Nonlinear quantum spectroscopy enhanced by parity-time symmetry

Abstract

Quantum spectroscopy based on nonlinear interferometers attracts increasing attention due to its unique practical advantages [1]. By tailoring spontaneous parametric down conversion (SPDC) for generation of frequency-correlated photons and their nonlocal quantum interference, it becomes possible to perform sensing and imaging across broad spectral ranges through simple detection of paired photons in the visible [2,3]. It was recently demonstrated that nonlinear integrated waveguides can improve the performance of quantum spectroscopy [4]. However, while fabrication of integrated circuits with multiple waveguides is well established, their applications for quantum spectroscopy remain largely undeveloped.