Determining the quantum expectation value by measuring a single photon

Fabrizio Piacentini; Alessio Avella; Enrico Rebufello; Rudi Lussana; Federica Villa; Alberto Tosi; Marco Gramegna; Giorgio Brida; Eliahu Cohen; Lev Vaidman; Ivo P. Degiovanni; Marco Genovese

doi:10.1038/nphys4223

Determining the quantum expectation value by measuring a single photon

Fabrizio Piacentini
, Alessio Avella
, Enrico Rebufello
, Rudi Lussana
, Federica Villa
, Alberto Tosi
, Marco Gramegna
, Giorgio Brida
, Eliahu Cohen
, Lev Vaidman
, Ivo P. Degiovanni
, Marco Genovese

Istituto Nazionale di Ricerca Metrologica
Polytechnic University of Turin
Polytechnic University of Milan
University of Bristol
Tel Aviv University

Research output: Contribution to journal › Article › peer-review

55 Scopus citations

Abstract

One description provides only probabilities for obtaining various eigenvalues of a quantum variable. The eigenvalues and the corresponding probabilities specify the expectation value of a physical observable, which is known to be a statistical property of an ensemble of quantum systems. In contrast to this paradigm, here we demonstrate a method for measuring the expectation value of a physical variable on a single particle, namely, the polarization of a single protected photon. This realization of quantum protective measurements could find applications in the foundations of quantum mechanics and quantum-enhanced measurements.

Original language	English
Pages (from-to)	1191-1194
Number of pages	4
Journal	Nature Physics
Volume	13
Issue number	12
DOIs	https://doi.org/10.1038/nphys4223
State	Published - 1 Dec 2017
Externally published	Yes

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10.1038/nphys4223

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author = "Fabrizio Piacentini and Alessio Avella and Enrico Rebufello and Rudi Lussana and Federica Villa and Alberto Tosi and Marco Gramegna and Giorgio Brida and Eliahu Cohen and Lev Vaidman and Degiovanni, \{Ivo P.\} and Marco Genovese",

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AU - Piacentini, Fabrizio

AU - Avella, Alessio

AU - Rebufello, Enrico

AU - Lussana, Rudi

AU - Villa, Federica

AU - Tosi, Alberto

AU - Gramegna, Marco

AU - Brida, Giorgio

AU - Cohen, Eliahu

AU - Vaidman, Lev

AU - Degiovanni, Ivo P.

AU - Genovese, Marco

PY - 2017/12/1

Y1 - 2017/12/1

N2 - One description provides only probabilities for obtaining various eigenvalues of a quantum variable. The eigenvalues and the corresponding probabilities specify the expectation value of a physical observable, which is known to be a statistical property of an ensemble of quantum systems. In contrast to this paradigm, here we demonstrate a method for measuring the expectation value of a physical variable on a single particle, namely, the polarization of a single protected photon. This realization of quantum protective measurements could find applications in the foundations of quantum mechanics and quantum-enhanced measurements.

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Determining the quantum expectation value by measuring a single photon

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