Polariton chemistry: Thinking inside the (photon) box

Abstract

The study of single quantum objects embedded in confined electromagnetic environments is the main focus of the field of cavity quantum electrodynamics (CQED). According to a recent historical account by the 2012 Nobel laureate Sergei Haroche (1), the origins of this field can be traced back to the early days of quantum mechanics, with the famous debate between Albert Einstein and Niels Bohr concerning a gedankenexperiment about a photon in a box. While Einstein invoked the photon in a box as a theoretical construct, he might not have imagined that such a concept would reincarnate decades later into one of the favorite experimental playgrounds for scientists to test, explore, and control quantum mechanics. In fact, atoms in optical cavities have become one of the quintessential building blocks of contemporary quantum technologies, giving rise to high-fidelity sources of single photons, platforms to recreate effective photon–photon interactions, or even quantum simulators of many-particle systems. In recent years, an interdisciplinary outlook at the crossroads of CQED and chemistry termed “polariton chemistry” (2, 3) has emerged, which is centered around the question: Can materials change their chemical properties merely by being immersed in an optical cavity? Far-reaching consequences could follow if the answer to this question is positive, as one could potentially bypass time-consuming synthetic modifications of materials by harnessing CQED effects as an alternative. Indeed, much experimental (4⇓–6) and theoretical evidence (7⇓–9) points toward the fact that under certain circumstances, modifications to photochemical and ground-state kinetics, energy transfer, and charge transport are possible with the use of optical cavities. In PNAS, Schafer et al. (10) present compelling theoretical and computational evidence in support of these statements. Schafer et al. perform a study of a minimalistic quantum mechanical model which demonstrates that molecular excitation energy and charge-transfer … [↵][1]1To whom correspondence may be addressed. Email: jyuenzhou{at}ucsd.edu or vmenon{at}ccny.cuny.edu. [1]: #xref-corresp-1-1