Manifestation of a nonclassical Berry phase of an electromagnetic field in atomic Ramsey interference

TL;DR

This paper demonstrates a nonclassical Berry phase of an electromagnetic field manifesting in atomic Ramsey interference, enabling new quantum gate implementations and analyzing effects of dissipation.

Contribution

It introduces a method to observe the quantum Berry phase in a field via atomic interference and proposes a novel approach for multiqubit geometric phase gates.

Findings

Berry phase can be observed in atomic Ramsey interference.

The method allows one-step multiqubit geometric phase gates.

Dissipation and fluctuations affect the phase and fringe visibility.

Abstract

The Berry phase acquired by an electromagnetic field undergoing an adiabatic and cyclic evolution in phase space is a purely quantum-mechanical effect of the field. However, this phase is usually accompanied by a dynamical contribution and cannot be manifested in any light-beam interference experiment because it is independent of the field state. We here show that such a phase can be produced using an atom coupled to a quantized field and driven by a slowly changing classical field, and it is manifested in atomic Ramsey interference oscillations. We also show how this effect may be applied to one-step implementation of multiqubit geometric phase gates, which is impossible by previous geometric methods. The effects of dissipation and fluctuations in the parameters of the pump field on the Berry phase and visibility of the Ramsey interference fringes are analyzed.