5,656 research outputs found
Deterministic Plug-and-Play for Quantum Communication
We present a scheme for secure deterministic quantum communication without
using entanglement, in a Plug-and-Play fashion. The protocol is completely
deterministic, both in the encoding procedure and in the control one, thus
doubling the communication rate with respect to other setups; moreover,
deterministic nature of transmission, apart from rendering unnecessary bases
revelation on the public channel, allows the realization of protocols like
`direct communication' and `quantum dialogue'. The encoding exploits the phase
degree of freedom of a photon, thus paving the way to an optical fiber
implementation, feasible with present day technology.Comment: 4 pages, 2 figures; one reference update
Quantum dynamics of a vibrational mode of a membrane within an optical cavity
Optomechanical systems are a promising candidate for the implementation of
quantum interfaces for storing and redistributing quantum information. Here we
focus on the case of a high-finesse optical cavity with a thin vibrating
semitransparent membrane in the middle. We show that robust and stationary
optomechanical entanglement could be achieved in the system, even in the
presence of nonnegligible optical absorption in the membrane. We also present
some preliminary experimental data showing radiation-pressure induced optical
bistability.Comment: 6 pages, 2 figures. Work presented at the conference QCMC 2010 held
on 19-23 July 2010 at the University of Queensland, Brisbane, Australi
Quantum dynamics of a high-finesse optical cavity coupled with a thin semi-transparent membrane
We study the quantum dynamics of the cavity optomechanical system formed by a
Fabry-Perot cavity with a thin vibrating membrane at its center. We first
derive the general multimode Hamiltonian describing the radiation pressure
interaction between the cavity modes and the vibrational modes of the membrane.
We then restrict the analysis to the standard case of a single cavity mode
interacting with a single mechanical resonator and we determine to what extent
optical absorption by the membrane hinder reaching a quantum regime for the
cavity-membrane system. We show that membrane absorption does not pose serious
limitations and that one can simultaneously achieve ground state cooling of a
vibrational mode of the membrane and stationary optomechanical entanglement
with state-of-the-art apparatuses.Comment: 14 pages, 7 figure
Artificial dataset generation to enhance the design exploration of residential buildings through data-informed energy load forecasting models
This study aims to assist urban planners and building designers in taking informed decisions based on energy performance – simulating a real-world urban development scenario – using limited computational resources. In particular, this paper proposes a new approach that integrates existing studies on building loads forecasting by using a Generative Adversarial Network (GAN) generated dataset based on significant geometrical parameters. This overcomes the needs for large datasets – often difficult to access.The results demonstrate that the data-driven approaches have addressed the buildings' load predictions with a reasonable accuracy while significantly reducing the calculation time required
Regge behavior saves string theory from causality violations
Higher-derivative corrections to the Einstein-Hilbert action are present in bosonic string theory leading to the potential causality violations recently pointed out by Camanho et al. [1]. We analyze in detail this question by considering high-energy string-brane collisions at impact parameters b ≤ l s (the string-length parameter) with l s ≫ R p (the characteristic scale of the D p -brane geometry). If we keep only the contribution of the massless states causality is violated for a set of initial states whose polarization is suitably chosen with respect to the impact parameter vector. Such violations are instead neatly avoided when the full structure of string theory — and in particular its Regge behavior — is taken into account
Optomechanically induced transparency in membrane-in-the-middle setup at room temperature
We demonstrate the analogue of electromagnetically induced transparency in a
room temperature cavity optomechanics setup formed by a thin semitransparent
membrane within a Fabry-P\'erot cavity. Due to destructive interference, a weak
probe field is completely reflected by the cavity when the pump beam is
resonant with the motional red sideband of the cavity. Under this condition we
infer a significant slowing down of light of hundreds of microseconds, which is
easily tuned by shifting the membrane along the cavity axis. We also observe
the associated phenomenon of electromagnetically induced amplification which
occurs due to constructive interference when the pump is resonant with the blue
sideband.Comment: 5 pages, 4 figure
Trigger-disabling Acquisition System for Quantum Key Distribution failsafe against Self-blinding
Modern single-photon detectors based on avalanche photodiodes offer
increasingly higher triggering speeds, thus fostering their use in several
fields, prominently in the recent area of Quantum Key Distribution. To reduce
the probability of an afterpulse, these detectors are usually equipped with a
circuitry that disables the trigger for a certain time after a positive
detection event, known as dead time. If the acquisition system connected to the
detector is not properly designed, efficiency issues arise when the triggering
rate is faster than the inverse of detector's dead-time. Moreover, when this
happens with two or more detectors used in coincidence, a security risk called
"self-blinding" can jeopardize the distribution of a secret quantum key. In
this paper we introduce a trigger-disabling circuitry based on an FPGA-driven
feedback loop, so to avoid the above-mentioned inconveniences. In the regime of
single-photon-attenuated light, the electronics dynamically accept a trigger
only after detectors' complete recovery from dead-time. This technique proves
useful to work with detectors at their maximum speed and to increase the
security of a quantum key distribution setup.Comment: 5 pages, 3 figures. Version 2 corrected and improve
Shedding Light on Diatom Photonics by means of Digital Holography
Diatoms are among the dominant phytoplankters in the worl's ocean, and their
external silica investments, resembling artificial photonics crystal, are
expected to play an active role in light manipulation. Digital holography
allowed studying the interaction with light of Coscinodiscus wailesii cell wall
reconstructing the light confinement inside the cell cytoplasm, condition that
is hardly accessible via standard microscopy. The full characterization of the
propagated beam, in terms of quantitative phase and intensity, removed a
long-standing ambiguity about the origin of the light. The data were discussed
in the light of living cell behavior in response to their environment
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