Experimental Violation of Bell's Inequality in Spatial-Parity Space

We report the first experimental violation of Bell's inequality in the spatial domain using the Einstein--Podolsky--Rosen state. Two-photon states generated via optical spontaneous parametric downconversion are shown to be entangled in the parity of their one-dimensional transverse spatial profile. Superpositions of Bell states are prepared by manipulation of the optical pump's transverse spatial parity--a classical parameter. The Bell-operator measurements are made possible by devising simple optical arrangements that perform rotations in the one-dimensional spatial-parity space of each photon of an entangled pair and projective measurements onto a basis of even--odd functions. A Bell-operator value of 2.389 +- 0.016 is recorded, a violation of the inequality by more than 24 standard deviations.Comment: 10 pages, 3 figures, 1 Tabl

High-sensitivity imaging with multi-mode twin beams

Twin entangled beams produced by single-pass parametric down-conversion (PDC) offer the opportunity to detect weak amount of absorption with an improved sensitivity with respect to standard techniques which make use of classical light sources. We propose a differential measurement scheme which exploits the spatial quantum correlation of type II PDC to image a weak amplitude object with a sensitivity beyond the standard quantum limit imposed by shot-noise.Comment: 13 pages, 8 figure

Simple model for 1/f noise

We present a simple stochastic mechanism which generates pulse trains exhibiting a power law distribution of the pulse intervals and a $1/f^\alpha$ power spectrum over several decades at low frequencies with $\alpha$ close to one. The essential ingredient of our model is a fluctuating threshold which performs a Brownian motion. Whenever an increasing potential $V(t)$ hits the threshold, $V(t)$ is reset to the origin and a pulse is emitted. We show that if $V(t)$ increases linearly in time, the pulse intervals can be approximated by a random walk with multiplicative noise. Our model agrees with recent experiments in neurobiology and explains the high interpulse interval variability and the occurrence of $1/f^\alpha$ noise observed in cortical neurons and earthquake data.Comment: 4 pages, 4 figure

Polarization-sensitive quantum-optical coherence tomography

We set forth a polarization-sensitive quantum-optical coherence tomography (PS-QOCT) technique that provides axial optical sectioning with polarization-sensitive capabilities. The technique provides a means for determining information about the optical path length between isotropic reflecting surfaces, the relative magnitude of the reflectance from each interface, the birefringence of the interstitial material, and the orientation of the optical axis of the sample. PS-QOCT is immune to sample dispersion and therefore permits measurements to be made at depths greater than those accessible via ordinary optical coherence tomography. We also provide a general Jones matrix theory for analyzing PS-QOCT systems and outline an experimental procedure for carrying out such measurements.Comment: 15 pages, 5 figures, to appear in Physical Review

Human Intent Prediction Using Markov Decision Processes

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97080/1/AIAA2012-2445.pd

Scaling-violation phenomena and fractality in the human posture control systems

By analyzing the movements of quiet standing persons by means of wavelet statistics, we observe multiple scaling regions in the underlying body dynamics. The use of the wavelet-variance function opens the possibility to relate scaling violations to different modes of posture control. We show that scaling behavior becomes close to perfect, when correctional movements are dominated by the vestibular system.Comment: 12 pages, 4 figures, to appear in Phys. Rev.

Entangled Electronic States in Multiple Quantum-Dot Systems

We present an analytically solvable model of $P$ colinear, two-dimensional quantum dots, each containing two electrons. Inter-dot coupling via the electron-electron interaction gives rise to sets of entangled ground states. These ground states have crystal-like inter-plane correlations and arise discontinously with increasing magnetic field. Their ranges and stabilities are found to depend on dot size ratios, and to increase with $P$.Comment: To appear in Physical Review B (in press). RevTeX file. Figures available from [email protected]

Demonstration of the Complementarity of One- and Two-Photon Interference

The visibilities of second-order (single-photon) and fourth-order (two-photon) interference have been observed in a Young's double-slit experiment using light generated by spontaneous parametric down-conversion and a photon-counting intensified CCD camera. Coherence and entanglement underlie one-and two-photon interference, respectively. As the effective source size is increased, coherence is diminished while entanglement is enhanced, so that the visibility of single-photon interference decreases while that of two-photon interference increases. This is the first experimental demonstration of the complementarity between single- and two-photon interference (coherence and entanglement) in the spatial domain.Comment: 21 pages, 7 figure

Quantum Phonon Optics: Coherent and Squeezed Atomic Displacements

In this paper we investigate coherent and squeezed quantum states of phonons. The latter allow the possibility of modulating the quantum fluctuations of atomic displacements below the zero-point quantum noise level of coherent states. The expectation values and quantum fluctuations of both the atomic displacement and the lattice amplitude operators are calculated in these states---in some cases analytically. We also study the possibility of squeezing quantum noise in the atomic displacement using a polariton-based approach.Comment: 6 pages, RevTe