18 research outputs found
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