Fundamental Physics at the Frontier of Noisy Quantum Computation}

Abstract

Quantum computing offers a new, orthogonal direction for investigating fundamental physics, extending beyond classical numerical methods and conventional observables. Realizing this potential requires directly confronting the noise limiting currently available quantum computers. Progress rests on advancing algorithms, interpreting their results, and managing their errors together. This thesis presents several advancements in the use of quantum simulation and quantum information to probe fundamental physics. The first is in the use of quantum computers to simulate collisions in quantum field theories. Central to these simulations are new wavepacket preparation and time evolution techniques that address the circuit depth bottleneck previously associated with these steps. Together with new error mitigation strategies well-suited to the quantum simulations, these developments allow for simulations with some of the largest effective circuit volumes to date. These methods enable the first quantum simulation providing numerical evidence for inelastic particle production, a key process in fundamental physics. Entanglement and magic (nonstabilizerness) generated in the dynamics of fundamental physical processes are simultaneously responsible for the classical and quantum hardness of Hamiltonian simulation. On quantum computers, entangling gates dominate the error budget of currently available devices, and non-Clifford operations that generate magic will consume the most resources in future fault-tolerant simulations. Motivated by this duality, the second advancement centers on the role quantum-information-theoretic quantities play in physical processes. Beyond mere correlations with the physics of the process, entanglement and magic are shown to probe the interactions present in scattering and hadronization dynamics. A precision study requires a complete quantification of algorithmic and hardware uncertainties, an outstanding goal as quantum simulations mature.The third advancement in this thesis addresses error management. A framework minimizing the effect of algorithmic errors in analog quantum simulations is presented. Device errors are confronted directly by performing an error-detected quantum computation. In a step toward fault tolerance, encoded quantum simulations are shown to improve estimation of local observables relative to unencoded runs. Together, the developments in this thesis mark practical progress toward fault-tolerant quantum simulations of fundamental physics capable of scientific discovery.