Time resolution at the quantum limit of two incoherent sources based on frequency resolved two-photon-interference

TL;DR

This paper demonstrates a quantum-enhanced method for time delay estimation between incoherent sources using frequency-resolved two-photon interference, achieving precision at the quantum limit with practical feasibility.

Contribution

It introduces a novel quantum interference technique that surpasses classical resolution limits for time delay estimation between incoherent sources.

Findings

Achieves half of the quantum limit in time delay precision.

Utilizes frequency-resolved two-photon interference phenomena.

Applicable to astronomy, microscopy, and radar ranging.

Abstract

The Rayleigh criterion is a widely known limit in the resolution of incoherent sources with classical measurements in the spatial domain. Unsurprisingly the estimation of the time delay between two weak incoherent signals is afflicted by an analogue problem. In this work, we show the emergence of two-photon quantum beats in the frequency domain from the interference at a beam splitter of a photon emitted by a reference source and one from the two incoherent weak signals. We demonstrate, based on this phenomena, that with a relatively low number of measurements of the frequencies of the interfering photons either bunching or antibunching at the beam splitter output one can achieve a precision amounting to half of the quantum limit, independently of both the mode structure of the photonic wavepackets and the time delay to be estimated. The feasibility of the technique makes it applicable in astronomy, microscopy, remote clocks synchronization and radar ranging