309 research outputs found
Papadopoulos v. Target: Finally Melting Away the Century-Old Natural Accumulation Standard in Massachusetts
Emergence of entanglement from a noisy environment: The case of polaritons
We show theoretically that polariton pairs with a high degree of polarization
entanglement can be produced through parametric scattering. We demonstrate that
it can emerge in coincidence experiments, even at low excitation densities
where the dynamics is dominated by incoherent photoluminesce. Our analysis is
based on a microscopic quantum statistical approach that treats coherent and
incoherent processes on an equal footing, thus allowing for a quantitative
assessment of the amount of entanglement under realistic experimental
conditions. This result puts forward the robustness of pair correlations in
solid-state devices, even when noise dominates one-body correlations.Comment: revised version. new figure
Spontaneous Conversion from Virtual to Real Photons in the Ultrastrong Coupling Regime
We show that a spontaneous release of virtual photon pairs can occur in a
quantum optical system in the ultrastrong coupling regime. In this regime,
which is attracting interest both in semiconductor and superconducting systems,
the light-matter coupling rate {\Omega}R becomes comparable to the bare
resonance frequency of photons {\omega}0. In contrast to the dynamical Casimir
effect and other pair creation mechanisms, this phenomenon does not require
external forces or time dependent parameters in the Hamiltonian.Comment: To appear on Phys. Rev. Let
Quantum complementarity of microcavity polaritons
We present an experiment that probes polariton quantum correlations by
exploiting quantum complementarity. Specifically, we find that polaritons in
two distinct idler-modes interfere if and only if they share the same
signal-mode so that "which-way" information cannot be gathered. The
experimental results prove the existence of polariton pair correlations that
store the "which-way" information. This interpretation is confirmed by a
theoretical analysis of the measured interference visibility in terms of
quantum Langevin equations
Photon Blockade in the Ultrastrong Coupling Regime
We explore photon coincidence counting statistics in the ultrastrong-coupling
regime where the atom-cavity coupling rate becomes comparable to the cavity
resonance frequency. In this regime usual normal order correlation functions
fail to describe the output photon statistics. By expressing the electric-field
operator in the cavity-emitter dressed basis we are able to propose correlation
functions that are valid for arbitrary degrees of light-matter interaction. Our
results show that the standard photon blockade scenario is significantly
modified for ultrastrong coupling. We observe parametric processes even for
two-level emitters and temporal oscillations of intensity correlation functions
at a frequency given by the ultrastrong photon emitter coupling. These effects
can be traced back to the presence of two-photon cascade decays induced by
counter-rotating interaction terms.Comment: minor revisions, supplementary information added, accepted for
publication in PR
Entanglement Dynamics of Two Independent Cavity-Embedded Quantum Dots
We investigate the dynamical behavior of entanglement in a system made by two
solid-state emitters, as two quantum dots, embedded in two separated
micro-cavities. In these solid-state systems, in addition to the coupling with
the cavity mode, the emitter is coupled to a continuum of leaky modes providing
additional losses and it is also subject to a phonon-induced pure dephasing
mechanism. We model this physical configuration as a multipartite system
composed by two independent parts each containing a qubit embedded in a
single-mode cavity, exposed to cavity losses, spontaneous emission and pure
dephasing. We study the time evolution of entanglement of this multipartite
open system finally applying this theoretical framework to the case of
currently available solid-state quantum dots in micro-cavities.Comment: 10 pages, 4 figures, to appear in Topical Issue of Physica Scripta on
proceedings of CEWQO 201
Total Hemi-overgrowth in Pigmentary Mosaicism of the (Hypomelanosis of) Ito Type: Eight Case Reports.
Pigmentary mosaicism of the (hypomelanosis of) Ito type is an umbrella term, which includes phenotypes characterized by mosaic hypopigmentation in the form of streaks, whorls, patchy, or more bizarre skin configurations (running along the lines of Blaschko): these cutaneous patterns can manifest as an isolated skin disorder (pigmentary mosaicism of the Ito type) or as a complex malformation syndrome in association with extracutaneous anomalies (most often of the musculoskeletal and/or nervous systems) (hypomelanosis of Ito). Affected individuals are anecdotally reported to have also partial or total body hemi-overgrowth (HOG), which often causes moderate to severe complications.We studied the occurrence and features of HOG in the 114 children and adults with mosaic pigmentary disorders of the Ito type diagnosed and followed up (from 2 to 22 years; average follow-up 16 years) at our Institutions.Eight patients (5 M, 3 F; aged 4 to 25 years; median age 16 years) out of the 114 analyzed (7%) fulfilled the criteria for unilateral HOG, with differences in diameter ranging from 0.4 to 4.0 cm (upper limbs) and 1.0 to 9.0 cm (lower limbs). Moreover, among these 8 patients, 5/8 filled in the 75th to 90th percentile for height; 6/8 had associated kyphoscoliosis; and 5/8 showed cognitive delays. No tumour complications were recorded. Overall, 6/8 HOG patients presented with additional (extracutaneous) syndromic manifestations, apart from the HOG (ie, with a clinical phenotype of hypomelanosis of Ito).The present study, which includes children and adults with the longest follow-up so far recorded, confirms the association between pigmentary mosaicism of the Ito type and HOG lowering previous estimates (7% vs 16%) for HOG in the context of mosaic hypopigmentation. A careful examination, looking at subtle to moderate asymmetries and associated complications within the spectrum of these mosaic pigmentary disorders, is recommended
Nonequilibrium Langevin Approach to Quantum Optics in Semiconductor Microcavities
Recently the possibility of generating nonclassical polariton states by means
of parametric scattering has been demonstrated. Excitonic polaritons propagate
in a complex interacting environment and contain real electronic excitations
subject to scattering events and noise affecting quantum coherence and
entanglement. Here we present a general theoretical framework for the realistic
investigation of polariton quantum correlations in the presence of coherent and
incoherent interaction processes. The proposed theoretical approach is based on
the {\em nonequilibrium quantum Langevin approach for open systems} applied to
interacting-electron complexes described within the dynamics controlled
truncation scheme. It provides an easy recipe to calculate multi-time
correlation functions which are key-quantities in quantum optics. As a first
application, we analyze the build-up of polariton parametric emission in
semiconductor microcavities including the influence of noise originating from
phonon induced scattering.Comment: some corrections in the presentation mad
Comment on "Imaging the Local Density of States of Optical Corrals"
In a recent letter Chicanne {\em et al.} [1] reported the experimental
observation of the electromagnetic local density of states LDOS established by
gold nanostructures. The obtained images have been compared with combinations
of partial LDOSs defined in terms of the imaginary part of the Green-tensor
calculated at the tip position.
Moreover just this comparison was the criterion for the choice of the optimum
tip design. These results support the point of view that ( is the unit vector used to define the effective
dipole associated to the illuminating tip) is the key quantity to interpret
SNOM images in analogy with the electronic LDOS measured by the scanning
tunneling microscope (STM). Rigorous Green-tensor analysis shows that (that is also the key quantity determining spontaneous decay rates
of molecular transitions) is not the correct key quantity, and that
measurements in Ref. [1] should have been compared with a different quantity.
Moreover the identification of with the detected SNOM signal
can lead to unphysical results
- …