Cavity QED nondemolition measurement scheme using quantized atomic motion

TL;DR

This paper proposes a quantum nondemolition measurement method for photon number in a cavity using ultracold atoms, leveraging quantum mechanical effects like effective mass and group velocity to achieve high accuracy with few atoms.

Contribution

It introduces a fully quantum mechanical scheme for photon number measurement using atomic motion, demonstrating high accuracy with minimal atomic interactions.

Findings

Photon number causes atomic wave packet splitting.

Few atoms suffice for near-perfect photon number resolution.

Long interaction times improve measurement efficiency.

Abstract

Considering ultracold atoms traversing a high-Q Fabry-Perot cavity, we theoretically demonstrate a quantum nondemolition measurement of the photon number. This fully quantum mechanical approach may be understood utilizing concepts as effective mass and group velocity of the atom. The various photon numbers induce a splitting of the atomic wave packet, and a time-of-flight measurement of the atom thereby reveals the photon number. While repeated atomic measurements increase the efficiency of the protocol, it is shown that by considering long interaction times only a few atoms are needed to resolve the photon number with almost perfect accuracy.