31 research outputs found
Universal dynamical decoupling of multiqubit states from environment
We study the dynamical decoupling of multiqubit states from environment. For
a system of m qubits, the nested Uhrig dynamical decoupling (NUDD) sequence can
efficiently suppress generic decoherence induced by system-environment
interaction to order N using (N+1)^2m pulses. We prove that the NUDD sequence
is universal, i.e., it can restore the coherence of m-qubit quantum system
independent of the details of system-environment interaction. We also construct
a general mapping between dynamical decoupling problems and discrete quantum
walks in certain functional spaces.Comment: 4+ pages, 2 figure
Exact prefactors in static and dynamic correlation functions of 1D quantum integrable models: applications to the Calogero-Sutherland, Lieb-Liniger and XXZ models
In this article we demonstrate a recently developed technique which addresses
the problem of obtaining non-universal prefactors of the correlation functions
of 1D systems at zero temperature. Our approach combines the effective field
theory description of generic 1D quantum liquids with the finite size scaling
of form factors (matrix elements) which are obtained using microscopic
techniques developed in the context of integrable models. We thus establish
exact analytic forms for the prefactors of the long-distance behavior of equal
time correlation functions as well as prefactors of singularities of dynamic
response functions. In this article our focus is on three specific integrable
models: the Calogero-Sutherland, Lieb-Liniger, and XXZ models.Comment: 95 pages and 8 figure
Nonuniversal prefactors in correlation functions of 1D quantum liquids
We develop a general approach to calculating "nonuniversal" prefactors in
static and dynamic correlation functions of 1D quantum liquids at zero
temperature, by relating them to the finite size scaling of certain matrix
elements (form factors). This represents a new, powerful tool for extracting
data valid in the thermodynamic limit from finite-size effects. As the main
application, we consider weakly interacting spinless fermions with an arbitrary
pair interaction potential, for which we perturbatively calculate certain
prefactors in static and dynamic correlation functions. We also
non-perturbatively evaluate prefactors of the long-distance behavior of
correlation functions for the exactly solvable Lieb-Liniger model of 1D bosons
The fate of 1D spin-charge separation away from Fermi points
We consider the dynamic response functions of interacting one dimensional
spin-1/2 fermions at arbitrary momenta. We build a non-perturbative
zero-temperature theory of the threshold singularities using mobile impurity
Hamiltonians. The interaction induced low-energy spin-charge separation and
power-law threshold singularities survive away from Fermi points. We express
the threshold exponents in terms of the spinon spectrum.Comment: 5 pages, 1 figur