Quantum-coherent nonlinear interferometry using electron-phonon systems for entanglement-assisted terahertz sensing

TL;DR

This paper develops a quantum-coherent model for nonlinear interferometry using electron-phonon systems, enabling entanglement-assisted terahertz sensing through phase-sensitive interference.

Contribution

It introduces a novel theoretical framework modeling active electron-phonon systems as nonlinear media in quantum interferometry, highlighting their role in entanglement generation and sensing.

Findings

Demonstrates two-stage entanglement buildup between photons mediated by material coherence.

Shows phase-sensitive interference allows indirect terahertz signal readout.

Establishes a general approach for active nonlinear quantum media in interferometry.

Abstract

We present a theoretical framework for quantum-coherent nonlinear interferometry in which the nonlinear medium is modeled as active electron-phonon quantum systems rather than a passive $\chi^{(2)}$ converter. By explicitly retaining the quantum coherence of the coupled electron-phonon-photon dynamics, our model describes a two-stage buildup of entanglement - first between signal and idler photons and subsequently between idler photons mediated by material coherence. This coherent light-matter interaction imprints the internal dynamics of the medium onto the interferometer output, yielding phase-sensitive interference that enables indirect readout of terahertz-band signal modes via near-infrared detection. The results reveal a route toward entanglement-assisted terahertz sensing and establish a general framework for treating nonlinear quantum media as active components in interferometric architectures.