Two remote counting events induced by a single photon

TL;DR

This paper theoretically demonstrates that a single photon can induce simultaneous detection events at two remote locations in a quantum system, revealing new quantum phenomena and enabling remote entanglement generation.

Contribution

It introduces a novel scheme showing how a single photon can excite two distant qubits simultaneously in the ultrastrong coupling regime, enabling new quantum effects.

Findings

Single-photon pulse can excite two remote qubits simultaneously.

Detection events can occur at two distant locations separated by the photon’s length.

Remote entanglement can be generated via a dissipative channel.

Abstract

Motivated by Einstein's thought experiment that a single quantum particle diffracted after a pinhole could in principle produce an action in two or several places on a hemispherical imaging screen, here we explore theoretically the possibility to simultaneously detect the action of a single photon at two remote places. This is considered in a cascade quantum system composed of two spatially distant cavities each coupled to a qubit in the ultrastrong coupling regime. We show that a single-photon pulse incident on the two cavities can simultaneously excite the two remote qubits and lead to two subsequent single-photon detection events even when the separation between them is comparable to the spatial length of the photon pulse. Our results not only uncover new facets of photons at a fundamental level but also have practical applications, such as the generation of remote entanglement by a single photon through a dissipative channel which is otherwise unattainable in the strong-coupling regime.