Heterodyne spectrometer sensitivity limit for quantum networking

TL;DR

This paper demonstrates a high-resolution, quantum-limited heterodyne spectrometer and establishes a fundamental sensitivity limit for broadband multi-spectral detection, comparing it with other spectrometer types and dim light sources.

Contribution

It introduces a proof-of-principle heterodyne spectrometer with picometer resolution and derives a generalized quantum sensitivity limit for broadband multi-spectral detection.

Findings

Heterodyne spectrometer achieves picometer resolution and quantum-limited sensitivity.

The sensitivity limit is less than that of single-photon detectors for dim sources.

Heterodyne detection is inadequate for detecting dim light sources like SPDC, Raman, and FWM, except for the brightest cases.

Abstract

Optical heterodyne detection-based spectrometers are attractive due to their relatively simple construction and ultra-high resolution. Here we demonstrate a proof-of-principle single-mode optical-fiber-based heterodyne spectrometer which has picometer resolution and quantum-limited sensitivity around 1550 nm. Moreover, we report a generalized quantum limit of detecting broadband multi-spectral-temporal-mode light using heterodyne detection, which provides a sensitivity limit on a heterodyne detection-based optical spectrometer. We then compare this sensitivity limit to several spectrometer types and dim light sources of interest, such as, spontaneous parametric downconversion, Raman scattering, and spontaneous four-wave mixing. We calculate the heterodyne spectrometer is significantly less sensitive than a single-photon detector and unable to detect these dim light sources, except for the brightest and narrowest-bandwidth examples.