Two proposals to protect a qubit using CQED techniques: inequality between atomic velocity dispersion and losses of a quantum memory

TL;DR

This paper proposes two CQED-based methods to enhance qubit preservation in lossy superconducting cavities, significantly increasing dwell time by controlling atomic interactions and beam preparation accuracy.

Contribution

It introduces two novel procedures for protecting a qubit from decay in a quantum memory, with a new inequality relating atomic velocity dispersion and cavity losses.

Findings

Dwell time of the qubit increases significantly with both procedures.

The second procedure yields a higher increase in dwell time.

A new relation between atomic beam preparation accuracy and cavity quality is established.

Abstract

We present in this work an analysis of the damage imposed by the atom on the field state inside a lossy superconducting cavity. To access such effects, we propose two procedures to preserve a qubit of the decay effects of an imperfect quantum memory: the first by means of an quasi-instantaneous phase kick applied in the atom, and the second by means of controlled resonant and dispersive interactions. We immediately demonstrate that, in both procedures, the dwell time of the qubit in the cavity increases significantly, being expressively higher for the second. A relation between the inaccuracy of the preparation of the atomic beam and the quality of the cavity arises naturally from our calculations for each procedure. This result is unprecedented, and sets out the rules to increase the dwell time of the qubit.