85 research outputs found
Diamond chemical vapor deposition on optical fibers for fluorescence waveguiding
A technique has been developed for depositing diamond crystals on the
endfaces of optical fibers and capturing the fluorescence generated by
optically active defects in the diamond into the fiber. This letter details the
diamond growth on optical fibers and transmission of fluorescence through the
fiber from the nitrogen-vacancy (N-V) color center in diamond. Control of the
concentration of defects incorporated during the chemical vapor deposition
(CVD) growth process is also demonstrated. These are the first critical steps
in developing a fiber coupled single photon source based on optically active
defect centers in diamond.Comment: 10 pages, 3 figure
The role of C2 in nanocrystalline diamond growth
This paper presents findings from a study of nanocrystalline diamond (NCD)
growth in a microwave plasma chemical vapour deposition (CVD) reactor. NCD
films were grown using Ar/H2/CH4 and He/H2/CH4 gas compositions. The resulting
films were characterised using Raman spectroscopy, scanning electron microscopy
and atomic force microscopy. Analysis revealed an estimated grain size of the
order of 50 nm, growth rates in the range 0.01 to 0.3 um/h and sp3 and sp2
bonded carbon content consistent with that expected for NCD. The C2 Swan band
was probed using cavity ring-down spectroscopy (CRDS) to measure the absolute
C2 (a) number density in the plasma during diamond film growth. The number
density in the Ar/H2/CH4 plasmas was in the range 2 to 4 x 10^12 cm-3, but
found to be present in quantities too low to measure in the He/H2/CH4 plasmas.
Optical emission spectrometry (OES) was employed to determine the relative
densities of the C2 excited state (d) in the plasma. The fact that similar NCD
material was grown whether using Ar or He as the carrier gas suggests that C2
does not play a major role in the growth of nanocrystalline diamond.Comment: 39 pages, 11 figure
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
Implantation of labelled single nitrogen vacancy centers in diamond using 15N
Nitrogen-vacancy (NV-) color centers in diamond were created by implantation
of 7 keV 15N (I = 1/2) ions into type IIa diamond. Optically detected magnetic
resonance was employed to measure the hyperfine coupling of the NV- centers.
The hyperfine spectrum from 15NV- arising from implanted 15N can be
distinguished from 14NV- centers created by native 14N (I = 1) sites. Analysis
indicates 1 in 40 implanted 15N atoms give rise to an optically observable
15NV- center. This report ultimately demonstrates a mechanism by which the
yield of NV- center formation by nitrogen implantation can be measured.Comment: 14 pages, 3 figures, to appear in Applied Physics Letter
Single photon quantum non-demolition in the presence of inhomogeneous broadening
Electromagnetically induced transparency (EIT) has been often proposed for
generating nonlinear optical effects at the single photon level; in particular,
as a means to effect a quantum non-demolition measurement of a single photon
field. Previous treatments have usually considered homogeneously broadened
samples, but realisations in any medium will have to contend with inhomogeneous
broadening. Here we reappraise an earlier scheme [Munro \textit{et al.} Phys.
Rev. A \textbf{71}, 033819 (2005)] with respect to inhomogeneities and show an
alternative mode of operation that is preferred in an inhomogeneous
environment. We further show the implications of these results on a potential
implementation in diamond containing nitrogen-vacancy colour centres. Our
modelling shows that single mode waveguide structures of length in single-crystal diamond containing a dilute ensemble of NV
of only 200 centres are sufficient for quantum non-demolition measurements
using EIT-based weak nonlinear interactions.Comment: 21 pages, 9 figures (some in colour) at low resolution for arXiv
purpose
Stark shift control of single optical centers in diamond
Lifetime limited optical excitation lines of single nitrogen vacancy (NV) defect centers in diamond have been observed at liquid helium temperature. They display unprecedented spectral stability over many seconds and excitation cycles. Spectral tuning of the spin selective optical resonances was performed via the application of an external electric field (i.e. the Stark shift). A rich variety of Stark shifts were observed including linear as well as quadratic components. The ability to tune the excitation lines of single NV centers has potential applications in quantum information processing
High-sensitivity diamond magnetometer with nanoscale resolution
We present a novel approach to the detection of weak magnetic fields that
takes advantage of recently developed techniques for the coherent control of
solid-state electron spin quantum bits. Specifically, we investigate a magnetic
sensor based on Nitrogen-Vacancy centers in room-temperature diamond. We
discuss two important applications of this technique: a nanoscale magnetometer
that could potentially detect precession of single nuclear spins and an optical
magnetic field imager combining spatial resolution ranging from micrometers to
millimeters with a sensitivity approaching few femtotesla/Hz.Comment: 29 pages, 4 figure
Enhanced spontaneous emission from nanodiamond colour centres on opal photonic crystal
Colour centres in diamond are promising candidates as a platform for quantum
technologies and biomedical imaging based on spins and/or photons. Controlling
the emission properties of colour centres in diamond is a key requirement for
developing efficient single photon sources with high collection efficiency. A
number of groups have produced enhancement in the emission rate over narrow
wavelength ranges by coupling single emitters in nanodiamond crystals to
resonant electromagnetic structures. Here we characterise in detail the
spontaneous emission rates of nitrogen-vacancy centres positioned in various
locations on a structured substrate. We show an average factor of 1.5
enhancement of the total emission rate when nanodiamonds are on an opal
photonic crystal surface, and observe changes in the lifetime distribution. We
present a model to explain these observations and associate the lifetime
properties with dipole orientation and polarization effects.Comment: 16 pages, 10 figure
Scalable quantum register based on coupled electron spins in a room temperature solid
Realization of devices based on quantum laws might lead to building
processors that outperform their classical analogues and establishing
unconditionally secure communication protocols. Solids do usually present a
serious challenge to quantum coherence. However, owing to their spin-free
lattice and low spin orbit coupling, carbon materials and particularly diamond
are suitable for hosting robust solid state quantum registers. We show that
scalable quantum logic elements can be realized by exploring long range
magnetic dipolar coupling between individually addressable single electron
spins associated with separate color centers in diamond. Strong distance
dependence of coupling was used to characterize the separation of single qubits
98 A with unprecedented accuracy (3 A) close to a crystal lattice spacing. Our
demonstration of coherent control over both electron spins, conditional
dynamics, selective readout as well as switchable interaction, opens the way
towards a room temperature solid state scalable quantum register. Since both
electron spins are optically addressable, this solid state quantum device
operating at ambient conditions provides a degree of control that is currently
available only for atomic systems.Comment: original submitted version of the manuscrip
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