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

Journal of the Physical Society of Japan

Quantum Discord Underlies the Optimal Scheme for Modifying the Overlap between Two States

Luis Roa, Alejandra Maldonado-Trapp, Cristian Ignacio Jara-Figueroa, M. L. Ladrón de Guevara

Published Mar 28, 2014• 3 citations
Publisher

Abstract

The processes for decreasing probabilistically and increasing deterministically the overlap between two quantum states must be assisted by an auxiliary quantum system. The probabilistic scheme is implemented through a unitary-reduction process, while the deterministic one is accomplished only with a joint unitary transformation. In both schemes a unitary operation is responsible for coupling the two involved systems thus introducing correlation between them. In this work we study the quantum correlations required to achieve the probabilistic scheme with optimal probability, and we characterize the quantum correlation involved in the deterministic procedure. We find a that both schemes can be accomplished with quantum discord and without entanglement. In addition, we propose a physical implementation of the probabilistic scheme with twin photons generated in the process of spontaneous parametric down-conversion. The states are encoded in the polarization of a single photon and the auxiliary system becomes its propagation path; the second photon is used for heralded detection.

DOI
10.7566/jpsj.83.044006

Related papers

Quantum discord required for modifying the overlap states

Luis Roa

In the schemes for decreasing probabilistically and increasing deterministically the overlap between two quantum states a unitary operation is responsible for coupling two quantum systems, thus introducing correlation between them. We study the quantum correlations required to achieve the task.

Research in Optical Sciences•Jan 1, 2014•0 citations

Requirement of Dissonance in Assisted Optimal State Discrimination

Fulin Zhang, Jing‐Ling Chen, L. C. Kwek +1 more

A fundamental problem in quantum information is to explore what kind of quantum correlations is responsible for successful completion of a quantum information procedure. Here we study the roles of entanglement, discord, and dissonance needed for optimal quantum state discrimination when the latter is assisted with an auxiliary system. In such process, we present a more general joint unitary transformation than the existing results. The quantum entanglement between a principal qubit and an ancilla is found to be completely unnecessary, as it can be set to zero in the arbitrary case by adjusting the parameters in the general unitary without affecting the success probability. This result also shows that it is quantum dissonance that plays as a key role in assisted optimal state discrimination and not quantum entanglement. A necessary criterion for the necessity of quantum dissonance based on the linear entropy is also presented. PACS numbers: 03.65.Ta, 03.67.Mn, 42.50.Dv.

arXiv:1208.2857•Scientific Reports•Jul 4, 2013•32 citations

Quantum dissonance is rejected in an overlap measurement scheme

Chang‐shui Yu, Jun Zhang, Heng Fan

The overlap measurement scheme accomplishes the evaluation of the overlap of two input quantum states by only measuring an introduced auxiliary qubit, irrespective of the complexity of the two input states. We find a counterintuitive phenomenon that no quantum dissonance can be found in the process of overlap measurement scheme, even though the auxiliary qubit might be entangled, classically correlated, or even uncorrelated with the two input states based on different types of input states. In principle, this provides an opposite but supplementary example to the remarkable algorithm of the deterministic quantum computation with one qubit in which no entanglement is present but quantum dissonance is necessary. Finally, we consider a simple overlap measurement model to demonstrate the continuous change (including potential sudden death of quantum discord) of the input states from entangled to product states by only adjusting some initial parameters.

arXiv:1211.2491•Physical Review A•Nov 13, 2012•9 citations

Unambiguous modification of non-orthogonal quantum states

Fabian A. Torres-Ruiz, J.F. Aguirre, A. Delgado +5 more

A probabilistic method for the unambiguous modification of non-orthogonal quantum states is proposed. This is based on conclusive modifications of the inner product between two pure quantum states in a discrimination-like process. We experimentally implemented this protocol by using two-photon polarization states generated in the process of spontaneous parametric down conversion. In the experiment, for codifying initial quantum states, we consider single photon states and heralded detection. As application, we show that when our protocol is applied to partially entangled states it allows a fine control of the amount of entanglement of the modified states.

•Aug 12, 2008•0 citations

Dissonance is Required for Assisted Optimal State Discrimination

Luis Roa, J. C. Retamal, M. Alid-Vaccarezza

The roles of quantum correlations, entanglement, discord, and dissonance needed for performing unambiguous quantum state discrimination assisted by an auxiliary system are studied. In general, this procedure for conclusive recognition between two nonorthogonal states relies on the availability of entanglement and discord. However, we find that there exist special cases for which the procedure can be successfully achieved without entanglement. In particular, we show that the optimal case for discriminating between two nonorthogonal states prepared with equal a priori probabilities does not require entanglement but quantum dissonance only.

