3,382 research outputs found
Entanglement analysis of isotropic spin-1 chains
We investigate entanglement spectra of the SO(3) bilinear-biquadratic spin-1
chain, a model with phases exhibiting spontaneous symmetry breaking (both
translation and spin rotation), points of enlarged symmetry, and a
symmetry-protected topological phase (the Haldane phase). Our analysis reveals
how these hallmark features are manifested in the entanglement spectra, and
highlights the versatility of entanglement spectra as a tool to study
one-dimensional quantum systems via small finite size realisations.Comment: 21 pages, 13 figure
Sign-problem-free Monte Carlo simulation of certain frustrated quantum magnets
We introduce a Quantum Monte Carlo (QMC) method which efficiently simulates
in a sign-problem-free way a broad class of frustrated models with
competing antiferromagnetic interactions. Our scheme uses the basis of total
spin eigenstates of clusters of spins to avoid the severe sign problem faced by
other QMC methods. We also flag important limitations of the new method, and
comment on possibilities for further progress.Comment: 6 pages + appendix with supplemental informatio
Measurement Protocol for the Entanglement Spectrum of Cold Atoms
Entanglement, and, in particular the entanglement spectrum, plays a major
role in characterizing many-body quantum systems. While there has been a surge
of theoretical works on the subject, no experimental measurement has been
performed to date because of the lack of an implementable measurement scheme.
Here, we propose a measurement protocol to access the entanglement spectrum of
many-body states in experiments with cold atoms in optical lattices. Our scheme
effectively performs a Ramsey spectroscopy of the entanglement Hamiltonian and
is based on the ability to produce several copies of the state under
investigation together with the possibility to perform a global swap gate
between two copies conditioned on the state of an auxiliary qubit. We show how
the required conditional swap gate can be implemented with cold atoms, either
by using Rydberg interactions or coupling the atoms to a cavity mode. We
illustrate these ideas on a simple (extended) Bose-Hubbard model where such a
measurement protocol reveals topological features of the Haldane phase
Permutation Symmetric Critical Phases in Disordered Non-Abelian Anyonic Chains
Topological phases supporting non-abelian anyonic excitations have been
proposed as candidates for topological quantum computation. In this paper, we
study disordered non-abelian anyonic chains based on the quantum groups
, a hierarchy that includes the FQH state and the proposed
Fibonacci state, among others. We find that for odd these
anyonic chains realize infinite randomness critical {\it phases} in the same
universality class as the permutation symmetric multi-critical points of
Damle and Huse (Phys. Rev. Lett. 89, 277203 (2002)). Indeed, we show that the
pertinent subspace of these anyonic chains actually sits inside the symmetric sector of the Damle-Huse model, and this symmetry stabilizes the phase.Comment: 13 page
Critical Ising modes in low-dimensional Kondo insulators
We present an Ising-like intermediate phase for one-dimensional Kondo
insulator systems. Resulting from a spinon splitting, its low-energy
excitations are critical Ising modes, whereas the triplet sector has a spectral
gap. It should occur as long as the RKKY oscillation amplitude dominates over
any direct exchange between localized spins. The chiral fixed point, however,
becomes unstable in the far Infra-Red limit due to prevalent fluctuations among
localized spins which induce gapless triplet excitations in the spectrum. Based
on previous numerical results, we obtain a paramagnetic disordered state ruled
by the correlation length of the single impurity Kondo model.Comment: 7 pages, RevTeX; last version: to be published in Physical Review
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