Generation and decoherence of soliton spatial superposition states

TL;DR

This paper models the creation of spatial superposition states in Bose-Einstein condensates, demonstrating how entanglement can be mapped from Rydberg atoms and analyzing decoherence effects due to atom losses.

Contribution

It introduces a variational many-body approach to model entanglement mapping and decoherence in condensates, extending beyond mean-field theory.

Findings

Superpositions of 400 atoms separated by 3 μm are achievable.

Coherence can last approximately 1 ms under realistic conditions.

The model confirms earlier estimates of superposition size and lifetime.

Abstract

Due to their coherence properties, dilute atomic gas Bose-Einstein condensates seem a versatile platform for controlled creation of mesoscopically entangled states with a large number of particles and also allow controlled studies of their decoherence. However, the creation of such a state intrinsically involves many-body quantum dynamics that cannot be captured by mean-field theory, and thus invalidates the most widespread methods for the description of condensates. We follow up on a proposal, in which a condensate cloud as a whole is brought into a superposition of two different spatial locations, by mapping entanglement from a strongly interacting Rydberg atomic system onto the condensate using off-resonant laser dressing [R. Mukherjee et al., Phys. Rev. Lett. 115 040401 (2015)]. A variational many-body Ansatz akin to recently developed multi-configurational methods allows us to model this entanglement mapping step explicitly, while still preserving the simplicity of mean-field physics for the description of each branch of the superposition. In the second part of the article, we model the decoherence process due to atom losses in detail. Altogether we confirm earlier estimates, that tightly localized clouds of 400 atoms can be brought into a quantum superposition of two locations about 3 {\mu}m apart and remain coherent for about 1 ms.