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

Unambiguous modification of non-orthogonal quantum states

Fabian A. Torres-Ruiz, J.F. Aguirre, A. Delgado, Leonardo Neves, G. Lima, Sebastião Pádua, Luis Roa, C. Saavedra

Published Aug 12, 2008• 0 citations
OpenAlex

Abstract

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.

Related papers

Unambiguous modification of nonorthogonal single- and two-photon polarization states

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

In this paper we propose a probabilistic method which allows an unambiguous modification of two nonorthogonal quantum states. We experimentally implement 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. We show that the application of this protocol to entangled states allows a fine control of the amount of entanglement of the initial state.

arXiv:0808.1730•Physical Review A•May 15, 2009•19 citations

Unambiguous preparation of non-orthogonal quantum states

Fabian A. Torres-Ruiz, J. Aguirre, A. Delgado +4 more

A probabilistic method for the unambiguous preparation of non-orthogonal polarization states is proposed. We show experimentally how this protocol is implemented by using two-photon states generated in the process of down conversion.

International Conference on Quantum Information•Jan 1, 2008•0 citations

Control of quantum interference in the quantum eraser

Leonardo Neves, G. Lima, J Aguirre +3 more

We have implemented an optical quantum eraser with the aim of studying this phenomenon in the context of state discrimination. An interfering single photon is entangled with another one serving as a which-path marker. As a consequence, the visibility of the interference as well as the which-path information are constrained by the overlap (measured by the inner product) between the which-path marker states, which in a more general situation are non-orthogonal. In order to perform which-path or quantum eraser measurements while analysing non-orthogonal states, we resort to a probabilistic method for the unambiguous modification of the inner product between the two states of the which-path marker in a discrimination-like process.

arXiv:0904.4242•New Journal of Physics•Jul 17, 2009•25 citations

Linearly independent pure-state decomposition and quantum state discrimination

Luis Roa, M. Alid-Vaccarezza, Alejandra Maldonado-Trapp

We put the pure-state decomposition mathematical property of a mixed state to a physical test. We present a protocol for preparing two known nonorthogonal quantum states with well-defined a priori probabilities. Hence we characterize all the possible decompositions of a rank-two mixed state by means of the complex overlap between the two involved states. The physical test proposes a scheme for quantum state recognition of one of the two linearly independent states that arise from the decomposition. We find that the two states associated with the balanced pure-state decomposition have the smaller overlap modulus and therefore the smallest probability of being discriminated conclusively, while in the nonconclusive process they have the highest probability of having an error. In addition, we design an experimental scheme that allows discriminating conclusively and optimally two nonorthogonal states prepared with different a priori probabilities. Thus we propose a physical implementation for this linearly independent pure-state decomposition and state discrimination test by using twin photons generated in the process of spontaneous parametric down-conversion. The information state is encoded in a one-photon polarization state, whereas the second single photon is used for heralded detection.

arXiv:1010.5533•Physical Review A•Aug 18, 2011•7 citations

Experimental Engineering of Photonic Quantum Entanglement

Stefanie Barz, G. Cronenberg, Philip John Walther

Entangled photons are a crucial resource for linear optical quantum communication and quantum computation. Besides the remarkable progress of photon state engineering using atomic memories (Kimble (2008); Yuan et al. (2008)) the majority of current experiments is based on the production of photon pairs in the process of spontaneous parametric down-conversion (SPDC), where the entangled photon pair is concluded from post-selection of randomly occurring coincidences. Here we present new insights into the heralded generation of photon states (Barz et al. (2010); Wagenknecht et al. (2010)) that are maximally entangled in polarization (Schrodinger (1935)) with linear optics and standard photon detection from SPDC (Kwiat et al. (1995)). We utilize the down-conversion state corresponding to the generation of three pairs of photons, where the coincident detection of four auxiliary photons unambiguously heralds the successful preparation of the entangled state (Śliwa & Banaszek (2003)). This controlled generation of entangled photon states is a significant step towards the applicability of a linear optics quantum network (Nielsen & Chuang (2000)), in particular for entanglement distribution (Bennett et al. (1996)), entanglement swapping (Kaltenbaek et al. (2009); Pan et al. (1998)), quantum teleportation (Bouwmeester et al. (1997)), quantum cryptography (Bennett & Brassard (1984); Ekert (1991); Jennewein et al. (2000)) and scalable approaches towards photonics-based quantum computing schemes (Browne & Rudolph (2004); Gottesman & Chuang (1999); Knill et al. (2001)).

