Bayesian feedback control of a two-atom spin-state in an atom-cavity system

TL;DR

This paper demonstrates real-time Bayesian feedback control of a two-atom spin system inside an optical cavity, stabilizing a quantum state that is otherwise inaccessible, with results closely matching simulations.

Contribution

It introduces a novel real-time feedback method using Bayesian updates to control and stabilize a complex quantum state in an atom-cavity system.

Findings

Successfully stabilizes a balanced two-atom mixed state

Achieves near-optimal control conditions

Experimental results agree with Monte-Carlo simulations

Abstract

We experimentally demonstrate real-time feedback control of the joint spin-state of two neutral Caesium atoms inside a high finesse optical cavity. The quantum states are discriminated by their different cavity transmission levels. A Bayesian update formalism is used to estimate state occupation probabilities as well as transition rates. We stabilize the balanced two-atom mixed state, which is deterministically inaccessible, via feedback control and find very good agreement with Monte-Carlo simulations. On average, the feedback loops achieves near optimal conditions by steering the system to the target state marginally exceeding the time to retrieve information about its state.