1,812 research outputs found
Spin gravitational resonance and graviton detection
We develop a gravitational analogue of spin magnetic resonance, called spin
gravitational resonance, whereby a gravitational wave interacts with a magnetic
field to produce a spin transition. In particular, an external magnetic field
separates the energy spin states of a spin-1/2 particle, and the presence of
the gravitational wave produces a perturbation in the components of the
magnetic field orthogonal to the gravitational wave propagation. In this
framework we test Dyson's conjecture that individual gravitons cannot be
detected. Although we find no fundamental laws preventing single gravitons
being detected with spin gravitational resonance, we show that it cannot be
used in practice, in support of Dyson's conjecture.Comment: 6 pages, 1 figur
Disorder Correlation Frequency Controlled Diffusion in the Jaynes-Cummings-Hubbard Model
We investigate time-dependent stochastic disorder in the one-dimensional
Jaynes-Cummings-Hubbard model and show that it gives rise to diffusive
behaviour. We find that disorder correlation frequency is effective in
controlling the level of diffusivity. In the defectless system the mean squared
displacement (MSD), which is a measure of the diffusivity, increases with
increasing disorder frequency. Contrastingly, when static defects are present
the MSD increases with disorder frequency only at lower frequencies; at higher
frequencies, increasing disorder frequency actually reduces the MSD
Gravitational Casimir effect
We derive the gravitonic Casimir effect with non-idealised boundary
conditions. This allows the quantification of the gravitonic contribution to
the Casimir effect from real bodies. We quantify the meagreness of the
gravitonic Casimir effect in ordinary matter. We also quantify the enhanced
effect produced by the speculated Heisenberg-Couloumb (H-C) effect in
superconductors, thereby providing a test for the validity of the H-C theory,
and consequently the existence of gravitons.Comment: 6 pages, 2 figure
Foldy-Wouthuysen transformation of the generalised Dirac Hamiltonian in a gravitational-wave background
Goncalves et al. derived a non-relativistic limit of the generalised Dirac
Hamiltonian in the presence of a gravitational wave, using the exact
Foldy-Wouthuysen transformation. This gave rise to the intriguing notion that
spin-precession may occur even in the absence of a magnetic field. We argue
that this effect is not physical as it is the result of a gauge-variant term
that was an artefact of a flawed application of the exact Foldy-Wouthuysen
transformation. In this paper we derive the correct non-relativistic limit of
the generalised Dirac Hamiltonian in the presence of a gravitational wave,
using both the exact and standard Foldy-Wouthuysen transformation. We show that
both transformations consistently produce a Hamiltonian where all terms are
gauge-invariant. Unfortunately however, we also show that this means the novel
spin-precession effect does not exist.Comment: 4 page
Colloquium: Quantum Batteries
Recent years have witnessed an explosion of interest in quantum devices for
the production, storage, and transfer of energy. In this Colloquium, we
concentrate on the field of quantum energy storage by reviewing recent
theoretical and experimental progress in quantum batteries. We first provide a
theoretical background discussing the advantages that quantum batteries offer
with respect to their classical analogues. We then review the existing quantum
many-body battery models and present a thorough discussion of important issues
related to their open nature. We finally conclude by discussing promising
experimental implementations, preliminary results available in the literature,
and perspectives.Comment: 36 pages, 12 figures, 311 references. Review and perspective article
on quantum batteries. Commissioned for Reviews of Modern Physics. Comments
and feedback are welcom
Reconfigurable quantum metamaterials
By coupling controllable quantum systems into larger structures we introduce
the concept of a quantum metamaterial. Conventional meta-materials represent
one of the most important frontiers in optical design, with applications in
diverse fields ranging from medicine to aerospace. Up until now however,
metamaterials have themselves been classical structures and interact only with
the classical properties of light. Here we describe a class of dynamic
metamaterials, based on the quantum properties of coupled atom-cavity arrays,
which are intrinsically lossless, reconfigurable, and operate fundamentally at
the quantum level. We show how this new class of metamaterial could be used to
create a reconfigurable quantum superlens possessing a negative index gradient
for single photon imaging. With the inherent features of quantum superposition
and entanglement of metamaterial properties, this new class of dynamic quantum
metamaterial, opens a new vista for quantum science and technology.Comment: 16 pages, 8 figure
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