176 research outputs found
Probing the spacetime structure of vacuum entanglement
We introduce a framework for probing the spacetime structure of vacuum
entanglement that exhibits infinite range correlations between the future and
the past, as well as spatially separated regions. Our results are
non-perturbative and analytical.Comment: I.F. previously published as Fuentes-Guridi and Fuentes-Schulle
On relativistic particle creation in Bose-Einstein condensates
We show that particle creation of Bogoliubov modes in a Bose-Einstein
condensate due to the accelerated motion of the trap is a genuinely
relativistic effect. To this end we show that Bogoliubov modes can be described
by a time rescaling of the Minkowski metric. A consequence of this is that
Rindler transformations are perceived by the phonons as generalised Rindler
transformations where the speed of light is replaced by the speed of sound,
enhancing particle creation at small velocities. Since the non-relativistic
limit of a Rindler transformation is just a Galilean transformation entailing
no length contraction or time dilation, we show that the effect vanishes in the
non-relativistic limit.Comment: This work provides further theoretical support to the results in Sci.
Rep. 4, 4996 (2014),
http://www.nature.com/srep/2014/140521/srep04996/full/srep04996.htm
Active Interferometry with Gaussian Channels
We consider an interferometer that contains active elements, such as a
parametric amplifier, with general two-mode Gaussian unitary channels rather
than the usually considered phase-shift channel. We concentrate on a scheme
based on the recently proposed pumped-up SU(1,1) active interferometer where
all input particles participate in the parameter estimation, and from which a
conventional SU(1,1) interferometer is a limiting case. Using the covariance
matrix formalism, we derive the quantum Fisher information of this active
interferometer with a general two-mode Gaussian unitary channel, as well as the
sensitivity for a number-sum measurement scheme, finding simple expressions for
the latter. As an example application, we apply our results to Bose-Einstein
condensates (BECs), and in particular a BEC gravitational-wave detector based
on resonance, finding that the sensitivity of the detector can be improved by
several orders of magnitude with this new interferometry scheme.Comment: 17 pages, 1 figur
Observer dependent entanglement
Understanding the observer-dependent nature of quantum entanglement has been
a central question in relativistic quantum information. In this paper we will
review key results on relativistic entanglement in flat and curved spacetime
and discuss recent work which shows that motion and gravity have observable
effects on entanglement between localized systems.Comment: Ivette Fuentes previously published as Ivette Fuentes-Guridi and
Ivette Fuentes-Schulle
Spatially extended Unruh-DeWitt detectors for relativistic quantum information
Unruh-DeWitt detectors interacting locally with a quantum field are systems
under consideration for relativistic quantum information processing. In most
works, the detectors are assumed to be point-like and, therefore, couple with
the same strength to all modes of the field spectrum. We propose the use of a
more realistic detector model where the detector has a finite size conveniently
tailored by a spatial profile. We design a spatial profile such that the
detector, when inertial, naturally couples to a peaked distribution of
Minkowski modes. In the uniformly accelerated case, the detector couples to a
peaked distribution of Rindler modes. Such distributions are of special
interest in the analysis of entanglement in non-inetial frames. We use our
detector model to show the noise detected in the Minkowski vacuum and in single
particle states is a function of the detector's acceleration.Comment: Revised for publication, 9 pages (+1 references page), 7 figure
Analog quantum simulation of gravitational waves in a Bose-Einstein condensate
We show how to vary the physical properties of a Bose-Einstein condensate
(BEC) in order to mimic an effective gravitational-wave spacetime. In
particular, we focus in the simulation of the recently discovered creation of
particles by real spacetime distortion in box-type traps. We show that, by
modulating the speed of sound in the BEC, the phonons experience the effects of
a simulated spacetime ripple with experimentally amenable parameters. These
results will inform the experimental programme of gravitational wave astronomy
with cold atoms.Comment: 9 pages. I. F. previously published as I. Fuentes-Guridi and
I.Fuentes-Schuller. v2: minor changes, references adde
Dynamical Casimir effect in curved spacetime
A boundary undergoing relativistic motion can create particles from quantum
vacuum fluctuations in a phenomenon known as the dynamical Casimir effect. We
examine the creation of particles, and more generally the transformation of
quantum field states, due to boundary motion in curved spacetime. We provide a
novel method enabling the calculation of the effect for a wide range of
trajectories and spacetimes. We apply this to the experimental scenario used to
detect the dynamical Casimir effect, now adopting the Schwarzschild metric, and
find novel resonances in particle creation as a result of the spacetime
curvature. Finally, we discuss a potential enhancement of the effect for the
phonon field of a Bose-Einstein condensate.Comment: 17 pages, 0 figures, 2 appendice
Optimal quantum estimation of the Unruh-Hawking effect
We address on general quantum-statistical grounds the problem of optimal
detection of the Unruh-Hawking effect. We show that the effect signatures are
magnified up to potentially observable levels if the scalar field to be probed
has high mean energy from an inertial perspective: The Unruh-Hawking effect
acts like an amplification channel. We prove that a field in a Fock inertial
state, probed via photon counting by a non-inertial detector, realizes the
optimal strategy attaining the ultimate sensitivity allowed by quantum
mechanics for the observation of the effect. We define the parameter regime in
which the effect can be reliably revealed in laboratory experiments, regardless
of the specific implementation.Comment: 4 pages, 2 figures. Close to published version. (I.F. previously
published as Fuentes-Guridi and Fuentes-Schuller
Ruling out stray thermal radiation in analogue black holes
Experimental searches for the thermal radiation from analogue black holes
require the measurement of very low temperatures in regimes where other thermal
noises may interfere or even mimic the sought-after effect. In this letter, we
parameterize the family of bosonic thermal channels which give rise to such
thermal effects and show that by use of coherent states and homodyne detection
one can rule out the non-Hawking contributions and identify those candidate
sources which arise from Hawking-like processes.Comment: 5 pages, 2 figure
Quantum discord in the Dynamical Casimir Effect
We analyse the generation of quantum discord by means of the dynamical
Casimir effect in superconducting waveguides modulated by superconducting
quantum interferometric devices. We show that for realistic experimental
parameters, the conditions for the existence of quantum discord are less
demanding than the previously considered for quantum entanglement or
non-classicality. The states with non-zero discord and zero entanglement
generated by the dynamical Casimir effect are a useful resource for quantum
cryptography.Comment: 4 pages, 2 figures. v2: minor changes, published versio
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