Incoherence of Bose-Einstein condensates at supersonic speeds due to quantum noise

TL;DR

This paper investigates how quantum noise causes incoherence and turbulence in supersonic Bose-Einstein condensates, especially around obstacles and disordered potentials, revealing new quantum dynamical phenomena.

Contribution

It provides a detailed analysis of quantum noise effects on supersonic BEC flow, highlighting incoherent atom scattering and turbulence formation, which were not previously well-understood.

Findings

Quantum fluctuations cause incoherent scattering of atoms.

Cherenkov radiation is suppressed by quantum noise.

Incoherent atom crescents form around obstacles and in disordered potentials.

Abstract

We calculate the effect of quantum noise in supersonic transport of Bose-Einstein condensates. When an obstacle obstructs the flow of atoms, quantum fluctuations cause atoms to be scattered incoherently into random directions. This suppresses the propagation of Cherenkov radiation, creating quantum turbulence and a crescent of incoherent atoms around the obstacle. We observe similar dynamics if the BEC is stirred by a laser beam: crescents of incoherent atoms are emitted from the laser's turning-points. Finally, we investigate supersonic flow through a disordered potential, and find that the quantum fluctuations generate an accumulation of incoherent atoms as the condensate enters the disorder.