Quantum Computer Simulation of Molecules in Optical Cavity

Various phenomena have been observed in molecule-cavity coupled systems, which are believed to hold potential for applications in transistors, lasers, and computational units, among others. However, theoretical methods for simulating molecules in optical cavities still require further development due to the complex couplings between electrons, phonons, and photons within the cavity. In this study, motivated by recent advances in quantum algorithms and quantum computing hardware, we propose a quantum computing algorithm tailored for molecules in optical cavities. Our method, based on a variational quantum algorithm and variational boson encoders, has its effectiveness validated on both quantum simulators and hardware. For aggregates within the cavity, described by the Holstein-Tavis-Cummings model, our approach demonstrates clear advantages over other quantum and classical methods, as proved by numerical benchmarks. Additionally, we apply this method to study the H₂ molecule in a cavity using a superconducting quantum computer and the Pauli-Fierz model. To enhance accuracy, we incorporate error mitigation techniques, such as readout and reference-state error mitigation, resulting in an 86% reduction in the average error.