Long-range quantum gate via Rydberg states of atoms in a thermal microwave cavity

TL;DR

This paper presents a method for implementing a universal quantum gate between distant atoms using Rydberg states in a microwave cavity, with robustness to cavity photon states and scalability to multiple ensembles.

Contribution

It introduces a scheme for long-range quantum gates via Rydberg states in a thermal microwave cavity, insensitive to cavity photon states, and scalable to many atomic ensembles.

Findings

Gate operation is robust against cavity photon number fluctuations.

The scheme enables ultralong-range interactions and entanglement.

Scalable to multiple atomic ensembles within a small microwave resonator.

Abstract

We propose an implementation of a universal quantum gate between pairs of spatially separated atoms in a microwave cavity at finite temperature. The gate results from reversible laser excitation of Rydberg states of atoms interacting with each other via exchange of virtual photons through a common cavity mode. Quantum interference of different transition paths between the two-atom ground and double-excited Rydberg states makes both the transition amplitude and resonance largely insensitive to the excitations in the microwave cavity "quantum bus" which can therefore be in any superposition or mixture of photon number states. Our scheme for attaining ultralong-range interactions and entanglement also applies to mesoscopic atomic ensembles in the Rydberg blockade regime and is scalable to many ensembles trapped within a centimeter sized microwave resonator.