124 research outputs found
Quantum simulation of Rindler transformations
We show how to implement a Rindler transformation of coordinates with an
embedded quantum simulator. A suitable mapping allows to realise the unphysical
operation in the simulated dynamics by implementing a quantum gate on an
enlarged quantum system. This enhances the versatility of embedded quantum
simulators by extending the possible in-situ changes of reference frames to the
non-inertial realm.Comment: 8 pages, 1 figure. v2: minor changes, published versio
Quantum detection of wormholes
We show how to use quantum metrology to detect a wormhole. A coherent state
of the electromagnetic field experiences a phase shift with a slight dependence
on the throat radius of a possible distant wormhole. We show that this tiny
correction is, in principle, detectable by homodyne measurements after long
propagation lengths for a wide range of throat radii and distances to the
wormhole, even if the detection takes place very far away from the throat,
where the spacetime is very close to a flat geometry. We use realistic
parameters from state-of-the-art long-baseline laser interferometry, both
Earth-based and space-borne. The scheme is, in principle, robust to optical
losses and initial mixedness.Comment: 5 pages, 4 figures. v2: minor changes, published versio
Quantum simulation of traversable wormhole spacetimes in a dc-SQUID array
We present an analog quantum simulator of spacetimes containing traversable
wormholes. A suitable spatial dependence in the external bias of a dc-SQUID
array mimics the propagation of light in a 1D wormhole background. The
impedance of the array places severe limitations on the type of spacetime that
we are able to implement. However, we find that wormhole throat radius in the
sub-mm range are achievable. We show how to modify this spacetime in order to
allow the existence of closed timelike curves. The quantum fluctuations of the
phase associated to the finite array impedance might be seen as an analogue of
Hawking's chronology protection mechanism.Comment: 5 pages, 4 figures. v2: title changed. Minor changes. Published
versio
Parameter estimation of wormholes beyond the Heisenberg limit
We propose to exploit the quantum properties of nonlinear media to estimate
the parameters of massless wormholes. The spacetime curvature produces a change
in length with respect to Minkowski spacetime that can be estimated in
principle with an interferometer. We use quantum metrology techniques to show
that the sensitivity is improved with nonlinear media and propose a nonlinear
Mach-Zehnder interferometer to estimate the parameters of massless wormholes
that scales beyond the Heisenberg limit
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
Quantum estimation via parametric amplification in circuit QED arrays
We propose a scheme for quantum estimation by means of parametric
amplification in circuit Quantum Electrodynamics. The modulation of a SQUID
interrupting a superconducting waveguide transforms an initial thermal two-mode
squeezed state in such a way that the new state is sensitive to the features of
the parametric amplifier. We find the optimal initial parameters which maximize
the Quantum Fisher Information. In order to achieve a large number of
independent measurements we propose to use an array of non-interacting
resonators. We show that the combination of both large QFI and large number of
measurements enables -in principle- the use of this setup for Quantum Metrology
applications.Comment: 6 pages, 7 figures v2:cosmetic changes, published versio
Dirac equation in exotic spacetimes
We find solutions of the Dirac equation in curved spacetime. In particular,
we consider 1+1 dimensional sections of several exotic metrics: the Alcubierre
metric, which describes a scenario that allows faster-than-light (FTL)
velocity; the G\"odel metric, that describes a universe containing closed
timelike curves (CTC); and the Kerr metric, which corresponds to the spacetime
of a rotating black hole. Moreover, we also show that the techniques that we
use in these cases can be extended to nonstatic metrics.Comment: 7 pages, 3 figure
Closed timelike curves and chronology protection in quantum and classical simulators
In principe, General Relativity seems to allow the existence of closed
timelike curves (CTC). However, when quantum effects are considered, it is
likely that their existence is prevented by some kind of chronological
protection mechanism, as Hawking conjectured. Confirming or refuting the
conjecture would require a full quantum theory of gravity. Meanwhile, the use
of simulations could shed some light on this issue. We propose simulations of
CTCs in a quantum system as well as in a classical one. In the quantum
simulation, some restrictions appear that are not present in the classical
setup, which could be interpreted as an analogue of a chronology protection
mechanism.Comment: 6 pages, 4 figures. v2: published versio
Dynamical Casimir Effect for Gaussian Boson Sampling
We show that the Dynamical Casimir Effect (DCE), realized on two multimode
coplanar waveguide resonators, implements a gaussian boson sampler (GBS). The
appropriate choice of the mirror acceleration that couples both resonators
translates into the desired initial gaussian state and many-boson interference
in a boson sampling network. In particular, we show that the proposed quantum
simulator naturally performs a classically hard task, known as scattershot
boson sampling. Our result unveils an unprecedented computational power of DCE,
and paves the way for using DCE as a resource for quantum simulation.Comment: 5 pages, 2 figures. v2:minor changes, published versio
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