324 research outputs found
Engineering asymmetric steady-state Einstein-Podolsky-Rosen steering in macroscopic hybrid systems
Generation of quantum correlations between separate objects is of
significance both in fundamental physics and in quantum networks. One important
challenge is to create the directional "spooky action-at-a-distanc" effects
that Schr\"{o}dinger called "steering" between two macroscopic and massive
objects. Here, we analyze a generic scheme for generating steering correlations
in cascaded hybrid systems in which two distant oscillators with effective
masses of opposite signs are coupled to a unidirectional light field, a setup
which is known to build up quantum correlations by means of quantum back-action
evasion. The unidirectional coupling of the first to the second oscillator via
the light field can be engineered to enhance steering in both directions and
provides an active method for controlling the asymmetry of steering. We show
that the resulting scheme can efficiently generate unconditional steady-state
Einstein-Podolsky-Rosen steering between the two subsystems, even in the
presence of thermal noise and optical losses. As a scenario of particular
technological interest in quantum networks, we use our scheme to engineer
enhanced steering from an untrusted node with limited tunability (in terms of
interaction strength and type with the light field) to a trusted, highly
tunable node, hence offering a path to implementing one-sided
device-independent quantum tasks.Comment: 11 pages, 8 figure
Integrated all-optical logic discriminators based on plasmonic bandgap engineering
Optical computing uses photons as information carriers, opening up the
possibility for ultrahigh-speed and ultrawide-band information processing.
Integrated all-optical logic devices are indispensible core components of
optical computing systems. However, up to now, little experimental progress has
been made in nanoscale all-optical logic discriminators, which have the
function of discriminating and encoding incident light signals according to
wavelength. Here, we report a strategy to realize a nanoscale all-optical logic
discriminator based on plasmonic bandgap engineering in a planar plasmonic
microstructure. Light signals falling within different operating wavelength
ranges are differentiated and endowed with different logic state encodings.
Compared with values previously reported, the operating bandwidth is enlarged
by one order of magnitude. Also the SPP light source is integrated with the
logic device while retaining its ultracompact size. This opens up a way to
construct on-chip all-optical information processors and artificial
intelligence systems.Comment: 4 figures 201
Role of thermal noise in tripartite quantum steering
The influence of thermal noise on bipartite and tripartite quantum steering
induced by a short laser pulse in a hybrid three-mode optomechanical system is
investigated. The calculation is carried out under the bad cavity limit, the
adiabatic approximation of a slowly varying amplitude of the cavity mode, and
with the assumption of driving the cavity mode with a blue detuned strong laser
pulse. Under such conditions, explicit expressions of the bipartite and
tripartite steering parameters are obtained, and the concept of collective
tripartite quantum steering, recently introduced by He and Reid [Phys. Rev.
Lett. 111, 250403 (2013)], is clearly explored. It is found that both bipartite
and tripartite steering parameters are sensitive functions of the initial state
of the modes and distinctly different steering behaviour could be observed
depending on whether the modes were initially in a thermal state or not. We
find that the initial thermal noise is more effective in destroying the
bipartite rather than the tripartite steering which, on the other hand, can
persist even for a large thermal noise. For the initial vacuum state of a
steered mode, the tripartite steering exists over the entire interaction time
even if the steering modes are in very noisy thermal states. When the steered
mode is initially in a thermal state, it can be collectively steered by the
other modes. There are thresholds for the average number of the thermal photons
above which the existing tripartite steering appears as the collective
steering. Finally, we point out that the collective steering may provide a
resource in a hybrid quantum network for quantum secret sharing protocol.Comment: 13 pages, 9 figure
Ultrawide-band Unidirectional Surface Plasmon Polariton Launchers
Plasmonic devices and circuits, bridging the gap between integrated photonic
and microelectronic technology, are promising candidates to realize on-chip
ultrawide-band and ultrahigh-speed information processing. Unfortunately, the
wideband surface plasmon source, one of the most important core components of
integrated plasmonic circuits, is still unavailable up to now. This has
seriously restricted the practical applications of plasmonic circuits. Here, we
report an ultrawide-band unidirectional surface plasmon polariton launcher with
high launching efficiency ratio and large extinction ratio, realized by
combining plasmonic bandgap engineering and linear interference effect. This
device offers excellent performances over an ultrabroad wavelength range from
690 to 900 nm, together with a high average launching efficiency ratio of 1.25,
large average extinction ratio of 30 dB, and ultracompact lateral dimension of
less than 4 um. Compared with previous reports, the operating bandwidth is
enlarged 210 folds, while the largest launching efficiency ratio, largest
extinction ratio, and small feature size are maintained simultaneously. This
provides a strategy for constructing on-chip surface plasmon source, and also
paving the way for the study of integrated plasmonic circuits.Comment: 4 figure
Plasmonic nano-resonator enhanced one-photon luminescence from single gold nanorods
Strong Stokes and anti-Stokes one-photon luminescence from single gold
nanorods is measured in experiments. It is found that the intensity and
polarization of the Stokes and anti-Stokes emissions are in strong correlation.
Our experimental observation discovered a coherent process in light emission
from single gold nanorods. We present a theoretical mode, based on the concept
of cavity resonance, for consistently understanding both Stokes and anti-Stokes
photoluminescence. Our theory is in good agreement of all our measurements.Comment: 14 pages, 7 figures, 2 table
Statistics of Chaotic Resonances in an Optical Microcavity
Distributions of eigenmodes are widely concerned in both bounded and open
systems. In the realm of chaos, counting resonances can characterize the
underlying dynamics (regular vs. chaotic), and is often instrumental to
identify classical-to-quantum correspondence. Here, we study, both
theoretically and experimentally, the statistics of chaotic resonances in an
optical microcavity with a mixed phase space of both regular and chaotic
dynamics. Information on the number of chaotic modes is extracted by counting
regular modes, which couple to the former via dynamical tunneling. The
experimental data are in agreement with a known semiclassical prediction for
the dependence of the number of chaotic resonances on the number of open
channels, while they deviate significantly from a purely
random-matrix-theory-based treatment, in general. We ascribe this result to the
ballistic decay of the rays, which occurs within Ehrenfest time, and
importantly, within the timescale of transient chaos. The present approach may
provide a general tool for the statistical analysis of chaotic resonances in
open systems.Comment: 5 pages, 5 figures, and a supplemental informatio
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