1,299 research outputs found
Non-linear photonic crystals as a source of entangled photons
Non-linear photonic crystals can be used to provide phase-matching for
frequency conversion in optically isotropic materials. The phase-matching
mechanism proposed here is a combination of form birefringence and phase
velocity dispersion in a periodic structure. Since the phase-matching relies on
the geometry of the photonic crystal, it becomes possible to use highly
non-linear materials. This is illustrated considering a one-dimensional
periodic AlGaAs / air structure for the generation of 1.5
m light. We show that phase-matching conditions used in schemes to create
entangled photon pairs can be achieved in photonic crystals.Comment: 4 pages, 3 figure
Resilience of multi-photon entanglement under losses
We analyze the resilience under photon loss of the bi-partite entanglement
present in multi-photon states produced by parametric down-conversion. The
quantification of the entanglement is made possible by a symmetry of the states
that persists even under polarization-independent losses. We examine the
approach of the states to the set of states with a positive partial transpose
as losses increase, and calculate the relative entropy of entanglement. We find
that some bi-partite distillable entanglement persists for arbitrarily high
losses.Comment: 5 pages, 3 figures, title changed, minor typographic errors correcte
Magnetic surface topology in decaying plasma knots
Article / Letter to editorLeids Instituut Onderzoek Natuurkund
Quantum dynamics of a qubit coupled with structured bath
The dynamics of an unbiased spin-boson model with Lorentzian spectral density
is investigated theoretically in terms of the perturbation theory based on a
unitary transformation. The non-equilibrium correlation function and
susceptibility are calculated for both the
off-resonance case and the on-resonance case
. The approach is checked by the Shiba's relation and the
sum rule. Besides, the coherent-incoherent transition point can be
determined, which has not been demonstrated for the structured bath by previous
authors up to our knowledge.Comment: 25 pages, 11 figure
Entanglement Purification through Zeno-like Measurements
We present a novel method to purify quantum states, i.e. purification through
Zeno-like measurements, and show an application to entanglement purification.Comment: 5 pages, 1 figure; Contribution to the Proceedings of "Mysteries,
Puzzles and Paradoxes in Quantum Mechanics", Gargnano, Italy, 2003 (to be
published in J. Mod. Opt.
Qubits entanglement dynamics modified by an effective atomic environment
We study entanglement dynamics of a couple of two-level atoms resonantly
interacting with a cavity mode and embedded in a dispersive atomic environment.
We show that in the absence of the environment the entanglement reaches its
maximum value when only one exitation is involved. Then, we find that the
atomic environment modifies that entanglement dynamics and induces a typical
collapse-revival structure even for an initial one photon Fock state of the
field.Comment: eight pages, two figure include
The photon blockade effect in optomechanical systems
We analyze the photon statistics of a weakly driven optomechanical system and
discuss the effect of photon blockade under single photon strong coupling
conditions. We present an intuitive interpretation of this effect in terms of
displaced oscillator states and derive analytic expressions for the cavity
excitation spectrum and the two photon correlation function . Our
results predict the appearance of non-classical photon correlations in the
combined strong coupling and sideband resolved regime, and provide a first
detailed understanding of photon-photon interactions in strong coupling
optomechanics
Resonant Scattering Can Enhance the Degree of Entanglement
Generation of entanglement between two qubits by scattering an entanglement
mediator is discussed. The mediator bounces between the two qubits and exhibits
a resonant scattering. It is clarified how the degree of the entanglement is
enhanced by the constructive interference of such bouncing processes. Maximally
entangled states are available via adjusting the incident momentum of the
mediator or the distance between the two qubits, but their fine tunings are not
necessarily required to gain highly entangled states and a robust generation of
entanglement is possible.Comment: 7 pages, 13 figure
Opto-mechanical micro-macro entanglement
We propose to create and detect opto-mechanical entanglement by storing one
component of an entangled state of light in a mechanical resonator and then
retrieving it. Using micro-macro entanglement of light as recently demonstrated
experimentally, one can then create opto-mechanical entangled states where the
components of the superposition are macroscopically different. We apply this
general approach to two-mode squeezed states where one mode has undergone a
large displacement. Based on an analysis of the relevant experimental
imperfections, the scheme appears feasible with current technology.Comment: 7 pages, 6 figures, to appear in PRL, submission coordinated with
Sekatski et al. who reported on similar result
Experimental violation of a spin-1 Bell inequality using maximally-entangled four-photon states
We demonstrate the first experimental violation of a spin-1 Bell inequality.
The spin-1 inequality is a calculation based on the Clauser, Horne, Shimony and
Holt formalism. For entangled spin-1 particles the maximum quantum mechanical
prediction is 2.552 as opposed to a maximum of 2, predicted using local hidden
variables. We obtained an experimental value of 2.27 using the
four-photon state generated by pulsed, type-II, stimulated parametric
down-conversion. This is a violation of the spin-1 Bell inequality by more than
13 standard deviations.Comment: 5 pages, 3 figures, Revtex4. Problem with figures resolve
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