Optical phase conjugation with less than a photon per degree of freedom

We demonstrate experimentally that optical phase conjugation can be used to focus light through strongly scattering media even when far less than a photon per optical degree of freedom is detected. We found that the best achievable intensity contrast is equal to the total number of detected photons, as long as the resolution of the system is high enough. Our results demonstrate that phase conjugation can be used even when the photon budget is extremely low, such as in high-speed focusing through dynamic media, or imaging deep inside tissue

Micromachined membrane particle filters

We report here several particle membrane filters (8 x 8 mm^2) with circular, hexagonal and rectangular through holes. By varying hole dimensions from 6 to 12 pm, opening factors from 4 to 45 % are achieved. In order to improve the filter robustness, a composite silicon nitride/Parylene membrane technology is developed. More importantly, fluid dynamic performance of the filters is also studied by both experiments and numerical simulations. It is found that the gaseous flow through the filters depends strongly on opening factors, and the measured pressure drops are much lower than that from numerical simulation using the Navier-Stokes equation. Interestingly, surface velocity slip can only account for a minor part of the discrepancy. This suggests that a very interesting topic for micro fluid mechanics research is identified

Quantum steering of electron wave function in an InAs Y-branch switch

We report experiments on gated Y-branch switches made from InAs ballistic electron wave guides. We demonstrate that gating modifies the electron wave functions as well as their interference pattern, causing the anti-correlated, oscillatory transconductances. Such previously unexpected phenomenon provides evidence of steering the electron wave function in a multi-channel transistor structure.Comment: 15 pages, including 3 figure

Two particles on a star graph II

We consider a two particle system on a star graph with delta-function interaction. A complete description of the eigensolutions with real momenta is given; specifically it is shown that all eigensolutions can be written as integrals in the momentum plane of sums of products of appropriate one particle solutions.Comment: typos corrected, minor changes, journal ref adde