Emulating Quantum Entangled Biphoton Spectroscopy Using Classical Light Pulses.

• DOI: 10.48550/arxiv.2306.14424
• Publication Date: 2023-08-31
• Authors: Liwen Ko; Robert L. Cook; K. Birgitta Whaley
• Keywords: Chemical Physics (physics.chem-ph); Quantum Physics; Physics - Chemical Physics; FOS: Physical sciences; Quantum Physics (quant-ph); 530

We show that for a class of quantum light spectroscopy (QLS) experiments using n = 0,1,2,$\cdots$ classical light pulses and an entangled photon pair (a biphoton state) where one photon acts as a reference without interacting with the matter sample, identical signals can be obtained by replacing the biphotons with classical-like coherent states of light, where these are defined explicitly in terms of the parameters of the biphoton states. An input-output formulation of quantum nonlinear spectroscopy is used to prove this equivalence. We demonstrate the equivalence numerically by comparing a classical pump - quantum probe experiment with the corresponding classical pump - classical probe experiment. This analysis shows that understanding the equivalence between entangled biphoton probes and carefully designed classical-like coherent state probes leads to quantum-inspired classical experiments and provides insights for future design of QLS experiments that could provide a true quantum advantage.