Topic
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.
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TL;DR: In this article, a technique for observing two-photon interference with isolated, unsynchronized sources for which the coherence times differ by several orders of magnitude is presented.
Abstract: If identical photons meet at a semi-transparent mirror they seem to leave in the same direction, an effect called ‘two-photon interference’. It has been known for some time that this effect should occur for photons generated by dissimilar sources with no common history, provided the measurement cannot distinguish between the photons. Here, we report a technique for observing such interference with isolated, unsynchronized sources for which the coherence times differ by several orders of magnitude. In an experiment we cause photons generated by different physical processes, with different photon statistics, to interfere. One of the sources is stimulated emission from a tunable laser, which has Poissonian statistics and a nanoelectronvolt bandwidth. The other is spontaneous emission from a quantum dot in a p–i–n diode with a few-microelectronvolt linewidth. We develop a theory to explain the visibility of interference, which is primarily limited by the timing resolution of our detectors.
74 citations
73 citations
TL;DR: A review of the progress and applications of two-photon (two-particle) interference over the last three decades can be found in this paper, with a focus on fermionic and bosonic quantum objects.
Abstract: Nearly 30 years ago, two-photon interference was observed, marking the beginning of a new quantum era. Indeed, two-photon interference has no classical analogue, giving it a distinct advantage for a range of applications. The peculiarities of quantum physics may now be used to our advantage to outperform classical computations, securely communicate information, simulate highly complex physical systems and increase the sensitivity of precise measurements. This separation from classical to quantum physics has motivated physicists to study two-particle interference for both fermionic and bosonic quantum objects. So far, two-particle interference has been observed with massive particles, among others, such as electrons and atoms, in addition to plasmons, demonstrating the extent of this effect to larger and more complex quantum systems. A wide array of novel applications to this quantum effect is to be expected in the future. This review will thus cover the progress and applications of two-photon (two-particle) interference over the last three decades.
73 citations
TL;DR: In this article, it was shown that weakly damped space-charge waves exist in photorefractive crystals with a sufficiently large lifetime and the dispersion law, the damping constant, and the quality factor of these waves and their dependence on the crystal parameters and on experimental conditions are found.
Abstract: It is shown that weakly damped space-charge waves exist in photorefractive crystals with a sufficiently large lifetime–mobility product. The dispersion law, the damping constant, and the quality factor of these waves and their dependence on the crystal parameters and on the experimental conditions are found. The instability of the fundamental grating against excitation of these waves is investigated; the fundamental grating is excited either by a moving interference pattern or by a standing interference pattern plus an oscillating external electric field. The dependence of the threshold and the characteristic exponent of the instability on the wave vectors of the exciting waves and on the experimental parameters is found for the three-dimensional case. It turns out that the strongest instabilities correspond to the cases of optimal enhancement of photoinduced gratings. The theory is compared with the experimental data for BSO crystals.
73 citations
TL;DR: Performance results reveal that the Kalman-filter method for power control provides a significant performance improvement, and performs noticeably better than the delta-modulation method and a simple scheme that uses the last measurement as predicted interference power.
Abstract: A Kalman-filter method for power control is proposed for broadband, packet-switched time division multiple access wireless networks. By exploiting the temporal correlation of co-channel interference, a Kalman filter is used to predict future interference power. Based on the predicted interference and estimated path gain between the transmitter and receiver, the transmission power is determined to achieve a desired signal-to-interference-plus-noise ratio (SINR). A condition to ensure power stability in the packet-switched environment is established and proven for a special case of the Kalman-filter method. The condition generalizes the existing one for a fixed path-gain matrix, as for circuit-switched networks. Performance results reveal that the Kalman-filter method for power control provides a significant performance improvement. Specifically, when messages consist of ten packets on average, the 90th and 95th percentile of the SINR by the new method are 3.79 dB and 5.46 dB above those when no power control is in use, and lie just 0.96 dB and 1.14 dB below the upper-bound performance of the optimal power control, respectively, in a system with four-sector cells and an interleaved frequency assignment of a reuse factor of 2/8. In addition, the new method performs noticeably better than the delta-modulation method and a simple scheme that uses the last measurement as predicted interference power. In an example of 8-PSK modulation and average message length of 20 packets, the SINR performance gain by the new method improves the network throughput by about 150% and 70%, relative to no power control and the simple scheme, respectively.
73 citations