Resource Estimates for Excited-State Calculations of Diarylethenes on Fault-Tolerant Photonic Quantum Computers

Abstract We estimate computational resources for computing excited-state energies of benchmark photochromic molecules of diarylethenes (DAEs) by using quantum phase estimation on photonic devices. The number of T gates, which determines the calculation time, and logical qubits for a simulation are estimated, considering the overhead of fault-tolerant computers. Three DAE molecules of increasing size are examined with active space sizes specified. Quantum resource estimation is conducted via Hamiltonian truncation within an active space of all valence π electrons in all