Coherence Equality and Communication in a Quantum Superposition

Abstract

In this paper, we introduce a "coherence equality" that is satisfied by any classical communication -- i.e., conveyed by a localized carrier traveling along well defined directions. In contrast, this equality is violated when the carrier is prepared in a quantum superposition of communication directions. This is phrased in terms of the success probability of a certain communication task, which results to be always constant and equal to 1/2 in the classical case. On the other hand, we develop two simple quantum schemes that deviate systematically from the classical value, thus violating the coherence equality. Such a violation can also be exploited as an operational way to witness spatial quantum superpositions without requiring the use of an interferometer, but only by means of spatially separated local measurements.

Published version. 5 pages, 2 figures, one Appendix

References in corpus (2)

• Quantum cryptography: Public key distribution and coin tossing
• Experimental Proof of Nonlocal Wavefunction Collapse for a Single Particle Using Homodyne Measurement

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