Electro-Optical Sampling of Single-Cycle THz Fields with Single-Photon Detectors

TL;DR

This paper demonstrates a quantum-enhanced method for measuring single-cycle THz fields using single-photon detectors and squeezed vacuum states, surpassing classical shot noise limitations in electro-optical sampling.

Contribution

It introduces a novel quantum metrology approach employing single-photon detectors and squeezed states for improved THz field measurement sensitivity.

Findings

Achieved THz field sensitivity limited by quantum probe state statistics

Demonstrated phase-locked single-photon detection for THz sampling

Paved the way for quantum-enhanced THz sensing techniques

Abstract

Electro-optical sampling of Terahertz fields with ultrashort pulsed probes is a well-established approach for directly measuring the electric field of THz radiation. This technique usually relies on balanced detection to record the optical phase shift brought by THz-induced birefringence. The sensitivity of electro-optical sampling is, therefore, limited by the shot noise of the probe pulse, and improvements could be achieved using quantum metrology approaches using, e.g., NOON states for Heisenberg-limited phase estimation. We report on our experiments on THz electro-optical sampling using single-photon detectors and a weak squeezed vacuum field as the optical probe. Our approach achieves field sensitivity limited by the probe state statistical properties using phase-locked single-photon detectors and paves the way for further studies targeting quantum-enhanced THz sensing.