Occurrence of Two Species of Old World Bees, \u3ci\u3eAnthidium Manicatum\u3c/i\u3e and \u3ci\u3eA. Oblongatum\u3c/i\u3e (Apoidea: Megachilidae), in Northern Ohio and Southern Michigan

Anthidium manicatum and A. oblongatum are two European bees species that have recently established themselves in North America. Anthidium manicatum has previously been documented in New York and Ontario, Canada, and A. oblongatum has been documented in New York, New Jersey, Maryland, and eastern Pennsylvania. We surveyed a number of sites in Ohio, Michigan, and Indiana for these species in 2000 and 2001, and found both bee species to have extended their ranges into northern Ohio, and A. manicatum to have moved into southern Michigan. We present a key identifying the four Anthidium species now known from northeastern North America

Switched Control of Electron Nuclear Spin Systems

In this article, we study control of electron-nuclear spin dynamics at magnetic field strengths where the Larmor frequency of the nucleus is comparable to the hyperfine coupling strength. The quantization axis for the nuclear spin differs from the static B_0 field direction and depends on the state of the electron spin. The quantization axis can be switched by flipping the state of electron spin, allowing for universal control on nuclear spin states. We show that by performing a sequence of flips (each followed by a suitable delay), we can perform any desired rotation on the nuclear spins, which can also be conditioned on the state of the electron spin. These operations, combined with electron spin rotations can be used to synthesize any unitary transformation on the coupled electron-nuclear spin system. We discuss how these methods can be used for design of experiments for transfer of polarization from the electron to the nuclear spins

Room temperature triggered single-photon source in the near infrared

We report the realization of a solid-state triggered single-photon source with narrow emission in the near infrared at room temperature. It is based on the photoluminescence of a single nickel-nitrogen NE8 colour centre in a chemical vapour deposited diamond nanocrystal. Stable single-photon emission has been observed in the photoluminescence under both continuous-wave and pulsed excitations. The realization of this source represents a step forward in the application of diamond-based single-photon sources to Quantum Key Distribution (QKD) under practical operating conditions.Comment: 10 page

Spin-flip and spin-conserving optical transitions of the nitrogen-vacancy centre in diamond

We map out the first excited state sublevel structure of single nitrogen-vacancy (NV) colour centres in diamond. The excited state is an orbital doublet where one branch supports an efficient cycling transition, while the other can simultaneously support fully allowed optical Raman spin-flip transitions. This is crucial for the success of many recently proposed quantum information applications of the NV defects. We further find that an external electric field can be used to completely control the optical properties of a single centre. Finally, a group theoretical model is developed that explains the observations and provides good physical understanding of the excited state structure

Experimental open air quantum key distribution with a single photon source

We present a full implementation of a quantum key distribution (QKD) system with a single photon source, operating at night in open air. The single photon source at the heart of the functional and reliable setup relies on the pulsed excitation of a single nitrogen-vacancy color center in diamond nanocrystal. We tested the effect of attenuation on the polarized encoded photons for inferring longer distance performance of our system. For strong attenuation, the use of pure single photon states gives measurable advantage over systems relying on weak attenuated laser pulses. The results are in good agreement with theoretical models developed to assess QKD security

Controlling the quantum dynamics of a mesoscopic spin bath in diamond

Understanding and mitigating decoherence is a key challenge for quantum science and technology. The main source of decoherence for solid-state spin systems is the uncontrolled spin bath environment. Here, we demonstrate quantum control of a mesoscopic spin bath in diamond at room temperature that is composed of electron spins of substitutional nitrogen impurities. The resulting spin bath dynamics are probed using a single nitrogen-vacancy (NV) centre electron spin as a magnetic field sensor. We exploit the spin bath control to dynamically suppress dephasing of the NV spin by the spin bath. Furthermore, by combining spin bath control with dynamical decoupling, we directly measure the coherence and temporal correlations of different groups of bath spins. These results uncover a new arena for fundamental studies on decoherence and enable novel avenues for spin-based magnetometry and quantum information processing

Отказоустойчивый многофазный асинхронный электропривод с несинусоидальными токами

Рассмотрен принцип построения многофазного асинхронного электропривода, позволяющего при неоднократных отказах преобразователя частоты и двигателя обеспечить отказоустойчивое управление, на основе программируемых несинусоидальных токов с восстановлением работоспособности за счет активизации алгоритма восстановления в управляющем микроконтроллере. Приведены результаты моделирования для аварийной ситуации типа "обрыв фазы" для случая трехфазного двигателя с частичным восстановлением работоспособности асинхронного двигателя