20 research outputs found
Observation of a prethermal discrete time crystal
The conventional framework for defining and understanding phases of matter
requires thermodynamic equilibrium. Extensions to non-equilibrium systems have
led to surprising insights into the nature of many-body thermalization and the
discovery of novel phases of matter, often catalyzed by driving the system
periodically. The inherent heating from such Floquet drives can be tempered by
including strong disorder in the system, but this can also mask the generality
of non-equilibrium phases. In this work, we utilize a trapped-ion quantum
simulator to observe signatures of a non-equilibrium driven phase without
disorder: the prethermal discrete time crystal (PDTC). Here, many-body heating
is suppressed not by disorder-induced many-body localization, but instead via
high-frequency driving, leading to an expansive time window where
non-equilibrium phases can emerge. We observe a number of key features that
distinguish the PDTC from its many-body-localized disordered counterpart, such
as the drive-frequency control of its lifetime and the dependence of
time-crystalline order on the energy density of the initial state. Floquet
prethermalization is thus presented as a general strategy for creating,
stabilizing and studying intrinsically out-of-equilibrium phases of matter.Comment: 9 + 10 pages, 3 + 6 figure
Simulating Meson Scattering on Spin Quantum Simulators
Studying high-energy collisions of composite particles, such as hadrons and
nuclei, is an outstanding goal for quantum simulators. However, preparation of
hadronic wave packets has posed a significant challenge, due to the complexity
of hadrons and the precise structure of wave packets. This has limited
demonstrations of hadron scattering on quantum simulators to date. Observations
of confinement and composite excitations in quantum spin systems have opened up
the possibility to explore scattering dynamics in spin models. In this article,
we develop two methods to create entangled spin states corresponding to wave
packets of composite particles in analog quantum simulators of Ising spin
Hamiltonians. One wave-packet preparation method uses the blockade effect
enabled by beyond-nearest-neighbor Ising spin interactions. The other method
utilizes a quantum-bus-mediated exchange, such as the native spin-phonon
coupling in trapped-ion arrays. With a focus on trapped-ion simulators, we
numerically benchmark both methods and show that high-fidelity wave packets can
be achieved in near-term experiments. We numerically study scattering of wave
packets for experimentally realizable parameters in the Ising model and find
inelastic-scattering regimes, corresponding to particle production in the
scattering event, with prominent and distinct experimental signals. Our
proposal, therefore, demonstrates the potential of observing inelastic
scattering in near-term quantum simulators.Comment: 18 pages, 4 main figures, 2 supplementary figure
Studies of strongly-correlated fermions in an optical lattice
Ultracold fermionic atoms in a disordered optical lattice can realize the disordered Fermi-Hubbard model, allowing investigations of the nature of strongly-correlated fermions in a minimal setting. This thesis describes two such studies. In the first, we observe the momentum relaxation of strongly-correlated fermions in the absence of disorder. We find a violation of the weak-scattering prediction for the scaling with temperature, which is analogous to the linear-in-temperature scaling of resistivity in substances called ``bad metals.'' In the second, we probe a disordered and strongly-correlated system using quenches of the interaction strength that take it far from equilibrium. We find that the relaxation of double occupancies following the quenches has distinct dynamical regimes controlled by the interplay of interactions and disorder. We present a minimal picture of the relaxation process that illustrates the origin of these regimes, which are related to the Mott--metal--Anderson transitions of the ground state at half-filling
Studies of strongly-correlated fermions in an optical lattice
Ultracold fermionic atoms in a disordered optical lattice can realize the disordered Fermi-Hubbard model, allowing investigations of the nature of strongly-correlated fermions in a minimal setting. This thesis describes two such studies. In the first, we observe the momentum relaxation of strongly-correlated fermions in the absence of disorder. We find a violation of the weak-scattering prediction for the scaling with temperature, which is analogous to the linear-in-temperature scaling of resistivity in substances called ``bad metals.'' In the second, we probe a disordered and strongly-correlated system using quenches of the interaction strength that take it far from equilibrium. We find that the relaxation of double occupancies following the quenches has distinct dynamical regimes controlled by the interplay of interactions and disorder. We present a minimal picture of the relaxation process that illustrates the origin of these regimes, which are related to the Mott--metal--Anderson transitions of the ground state at half-filling