1,799 research outputs found
Proposal for entangling remote micromechanical oscillators via optical measurements
We propose an experiment to create and verify entanglement between remote
mechanical objects by use of an optomechanical interferometer. Two optical
cavities, each coupled to a separate mechanical oscillator, are coherently
driven such that the oscillators are laser cooled to the quantum regime. The
entanglement is induced by optical measurement and comes about by combining the
output from the two cavities to erase which-path information. It can be
verified through measurements of degrees of second-order coherence of the
optical output field. The experiment is feasible in the regime of weak
optomechanical coupling. Realistic parameters for the membrane-in-the-middle
geometry suggest entangled state lifetimes on the order of milliseconds.Comment: 4 pages, 2 figures + supplementary material (7 pages, 2 figs).
Updates in v2: New Eq. (7) and Fig. 1 - results unchanged. Added
supplementary material with various details. Updates in v3: Minor changes,
journal ref. adde
Effects of frequency correlation in linear optical entangling gate operated with independent photons
Bose-Einstein coalescence of independent photons at the surface of a beam
splitter is the physical process that allows linear optical quantum gates to be
built. When distinct parametric down-conversion events are used as an
independent photon source, distinguishability arises form the energy
correlation of each photon with its twin. We find that increasing the pump
bandwidth may help in improving the visibility of non-classical interference
and reaching a level of near perfect indistinguishability. PACS: 03.67.Mn,
42.65.Lm, 42.50.St.Comment: Replaced with published versio
Broadening the bandwidth of entangled photons: a step towards the generation of extremely short biphotons
We demonstrate a technique that allows to fully control the bandwidth of
entangled photons independently of the frequency band of interest and of the
nonlinear crystal. We show that this technique allows to generate nearly
transform-limited biphotons with almost one octave of bandwidth (hundreds of
THz) which corresponds to correlation times of just a few femtoseconds. The
presented method becomes an enabling tool for attosecond entangled-photons
quantum optics. The technique can also be used to generate paired photons with
a very high degree of entanglement.Comment: 4 page
Highly efficient single photon emission from single quantum dots within a two-dimensional photonic bandgap
We report highly efficient single photon generation from InGaAs
self-assembled quantum dots emitting within a two-dimensional photonic bandgap.
A strongly suppressed multiphoton probability is obtained for single quantum
dots in bulk GaAs and those emitting into the photonic bandgap. In the latter
case, photoluminescence saturation spectroscopy is employed to measure a ~17
times enhancement of the average photon extraction efficiency, when compared to
quantum dots in bulk GaAs. For quantum dots in the photonic crystal we measure
directly an external quantum efficiency up to 26%, much higher than for quantum
dots on the same sample without a tailored photonic environment. The results
show that highly efficient quantum dot single photon sources can be realized,
without the need for complex nanopositioning techniques
Economic evaluation of the treatment of grade II haemorrhoids : a comparison of stapled haemorrhoidopexy and rubber band ligation.
The definitive version is available at www3.interscience.wiley.comPeer reviewedPostprin
Anomalous lack of decoherence of the Macroscopic Quantum Superpositions based on phase-covariant Quantum Cloning
We show that all Macroscopic Quantum Superpositions (MQS) based on
phase-covariant quantum cloning are characterized by an anomalous high
resilence to the de-coherence processes. The analysis supports the results of
recent MQS experiments and leads to conceive a useful conjecture regarding the
realization of complex decoherence - free structures for quantum information,
such as the quantum computer.Comment: 4 pages, 3 figure
Randomised controlled trial comparing rubber band ligation with stapled haemorrhoidopexy for Grade II circumferential haemorrhoids : Long-term results
Peer reviewedPostprin
On Wheeler's delayed-choice Gedankenexperiment and its laboratory realization
Here, we present an analysis and interpretation of the experiment performed
by Jacques et al. (2007 Science 315, 966), which represents a realization of
Wheeler's delayed-choice Gedankenexperiment. Our analysis is based on the
evolution of the photon state, since the photon enters into the Mach-Zehnder
interferometer with a removable beam-splitter until it exits. Given the same
incident photon state onto the output beam-splitter, BS_output, the photon's
state at the exit will be very different depending on whether BS_output is on
or off. Hence, the statistics of photon counts collected by the two detectors,
positioned along orthogonal directions at the exit of the interferometer, is
also going to be very different in either case. Therefore, it is not that the
choice of inserting (on) or removing (off) a beam-splitter leads to a delayed
influence on the photon behavior before arriving at the beam-splitter, but that
such a choice influences the photon state at and after BS_output, i.e., after
it has exited from the Mach-Zehnder interferometer. The random on/off choice at
BS_output has no delayed effect on the photon to behave as a wave or a
corpuscle at the entrance and inside the interferometer, but influences the
subsequent evolution of the photon state incident onto BS_output.Comment: 7 pages, 4 figure
Fidelity for imperfect postselection
We describe a simple measure of fidelity for mixed state postselecting
devices. The measure is most appropriate for postselection where the task
performed by the output is only effected by a specific state.Comment: 8 Pages, 8 Figure
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