Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:0711.4712 · Physical Review A

Programmable discriminator of coherent states: Experimental realization

Lucie Bartůšková, Antonín Černoch, Jan Soubusta, Miloslav Dušek

Published Mar 28, 2008• 30 citations
arXivHTMLPDF

Abstract

An optical implementation of the recently proposed unambiguous identification of coherent states is presented. Our system works as a programmable discriminator between two, in general nonorthogonal, weak coherent states. The principle of operation lies in the interference of three light beams--two program states and one unknown coherent state which can be equal to either one of the two program states. The experiment is based on fiber optics. Its results confirm theoretical predictions, and the experimental setup can be straightforwardly extended for higher numbers of program states.

DOI
10.1103/physreva.77.034306

Related papers

Experimental realization of a programmable quantum-state discriminator and a phase-covariant quantum multimeter

Jan Soubusta, Antonín Černoch, Jaromı́r Fiurášek +1 more

We present an optical implementation of two programmable quantum measurement devices. The first one serves for unambiguous discrimination of two nonorthogonal states of a qubit. The particular pair of states to be discriminated is specified by the quantum state of a program qubit. The second device can perform von Neumann measurements on a single qubit in any basis located on the equator of the Bloch sphere. Again, the basis is selected by the state of a program qubit. In both cases the data and program qubits are represented by polarization states of photons. The experimental apparatus exploits the fact that two Bell states can be distinguished solely by means of linear optics. The outcome corresponding to the remaining two Bell states represents an inconclusive result.

arXiv:quant-ph/0401166•Physical Review A•May 17, 2004•19 citations

Unambiguous identification of coherent states: Searching a quantum database

Michal Sedlák, Mário Ziman, Ondřej Přibyla +2 more

We consider an unambiguous identification of an unknown coherent state with one of two unknown coherent reference states. Specifically, we consider two modes of an electromagnetic field prepared in unknown coherent states $\ensuremath{\mid}{\ensuremath{\alpha}}_{1}⟩$ and $\ensuremath{\mid}{\ensuremath{\alpha}}_{2}⟩$, respectively. The third mode is prepared either in the state $\ensuremath{\mid}{\ensuremath{\alpha}}_{1}⟩$ or in the state $\ensuremath{\mid}{\ensuremath{\alpha}}_{2}⟩$. The task is to identify (unambiguously) which of the two modes are in the same state. We present a scheme consisting of three beam splitters capable to perform this task. Although we do not prove the optimality, we show that the performance of the proposed setup is better than the generalization of the optimal measurement known for a finite-dimensional case. We show that a single beam splitter is capable to perform an unambiguous quantum state comparison for coherent states optimally. Finally, we propose an experimental setup consisting of $2N\ensuremath{-}1$ beam splitters for unambiguous identification among $N$ unknown coherent states. This setup can be considered as a search in a quantum database. The elements of the database are unknown coherent states encoded in different modes of an electromagnetic field. The task is to specify the two modes that are excited in the same, though unknown, coherent state.

arXiv:0706.1892•Physical Review A•Aug 23, 2007•29 citations

Optical realization of the unambiguous discriminator for unknown quantum states

Xiaohua Wu, Yixi Gong

With a single-photon representation of the quantum states and a multirail optical network for performing the unitary transformation, we give a scheme for an optical implementation of the universal programmable quantum state discriminator that unambiguously discriminates between two unknown states with optimal probability of success.

Physical Review A•Oct 16, 2008•9 citations

Optical Realization of Optimal Unambiguous Discrimination for Pure and Mixed Quantum States

Masoud Mohseni, Aephraim M. Steinberg, János A. Bergou

Quantum mechanics forbids deterministic discrimination among nonorthogonal states. Nonetheless, the capability to distinguish nonorthogonal states unambiguously is an important primitive in quantum information processing. In this work, we experimentally implement generalized measurements in an optical system and demonstrate the first optimal unambiguous discrimination between three nonorthogonal states, with a success rate of 55%, to be compared with the 25% maximum achievable using projective measurements. Furthermore, we present the first realization of unambiguous discrimination between a pure state and a nonorthogonal mixed state.

arXiv:quant-ph/0401002•Physical Review Letters•Nov 9, 2004•119 citations

Unambiguous identification of coherent states. II. Multiple resources

Michal Sedlák, Mário Ziman, Vladimír Bužek +1 more

We analyze unambiguous identification of coherent states of an electromagnetic field. In particular, we study possible generalizations of an optical setup proposed in Sedl\'ak et al. [Phys. Rev. A 76, 022326 (2007)]. We show how the unambiguous identification of coherent states can be performed in a general case when multiple copies of unknown and reference states are available. Under the condition that the experimental setup consists only of linear optical elements and photodetectors, we prove the optimality of the setup. We also investigate whether reference states after the measurement can be ``recovered'' and further used for subsequent unambiguous identification tasks. We show that in spite of the fact that the recovered reference states are disturbed by measurements, they can be repeatedly used for unambiguous identifications. We analyze the influence of particular type of noise in the preparation of the unknown and the reference coherent states on the performance of our unambiguous-identification setup.

