Prospects for improving chemical control with a fault-tolerant quantum computer

A longstanding goal is to use laser fields to coherently control the dynamics of quantum systems, such as atoms and molecules. In pursuit of this goal, simulations are essential for designing laser fields that achieve a desired control outcome. In this talk, we propose a protocol for using a fault-tolerant quantum computer to improve a laser control pulse that suffers from classical modeling approximations. This protocol combines a first-quantized discretization of the system with Trotterized dynamics and coherent estimation of the cost function. Numerical optimizations reduce Trotter steps and circuit repetitions while recent analysis improves the cost of quantum arithmetic. Starting from a previously optimized pulse based on classical modeling approximations greatly reduces the iterations needed during re-optimization with the quantum computer. Hybrid quantum-classical optimization only uses the quantum computer to simulate the dynamics, keeping the circuit depth relatively low. The result for an application-scale problem is T counts of 10^13-10^17 and T depths of 10^10-10^14, suggesting chemical control is a potential application with implications for both science and industry.