InTech eBooks•Mar 21, 2012•0 citations

Heralded orthogonalisation of coherent states and their conversion to discrete-variable superpositions

Regina Kruse, Christine Silberhorn, Tim J. Bartley

Abstract The nonorthogonality of coherent states is a fundamental property which prevents them from being perfectly and deterministically discriminated. Here, we present an experimentally feasible protocol for the probabilistic orthogonalisation of a pair of coherent states, independent of their amplitude and phase. In contrast to unambiguous state discrimination, a successful operation of our protocol is heralded without measuring the states. As such, they remain suitable for further manipulation and the obtained orthogonal states serve as a discretevariable basis. Therefore, our protocol doubles as a simple continuous-to-discrete variable converter, which may find application in hybrid continuous-discrete quantum information processing protocols.

arXiv:1702.00200•Quantum Measurements and Quantum Metrology•Dec 20, 2017•2 citations
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.
In this paper we propose a probabilistic method which allows an unambiguous modification of two nonorthogonal quantum states. We experimentally implement 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. We show that the application of this protocol to entangled states allows a fine control of the amount of entanglement of the initial state.
We have implemented an optical quantum eraser with the aim of studying this phenomenon in the context of state discrimination. An interfering single photon is entangled with another one serving as a which-path marker. As a consequence, the visibility of the interference as well as the which-path information are constrained by the overlap (measured by the inner product) between the which-path marker states, which in a more general situation are non-orthogonal. In order to perform which-path or quantum eraser measurements while analysing non-orthogonal states, we resort to a probabilistic method for the unambiguous modification of the inner product between the two states of the which-path marker in a discrimination-like process.
We put the pure-state decomposition mathematical property of a mixed state to a physical test. We present a protocol for preparing two known nonorthogonal quantum states with well-defined a priori probabilities. Hence we characterize all the possible decompositions of a rank-two mixed state by means of the complex overlap between the two involved states. The physical test proposes a scheme for quantum state recognition of one of the two linearly independent states that arise from the decomposition. We find that the two states associated with the balanced pure-state decomposition have the smaller overlap modulus and therefore the smallest probability of being discriminated conclusively, while in the nonconclusive process they have the highest probability of having an error. In addition, we design an experimental scheme that allows discriminating conclusively and optimally two nonorthogonal states prepared with different a priori probabilities. Thus we propose a physical implementation for this linearly independent pure-state decomposition and state discrimination test by using twin photons generated in the process of spontaneous parametric down-conversion. The information state is encoded in a one-photon polarization state, whereas the second single photon is used for heralded detection.
Entangled photons are a crucial resource for linear optical quantum communication and quantum computation. Besides the remarkable progress of photon state engineering using atomic memories (Kimble (2008); Yuan et al. (2008)) the majority of current experiments is based on the production of photon pairs in the process of spontaneous parametric down-conversion (SPDC), where the entangled photon pair is concluded from post-selection of randomly occurring coincidences. Here we present new insights into the heralded generation of photon states (Barz et al. (2010); Wagenknecht et al. (2010)) that are maximally entangled in polarization (Schrodinger (1935)) with linear optics and standard photon detection from SPDC (Kwiat et al. (1995)). We utilize the down-conversion state corresponding to the generation of three pairs of photons, where the coincident detection of four auxiliary photons unambiguously heralds the successful preparation of the entangled state (Śliwa & Banaszek (2003)). This controlled generation of entangled photon states is a significant step towards the applicability of a linear optics quantum network (Nielsen & Chuang (2000)), in particular for entanglement distribution (Bennett et al. (1996)), entanglement swapping (Kaltenbaek et al. (2009); Pan et al. (1998)), quantum teleportation (Bouwmeester et al. (1997)), quantum cryptography (Bennett & Brassard (1984); Ekert (1991); Jennewein et al. (2000)) and scalable approaches towards photonics-based quantum computing schemes (Browne & Rudolph (2004); Gottesman & Chuang (1999); Knill et al. (2001)).
Abstract The nonorthogonality of coherent states is a fundamental property which prevents them from being perfectly and deterministically discriminated. Here, we present an experimentally feasible protocol for the probabilistic orthogonalisation of a pair of coherent states, independent of their amplitude and phase. In contrast to unambiguous state discrimination, a successful operation of our protocol is heralded without measuring the states. As such, they remain suitable for further manipulation and the obtained orthogonal states serve as a discretevariable basis. Therefore, our protocol doubles as a simple continuous-to-discrete variable converter, which may find application in hybrid continuous-discrete quantum information processing protocols.