91 research outputs found
Measurement and Control of Single Nitrogen-Vacancy Center Spins above 600 K
We study the spin and orbital dynamics of single nitrogen-vacancy (NV)
centers in diamond between room temperature and 700 K. We find that the ability
to optically address and coherently control single spins above room temperature
is limited by nonradiative processes that quench the NV center's
fluorescence-based spin readout between 550 and 700 K. Combined with electronic
structure calculations, our measurements indicate that the energy difference
between the 3E and 1A1 electronic states is approximately 0.8 eV. We also
demonstrate that the inhomogeneous spin lifetime (T2*) is temperature
independent up to at least 625 K, suggesting that single NV centers could be
applied as nanoscale thermometers over a broad temperature range.Comment: 8 pages, 5 figures, and 14 pages of supplemental material with
additional figures. Title change and minor revisions from previous version.
DMT and DJC contributed equally to this wor
Theoretical model of the dynamic spin polarization of nuclei coupled to paramagnetic point defects in diamond and silicon carbide
Dynamic nuclear spin polarization (DNP) mediated by paramagnetic point
defects in semiconductors is a key resource for both initializing nuclear
quantum memories and producing nuclear hyperpolarization. DNP is therefore an
important process in the field of quantum-information processing,
sensitivity-enhanced nuclear magnetic resonance, and nuclear-spin-based
spintronics. DNP based on optical pumping of point defects has been
demonstrated by using the electron spin of nitrogen-vacancy (NV) center in
diamond, and more recently, by using divacancy and related defect spins in
hexagonal silicon carbide (SiC). Here, we describe a general model for these
optical DNP processes that allows the effects of many microscopic processes to
be integrated. Applying this theory, we gain a deeper insight into dynamic
nuclear spin polarization and the physics of diamond and SiC defects. Our
results are in good agreement with experimental observations and provide a
detailed and unified understanding. In particular, our findings show that the
defects' electron spin coherence times and excited state lifetimes are crucial
factors in the entire DNP process
High fidelity bi-directional nuclear qubit initialization in SiC
Dynamic nuclear polarization (DNP) is an attractive method for initializing
nuclear spins that are strongly coupled to optically active electron spins
because it functions at room temperature and does not require strong magnetic
fields. In this Letter, we demonstrate that DNP, with near-unity polarization
efficiency, can be generally realized in weakly coupled hybrid registers, and
furthermore that the nuclear spin polarization can be completely reversed with
only sub-Gauss magnetic field variations. This mechanism offers new avenues for
DNP-based sensors and radio-frequency free control of nuclear qubits
Electron spin resonance of nitrogen-vacancy centers in optically trapped nanodiamonds
Using an optical tweezers apparatus, we demonstrate three-dimensional control
of nanodiamonds in solution with simultaneous readout of ground-state
electron-spin resonance (ESR) transitions in an ensemble of diamond
nitrogen-vacancy (NV) color centers. Despite the motion and random orientation
of NV centers suspended in the optical trap, we observe distinct peaks in the
measured ESR spectra qualitatively similar to the same measurement in bulk.
Accounting for the random dynamics, we model the ESR spectra observed in an
externally applied magnetic field to enable d.c. magnetometry in solution. We
estimate the d.c. magnetic field sensitivity based on variations in ESR line
shapes to be ~50 microTesla/Hz^1/2. This technique may provide a pathway for
spin-based magnetic, electric, and thermal sensing in fluidic environments and
biophysical systems inaccessible to existing scanning probe techniques.Comment: 29 pages, 13 figures for manuscript and supporting informatio
Isolated spin qubits in SiC with a high-fidelity infrared spin-to-photon interface
The divacancies in SiC are a family of paramagnetic defects that show promise
for quantum communication technologies due to their long-lived electron spin
coherence and their optical addressability at near-telecom wavelengths.
Nonetheless, a mechanism for high-fidelity spin-to-photon conversion, which is
a crucial prerequisite for such technologies, has not yet been demonstrated.
Here we demonstrate a high-fidelity spin-to-photon interface in isolated
divacancies in epitaxial films of 3C-SiC and 4H-SiC. Our data show that
divacancies in 4H-SiC have minimal undesirable spin-mixing, and that the
optical linewidths in our current sample are already similar to those of recent
remote entanglement demonstrations in other systems. Moreover, we find that
3C-SiC divacancies have millisecond Hahn-echo spin coherence time, which is
among the longest measured in a naturally isotopic solid. The presence of
defects with these properties in a commercial semiconductor that can be
heteroepitaxially grown as a thin film on shows promise for future quantum
networks based on SiC defects.Comment: 26 pages, 4 figure
Stark Tuning and Electrical Charge State Control of Single Divacancies in Silicon Carbide
Neutrally charged divacancies in silicon carbide (SiC) are paramagnetic color
centers whose long coherence times and near-telecom operating wavelengths make
them promising for scalable quantum communication technologies compatible with
existing fiber optic networks. However, local strain inhomogeneity can randomly
perturb their optical transition frequencies, which degrades the
indistinguishability of photons emitted from separate defects, and hinders
their coupling to optical cavities. Here we show that electric fields can be
used to tune the optical transition frequencies of single neutral divacancy
defects in 4H-SiC over a range of several GHz via the DC Stark effect. The same
technique can also control the charge state of the defect on microsecond
timescales, which we use to stabilize unstable or non-neutral divacancies into
their neutral charge state. Using fluorescence-based charge state detection, we
show both 975 nm and 1130 nm excitation can prepare its neutral charge state
with near unity efficiency.Comment: 12 pages, 4 figure
Optical polarization of nuclear spins in silicon carbide
We demonstrate optically pumped dynamic nuclear polarization of 29-Si nuclear
spins that are strongly coupled to paramagnetic color centers in 4H- and
6H-SiC. The 99 +/- 1% degree of polarization at room temperature corresponds to
an effective nuclear temperature of 5 microKelvin. By combining ab initio
theory with the experimental identification of the color centers' optically
excited states, we quantitatively model how the polarization derives from
hyperfine-mediated level anticrossings. These results lay a foundation for
SiC-based quantum memories, nuclear gyroscopes, and hyperpolarized probes for
magnetic resonance imaging.Comment: 21 pages including supplementary information; four figures in main
text and one tabl
Optical Polarization of Nuclear Spins in Silicon Carbide
We demonstrate optically pumped dynamic nuclear polarization of 29Si nuclear spins that are strongly coupled to paramagnetic color centers in 4H- and 6H-SiC. The 99 ± 1% degree of polarization at room temperature corresponds to an effective nuclear temperature of 5 K. By combining ab initio theory with the experimental identification of the color centers’ optically excited states, we quantitatively model how the polarization derives from hyperfine-mediated level anticrossings. These results lay a foundation for SiC-based quantum memories, nuclear gyroscopes, and hyperpolarized probes for magnetic resonance imaging
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