Marty Stevens: The Quest for Entangled 2-Photon Absorption: A Cautionary Tale

Marty Stevens

NIST

Tuesday, June 11th, 2024

Time: 11:30 am - 12:30 pm

Location: Elings Hall 1601

Abstract: Over 30 years ago, it was recognized that the energy-time correlations shared by entangled-photon pairs could lead to an increased efficiency of 2-photon absorption at low photon flux. There was hope that this might enable 2-photon microscopy deep inside living specimens without damaging or disrupting biological processes. Recent years have seen claims in the literature of entangled 2-photon absorption (E2PA) in fluorescent molecules, including reports that E2PA may be several orders of magnitude more efficient than its classical counterpart. However, reproducibility of these results has remained elusive. Over the past 5 years, our team of researchers at NIST and the University of Colorado has performed a set of careful fluorescence and transmission measurements while attempting (and failing) to observe E2PA. Our measurements allow us to place upper bounds on the E2PA cross sections that are several orders of magnitude lower than previous reports. Other research teams around the world are now reporting similar negative results. I will discuss these outcomes and what they mean for the future of entangled 2-photon absorption microscopy.