Dynamical quantum phase transitions in a noisy lattice gauge theory

Abstract

Lattice gauge theories (LGTs) form an intriguing class of theories highly relevant to both highenergy particle physics and low-energy condensed matter physics with the rapid development of engineered quantum devices providing new tools to study e.g. dynamics of such theories. The massive Schwinger model is known to exhibit intricate properties of more complicated theories and has recently been shown to undergo dynamical quantum phase transitions out of equilibrium. With current technology, noise is inevitable and potentially fatal for a successful quantum simulation. This paper studies the dynamics subject to noise of a (1 + 1)D U(1) quantum link model following a quench of the sign of the mass term. We find that not only is the system capable of handling noise at rates realistic in NISQ-era devices, promising the possiblity to study the target dynamics with current technology, but the effect of noise can be understood in terms of simple models. Specifically the gauge-breaking nature of bit-flip channels results in exponential dampening of state amplitudes, and thus observables, which does not affect the structures of interest. This is especially important as it demonstrates that the gauge theory can be successfully studied with devices that only exhibit approximate gauge invariance.

Quantum computation of dynamical quantum phase transitions and entanglement tomography in a lattice gauge theory

“…A more complete approach would be solving a Lindblad equation of the quantum circuit, see e.g., Ref. [97] for a study of the presented model, but this route will not be explored here. The EHT analysis using the BW ansatz presented in section III is repeated using M[ρ A ] instead of ρ A in the fit, separately for three local decoherence error models Eqs.…”

“…[87][88][89][90][91][92][93][94][95], and later predicted to occur in gauge theories as well [1,96]. Importantly, this phenomenon is shown to be an ideal candidate for exploration with existing analog and digital devices, since it persists in small systems and on short time scales [1,97,98]. DQPTs are manifest in non-equal time correlation functions and nonequal time wavefunction overlaps (Loschmidt echos), and in the Schwinger model they are related to an underlying topological transition [1].…”