Paradoxical consequences of multipath coherence: Perfect interaction-free measurements

Zhao, Z and Mondal, S and Markiewicz, M and Rutkowski, A and Dakic, B and Laskowski, W and Paterek, T (2018) Paradoxical consequences of multipath coherence: Perfect interaction-free measurements. In: PHYSICAL REVIEW A, 98 (2).

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Abstract

Quantum coherence can be used to infer the presence of a detector without triggering it. Here we point out that, according to quantum mechanics, such interaction-free measurements cannot be perfect, i.e., in a single-shot experiment one has strictly positive probability to activate the detector. We formalize the extent to which such measurements are forbidden by deriving a trade-off relation between the probability of activation and the probability of an inconclusive interaction-free measurement. Our description of interaction-free measurements is theory independent and allows derivations of similar relations in models generalizing quantum mechanics. We provide the trade-off for the density cube formalism, which extends the quantum model by permitting coherence between more than two paths. The trade-off obtained hints at the possibility of perfect interaction-free measurements and indeed we construct their explicit examples. Such measurements open up a paradoxical possibility where we can learn by means of interference about the presence of an object in a given location without ever detecting a probing particle in that location. We therefore propose that absence of perfect interaction-free measurement is a natural postulate expected to hold in all physical theories. As shown, it holds in quantum mechanics and excludes the models with multipath coherence.

Item Type:	Journal Article
Publication:	PHYSICAL REVIEW A
Publisher:	AMER PHYSICAL SOC, ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
Additional Information:	Copyright of this article belong to AMER PHYSICAL SOC, ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
Department/Centre:	Division of Physical & Mathematical Sciences > Physics
Date Deposited:	20 Aug 2018 15:36
Last Modified:	11 Oct 2018 12:51
URI:	http://eprints.iisc.ac.in/id/eprint/60468

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