Physical Review Letters•Aug 16, 2011•122 citations

Two-step procedure to discriminate discordant from classical correlated or factorized states

S. Cialdi, Andrea Smirne, Matteo G. A. Paris +2 more

We devise and experimentally realize a procedure capable of detecting and distinguishing quantum discord and classical correlations as well the presence of factorized states in a joint system-environment setting. Our scheme builds on recent theoretical results showing how the distinguishability between two reduced states of a quantum system in a bipartite setting can convey important information about the correlations present in the bipartite state and the interaction between the subsystems. The two addressed subsystems are the polarization and spatial degrees of freedom of the signal beam generated by parametric down-conversion, which are suitably prepared by the idler beam. Different global and local operations allow for the detection of different correlations by studying via state tomography the trace distance behavior between suitable polarization subsystem states.

arXiv:1411.3543•Physical Review A•Nov 4, 2014•32 citations
The processes for decreasing probabilistically and increasing deterministically the overlap between two quantum states must be assisted by an auxiliary quantum system. The probabilistic scheme is implemented through a unitary-reduction process, while the deterministic one is accomplished only with a joint unitary transformation. In both schemes a unitary operation is responsible for coupling the two involved systems thus introducing correlation between them. In this work we study the quantum correlations required to achieve the probabilistic scheme with optimal probability, and we characterize the quantum correlation involved in the deterministic procedure. We find a that both schemes can be accomplished with quantum discord and without entanglement. In addition, we propose a physical implementation of the probabilistic scheme with twin photons generated in the process of spontaneous parametric down-conversion. The states are encoded in the polarization of a single photon and the auxiliary system becomes its propagation path; the second photon is used for heralded detection.
A fundamental problem in quantum information is to explore what kind of quantum correlations is responsible for successful completion of a quantum information procedure. Here we study the roles of entanglement, discord, and dissonance needed for optimal quantum state discrimination when the latter is assisted with an auxiliary system. In such process, we present a more general joint unitary transformation than the existing results. The quantum entanglement between a principal qubit and an ancilla is found to be completely unnecessary, as it can be set to zero in the arbitrary case by adjusting the parameters in the general unitary without affecting the success probability. This result also shows that it is quantum dissonance that plays as a key role in assisted optimal state discrimination and not quantum entanglement. A necessary criterion for the necessity of quantum dissonance based on the linear entropy is also presented. PACS numbers: 03.65.Ta, 03.67.Mn, 42.50.Dv.
The overlap measurement scheme accomplishes the evaluation of the overlap of two input quantum states by only measuring an introduced auxiliary qubit, irrespective of the complexity of the two input states. We find a counterintuitive phenomenon that no quantum dissonance can be found in the process of overlap measurement scheme, even though the auxiliary qubit might be entangled, classically correlated, or even uncorrelated with the two input states based on different types of input states. In principle, this provides an opposite but supplementary example to the remarkable algorithm of the deterministic quantum computation with one qubit in which no entanglement is present but quantum dissonance is necessary. Finally, we consider a simple overlap measurement model to demonstrate the continuous change (including potential sudden death of quantum discord) of the input states from entangled to product states by only adjusting some initial parameters.
A probabilistic method for the unambiguous modification of non-orthogonal quantum states is proposed. This is based on conclusive modifications of the inner product between two pure quantum states in a discrimination-like process. We experimentally implemented this protocol by using two-photon polarization states generated in the process of spontaneous parametric down conversion. In the experiment, for codifying initial quantum states, we consider single photon states and heralded detection. As application, we show that when our protocol is applied to partially entangled states it allows a fine control of the amount of entanglement of the modified states.
The roles of quantum correlations, entanglement, discord, and dissonance needed for performing unambiguous quantum state discrimination assisted by an auxiliary system are studied. In general, this procedure for conclusive recognition between two nonorthogonal states relies on the availability of entanglement and discord. However, we find that there exist special cases for which the procedure can be successfully achieved without entanglement. In particular, we show that the optimal case for discriminating between two nonorthogonal states prepared with equal a priori probabilities does not require entanglement but quantum dissonance only.
We devise and experimentally realize a procedure capable of detecting and distinguishing quantum discord and classical correlations as well the presence of factorized states in a joint system-environment setting. Our scheme builds on recent theoretical results showing how the distinguishability between two reduced states of a quantum system in a bipartite setting can convey important information about the correlations present in the bipartite state and the interaction between the subsystems. The two addressed subsystems are the polarization and spatial degrees of freedom of the signal beam generated by parametric down-conversion, which are suitably prepared by the idler beam. Different global and local operations allow for the detection of different correlations by studying via state tomography the trace distance behavior between suitable polarization subsystem states.