arXiv subjects

Shuohang Wu

Publications and source records attributed to Shuohang Wu.

3 recordsLinked to original sources

arXiv2024

Universal critical dynamics of quantum geometry

In this study, we prove that the quantum critical point in the ground state of quantum many-body systems, can also govern the universal dynamical behavior when the systems are driven far from equilibrium, which can be captured by the evolution of the quantum geometry of the systems. By investigating quantum quench dynamics in quadratic fermionic models, we prove that the quantum volume of these systems typically grows linearly over time, with a growth velocity demonstrating universal behavior: its first derivative over the control parameter exhibits a discontinuity at the quantum critical point, with an universal jump value that is independent of specific models, but is crucially determined by the system dimension. This result reveals universal dynamical properties of non-equilibrium quantum many-body systems

cond-mat.quant-gas↗

arXiv2022

Feedback-induced interactive dynamics: unitary but dissipative evolution

The time evolution of a physical system is generally described by a differential equation, which can be solved numerically by adopting a difference scheme with space-time discretization. This discretization, as a numerical artifact, results in accumulated errors during evolution thus usually plays a negative role in simulations. In a quantum circuit, however, the ``evolution time'' is represented by the depth of the circuit layer, thus is intrinsically discrete. Hence, the discretization-induced error therein is not a numerical artifact, but a physical observable effect responsible for remarkable nonequilibrium phenomena absent in conventional quantum dynamics. In this paper, we show that the combination of measurement feedback and temporal discretization can give rise to a new type of quantum dynamics characterized by unitary but dissipative evolution. As physical consequences of such an unitary but dissipative evolution, a nonequilibrium steady state with spontaneous symmetry breaking is revealed in a zero-dimensional (single-qubit) system. A localization mechanism distinct from that in the well-established Anderson localization has also been proposed in an one-dimensional interactive quantum system.

quant-ph↗

arXiv2022

Nonergodic delocalized paramagnetic states in quantum neural networks

Typically, it is assumed that a high-energy eigenstate of a generic interacting quantum many-body Hamiltonian is thermal and obeys the eigenstate thermalization hypothesis. In this work, we show that the paramagnetic phase of a quantum Hopfield neural network model is delocalized but nonergodic. The combination of permutational symmetry and frustration in this model organize its high-energy eigenstates into clusters, which can each be considered a large quantum spin and has no correlation with others. This model provides another ergodicity-breaking mechanism in quantum many-body systems.

cond-mat.dis-nn↗