9 research outputs found
Topological Valley Currents in Gapped Dirac Materials
Gapped 2D Dirac materials, in which inversion symmetry is broken by a
gap-opening perturbation, feature a unique valley transport regime. The system
ground state hosts dissipationless persistent valley currents existing even
when topologically protected edge modes are absent or when they are localized
due to edge roughness. Topological valley currents in such materials are
dominated by bulk currents produced by electronic states just beneath the gap
rather than by edge modes. Dissipationless currents induced by an external bias
are characterized by a quantized half-integer valley Hall conductivity. The
under-gap currents dominate magnetization and the charge Hall effect in a
light-induced valley-polarized state.Comment: 5pgs 3fg
Size of bulk fermions in the SYK model
The study of quantum gravity in the form of the holographic duality has uncovered and motivated the detailed investigation of various diagnostics of quantum chaos. One such measure is the operator size distribution, which characterizes the size of the support region of an operator and its evolution under Heisenberg evolution. In this work, we examine the role of the operator size distribution in holographic duality for the Sachdev-Ye-Kitaev (SYK) model. Using an explicit construction of AdSâ‚‚ bulk fermion operators in a putative dual of the low temperature SYK model, we study the operator size distribution of the boundary and bulk fermions. Our result provides a direct derivation of the relationship between (effective) operator size of both the boundary and bulk fermions and bulk SL(2; â„ť) generators
Size of bulk fermions in the SYK model
The study of quantum gravity in the form of the holographic duality has
uncovered and motivated the detailed investigation of various diagnostics of
quantum chaos. One such measure is the operator size distribution, which
characterizes the size of the support region of an operator and its evolution
under Heisenberg evolution. In this work, we examine the role of the operator
size distribution in holographic duality for the Sachdev-Ye-Kitaev (SYK) model.
Using an explicit construction of AdS bulk fermion operators in a putative
dual of the low temperature SYK model, we study the operator size distribution
of the boundary and bulk fermions. Our result provides a direct derivation of
the relationship between (effective) operator size of both the boundary and
bulk fermions and bulk generators.Comment: 41 pages, 10 figure
Measurement-induced entanglement and teleportation on a noisy quantum processor
Measurement has a special role in quantum theory: by collapsing the
wavefunction it can enable phenomena such as teleportation and thereby alter
the "arrow of time" that constrains unitary evolution. When integrated in
many-body dynamics, measurements can lead to emergent patterns of quantum
information in space-time that go beyond established paradigms for
characterizing phases, either in or out of equilibrium. On present-day NISQ
processors, the experimental realization of this physics is challenging due to
noise, hardware limitations, and the stochastic nature of quantum measurement.
Here we address each of these experimental challenges and investigate
measurement-induced quantum information phases on up to 70 superconducting
qubits. By leveraging the interchangeability of space and time, we use a
duality mapping, to avoid mid-circuit measurement and access different
manifestations of the underlying phases -- from entanglement scaling to
measurement-induced teleportation -- in a unified way. We obtain finite-size
signatures of a phase transition with a decoding protocol that correlates the
experimental measurement record with classical simulation data. The phases
display sharply different sensitivity to noise, which we exploit to turn an
inherent hardware limitation into a useful diagnostic. Our work demonstrates an
approach to realize measurement-induced physics at scales that are at the
limits of current NISQ processors
Non-Abelian braiding of graph vertices in a superconducting processor
Indistinguishability of particles is a fundamental principle of quantum
mechanics. For all elementary and quasiparticles observed to date - including
fermions, bosons, and Abelian anyons - this principle guarantees that the
braiding of identical particles leaves the system unchanged. However, in two
spatial dimensions, an intriguing possibility exists: braiding of non-Abelian
anyons causes rotations in a space of topologically degenerate wavefunctions.
Hence, it can change the observables of the system without violating the
principle of indistinguishability. Despite the well developed mathematical
description of non-Abelian anyons and numerous theoretical proposals, the
experimental observation of their exchange statistics has remained elusive for
decades. Controllable many-body quantum states generated on quantum processors
offer another path for exploring these fundamental phenomena. While efforts on
conventional solid-state platforms typically involve Hamiltonian dynamics of
quasi-particles, superconducting quantum processors allow for directly
manipulating the many-body wavefunction via unitary gates. Building on
predictions that stabilizer codes can host projective non-Abelian Ising anyons,
we implement a generalized stabilizer code and unitary protocol to create and
braid them. This allows us to experimentally verify the fusion rules of the
anyons and braid them to realize their statistics. We then study the prospect
of employing the anyons for quantum computation and utilize braiding to create
an entangled state of anyons encoding three logical qubits. Our work provides
new insights about non-Abelian braiding and - through the future inclusion of
error correction to achieve topological protection - could open a path toward
fault-tolerant quantum computing