Interference (wave propagation)

About: Interference (wave propagation) is a research topic. Over the lifetime, 26086 publications have been published within this topic receiving 321110 citations.

Controlled dephasing of electrons by non-gaussian shot noise

Abstract: In a ‘controlled dephasing’ experiment1,2,3, an interferometer loses its coherence owing to entanglement of the interfering electron with a controlled quantum system, which effectively is equivalent to path detection. In previous experiments, only partial dephasing was achieved owing to weak interactions between many detector electrons and the interfering electron, leading to a gaussian-phase randomizing process4,5,6,7,8,9,10,11. Here, we report the opposite extreme, where interference is completely destroyed by a few (that is, one to three) detector electrons, each of which has a strong randomizing effect on the phase. We observe quenching of the interference pattern in a periodic, lobe-type fashion as the detector current is varied, and with a peculiar V-shaped dependence on the detector’s partitioning. We ascribe these features to the non-gaussian nature of the noise, which is also important for qubit decoherence12. In other words, the interference seems to be highly sensitive to the full counting statistics of the detector’s shot noise13,14,15,16.

A path link model for ultra wide band pulse transmissions

Abstract: Pulsed UWB (ultra wide band) signals are more nearly transient phenomena than they are continuous waves. Multipath effects for the most part manifest themselves as time delayed replicants of the pulses. Short pulses propagate with the free space law, and only when the differential delay among pulses and replicants is less than about half the pulse length do the signals exhibit destructive interference. The propagation model described here is based on the free space law with the additional effect of transmission losses through typical home or office walls. The conditions for destructive inference of pulses is also derived.

Hollow-Core Microstructured Optical Fiber Gas Sensors

Abstract: Recent progress in gas detection with hollow-core microstructured optical fibers (HC-MOFs) and direct absorption/photothermal interferometry spectroscopy are reported. For direct-absorption sensors, the issue of mode interference noise is addressed and techniques to minimize such a noise are experimentally demonstrated. Large-scale drilling of hundreds of low-loss micro-channels along a single HC-MOF is performed, and reduction of diffusion-limited response time from hours to ∼40 s is demonstrated with a 2.3-m-long HC-MOF. For photothermal inteferometry sensors, novel detection configurations based on respectively a Sagnac interferometer and an in-fiber modal interferometer are experimentally demonstrated. The Sagnac configuration avoids the need for complex servo-control for interferometer stabilization while the in-fiber configuration simplifies the detection, reducing the size and cost of the sensor system. Sub ppm gas detection can be achieved easily with photothermal interferometry HC-MOF sensors but is difficult to achieve for direct-absorption sensors with the current commercial HC-MOFs.

Capacity limits of MIMO channels with co-channel interference

Abstract: We consider both analytically and via Monte Carlo simulation the variation of the information theoretic capacity of multiple-input, multiple output (MIMO) communication systems. We present a way of explicitly examining the effect of interference on the MIMO sub-channel gains. Using this, we derive asymptotic lower bounds on capacity with many interferers and in high interference-to-noise ratio and present simulation results for them. We also study the behaviour of the capacity as a function of the number of interferers, the interference-to-noise ratio (INR) and the transmit and receive array sizes. It is found that, in interference, the benefit of providing multiple transmit antennas is very small indeed from a capacity perspective, whilst the number of receive antennas is critical both to the capacity and the number of users the system can mitigate interference from. Unusually, it is seen that, with a modification of the MIMO channel matrix to incorporate interference, higher correlation in the channel yields higher capacity rather than the more familiar desire for decorrelated channels.

Reduction of polarization effects in interference coatings.

Abstract: A design procedure is developed which yields layer combinations having a polarization independent effective index of refraction. A method of transforming massive media to nonpolarizing effective massive media is shown. These two design techniques are then applied to the problem of making polarization independent metal–dielectric–metal interference filters and polarization independent beam splitters.