1,503 research outputs found
Continuous variable quantum teleportation with sculptured and noisy non-Gaussian resources
We investigate continuous variable (CV) quantum teleportation using relevant
classes of non-Gaussian states of the radiation field as entangled resources.
First, we introduce the class two-mode squeezed symmetric superposition of Fock
states, including finite truncations of twin-beam Gaussian states as special
realizations. These states depend on a set of free independent parameters that
can be adjusted for the optimization of teleportation protocols, with an
enhancement of the success probability of teleportation both for coherent and
Fock input states. We show that the optimization procedure reduces the
entangled resources to truncated twin beam states, which thus represents an
optimal class of non-Gaussian resources for quantum teleportation. We then
introduce a further class of two-mode non-Gaussian entangled resources, in the
form of squeezed cat-like states. We analyze the performance and the properties
of such states when optimized for (CV) teleportation, and compare them to the
optimized squeezed Bell-like states introduced in a previous work
\cite{CVTelepNoi}. We discuss how optimal resources for teleportation are
characterized by a suitable balance of entanglement content and squeezed vacuum
affinity. We finally investigate the effects of thermal noise on the efficiency
of quantum teleportation. To this aim, a convenient framework is to describe
noisy entangled resources as linear superpositions of non-Gaussian state and
thermal states. Although the presence of the thermal component strongly reduces
the teleportation fidelity, noisy non-Gaussian states remain preferred
resources when compared to noisy twin-beam Gaussian states.Comment: 11 pages, 8 figures. Largely revised and expanded version. New
material and sections added. To appear in EPJ-ST (Proceedings of the Central
European Workshop on Quantum Optics 2007. 14th Edition, 1-5 June 2007,
Palermo, Italy
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The development of a novel 'steerable' bougie to assist in airway management
Videolaryngoscopy(VL) is increasingly used and has been proposed as a standard of care (BJA Editorial 2015). VL has several important benefits over conventional laryngoscopy. By means of a camera at the distal end of the instrument, the larynx can be visualised even when it is impossible to obtain a straight line of sight and the use of a camera and display facilitates recording and teaching. In some patients, VL allows a good view of the larynx but due to the angles involved intubation itself is still difficult (2). The traditional bougie, being long, flexible, narrow and having some intrinsic memory can often be placed within the trachea when the view is limited. They do, however, have limitations– the shape retention is often short lived and there is no ability to ‘steer’ the tip, so directional control in-‐situ is limited. This can be frustrating for clinicians, and potentially dangerous for patients (3
Dymanics of Generalized Coherent States
We show that generalized coherent states follow Schr\"{o}dinger dynamics in
time-dependent potentials. The normalized wave-packets follow a classical
evolution without spreading; in turn, the Schr\"{o}dinger potential depends on
the state through the classical trajectory. This feedback mechanism with
continuous dynamical re-adjustement allows the packets to remain coherent
indefinetely.Comment: 8 pages, plain latex, no figure
Realistic continuous-variable quantum teleportation with non-Gaussian resources
We present a comprehensive investigation of nonideal continuous-variable
quantum teleportation implemented with entangled non-Gaussian resources. We
discuss in a unified framework the main decoherence mechanisms, including
imperfect Bell measurements and propagation of optical fields in lossy fibers,
applying the formalism of the characteristic function. By exploiting
appropriate displacement strategies, we compute analytically the success
probability of teleportation for input coherent states, and two classes of
non-Gaussian entangled resources: Two-mode squeezed Bell-like states (that
include as particular cases photon-added and photon-subtracted de-Gaussified
states), and two-mode squeezed cat-like states. We discuss the optimization
procedure on the free parameters of the non-Gaussian resources at fixed values
of the squeezing and of the experimental quantities determining the
inefficiencies of the non-ideal protocol. It is found that non-Gaussian
resources enhance significantly the efficiency of teleportation and are more
robust against decoherence than the corresponding Gaussian ones. Partial
information on the alphabet of input states allows further significant
improvement in the performance of the non-ideal teleportation protocol.Comment: 14 pages, 6 figure
Continuous variable quantum teleportation with non-Gaussian resources
We investigate continuous variable quantum teleportation using non-Gaussian
states of the radiation field as entangled resources. We compare the
performance of different classes of degaussified resources, including two-mode
photon-added and two-mode photon-subtracted squeezed states. We then introduce
a class of two-mode squeezed Bell-like states with one-parameter dependence for
optimization. These states interpolate between and include as subcases
different classes of degaussified resources. We show that optimized squeezed
Bell-like resources yield a remarkable improvement in the fidelity of
teleportation both for coherent and nonclassical input states. The
investigation reveals that the optimal non-Gaussian resources for continuous
variable teleportation are those that most closely realize the simultaneous
maximization of the content of entanglement, the degree of affinity with the
two-mode squeezed vacuum and the, suitably measured, amount of non-Gaussianity.Comment: 12 pages, 12 figure
Diffusion Processes and Coherent States
It is shown that stochastic processes of diffusion type possess, in all
generality, a structure of uncertainty relations and of coherent and squeezed
states. This fact is used to obtain, via Nelson stochastic formulation of
quantum mechanics, the harmonic-oscillator coherent and squeezed states. The
method allows to derive new minimum uncertainty states in time-dependent
oscillator potentials and for the Caldirola-Kanai model of quantum damped
oscillator.Comment: 11 pages, plain LaTe
Seismic scattering and absorption mapping from intermediate-depth earthquakes reveals complex tectonic interactions acting in the Vrancea region and surroundings (Romania)
The present study was performed during a stay at the University of Münster financed by a grant awarded by the German Academic Exchange Service (DAAD) in 2014. Data used in the present study were provided by the National Institute for Earth Physics (Romania) and processed within the National Data Centre in Magurele. Seismic Analysis Code (SAC) (Goldstein and Snoke, 2005) and GMT (Wessel et al., 2013) codes were used. We thank the College of Physical Sciences (University of Aberdeen) and the Santander Mobility Award for providing travel grant to LDS to complete this manuscript. We are grateful as well to the anonymous reviewer for his useful remarks which helped us to improve the paper.Peer reviewedPostprin
Tunable non-Gaussian resources for continuous-variable quantum technologies
We introduce and discuss a set of tunable two-mode states of
continuous-variable systems, as well as an efficient scheme for their
experimental generation. This novel class of tunable entangled resources is
defined by a general ansatz depending on two experimentally adjustable
parameters. It is very ample and flexible as it encompasses Gaussian as well as
non-Gaussian states. The latter include, among others, known states such as
squeezed number states and de-Gaussified photon-added and photon-subtracted
squeezed states, the latter being the most efficient non-Gaussian resources
currently available in the laboratory. Moreover, it contains the classes of
squeezed Bell states and even more general non-Gaussian resources that can be
optimized according to the specific quantum technological task that needs to be
realized. The proposed experimental scheme exploits linear optical operations
and photon detections performed on a pair of uncorrelated two--mode Gaussian
squeezed states. The desired non-Gaussian state is then realized via ancillary
squeezing and conditioning. Two independent, freely tunable experimental
parameters can be exploited to generate different states and to optimize the
performance in implementing a given quantum protocol. As a concrete instance,
we analyze in detail the performance of different states considered as
resources for the realization of quantum teleportation in realistic conditions.
For the fidelity of teleportation of an unknown coherent state, we show that
the resources associated to the optimized parameters outperform, in a
significant range of experimental values, both Gaussian twin beams and
photon-subtracted squeezed states.Comment: 13 pages, 7 figure
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