# Purity oscillations in coupled Bose-Einstein condensates

## TL;DR

This paper demonstrates that purity oscillations observed in open quantum systems with gain and loss also occur in closed systems with subsystems experiencing particle gain and loss, using cold atom lattice setups.

## Contribution

It reveals that purity oscillations are not exclusive to open systems and can occur in closed systems with internal gain and loss mechanisms, supported by experimental proposals.

## Key findings

- Purity oscillations occur in closed quantum systems with gain and loss.
- Two lattice setups show pronounced purity oscillations.
- Purity oscillations can be observed via interference contrast.

## Abstract

It is shown that the distinct oscillations of the purity of the single-particle density matrix for many-body open quantum systems with balanced gain and loss reported by Dast et al. [Phys. Rev. A 93, 033617 (2016)] can also be found in closed quantum systems of which subsystems experience a gain and loss of particles. This is demonstrated with two different lattice setups for cold atoms, viz. a ring of six lattice sites with periodic boundary conditions and a linear chain of four lattice wells. In both cases pronounced purity oscillations are found, and it is shown that they can be made experimentally accessible via the average contrast in interference experiments.