Photon-induced Self Trapping and Entanglement of a Bosonic Josephson Junction Inside an Optical Resonator

TL;DR

This paper explores how photons inside an optical resonator can control and induce self-trapping and entanglement in a Bosonic Josephson junction, enabling state manipulation with weaker interactions than usual.

Contribution

It introduces a novel method of controlling atomic tunneling and ground state transitions using cavity photons, facilitating the creation of Schrödinger's cat states with weaker interatomic interactions.

Findings

Photon control enables self-trapping and state crossover.

Ground state can be driven from coherent to cat state.

Entanglement entropy peaks at state transition.

Abstract

We study the influence of photons on the dynamics and the ground state of the atoms in a Bosonic Josephson junction inside an optical resonator. The system is engineered in such a way that the atomic tunneling can be tuned by changing the number of photons in the cavity. In this setup the cavity photons are a new means of control, which can be utilized both in inducing self-trapping solutions and in driving the crossover of the ground state from an atomic coherent state to a Schr\"odinger's cat state. This is achieved, for suitable setup configurations, with interatomic interactions weaker than those required in the absence of cavity. This is corroborated by the study of the entanglement entropy. In the presence of a laser, this quantum indicator attains its maximum value (which marks the formation of the cat-like state and, at a semiclassical level, the onset of self-trapping) for attractions smaller than those of the bare junction.