The origin of phase in the interference of Bose-Einstein condensates

TL;DR

This paper explores the origin of phase in Bose-Einstein condensate interference, showing how phase can emerge from Fock states and linking it to measurement procedures and symmetry considerations.

Contribution

It demonstrates that phase can arise from Fock states and provides a method to prepare phase states from number states, clarifying the theoretical basis of interference.

Findings

Phase can originate from Fock states with definite particle numbers.

Measurement analysis offers a way to prepare phase states.

Connection established between phase emergence and symmetry concepts.

Abstract

We consider the interference of two overlapping ideal Bose-Einstein condensates. The usual description of this phenomenon involves the introduction of a so-called condensate wave functions having a definite phase. We investigate the origin of this phase and the theoretical basis of treating interference. It is possible to construct a phase state, for which the particle number is uncertain, but phase is known. However, how one would prepare such a state before an experiment is not obvious. We show that a phase can also arise from experiments using condensates in Fock states, that is, having known particle numbers. Analysis of measurements in such states also gives us a prescription for preparing phase states. The connection of this procedure to questions of ``spontaneously broken gauge symmetry'' and to ``hidden variables'' is mentioned.