On Quantum Simulation of QED in Coulomb Gauge

Abstract: A recent work (Li, 2406.01204) considered quantum simulation of Quantum Electrodynamics (QED) on a lattice in the Coulomb gauge with gauge degrees of freedom represented in the occupation basis in momentum space. Here we consider representing the gauge degrees of freedom in field basis in position space and develop a quantum algorithm for real-time simulation. We show that the Coulomb gauge Hamiltonian is equivalent to the temporal gauge Hamiltonian when acting on physical states consisting of fermion and transverse gauge fields. The Coulomb gauge Hamiltonian guarantees that the unphysical longitudinal gauge fields do not propagate and thus there is no need to impose any constraint. The local gauge field basis and the canonically conjugate variable basis are swapped efficiently using the quantum Fourier transform. We prove that the qubit cost to represent physical states and the gate depth for real-time simulation scale polynomially with the lattice size, energy, time, accuracy and Hamiltonian parameters. We focus on the lattice theory without discussing the continuum limit or the UV completion of QED.