Suppression and enhancement of decoherence in an atomic Josephson junction

TL;DR

This paper investigates how atom-atom interactions influence decoherence in a Bose-Josephson junction under noise, revealing that interactions can both suppress phase decoherence and enhance number-related decoherence, with implications for atomtronic circuits.

Contribution

It provides a detailed analysis of how interactions modulate different types of noise-induced decoherence in atomic Josephson junctions, offering insights for designing robust atomtronic devices.

Findings

Interactions reduce phase noise dephasing by half.

Interactions amplify decoherence from number noise and atom loss.

Results are based on a simple atom chip model for practical parameter mapping.

Abstract

We examine the role of interactions for a Bose gas trapped in a double-well potential ("Bose-Josephson junction") when external noise is applied and the system is initially delocalized with equal probability amplitudes in both sites. The noise may have two kinds of effects: loss of atoms from the trap, and random shifts in the relative phase or number difference between the two wells. The effects of phase noise are mitigated by atom-atom interactions and tunneling, such that the dephasing rate may be reduced to half its single-atom value. Decoherence due to number noise (which induces fluctuations in the relative atom number between the wells) is considerably enhanced by the interactions. A similar scenario is predicted for the case of atom loss, even if the loss rates from the two sites are equal. In fact, interactions convert the increased uncertainty in atom number (difference) into (relative) phase diffusion and reduce the coherence across the junction. We examine the parameters relevant for these effects using a simple model of the trapping potential based on an atom chip device. These results provide a framework for mapping the dynamical range of barriers engineered for specific applications and sets the stage for more complex circuits ("atomtronics").