Quantum Non-Demolition Photon Counting in a 2d Rydberg Atom Array

TL;DR

This paper proposes a quantum non-demolition photon counting protocol using Rydberg atom arrays, enabling photon number measurement, state distillation, and discrimination with robustness to noise.

Contribution

It introduces a novel QND photon counting method leveraging Rydberg arrays, combining photon storage, Rabi oscillations, and measurements for enhanced quantum photonic control.

Findings

The protocol achieves photon number measurement via Rydberg state oscillations.

It can distill Fock states from arbitrary initial states.

The method remains effective under realistic noise conditions.

Abstract

Rydberg arrays merge the collective behavior of ordered atomic arrays with the controllability and optical nonlinearities of Rydberg systems, resulting in a powerful platform for realizing photonic many-body physics. As an application of this platform, we propose a protocol for quantum non-demolition (QND) photon counting. Our protocol involves photon storage in the Rydberg array, an observation phase consisting of a series of Rabi flops to a Rydberg state and measurements, and retrieval of the stored photons. The Rabi frequency experiences a $\sqrt{n}$ collective enhancement, where $n$ is the number of photons stored in the array. Projectively measuring the presence or absence of a Rydberg excitation after oscillating for some time is thus a weak measurement of photon number. We demonstrate that the photon counting protocol can be used to distill Fock states from arbitrary pure or mixed initial states and to perform photonic state discrimination. We confirm that the protocol still works in the presence of experimentally realistic noise.