Ray splitting in paraxial optical cavities

We present a numerical investigation of the ray dynamics in a paraxial optical cavity when a ray splitting mechanism is present. The cavity is a conventional two-mirror stable resonator and the ray splitting is achieved by inserting an optical beam splitter perpendicular to the cavity axis. We show that depending on the position of the beam splitter the optical resonator can become unstable and the ray dynamics displays a positive Lyapunov exponent.Comment: 13 pages, 7 figures, 1 tabl

Conditional beam splitting attack on quantum key distribution

We present a novel attack on quantum key distribution based on the idea of adaptive absorption [calsam01]. The conditional beam splitting attack is shown to be much more efficient than the conventional beam spitting attack, achieving a performance similar to the, powerful but currently unfeasible, photon number splitting attack. The implementation of the conditional beam splitting attack, based solely on linear optical elements, is well within reach of current technology.Comment: Submitted to Phys. Rev.

Processing asymmetry of transitions between order and disorder in human auditory cortex

Purpose: To develop an algorithm to resolve intrinsic problems with dose calculations using pencil beams when particles involved in each beam are overreaching a lateral density interface or when they are detouring in a laterally heterogeneous medium. Method and Materials: A finding on a Gaussian distribution, such that it can be approximately decomposed into multiple narrower, shifted, and scaled ones, was applied to dynamic splitting of pencil beams implemented in a dose calculation algorithm for proton and ion beams. The method was tested in an experiment with a range-compensated carbon-ion beam. Its effectiveness and efficiency were evaluated for carbon-ion and proton beams in a heterogeneous phantom model. Results: The splitting dose calculation reproduced the detour effect observed in the experiment, which amounted to about 10% at a maximum or as large as the lateral particle-disequilibrium effect. The proton-beam dose generally showed large scattering effects including the overreach and detour effects. The overall computational times were 9 s and 45 s for non-splitting and splitting carbon-ion beams and 15 s and 66 s for non-splitting and splitting proton beams. Conclusions: The beam-splitting method was developed and verified to resolve the intrinsic size limitation of the Gaussian pencil-beam model in dose calculation algorithms. The computational speed slowed down by factor of 5, which would be tolerable for dose accuracy improvement at a maximum of 10%, in our test case.AAPM Annual Meeting 200

Coherent and Dynamic Beam Splitting based on Light Storage in Cold Atoms

We demonstrate a coherent and dynamic beam splitter based on light storage in cold atoms. An input weak laser pulse is first stored in a cold atom ensemble via electromagnetically-induced transparency (EIT). A set of counter-propagating control fields, applied at a later time, retrieves the stored pulse into two output spatial modes. The high visibility interference between the two output pulses clearly demonstrates that the beam splitting process is coherent. Furthermore, by manipulating the control lasers, it is possible to dynamically control the storage time, the power splitting ratio, the relative phase, and the optical frequencies of the output pulses. The active beam splitter demonstrated in this work is expected to significantly reduce the resource requirement in photonic quantum information and in all-optical information processing as a single cold atom ensemble can functionally replace a variety of optical elements, including beam splitters, mirrors, phase shifters, and optical quantum memories

Partitioning of on-demand electron pairs

We demonstrate the high fidelity splitting of electron pairs emitted on demand from a dynamic quantum dot by an electronic beam splitter. The fidelity of pair splitting is inferred from the coincidence of arrival in two detector paths probed by a measurement of the partitioning noise. The emission characteristic of the on-demand electron source is tunable from electrons being partitioned equally and independently to electron pairs being split with a fidelity of 90%. For low beam splitter transmittance we further find evidence of pair bunching violating statistical expectations for independent fermions

Dynamic Modulation Yields One-Way Beam Splitting

This article demonstrates the realization of an extraordinary beam splitter based on nonreciprocal and synchronized photonic transitions in obliquely illuminated space-time-modulated (STM) slabs which impart the coherent temporal frequency and spatial frequency shifts. As a consequence of such unusual photonic transitions, a one-way beam splitting and amplification is exhibited by the STM slab. Beam splitting is a vital operation for various optical and photonic systems, ranging from quantum computation to fluorescence spectroscopy and microscopy. Despite the beam splitting is conceptually a simple operation, the performance characteristics of beam splitters significantly influence the repeatability and accuracy of the entire optical system. As of today, there has been no approach exhibiting a nonreciprocal beam splitting accompanied with transmission gain and an arbitrary splitting angle. Here, we show that oblique illumination of a periodic and semi-coherent dynamically-modulated slab results in coherent photonic transitions between the incident light beam and its counterpart space-time harmonic (STH). Such photonic transitions introduce a unidirectional synchronization and momentum exchange between two STHs with same temporal frequencies, but opposite spatial frequencies. Such a beam splitting technique offers high isolation, transmission gain and zero beam tilting, and is expected to drastically decrease the resource and isolation requirements in optical and photonic systems. In addition to the analytical solution, we provide a closed-form solution for the electromagnetic fields in STM structures, and accordingly, investigate the properties of the wave isolation and amplification in subluminal, superluminal and luminal ST modulations

Analysis of Narrow s-channel Resonances at Lepton Colliders

The procedures for studying a single narrow s-channel resonance or nearly degenerate resonances at a lepton collider, especially a muon collider, are discussed. In particular, we examine four methods for determining the parameters of a narrow s-channel resonance: scanning the resonance, measuring the convoluted cross section, measuring the Breit-Wigner area, and sitting on the resonance while varying the beam energy resolution. This latter procedure is new and appears to be potentially very powerful. Our focus is on computing the errors in resonance parameters resulting from uncertainty in the beam energy spread. Means for minimizing these errors are discussed. The discussion is applied to the examples of a light SM-Higgs, of the lightest pseudogoldstone boson of strong electroweak breaking, and of the two spin-1 resonances of the Degenerate BESS model (assuming that the beam energy spread is less than their mass splitting). We also examine the most effective procedures for nearly degenerate resonances, and apply these to the case of Degenerate BESS resonances with mass splitting of order the beam energy spread.Comment: 63 pages, 16 figure

Prospects of In-Flight Hyperfine Spectroscopy of (Anti)Hydrogen for Tests of CPT Symmetry

The ground-state hyperfine splitting of antihydrogen promises one of the most sensitive tests of CPT symmetry. The ASACUSA collaboration is pursuing a measurement of this splitting in a Rabi-type experiment using a polarized beam from a CUSP magnet at the Antiproton Decelerator of CERN. With the initial intention of characterizing the Rabi apparatus, a polarized source of cold hydrogen was built and the $\sigma_1$ transition of hydrogen was measured to a few ppb precision. A measurement of the $\pi_1$ transition is being prepared. The availability of this beam opens the possibility to perform first measurements of some coefficients within the nonminimal Standard-Model Extension.Comment: Presented at the Seventh Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, June 20-24, 201