Theory of remote entanglement via quantum-limited phase-preserving amplification

TL;DR

This paper demonstrates how a quantum-limited phase-preserving amplifier can enable remote entanglement of qubits through continuous joint measurement, providing a scalable and flexible approach with detailed theoretical analysis.

Contribution

It introduces a novel method using a phase-preserving amplifier as a which-path eraser for remote entanglement, including an analytic solution for the stochastic master equation.

Findings

Successful entanglement generation between distant qubits.

Analytic solution for the quantum filter of the measurement process.

Dependence of entanglement quality on losses and measurement inefficiencies.

Abstract

We show that a quantum-limited phase-preserving amplifier can act as a which-path information eraser when followed by heterodyne detection. This 'beam splitter with gain' implements a continuous joint measurement on the signal sources. As an application, we propose heralded concurrent remote entanglement generation between two qubits coupled dispersively to separate cavities. Dissimilar qubit-cavity pairs can be made indistinguishable by simple engineering of the cavity driving fields providing further experimental flexibility and the prospect for scalability. Additionally, we find an analytic solution for the stochastic master equation, a quantum filter, yielding a thorough physical understanding of the nonlinear measurement process leading to an entangled state of the qubits. We determine the concurrence of the entangled states and analyze its dependence on losses and measurement inefficiencies.