Fiber-optical analogue of the event horizon

The physics at the event horizon resembles the behavior of waves in moving media. Horizons are formed where the local speed of the medium exceeds the wave velocity. We use ultrashort pulses in microstructured optical fibers to demonstrate the formation of an artificial event horizon in optics. We observed a classical optical effect, the blue-shifting of light at a white-hole horizon. We also show by theoretical calculations that such a system is capable of probing the quantum effects of horizons, in particular Hawking radiation.Comment: MEDIA EMBARGO. This paper is subject to the media embargo of Scienc

Superantenna made of transformation media

We show how transformation media can make a superantenna that is either completely invisible or focuses incoming light into a needle-sharp beam. Our idea is based on representating three-dimensional space as a foliage of sheets and performing two-dimensional conformal maps on each shee

Perfect imaging: they don't do it with mirrors

Imaging with a spherical mirror in empty space is compared with the case when the mirror is filled with the medium of Maxwell's fish eye. Exact time-dependent solutions of Maxwell's equations show that perfect imaging is not achievable with an electrical ideal mirror on its own, but with Maxwell's fish eye in the regime when it implements a curved geometry for full electromagnetic waves

Reply on the ``Comment on `Loss-error compensation in quantum- state measurements' ''

The authors of the Comment [G. M. D'Ariano and C. Macchiavello to be published in Phys. Rev. A, quant-ph/9701009] tried to reestablish a 0.5 efficiency bound for loss compensation in optical homodyne tomography. In our reply we demonstrate that neither does such a rigorous bound exist nor is the bound required for ruling out the state reconstruction of an individual system [G. M. D'Ariano and H. P. Yuen, Phys. Rev. Lett. 76, 2832 (1996)].Comment: LaTex, 2 pages, 1 Figure; to be published in Physical Review

Switching Exciton Pulses Through Conical Intersections

Exciton pulses transport excitation and entanglement adiabatically through Rydberg aggregates, assemblies of highly excited light atoms, which are set into directed motion by resonant dipole-dipole interaction. Here, we demonstrate the coherent splitting of such pulses as well as the spatial segregation of electronic excitation and atomic motion. Both mechanisms exploit local nonadiabatic effects at a conical intersection, turning them from a decoherence source into an asset. The intersection provides a sensitive knob controlling the propagation direction and coherence properties of exciton pulses. The fundamental ideas discussed here have general implications for excitons on a dynamic network.Comment: Letter with 4 pages and 4 figures. Supplemental material with 4 pages and 4 figure

Comment on "Relativistic Effects of Light in Moving Media with Extremely Low Group Velocity"

In [cond-mat/9906332; Phys. Rev. Lett. 84, 822 (2000)] and [physics/9906038; Phys. Rev. A 60, 4301 (1999)] Leonhardt and Piwnicki have presented an interesting analysis of how to use a flowing dielectric fluid to generate a so-called "optical black hole". Qualitatively similar phenomena using acoustical processes have also been much investigated. Unfortunately there is a subtle misinterpretation in the Leonhardt-Piwnicki analysis regarding these "optical black holes": While it is clear that "optical black holes" can certainly exist as theoretical constructs, and while the experimental prospects for actually building them in the laboratory are excellent, the particular model geometries that Leonhardt and Piwnicki write down as alleged examples of "optical black holes" are in fact not black holes at all.Comment: one page comment, uses ReV_TeX 3; discussion clarified; basic physical results unaltere

Partial Transmutation of Singularities in Optical Instruments

Some interesting optical instruments such as the Eaton lens and the Invisible Sphere require singularities of the refractive index for their implementation. We show how to transmute those singularities into harmless topological defects in anisotropic media without the need for anomalous material properties

Perfect imaging with geodesic waveguides

Transformation optics is used to prove that a spherical waveguide filled with an isotropic material with radial refractive index n=1/r has radial polarized modes (i.e. the electric field has only radial component) with the same perfect focusing properties as the Maxwell Fish-Eye lens. The approximate version of that device using a thin waveguide with a homogenous core paves the way to experimentally prove perfect imaging in the Maxwell Fish Eye lens

Quantum levitation by left-handed metamaterials

Left-handed metamaterials make perfect lenses that image classical electromagnetic fields with significantly higher resolution than the diffraction limit. Here we consider the quantum physics of such devices. We show that the Casimir force of two conducting plates may turn from attraction to repulsion if a perfect lens is sandwiched between them. For optical left-handed metamaterials this repulsive force of the quantum vacuum may levitate ultra-thin mirrors

Metacognitive self-reflectivity moderates the relationship between distress tolerance and empathy in schizophrenia

Deficits in empathy seen in schizophrenia are thought to play a major role in the social dysfunction seen in the disorder. However, little work has investigated potential determinants of empathic deficits. This study aimed to fill that gap by examining the effects of two variables on empathy – distress tolerance and metacognitive self-reflectivity. Fifty-four people with schizophrenia-spectrum disorders receiving services at an urban VA or community mental health center were assessed for empathy, metacognition, and distress tolerance. Bivariate correlations and moderation methods were used to ascertain associations amongst these variables and examine interactions. Results revealed that, against hypotheses, empathy was not related at the bivariate level to either distress tolerance or metacognitive self-reflectivity. However, consistent with hypotheses, moderation analyses revealed that participants with higher self-reflectivity showed no relationship between distress tolerance and empathy, while those with lower self-reflectivity showed a relationship such that reduced ability to tolerate distress predicted reduced empathy. Taken together, results of this study suggest that lack of distress tolerance can negatively affect empathy in people with schizophrenia with lesser capacity for metacognitive self-reflection; thus, fostering self-reflectivity may help overcome that negative impact. Future work is needed investigating the impact of metacognitively-tailored interventions on empathy in this population