arXiv:0901.3206•Physical Review A•Jun 9, 2009•10 citations

Universal Programmable Quantum State Discriminator that is Optimal for Unambiguously Distinguishing between Unknown States

János A. Bergou, Mark S. Hillery

We construct a device that can unambiguously discriminate between two unknown quantum states. The unknown states are provided as inputs, or programs, for the program registers, and a third system, which is guaranteed to be prepared in one of the states stored in the program registers, is fed into the data register of the device. The device will then, with some probability of success, tell us whether the unknown state in the data register matches the state stored in the first or the second program register. We show that the optimal device, i.e., the one that maximizes the probability of success, is universal. It does not depend on the actual unknown states that we wish to discriminate.

arXiv:quant-ph/0504201•Physical Review Letters•Apr 25, 2005•96 citations
An optical implementation of the recently proposed unambiguous identification of coherent states is presented. Our system works as a programmable discriminator between two, in general nonorthogonal, weak coherent states. The principle of operation lies in the interference of three light beams--two program states and one unknown coherent state which can be equal to either one of the two program states. The experiment is based on fiber optics. Its results confirm theoretical predictions, and the experimental setup can be straightforwardly extended for higher numbers of program states.
We present an optical implementation of two programmable quantum measurement devices. The first one serves for unambiguous discrimination of two nonorthogonal states of a qubit. The particular pair of states to be discriminated is specified by the quantum state of a program qubit. The second device can perform von Neumann measurements on a single qubit in any basis located on the equator of the Bloch sphere. Again, the basis is selected by the state of a program qubit. In both cases the data and program qubits are represented by polarization states of photons. The experimental apparatus exploits the fact that two Bell states can be distinguished solely by means of linear optics. The outcome corresponding to the remaining two Bell states represents an inconclusive result.
We consider an unambiguous identification of an unknown coherent state with one of two unknown coherent reference states. Specifically, we consider two modes of an electromagnetic field prepared in unknown coherent states $\ensuremath{\mid}{\ensuremath{\alpha}}_{1}⟩$ and $\ensuremath{\mid}{\ensuremath{\alpha}}_{2}⟩$, respectively. The third mode is prepared either in the state $\ensuremath{\mid}{\ensuremath{\alpha}}_{1}⟩$ or in the state $\ensuremath{\mid}{\ensuremath{\alpha}}_{2}⟩$. The task is to identify (unambiguously) which of the two modes are in the same state. We present a scheme consisting of three beam splitters capable to perform this task. Although we do not prove the optimality, we show that the performance of the proposed setup is better than the generalization of the optimal measurement known for a finite-dimensional case. We show that a single beam splitter is capable to perform an unambiguous quantum state comparison for coherent states optimally. Finally, we propose an experimental setup consisting of $2N\ensuremath{-}1$ beam splitters for unambiguous identification among NNN unknown coherent states. This setup can be considered as a search in a quantum database. The elements of the database are unknown coherent states encoded in different modes of an electromagnetic field. The task is to specify the two modes that are excited in the same, though unknown, coherent state.
Quantum mechanics forbids deterministic discrimination among nonorthogonal states. Nonetheless, the capability to distinguish nonorthogonal states unambiguously is an important primitive in quantum information processing. In this work, we experimentally implement generalized measurements in an optical system and demonstrate the first optimal unambiguous discrimination between three nonorthogonal states, with a success rate of 55%, to be compared with the 25% maximum achievable using projective measurements. Furthermore, we present the first realization of unambiguous discrimination between a pure state and a nonorthogonal mixed state.
We analyze unambiguous identification of coherent states of an electromagnetic field. In particular, we study possible generalizations of an optical setup proposed in Sedl\'ak et al. [Phys. Rev. A 76, 022326 (2007)]. We show how the unambiguous identification of coherent states can be performed in a general case when multiple copies of unknown and reference states are available. Under the condition that the experimental setup consists only of linear optical elements and photodetectors, we prove the optimality of the setup. We also investigate whether reference states after the measurement can be ``recovered'' and further used for subsequent unambiguous identification tasks. We show that in spite of the fact that the recovered reference states are disturbed by measurements, they can be repeatedly used for unambiguous identifications. We analyze the influence of particular type of noise in the preparation of the unknown and the reference coherent states on the performance of our unambiguous-identification setup.
We construct a device that can unambiguously discriminate between two unknown quantum states. The unknown states are provided as inputs, or programs, for the program registers, and a third system, which is guaranteed to be prepared in one of the states stored in the program registers, is fed into the data register of the device. The device will then, with some probability of success, tell us whether the unknown state in the data register matches the state stored in the first or the second program register. We show that the optimal device, i.e., the one that maximizes the probability of success, is universal. It does not depend on the actual unknown states that we wish to discriminate.