Engineering non-equilibrium quantum phase transitions via causally gapped Hamiltonians

TL;DR

This paper develops a phenomenological framework for controlling quantum phase transitions through causally-induced gaps, enabling exponential suppression of defects and outperforming standard adiabatic methods in disordered quantum systems.

Contribution

It introduces a novel approach to engineer non-equilibrium quantum critical dynamics using causally-induced gaps, with demonstrated exponential improvements over traditional adiabatic quantum computing.

Findings

Causally-induced non-adiabatic transitions suppress topological defects exponentially.

Exact numerical simulations show exponential performance gains over adiabatic quantum computing.

Scaling relations reveal causal gaps narrow slower than polynomial with system size.

Abstract

We introduce a phenomenological theory for many-body control of critical phenomena by engineering causally-induced gaps for quantum Hamiltonian systems. The core mechanisms are controlling information flow within and/or between clusters that are created near a quantum critical point. To this end, we construct inhomogeneous quantum phase transitions via designing spatio-temporal quantum fluctuations. We show how non-equilibrium evolution of disordered quantum systems can create new effective correlation length scales and effective dynamical critical exponents. In particular, we construct a class of causally-induced non-adiabatic quantum annealing transitions for strongly disordered quantum Ising chains leading to exponential suppression of topological defects beyond standard Kibble-Zurek predictions. Using exact numerical techniques for 1D quantum Hamiltonian systems, we demonstrate that our approach exponentially outperform adiabatic quantum computing. Using Strong-Disorder Renormalization Group (SDRG), we demonstrate the universality of inhomogeneous quantum critical dynamics and exhibit the causal zones reconstructions during SDRG flow. We derive a scaling relation for minimal causal gaps showing they narrow more slowly than any polynomial with increasing size of system, in contrast to stretched exponential scaling in standard adiabatic evolution. Furthermore, we demonstrate similar scaling behaviour for random cluster-Ising Hamiltonians with higher order interactions.