regime where states are discriminated without errors. It would however be very interesting (from an experimentalists point of view), to see whether a realistic experimental realisation of our strategy may outperform a practical "error-free" receiver as implemented in ref [22] (or the ideal proposed in Ref. [19]), since the measurements of such a device will also not result in error free data [22].…”

Section: Comparison Of Measurement Strategiesmentioning

confidence: 99%

“…A similar receiver for a set of unknown coherent states was proposed in [20]. The receiver is based on quantum comparison of coherent states [21] and was recently demonstrated for two unknown coherent states [22]. The optimality of the receiver for unknown states is shown in [23].…”

Section: Introductionmentioning

confidence: 99%

Discrimination of optical coherent states using a photon number resolving detector

Wittmann

Andersen

Leuchs

2010

Journal of Modern Optics

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The discrimination of non-orthogonal quantum states with reduced or without errors is a fundamental task in quantum measurement theory. In this work, we investigate a quantum measurement strategy capable of discriminating two coherent states probabilistically with significantly smaller error probabilities than can be obtained using non-probabilistic state discrimination. We find that appropriate postselection of the measurement data of a photon number resolving detector can be used to discriminate two coherent states with small error probability. We compare our new receiver to an optimal intermediate measurement between minimum error discrimination and unambiguous state discrimination.

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“…One further comparison that we can make is with a "classical amplifier" using unambiguous state discrimina tion (USD) [32][33][34] to determine the phase of the coherent states without error. This approach offers the potential of arbitrarily large amplification by creating coherent states with the same phase as the input states, but with any desired magnitude.…”

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confidence: 99%

Experimental Implementation of a Quantum Optical State Comparison Amplifier

et al. 2015

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We present an experimental demonstration of a practical nondeterministic quantum optical amplification scheme that employs two mature technologies, state comparison and photon subtraction, to achieve amplification of known sets of coherent states with high fidelity. The amplifier uses coherent states as a resource rather than single photons, which allows for a relatively simple light source, such as a diode laser, providing an increased rate of amplification. The amplifier is not restricted to low amplitude states. With respect to the two key parameters, fidelity and the amplified state production rate, we demonstrate significant improvements over previous experimental implementations, without the requirement of complex photonic components. Such a system may form the basis of trusted quantum repeaters in nonentanglement-based quantum communications systems with known phase alphabets, such as quantum key distribution or quantum digital signatures.

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Programmable discriminator of coherent states: Experimental realization

Cited by 31 publications

References 23 publications

Identification of a reversible quantum gate: assessing the resources

Identification of a reversible quantum gate: assessing the resources

Discrimination of optical coherent states using a photon number resolving detector

Experimental Implementation of a Quantum Optical State Comparison Amplifier

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