Application of resource theory to bound a molecular switch's probability of switching

Resource theories have mushroomed across quantum information theory recently. These models capture how constraints limit the operations one can perform and the systems one can access. In a fixed-temperature environment, for instance, the first law of thermodynamics constrains operations to preserve energy. Scores of resource-theory theorems have been proved. Can they inform science beyond quantum information theory? Can resource theories answer pre-existing questions about the real physical world? We argue affirmatively, illustrating with photoisomers, or molecular switches.

Photoisomers appear across nature and technologies, from our eyes to solar-fuel cells. How effectively can these switches switch? A general answer defies standard analyses, because photoisomers are small, quantum, and far from equilibrium. We model a photoisomer in a thermodynamic resource theory, then upper-bound the switching probability using thermomajorization, a resource-theory result that extends the second law of thermodynamics to small scales. Thermomajorization constrains the yield tightly if a laser barely excites the molecule, as in solar-fuel experiments. This work demonstrates that thermodynamic resource theories can illuminate nature, experiments, and materials. NYH and Limmer, Phys. Rev. A 101, 042116 (2020). NYH, in Eddington, Wheeler, and the Limits of Knowledge, Eds. Durham and Rickles, Springer (2017) arXiv:1509.03873.