24,468 research outputs found
Bright bichromatic entanglement and quantum dynamics of sum frequency generation
We investigate the quantum properties of the well-known process of sum
frequency generation, showing that it is potentially a very useful source of
non-classical states of the electromagnetic field, some of which are not
possible with the more common techniques. We show that it can produce
quadrature squeezed light, bright bichromatic entangled states and symmetric
and asymmetric demonstrations of the Einstein-Podolsky-Rosen paradox. We also
show that the semiclassical equations totally fail to describe the mean-field
dynamics when the cavity is strongly pumped
Quantum ultra-cold atomtronics
It is known that a semi-classical analysis is not always adequate for
atomtronics devices, but that a fully quantum analysis is often necessary to
make reliable predictions. While small numbers of atoms at a small number of
sites are tractable using the density matrix, a fully quantum analysis is often
not straightforward as the system becomes larger. We show that the fully
quantum positive-P representation is then a viable calculational tool. We
postulate an atomtronic phase-gate consisting of four wells in a Bose-Hubbard
configuration, for which the semi-classical dynamics are controllable using the
phase of the atomic mode in one of the wells. We show that the quantum
predictions of the positive-P representation for the performance of this device
have little relation to those found semi-classically, and that the performance
depends markedly on the actual quantum states of the initially occupied modes.
We find that initial coherent states lead to closest to classical dynamics, but
that initial Fock states give results that are quite different. A fully quantum
analysis also opens the door for deeply quantum atomtronics, in which
properties such as entanglement and EPR (Einstein-Podolsky-Rosen) steering
become valuable technical properties of a device.Comment: 12 pages, 6 figures, submitted to Phys. Rev
A quantum correlated twin atom laser from a Bose-Hubbard system
We propose and evaluate a method to construct a quantum correlated twin atom
laser using a pumped and damped Bose-Hubbard inline trimer which can operate in
a stationary regime. With pumping via a source condensate filling the middle
well and damping using either an electron beam or optical means at the two end
wells, we show that bipartite quantum correlations build up between the ends of
the chain, and that these can be measured either in situ or in the outcoupled
beams. While nothing similar to our system has yet been achieved
experimentally, recent advances mean that it should be practically realisable
in the near future.Comment: 15 pages, 8 figures, theory. Typos fixed and material added to
introductio
Accounting for Multiplicity in Calculating Eta Earth
Using the updated exoplanet population parameters of our previous study,
which includes the planetary radius updates from Gaia DR2 and an inferred
multiplicity distribution, we provide a revised calculation.
This is achieved by sampling planets from our derived population model and
determining which planets meet our criterion for habitability. To ensure robust
results, we provide probabilities calculated over a range of upper radius
limits. Our most optimistic criterion for habitability provides an
value of . We also
consider the effects of multiplicity and the number of habitable planets each
system may contain. Our calculation indicates that of GK dwarfs
have more than one planet within their habitable zone. This optimistic
habitability criterion also suggests that of solar-like stars
will harbor 5 or more habitable planets. These tightly packed highly habitable
system should be extremely rare, but still possible. Even with our most
pessimistic criterion we still expect that of solar-like stars
harbor more than one habitable planet.Comment: 7 pages, 1 figure; Accepted for publication in MNRA
Tripartite entanglement from interlinked parametric interactions
We examine the tripartite entanglement properties of an optical system using
interlinked interactions, recently studied experimentally in terms
of its phase-matching properties by Bondani et al [M. Bondani, A. Allevi, E.
Gevinti, A. Agliati, and A. Andreoni, arXiv:quant-ph/0604002.]. We show that
the system does produce output modes which are genuinely tripartite entangled
and that detection of this entanglement depends crucially on the correlation
functions which are measured, with a three-mode Einstein-Podolsky-Rosen
inequality being the most sensitive.Comment: 15 pages, 5 figure
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