4,973 research outputs found
Nonlinear optomechanical pressure
A transparent material exhibits ultra-fast optical nonlinearity and is
subject to optical pressure if irradiated by a laser beam. However, the effect
of nonlinearity on optical pressure is often overlooked, even if a nonlinear
optical pressure may be potentially employed in many applications, as optical
manipulation, biophysics, cavity optomechanics, quantum optics, optical
tractors, and is relevant in fundamental problems as the Abraham-Minkoswky
dilemma, or the Casimir effect. Here we show that an ultra-fast nonlinear
polarization gives indeed a contribution to the optical pressure that also is
negative in certain spectral ranges; the theoretical analysis is confirmed by
first-principles simulations. An order of magnitude estimate shows that the
effect can be observable by measuring the deflection of a membrane made by
graphene.Comment: 10 pages, 6 figures, minor corrections to text and references,
Physical Review A, to be publishe
An introduction to ghost imaging: quantum and classical
Ghost imaging has been a subject of interest to the quantum optics community for the past 20 years. Initially seen as manifestation of quantum spookiness, it is now recognized as being implementable in both single- and many-photon number regimes. Beyond its scientific curiosity, it is now feeding novel imaging modalities potentially offering performance attributes that traditional approaches cannot match
Finite-key security analysis for multilevel quantum key distribution
We present a detailed security analysis of a d-dimensional quantum key
distribution protocol based on two and three mutually unbiased bases (MUBs)
both in an asymptotic and finite key length scenario. The finite secret key
rates are calculated as a function of the length of the sifted key by (i)
generalizing the uncertainly relation-based insight from BB84 to any d-level
2-MUB QKD protocol and (ii) by adopting recent advances in the second-order
asymptotics for finite block length quantum coding (for both d-level 2- and
3-MUB QKD protocols). Since the finite and asymptotic secret key rates increase
with d and the number of MUBs (together with the tolerable threshold) such QKD
schemes could in principle offer an important advantage over BB84. We discuss
the possibility of an experimental realization of the 3-MUB QKD protocol with
the orbital angular momentum degrees of freedom of photons.Comment: v4: close to the published versio
X-Ray Diffraction Study of the Internal Structure of Supercooled Water
A Bragg X-ray spectrometer equipped with a volume-sensitive Geiger counter and Soller slits and employing filtered molybdenum Ka radiation was used to obtain a set of diffracted intensity curves as a Punction of angle for supercooled water. Diffracted intensity curves in the temperature region of 21 to -16 C were obtained. The minimum between the two main diffraction peaks deepened continuously with lowering temperature, indicating a gradual change in the internal structure of the water. No discontinuity in this trend was noted at the melting point. The internal structure of supercooled water was concluded to become progressively more ice-like as the temperature is lowered
Generation of Caustics and Spatial Rogue Waves from Nonlinear Instability
Caustics are natural phenomena in which nature concentrates the energy of
waves. Although, they are known mostly in optics, caustics are intrinsic to all
wave phenomena. For example, studies show that fluctuations in the profile of
an ocean floor can generate random caustics and focus the energy of tsunami
waves. Caustics share many similarities to rogue waves, as they both exhibit
heavy-tailed distribution, i.e. an overpopulation of large events. Linear
Schr\"odinger-type equations are usually used to explain the wave dynamics of
caustics. However, in that the wave amplitude increases dramatically in
caustics, nonlinearity is inevitable in many systems. In this Letter, we
investigate the effect of nonlinearity on the formation of optical caustics. We
show experimentally that, in contrast to linear systems, even small phase
fluctuations can generate strong caustics upon nonlinear propagation. We
simulated our experiment based on the nonlinear Schr\"odinger equation (NLSE)
with Kerr-type nonlinearity, which describes the wave dynamics not only in
optics, but also in some other physical systems such as oceans. Therefore, our
results may also aid our understanding of ocean phenomena.Comment: 5 pages, 4 figure
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