44 research outputs found
Quantum and classical spin network algorithms for -deformed Kogut-Susskind gauge theories
Treating the infinite-dimensional Hilbert space of non-abelian gauge theories
is an outstanding challenge for classical and quantum simulations. Here, we
introduce -deformed Kogut-Susskind lattice gauge theories, obtained by
deforming the defining symmetry algebra to a quantum group. In contrast to
other formulations, our proposal simultaneously provides a controlled
regularization of the infinite-dimensional local Hilbert space while preserving
essential symmetry-related properties. This enables the development of both
quantum as well as quantum-inspired classical Spin Network Algorithms for
-deformed gauge theories (SNAQs). To be explicit, we focus on SU(2)
gauge theories, that are controlled by the deformation parameter and
converge to the standard SU(2) Kogut-Susskind model as .
In particular, we demonstrate that this formulation is well suited for
efficient tensor network representations by variational ground-state
simulations in 2D, providing first evidence that the continuum limit can be
reached with . Finally, we develop a scalable quantum
algorithm for Trotterized real-time evolution by analytically diagonalizing the
SU(2) plaquette interactions. Our work gives a new perspective for the
application of tensor network methods to high-energy physics and paves the way
for quantum simulations of non-abelian gauge theories far from equilibrium
where no other methods are currently available.Comment: 5+4 pages, 4+1 figure
Robust Topological Order in Fermionic Z(2) Gauge Theories: From Aharonov-Bohm Instability to Soliton-Induced Deconfinement
Topologically ordered phases of matter, although stable against local perturbations, are usually restricted to relatively small regions in phase diagrams. Thus, their preparation requires a precise fine-tunning of the system's parameters, a very challenging task in most experimental setups. In this work, we investigate a model of spinless fermions interacting with dynamical Z2 gauge fields on a cross-linked ladder and show evidence of topological order throughout the full parameter space. In particular, we show how a magnetic flux is spontaneously generated through the ladder due to an Aharonov-Bohm instability, giving rise to topological order even in the absence of a plaquette term. Moreover, the latter coexists here with a symmetry-protected topological phase in the matter sector, which displays fractionalized gauge-matter edge states and intertwines with it by a flux-threading phenomenon. Finally, we unveil the robustness of these features through a gauge frustration mechanism, akin to geometric frustration in spin liquids, allowing topological order to survive to arbitrarily large quantum fluctuations. In particular, we show how, at finite chemical potential, topological solitons are created in the gauge field configuration, which bound to fermions and form Z2 deconfined quasiparticles. The simplicity of the model makes it an ideal candidate for 2D gauge theory phenomena, as well as exotic topological effects, to be investigated using cold-atom quantum simulators
Tuning long-range fermion-mediated interactions in cold-atom quantum simulators
Engineering long-range interactions in cold-atom quantum simulators can lead
to exotic quantum many-body behavior. Fermionic atoms in ultracold atomic
mixtures can act as mediators, giving rise to long-range RKKY-type interactions
characterized by the dimensionality and density of the fermionic gas. Here, we
propose several tuning knobs, accessible in current experimental platforms,
that allow to further control the range and shape of the mediated interactions,
extending the existing quantum simulation toolbox. In particular, we include an
additional optical lattice for the fermionic mediator, as well as anisotropic
traps to change its dimensionality in a continuous manner. This allows us to
interpolate between power-law and exponential decays, introducing an effective
cutoff for the interaction range, as well as to tune the relative interaction
strengths at different distances. Finally, we show how our approach allows to
investigate frustrated regimes that were not previously accessible, where
symmetry-protected topological phases as well as chiral spin liquids emerge.Comment: 5 pages, 4 figure
Scar States in Deconfined Lattice Gauge Theories
The weak ergodicity breaking induced by quantum many-body scars (QMBS)
represents an intriguing concept that has received great attention in recent
years due to its relation to unusual non-equilibrium behaviour. Here we reveal
that this phenomenon can occur in a previously unexplored regime of a lattice
gauge theory, where QMBS emerge due to the presence of an extensive number of
local constraints. In particular, by analyzing the gauged Kitaev model, we
provide an example where QMBS appear in a regime where charges are deconfined.
By means of both numerical and analytical approaches, we find a variety of
scarred states far away from the regime where the model is integrable. The
presence of these states is revealed both by tracing them directly from the
analytically reachable limit, as well as by quantum quenches showing persistent
oscillations for specific initial states.Comment: second modified version, comments welcom