Optimal qubit circuits for quantum-enhanced telescopes

TL;DR

This paper introduces two optimal quantum phase-estimation protocols for long-baseline interferometry, leveraging distributed entanglement to improve photon transmission and measurement efficiency in quantum-enhanced telescopes.

Contribution

It presents a new sequence of nonlinear optical gates and a modified protocol that reduces resource requirements while achieving optimal phase estimation.

Findings

Protocols saturate the Cramér-Rao bound.

Reduced number of ancilla qubits and gate operations.

Enhanced photon transmission in quantum interferometry.

Abstract

We propose two optimal phase-estimation schemes that can be used for quantum-enhanced long-baseline interferometry. By using distributed entanglement, it is possible to eliminate the loss of stellar photons during transmission over the baselines. The first protocol is a sequence of gates using nonlinear optical elements, optimized over all possible measurement schemes to saturate the Cram\'er-Rao bound. The second approach builds on an existing protocol, which encodes the time of arrival of the stellar photon into a quantum memory. Our modified version reduces both the number of ancilla qubits and the number of gate operations by a factor of two.