17-29 August 2017
Europe/Athens timezone
CONFERENCE PHOTO: https://indico.cern.ch/event/559774/overview#preview:2369137

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Weak Measurements: from Measuring Non-Commuting Observables and Testing Quantum Contextuality to Protective Measurements

25 Aug 2017, 11:30
30m
Room 2 ()

Room 2

Talk Workshop on Quantum Foundations and Quantum Information Workshop on Quantum Foundations and Quantum Information

Speaker

Dr Fabrizio Piacentini (Istituto Nazionale di Ricerca Metrologica, strada delle Cacce 91, IT-10135 Torino, Italy)

Description

Measurements are the very basis of Physics, especially in Quantum Mechanics (QM), where they assume even a more fundamental role because of the wave function collapse occurring after a “strong” (projective) measurement. Furthermore, measuring a quantum-mechanical observable completely erases the information on its conjugate one (e.g., position measurement erases information on momentum, and vice-versa).
Nevertheless, in QM other kinds of measurement are possible. For example, wave function collapse can be overcome through Weak Measurements, i.e. measurements performed with an interaction weak enough to avoid inducing the original state collapse, featuring several interesting properties.
An example of these are weak values [1-3], realised for the first time in [4-6], that have been used for addressing fundamental questions [7-12] as Contextuality and are also a tool for Quantum Metrology [13-19].
One of the most intriguing properties of Weak Measurements is that, since they are not affected by wave function collapse, they can allow gathering simultaneous information on non-commuting observables [20], impossible with the standard (projective) measurement protocols.
A second example is offered by Protective Measurements [21], a new technique able to extract information on the expectation value of an observable even measuring a single particle.
In this talk, after a general introduction to WMs, we present the first realisation of sequential weak value measurements [22], i.e. a measurement of the weak value of (incompatible) polarizations in sequence on a single photon.
Then, we present an experiment addressed to explore the connection between anomalous weak values and Contextuality [23], showing a clear violation of the inequality proposed in [12] while satisfying all the additional theoretical requests, unequivocally demonstrating the contextual nature of weak values.
Finally, we present and discuss the first implementation of Protective Measurements, showing unprecedented measurement capability and demonstrating how the expectation value of an observable can be obtained even with a single experiment on a single particle.

References:

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[2] B.Tamir and E. Cohen, Quanta 2, 7 (2013).

[3] Y. Aharonov, D. Z. Albert, and L. Vaidman, Phys. Rev. Lett. 60, 1351 (1988).

[4] N. W. M. Ritchie, J. G. Story, and R. G. Hulet, Phys. Rev. Lett. 66, 1107 (1991).

[5] G. J. Pryde, J. L. O’Brien, A. G. White, T. C. Ralph, and H. M. Wiseman, Phys. Rev. Lett. 94, 220405 (2005).

[6] O. Hosten and P. Kwiat, Science 319, 787 (2008).

[7] Y. Aharonov et al., Phys. Lett. A 301, 130 (2002).

[8] H. M. Wiseman, New J. Phys. 9, 165 (2007).

[9] R. Mir, J. S. Lundeen, M. W. Mitchell, A. M. Steinberg, J. L. Garretson, and H. M. Wiseman, New J. Phys. 9, 287 (2007).

[10] N. S. Williams and A. N. Jordan, Phys. Rev. Lett. 100, 026804 (2008).

[11] M. E. Goggin, M. P. Almeida, M. Barbieri, B. P. Lanyon, J. L. O’Brien, A. G. White, and G. J. Pryde, PNAS 108, 1256 (2011).

[12] M. Pusey, Phys. Rev. Lett. 113, 200401 (2014).

[13] O. Hosten and P. Kwiat, Science 319, 787 (2008).

[14] K. J. Resch, Science 319, 733 (2008).

[15] P. B. Dixon, D. J. Starling, A. N. Jordan, and J. C. Howell, Phys. Rev. Lett. 102, 173601 (2009).

[16] J. M. Hogan, J. Hammer, S.-W. Chiow, S. Dickerson, D. M. S. Johnson, T. Kovachy, A. Sugerbaker, and M. A. Kasevich, Opt. Lett. 36, 1698 (2011).

[17] O. S. Magaña-Loaiza, M. Mirhosseini, B. Rodenburg, and R. W. Boyd, Phys. Rev. Lett. 112, 200401 (2014).

[18] J. Salvail et al., Nature Phot. DOI 10.1038;

[19] J. Lundeen, B. Sutherland, A. Patel, C. Stewart, and C. Bamber, Nature 474, 188 (2011).

[20] G. Mitchison, R. Jozsa and S.Popescu PRA 76, 062105 (2007).

[21] Y. Aharonov and L. Vaidman, Phys. Lett. A 178, 38 (1993).

[22] F. Piacentini et al., Phys. Rev. Lett. 117, 170402 (2016).

[23] F. Piacentini et al., Phys. Rev. Lett. 116, 180401 (2016).

Topic: Mini-workshop: Quantum Foundations and Quantum Information

Primary author

Dr Fabrizio Piacentini (Istituto Nazionale di Ricerca Metrologica, strada delle Cacce 91, IT-10135 Torino, Italy)

Co-authors

Dr Alessio Avella (Istituto Nazionale di Ricerca Metrologica, strada delle Cacce 91, IT-10135 Torino, Italy) Dr Rudi Lussana (Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, piazza Leonardo da Vinci 32, IT- 20133 Milano, Italy) Dr Federica Villa (Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, piazza Leonardo da Vinci 32, IT- 20133 Milano, Italy) Mr Enrico Rebufello (Istituto Nazionale di Ricerca Metrologica, strada delle Cacce 91, IT-10135 Torino, Italy and Politecnico di Torino, corso Duca degli Abruzzi 24, IT- 10129 Torino, Italy) Prof. Alberto Tosi (Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, piazza Leonardo da Vinci 32, IT- 20133 Milano, Italy) Prof. Franco Zappa (Politecnico di Milano, Dipartimento di Elettronica, Informazione e Bioingegneria, piazza Leonardo da Vinci 32, IT- 20133 Milano, Italy) Dr Marco Gramegna (Istituto Nazionale di Ricerca Metrologica, strada delle Cacce 91, IT-10135 Torino, Italy) Dr Giorgio Brida (Istituto Nazionale di Ricerca Metrologica, strada delle Cacce 91, IT-10135 Torino, Italy) Dr Eliahu Cohen (H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, BS8 1TL, U.K) Prof. Lev Vaidman (Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 6997801, Israel) Dr Ivo Pietro Degiovanni (Istituto Nazionale di Ricerca Metrologica, strada delle Cacce 91, IT-10135 Torino, Italy) Dr Marco Genovese (Istituto Nazionale di Ricerca Metrologica, strada delle Cacce 91, IT-10135 Torino, Italy)

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