Direct observation of dynamical quasi-condensation on a quantum computer

Abstract

Hard-core bosons (HCB) in one dimension are predicted to show surprisingly interesting dynamics after a quantum quench. Far from equilibrium, quasi-condensation at finite momenta has been observed in numerical studies, while the equilibrium state at late times is expected to violate conventional thermodynamics. The integrability of the model supposedly constraints the momentum distribution to approach a generalized Gibbs ensemble. The experimental observation of these phenomena has proven non-trivial, as optical lattice platforms do not directly access the momentum distribution. NISQ devices overcome this limitation. We use circuit compression in order to simulate dynamics to arbitrarily long times with negligible Trotter-error on IBMQ and directly observe quasi-condensation. Coherence is maintained across all time scales as indicated by the lowest natural orbitals. The equilibrium distribution at late times is seemingly well described by a Gibbs ensemble, indicating that small but finite systematic errors perturb the hard-core boson model away from integrability. We demonstrate that quantum simulation provides observational access to HCB physics.