400 research outputs found
Prethermal Strong Zero Modes and Topological Qubits
We prove that quantum information encoded in some topological excitations,
including certain Majorana zero modes, is protected in closed systems for a
time scale exponentially long in system parameters. This protection holds even
at infinite temperature. At lower temperatures the decay time becomes even
longer, with a temperature dependence controlled by an effective gap that is
parametrically larger than the actual energy gap of the system. This
non-equilibrium dynamical phenomenon is a form of prethermalization, and occurs
because of obstructions to the equilibriation of edge or defect degrees of
freedom with the bulk. We analyze the ramifications for ordered and topological
phases in one, two, and three dimensions, with examples including Majorana and
parafermionic zero modes in interacting spin chains. Our results are based on a
non-perturbative analysis valid in any dimension, and they are illustrated by
numerical simulations in one dimension. We discuss the implications for
experiments on quantum-dot chains tuned into a regime supporting end Majorana
zero modes, and on trapped ion chains.Comment: 20 pages. v2: reorganized and added overview sectio
Long coherence times for edge spins
We show that in certain one-dimensional spin chains with open boundary
conditions, the edge spins retain memory of their initial state for very long
times. The long coherence times do not require disorder, only an ordered phase.
In the integrable Ising and XYZ chains, the presence of a strong zero mode
means the coherence time is infinite, even at infinite temperature. When Ising
is perturbed by interactions breaking the integrability, the coherence time
remains exponentially long in the perturbing couplings. We show that this is a
consequence of an edge "almost" strong zero mode that almost commutes with the
Hamiltonian. We compute this operator explicitly, allowing us to estimate
accurately the plateau value of edge spin autocorrelator.Comment: 13 pages, 13 figures; references adde
Through Education & Economic Development
I. Securing Full Share In the Economic Bounty II. Building Momentum Towards Success III. HBCUs as Catalysts For Entrepreneurship IV. The Government As a Collaborato
Distinct Floquet topological classifications from color-decorated frequency lattices with space-time symmetries
We consider nontrivial topological phases in Floquet systems using unitary
loops and stroboscopic evolutions under a static Floquet Hamiltonian in
the presence of dynamical space-time symmetries . While the latter has been
subject of out-of-equilibrium classifications that extend the ten-fold way and
systems with additional crystalline symmetries to periodically driven systems,
we explore the anomalous topological zero modes that arise in from the
coexistence of a dynamical space-time symmetry and antisymmetry of ,
and classify them using a frequency-domain formulation. Moreover, we provide an
interpretation of the resulting Floquet topological phases using a frequency
lattice with a decoration represented by color degrees of freedom on the
lattice vertices. These colors correspond to the coefficient of the group
extension of along the frequency lattice, given by . The distinct topological classifications that arise at different
energy gaps in its quasi-energy spectrum are described by the torsion product
of the cohomology group classifying the group extension.Comment: 4 pages + supplementary materia
Exercise intervention in people with cancer undergoing adjuvant cancer treatment following surgery: a systematic review
BackgroundRemaining physically active during and after cancer treatment is known to improve associated adverse effects, improve overall survival and reduce the probability of relapse. This systematic review addresses the question: is an exercise training programme beneficial in people with cancer undergoing adjuvant cancer treatment following surgery.MethodsA systematic database search of Embase, Ovid, Medline without Revisions, SPORTDiscus, Web of Science, Cochrane Library and ClinicalTrials.gov for any randomised controlled trials (RCT) or non-RCT addressing the effect of an exercise training programme in those having adjuvant cancer treatment following surgery was conducted.ResultsThe database search yielded 6489 candidate abstracts of which 94 references included the required terms. A total of 17 articles were included in this review. Exercise training is safe and feasible in the adjuvant setting and furthermore may improve measures of physical fitness and health related quality of life (HRQoL).ConclusionThis is the first systematic review on exercise training interventions in people with cancer undergoing adjuvant cancer treatment following surgery. Due to the lack of adequately powered RCTs in this area, it remains unclear whether exercise training in this context improves clinical outcomes other physical fitness and HRQoL. It remains unclear what is the optimal timing of initiation of an exercise programme and what are the best combinations of elements within an exercise training programme to optimise training efficacy. Furthermore, it is unclear if initiating such exercise programmes at cancer diagnosis may have a long-lasting effect on physically activity throughout the subsequent life course
- …