Quantum matter wave dynamics with moving mirrors

When a stationary reflecting wall acting as a perfect mirror for an atomic beam with well defined incident velocity is suddenly removed, the density profile develops during the time evolution an oscillatory pattern known as diffraction in time. The interference fringes are suppressed or their visibility is diminished by several effects such as averaging over a distribution of incident velocities, apodization of the aperture function, atom-atom interactions, imperfect reflection or environmental noise. However, when the mirror moves with finite velocity along the direction of propagation of the beam, the visibility of the fringes is enhanced. For mirror velocities below beam velocity, as used for slowing down the beam, the matter wave splits into three regions separated by space-time points with classical analogues. For mirror velocities above beam velocity a visibility enhancement occurs without a classical counterpart. When the velocity of the beam approaches that of the mirror the density oscillations rise by a factor 1.8 over the stationary value.Comment: 5.2 pages, 6 figure

H1 photonic crystal cavitites for hybrid quantum information protocols

Hybrid quantum information protocols are based on local qubits, such as trapped atoms, NV centers, and quantum dots, coupled to photons. The coupling is achieved through optical cavities. Here we demonstrate far-field optimized H1 photonic crystal membrane cavities combined with an additional back reflection mirror below the membrane that meet the optical requirements for implementing hybrid quantum information protocols. Using numerical optimization we find that 80% of the light can be radiated within an objective numerical aperture of 0.8, and the coupling to a single-mode fiber can be as high as 92%. We experimentally prove the unique external mode matching properties by resonant reflection spectroscopy with a cavity mode visibility above 50%.Comment: 14 pages, 11 figure

Two photon quantum interference in plasmonics - Theory and Applications

We report perfect two photon quantum interference with near-unity visibility in a resonant tunneling plasmonic structure in folded Kretschmann geometry. This is despite absorption-induced loss of unitarity in plasmonic systems. The effect is traced to perfect destructive interference between the squares of amplitude reflection and transmission coefficients. We further highlight yet another remarkable potential of coincidence measurements as a probe with better resolution as compared to standard spectroscopic techniques. The finer features show up in both angle resolved and frequency resolved studies.Comment: 5 pages, 6 figure

Recognition and reconstruction of coherent energy with application to deep seismic reflection data

Reflections in deep seismic reflection data tend to be visible on only a limited number of traces in a common midpoint gather. To prevent stack degeneration, any noncoherent reflection energy has to be removed. In this paper, a standard classification technique in remote sensing is presented to enhance data quality. It consists of a recognition technique to detect and extract coherent energy in both common shot gathers and fi- nal stacks. This technique uses the statistics of a picked seismic phase to obtain the likelihood distribution of its presence. Multiplication of this likelihood distribution with the original data results in a “cleaned up” section. Application of the technique to data from a deep seismic reflection experiment enhanced the visibility of all reflectors considerably. Because the recognition technique cannot produce an estimate of “missing” data, it is extended with a reconstruction method. Two methods are proposed: application of semblance weighted local slant stacks after recognition, and direct recognition in the linear tau-p domain. In both cases, the power of the stacking process to increase the signal-to-noise ratio is combined with the direct selection of only specific seismic phases. The joint application of recognition and reconstruction resulted in data images which showed reflectors more clearly than application of a single technique

Vehicle Combustion Quality Monitoring:A scene visibility-level based non-invasive approach

Pollutants interfere with light, restrict its reflection and so impair visibility. Scene visibility level is therefore used as a measure of air quality and pollution. Treating emission efflux as "some additional noise causing visibility impairment," this work examines if the extracted visibility index from a thermal infrared (TIR) image can help in qualitative assessment of combustion efficiency. The thin-film regime like two dimensional TIR images of unleaded-petroleum run vehicles' exhaust-plumes were first accommodated for time and space related compositional effects. The estimated ratios of visibility indices obtained from two sequential TIR images of the same exhaust plume were compared with their respective electrochemically sensed levels of oxides of nitrogen and combustibles. Initial results suggest that visibility indices extracted from TIR images of emission efflux would help in distinguishing low from high levels of emissions. TIR images can therefore assist in qualitative assessment of engine combustion efficiency

Coexistence of full which-path information and interference in Wheelers delayed choice experiment with photons

We present a computer simulation model that is a one-to-one copy of an experimental realization of Wheeler's delayed choice experiment that employs a single photon source and a Mach-Zehnder interferometer composed of a 50/50 input beam splitter and a variable output beam splitter with adjustable reflection coefficient $R$ (V. Jacques {\sl et al.}, Phys. Rev. Lett. 100, 220402 (2008)). For $0\le R\le 0.5$, experimentally measured values of the interference visibility $V$ and the path distinguishability $D$, a parameter quantifying the which-path information WPI, are found to fulfill the complementary relation $V^2+D^2\le 1$, thereby allowing to obtain partial WPI while keeping interference with limited visibility. The simulation model that is solely based on experimental facts, that satisfies Einstein's criterion of local causality and that does not rely on any concept of quantum theory or of probability theory, reproduces quantitatively the averages calculated from quantum theory. Our results prove that it is possible to give a particle-only description of the experiment, that one can have full WPI even if D=0, V=1 and therefore that the relation $V^2+D^2\le 1$ cannot be regarded as quantifying the notion of complementarity.Comment: Physica E, in press; see also http://www.compphys.ne

Visibility Extension via Reflection

This paper studies a variant of the Art Gallery problem in which the "walls" can be replaced by \emph{reflecting-edges}, which allows the guard to see further and thereby see a larger portion of the gallery. We study visibility with specular and diffuse reflections. The number of times a ray can be reflected can be taken as a parameter. The Art Gallery problem has two primary versions: point guarding and vertex guarding. Both versions are proven to be NP-hard by Lee and Aggarwal. We show that several cases of the generalized problem are NP-hard, too. We managed to do this by reducing the 3-SAT and the Subset-Sum problems to the various cases of the generalized problem. We also illustrate that if $\cal P$ is a funnel or a weak visibility polygon, the problem becomes more straightforward and can be solved in polynomial time. We generalize the $\mathcal{O}(\log n)$-approximation ratio algorithm of the vertex guarding problem to work in the presence of reflection. For a bounded $r$, the generalization gives a polynomial-time algorithm with $\mathcal{O}(\log n)$-approximation ratio for several special cases of the generalized problem. Furthermore, Chao Xu proved that although reflection helps the visibility of guards to be expanded, similar to the normal guarding problem, even considering $r$ specular reflections we may need $\lfloor \frac{n}{3} \rfloor$ guards to cover a simple polygon $\cal P$. In this article, we prove that considering $r$ diffuse reflections the minimum number of vertex or boundary guards required to cover $\cal P$ decreases to $\lceil \frac{\alpha}{1+ \lfloor \frac{r}{4} \rfloor} \rceil$, where $\alpha$ indicates the minimum number of guards required to cover $\cal P$ without reflection. funnel or a weak visibility polygon, then the problem becomes more straightforward and can be solved in polynomial time.Comment: 32 pages, 10 figure