Theory of cavity-enhanced non-destructive detection of photonic qubits in a solid-state atomic ensemble

TL;DR

This paper proposes a cavity-enhanced method for non-destructive detection of photonic qubits in a solid-state ensemble, enabling quantum information applications with high success probability and low loss.

Contribution

It introduces a novel cavity-based scheme for non-destructive photonic qubit detection using a solid-state ensemble, with analysis of phase imprinting and detection robustness.

Findings

Cavity causes probe phase spreading dependent on photon number.

Detection remains non-destructive despite phase spreading.

Potential for high success probability and low loss implementations.

Abstract

Non-destructive detection of photonic qubits will enable important applications in photonic quantum information processing and quantum communications. Here, we present an approach based on a solid-state cavity containing an ensemble of rare-earth ions. First a probe pulse containing many photons is stored in the ensemble. Then a single signal photon, which represents a time-bin qubit, imprints a phase on the ensemble that is due to the AC Stark effect. This phase does not depend on the exact timing of the signal photon, which makes the detection insensitive to the time-bin qubit state. Then the probe pulse is retrieved and its phase is detected via homodyne detection. We show that the cavity leads to a dependence of the imprinted phase on the {\it probe} photon number, which leads to a spreading of the probe phase, in contrast to the simple shift that occurs in the absence of a cavity. However, we show that this scenario still allows non-destructive detection of the signal. We discuss potential implementations of the scheme, showing that high success probability and low loss should be simultaneously achievable.