Ultrafast control of donor-bound electron spins with single detuned optical pulses

The ability to control spins in semiconductors is important in a variety of fields including spintronics and quantum information processing. Due to the potentially fast dephasing times of spins in the solid state [1-3], spin control operating on the picosecond or faster timescale may be necessary. Such speeds, which are not possible to attain with standard electron spin resonance (ESR) techniques based on microwave sources, can be attained with broadband optical pulses. One promising ultrafast technique utilizes single broadband pulses detuned from resonance in a three-level Lambda system [4]. This attractive technique is robust against optical pulse imperfections and does not require a fixed optical reference phase. Here we demonstrate the principle of coherent manipulation of spins theoretically and experimentally. Using this technique, donor-bound electron spin rotations with single-pulse areas exceeding pi/4 and two-pulses areas exceeding pi/2 are demonstrated. We believe the maximum pulse areas attained do not reflect a fundamental limit of the technique and larger pulse areas could be achieved in other material systems. This technique has applications from basic solid-state ESR spectroscopy to arbitrary single-qubit rotations [4, 5] and bang-bang control[6] for quantum computation.Comment: 15 pages, 4 figures, submitted 12/2008. Since the submission of this work we have become aware of related work: J. Berezovsky, M. H. Mikkelsen, N. G. Stoltz, L. A. Coldren, and D. D. Awschalom, Science 320: 349-352 (2008

Resonant enhancement of the zero-phonon emission from a color center in a diamond cavity

We demonstrate coupling of the zero-phonon line of individual nitrogen-vacancy centers and the modes of microring resonators fabricated in single-crystal diamond. A zero-phonon line enhancement exceeding ten-fold is estimated from lifetime measurements at cryogenic temperatures. The devices are fabricated using standard semiconductor techniques and off-the-shelf materials, thus enabling integrated diamond photonics.Comment: 5 pages, 4 figure

A Diamond Nanowire Single Photon Antenna

The development of a robust light source that emits one photon at a time is an outstanding challenge in quantum science and technology. Here, at the transition from many to single photon optical communication systems, fully quantum mechanical effects may be utilized to achieve new capabilities, most notably perfectly secure communication via quantum cryptography. Practical implementations place stringent requirements on the device properties, including stable photon generation, room temperature operation, and efficient extraction of many photons. Single photon light emitting devices based on fluorescent dye molecules, quantum dots, and carbon nanotube material systems have all been explored, but none have simultaneously demonstrated all criteria. Here, we describe the design, fabrication, and characterization of a bright source of single photons consisting of an individual Nitrogen-vacancy color center (NV center) in a diamond nanowire operating in ambient conditions. The nanowire plays a positive role in increasing the number of single photons collected from the NV center by an order of magnitude over devices based on bulk diamond crystals, and allows operation at an order of magnitude lower power levels. This result enables a new class of nanostructured diamond devices for room temperature photonic and quantum information processing applications, and will also impact fields as diverse as biological and chemical sensing, opto-mechanics, and scanning-probe microscopy.Comment: 16 pages, 4 figures, v2: Includes improved reference list; modified figure 1 to show a large array of NW and FDTD simulation of field profile; direct experimental comparsion of several bulk/NW devices in figure

Enhanced Single Photon Emission from a Diamond-Silver Aperture

We have developed a scalable method for coupling single color centers in diamond to plasmonic resonators and demonstrated Purcell enhancement of the single photon emission rate of nitrogen-vacancy (NV) centers. Our structures consist of single nitrogen-vacancy (NV) center-containing diamond nanoposts embedded in a thin silver film. We have utilized the strong plasmon resonances in the diamond-silver apertures to enhance the spontaneous emission of the enclosed dipole. The devices were realized by a combination of ion implantation and top-down nanofabrication techniques, which have enabled deterministic coupling between single NV centers and the plasmonic modes for multiple devices in parallel. The plasmon-enhanced NV centers exhibited over six-fold improvements in spontaneous emission rate in comparison to bare nanoposts and up to a factor of 3.6 in radiative lifetime reduction over bulk samples, with comparable increases in photon counts. The hybrid diamond-plasmon system presented here could provide a stable platform for the implementation of diamond-based quantum information processing and magnetometry schemes.Comment: 16 pages, 4 figure

Prediction and measurement of the size-dependent stability of fluorescence in diamond over the entire nanoscale

Fluorescent defects in non-cytotoxic diamond nanoparticles are candidates for qubits in quantum computing, optical labels in biomedical imaging and sensors in magnetometry. For each application these defects need to be optically and thermodynamically stable, and included in individual particles at suitable concentrations (singly or in large numbers). In this letter, we combine simulations, theory and experiment to provide the first comprehensive and generic prediction of the size, temperature and nitrogen-concentration dependent stability of optically active NV defects in nanodiamonds.Comment: Published in Nano Letters August 2009 24 pages, 6 figure

Inheritance of resistance to grassy stunt virus and its vector in rice

This article does not have an abstract

An assessment of the quality of life in hemodialysis patients using the WHOQOL-BREF questionnaire

A cross-sectional study was conducted to evaluate the quality of life (QOL) of hemodialysis patients. An attempt was made to compare the QOL of hemodialysis patients with the QOL of the general population, renal transplant patients, and patients with a chronic disease, in this case, asthma. The WHOQOL-BREF questionnaire was used to assess the quality of life. Hemodialysis patients who had completed three months of maintenance hemodialysis (n = 75) were enrolled into the study. The quality of life of hemodialysis patients was found to be significantly impaired (P < 0.05) in comparison to healthy individuals of the general population, particularly with respect to the physical, psychological, and social relationship domains. In comparison to the quality of life of renal transplant patients, the quality of life of hemodialysis patients was significantly (P < 0.05) lower in all the four WHOQOL-BREF domains. Only in the environmental dimension was the quality of life of hemodialysis patients found to be significantly lower than that of the asthma patients. Female hemodialysis patients showed significantly (P < 0.05) lower quality of life than did male patients in the psychological and environmental dimensions of WHOQOL-BREF. A positive association was seen between higher education and the psychological functioning and the environmental dimensions of WHOQOL-BREF. Thus, the quality of life of hemodialysis patients was found to be considerably impaired when compared to that of healthy individuals of the general population as well as of renal transplant patients

Unusual Fungal Infections in Renal Transplant Recipients

Fungal infections are an important cause of morbidity and mortality in renal transplant recipients. The causative agent and the risk factors differ depending on the period after the kidney transplant. Also the incidence varies according to the geographical area. We are reporting three cases of fungal infections in renal transplant recipients. Two of them have etiological agents which are common among immunosuppressed patients, but with an atypical clinical presentation, while one of them is a subcutaneous infection caused by a less frequent dematiaceous fungus, Aureobasidium pullulans. These cases highlight how a high index of clinical suspicion and prompt diagnosis is very much essential for better outcome. The emerging fungal infections and paucity of data regarding their management pose a challenge to the transplant physicians