6 research outputs found
Quantum work statistics, Loschmidt echo and information scrambling
A universal relation is established between the quantum work probability
distribution of an isolated driven quantum system and the Loschmidt echo
dynamics of a two-mode squeezed state. When the initial density matrix is
canonical, the Loschmidt echo of the purified double thermofield state provides
a direct measure of information scrambling and can be related to the analytic
continuation of the partition function. Information scrambling is then
described by the quantum work statistics associated with the time-reversal
operation on a single copy, associated with the sudden negation of the system
Hamiltonian.Comment: 6 pages, 1 figure, published versio
Crossing the superfluid-supersolid transition of an elongated dipolar condensate
We provide a theoretical characterization of the dynamical crossing of the
superfluid-supersolid phase transition for a dipolar condensate confined in an
elongated trap, as observed in the recent experiment by G. Biagioni et al.
[Phys. Rev. X 12, 021019 (2022)]. By means of the extended Gross-Pitaevskii
theory, which includes the Lee-Huang-Yang quantum fluctuation correction, we
first analyze the ground state configurations of the system as a function of
the interparticle scattering length, for both trap configurations employed in
the experiment. Then, we discuss the effects of the ramp velocity, by which the
scattering length is tuned across the transition, on the collective excitations
of the system in both the superfluid and supersolid phases. We find that, when
the transverse confinement is sufficiently strong and the transition has a
smooth (continuous) character, the system essentially displays a (quasi) 1D
behavior, its excitation dynamics being dominated by the axial breathing modes.
Instead, for shallower transverse trapping, when the transition becomes
discontinuous, the collective excitations of the supersolid display a coupling
with the transverse modes, signalling the onset of a dimensional crossover.Comment: 9 pages, 8 figure
Transition from discrete to continuous time of arrival distribution for a quantum particle
We show that the Kijowski distribution for time of arrivals in the entire
real line is the limiting distribution of the time of arrival distribution in a
confining box as its length increases to infinity. The dynamics of the confined
time of arrival eigenfunctions is also numerically investigated and
demonstrated that the eigenfunctions evolve to have point supports at the
arrival point at their respective eigenvalues in the limit of arbitrarilly
large confining lengths, giving insight into the ideal physical content of the
Kijowsky distribution.Comment: Accepted for publication in Phys. Rev.
Real clocks and the Zeno effect
Real clocks are not perfect. This must have an effect in our predictions for
the behaviour of a quantum system, an effect for which we present a unified
description encompassing several previous proposals. We study the relevance of
clock errors in the Zeno effect, and find that generically no Zeno effect can
be present (in such a way that there is no contradiction with currently
available experimental data). We further observe that, within the class of
stochasticities in time addressed here, there is no modification in emission
lineshapes.Comment: 12 a4 pages, no figure
Quantum evolution according to real clocks
We characterize good clocks, which are naturally subject to fluctuations, in
statistical terms. We also obtain the master equation that governs the
evolution of quantum systems according to these clocks and find its general
solution. This master equation is diffusive and produces loss of coherence.
Moreover, real clocks can be described in terms of effective interactions that
are nonlocal in time. Alternatively, they can be modeled by an effective
thermal bath coupled to the system.Comment: RevTeX 3.01, 6 page