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:quant-ph/0312072 · Physical Review Letters

Measuring Entangled Qutrits and Their Use for Quantum Bit Commitment

Nathan K. Langford, R. B. Dalton, M. Harvey, Jeremy L. O’Brien, Geoff J. Pryde, Alexei Gilchrist, Stephen D. Bartlett, Andrew G. White

Published Jul 26, 2004• 349 citations
arXivHTMLPDF

Abstract

We produce and holographically measure entangled qudits encoded in transverse spatial modes of single photons. With the novel use of a quantum state tomography method that only requires two-state superpositions, we achieve the most complete characterization of entangled qutrits to date. Ideally, entangled qutrits provide better security than qubits in quantum bit commitment: we model the sensitivity of this to mixture and show experimentally and theoretically that qutrits with even a small amount of decoherence cannot offer increased security over qubits.

DOI
10.1103/physrevlett.93.053601

Related papers

Holography, vortices and qudits: encoding quantum information in optical spatial modes

Nathan K. Langford, R. B. Dalton, Alexei Gilchrist +5 more

Using quantum state tomography, we completely characterise entangled qubits and qutrits encoded in photons in different transverse spatial modes. We investigate using such entangled qutrits for quantum bit commitment, the basis of quantum coin flipping.

Conference on Lasers and Electro-Optics•Jan 1, 2004•0 citations

Holography, vortices and qudits: Encoding quantum information in optical spatial modes

Nathan K. Langford, R. B. Dalton, Alexei Gilchrist +5 more

Using quantum state tomography, we completely characterise entangled qubits and qutrits encoded in photons in different transverse spatial modes. We investigate using such entangled qutrits for quantum bit commitment, the basis of quantum coin flipping.

OSA Trends in Optics and Photonics Series•Jan 1, 2004•0 citations

Holography, vortices and qudits: encoding quantum information in optical spatial modes

NK Langford, RB Dalton, Alexei Gilchrist +5 more

Using quantum state tomography, we completely characterise entangled qubits and qutrits encoded in photons in different transverse spatial modes. We investigate using such entangled qutrits for quantum bit commitment, the basis of quantum coin flipping

•May 21, 2004•0 citations

Experimental characterization of two spatial qutrits using entanglement witnesses

A. J. Gutiérrez-Esparza, Wanderson M. Pimenta, Breno Marques +3 more

We present an experimental technique for a complete characterization of entanglement in a two-qutrit state generated using transverse spatial correlations of two parametric down-converted photons. We verify entanglement for a particular case via entanglement witness operators which are decomposed into a sum of local observables of single path and superposition projection operators. Experimentally, these operators are accomplished by using a spatial light modulator and a polarizing beam splitter which allow to modulate the amplitude of individually chosen path states. The quantification of entanglement is computed by the negativity obtained from the expectation values of the entanglement witnesses implemented.

Optics Express•Nov 7, 2012•14 citations

Entanglement witnesses and detection of nonlocal superpositions

A. J. Gutiérrez-Esparza, Wanderson M. Pimenta, Breno Marques +5 more

A complete characterization of entanglement in a two-qutrit state generated using the transverse spatial correlations of two parametric down-converted photons is discussed. We verify entanglement for a particular case via entanglement witness operators which are decomposed into a sum of local observables. Experimentally, these operators are accomplished by using a spatial light modulator and a polarizing beam splitter. The quantification of entanglement is computed by the negativity. We also realize an experiment for the verification of the Schmidt number of quantum correlated photons. This measure of entanglement counts the number of global superpositions of product states which are needed to describe a compound quantum system. For unraveling a certain value of this measure, a family of entanglement and Schmidt number tests is constructed.

Latin America Optics and Photonics Conference•Jan 1, 2014•0 citations

Shaping frequency-entangled qudits

Christof Bernhard, Bänz Bessire, Thomas Feurer +1 more

We demonstrate the creation, characterization, and manipulation of frequency-entangled qudits by shaping the energy spectrum of entangled photons. The generation of maximally entangled qudit states is verified up to dimension $d=4$ through tomographic quantum-state reconstruction. Subsequently, we measure Bell parameters for qubits and qutrits as a function of their degree of entanglement. In agreement with theoretical predictions, we observe that for qutrits the Bell parameter is less sensitive to a varying degree of entanglement than for qubits. For frequency-entangled photons, the dimensionality of a qudit is ultimately limited by the bandwidth of the pump laser and can be on the order of a few millions.

arXiv:1303.6202•Physical Review A•Sep 23, 2013•104 citations
We produce and holographically measure entangled qudits encoded in transverse spatial modes of single photons. With the novel use of a quantum state tomography method that only requires two-state superpositions, we achieve the most complete characterization of entangled qutrits to date. Ideally, entangled qutrits provide better security than qubits in quantum bit commitment: we model the sensitivity of this to mixture and show experimentally and theoretically that qutrits with even a small amount of decoherence cannot offer increased security over qubits.
We present an experimental technique for a complete characterization of entanglement in a two-qutrit state generated using transverse spatial correlations of two parametric down-converted photons. We verify entanglement for a particular case via entanglement witness operators which are decomposed into a sum of local observables of single path and superposition projection operators. Experimentally, these operators are accomplished by using a spatial light modulator and a polarizing beam splitter which allow to modulate the amplitude of individually chosen path states. The quantification of entanglement is computed by the negativity obtained from the expectation values of the entanglement witnesses implemented.
A complete characterization of entanglement in a two-qutrit state generated using the transverse spatial correlations of two parametric down-converted photons is discussed. We verify entanglement for a particular case via entanglement witness operators which are decomposed into a sum of local observables. Experimentally, these operators are accomplished by using a spatial light modulator and a polarizing beam splitter. The quantification of entanglement is computed by the negativity. We also realize an experiment for the verification of the Schmidt number of quantum correlated photons. This measure of entanglement counts the number of global superpositions of product states which are needed to describe a compound quantum system. For unraveling a certain value of this measure, a family of entanglement and Schmidt number tests is constructed.
We demonstrate the creation, characterization, and manipulation of frequency-entangled qudits by shaping the energy spectrum of entangled photons. The generation of maximally entangled qudit states is verified up to dimension d=4d=4d=4 through tomographic quantum-state reconstruction. Subsequently, we measure Bell parameters for qubits and qutrits as a function of their degree of entanglement. In agreement with theoretical predictions, we observe that for qutrits the Bell parameter is less sensitive to a varying degree of entanglement than for qubits. For frequency-entangled photons, the dimensionality of a qudit is ultimately limited by the bandwidth of the pump laser and can be on the order of a few millions.