Determining the quantum expectation value by measuring a single photon
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.
- Publication:
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Nature Physics
- Pub Date:
- December 2017
- DOI:
- 10.1038/nphys4223
- arXiv:
- arXiv:1706.08918
- Bibcode:
- 2017NatPh..13.1191P
- Keywords:
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- Quantum Physics
- E-Print:
- Nature Physics, in press (this version corresponds to the one initially submitted to Nature Physics)