Speaker
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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[23] F. Piacentini et al., Phys. Rev. Lett. 116, 180401 (2016).
| Topic: | Mini-workshop: Quantum Foundations and Quantum Information |
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