Qubit-Initialisation and Readout with Finite Coherent Amplitudes in Cavity QED

TL;DR

This paper explores a method for transferring quantum information from a two-level atom to a cavity field with finite coherent amplitude, enabling effective qubit readout and initialization in cavity QED systems.

Contribution

It introduces a protocol for unitary transfer of atomic qubit states to finite amplitude coherent states, extending previous infinite amplitude models.

Findings

High purity state transfer achieved with proper amplitude and timing

Method enables effective atomic state readout via cavity field measurement

Supports initialization of atomic states with high fidelity

Abstract

We consider a unitary transfer of an arbitrary state of a two-level atomic qubit in a cavity to the finite amplitude coherent state cavity field. Such transfer can be used to either provide an effective readout measurement on the atom by a subsequent measurement on the light field or as a method for initializing a fixed atomic state - a so-called "attractor state", studied previously for the case of an infinitely strong cavity field. We show that with a suitable adjustment of the coherent amplitude and evolution time the qubit transfers all its information to the field, attaining a selected state of high purity irrespectively of the initial state.