79 research outputs found
Suppression of Pulsed Dynamic Nuclear Polarization by Many-Body Spin Dynamics
We study a mechanism by which nuclear hyperpolarization due to the
polarization transfer from a microwave-pulse-controlled electron spin is
suppressed. From analytical and numerical calculations of the unitary dynamics
of multiple nuclear spins, we uncover that, combined with the formation of the
dark state within a cluster of nuclei, coherent higher-order nuclear spin
dynamics impose limits on the efficiency of the polarization transfer even in
the absence of mundane depolarization processes such as nuclear spin diffusion
and relaxation. Furthermore, we show that the influence of the dark state can
be partly mitigated by introducing a disentangling operation. Our analysis is
applied to the nuclear polarizations observed in C nuclei coupled with a
single nitrogen-vacancy center in diamond [Science 374, 1474 (2021) by J.
Randall et al.]. Our work sheds light on collective engineering of nuclear
spins as well as future designs of pulsed dynamic nuclear polarization
protocols
Nitrogen isotope effects on boron vacancy quantum sensors in hexagonal boron nitride
Recently, there has been growing interest in researching the use of hexagonal
boron nitride (hBN) for quantum technologies. Here we investigate nitrogen
isotope effects on boron vacancy (V) defects, one of the candidates
for quantum sensors, in N isotopically enriched hBN synthesized using
metathesis reaction. The Raman shifts are scaled with the reduced mass,
consistent with previous work on boron isotope enrichment. We obtain nitrogen
isotopic composition dependent optically detected magnetic resonance spectra of
V defects and determine the hyperfine interaction parameter of
N spin to be -64 MHz. Our investigation provides a design policy for
hBNs for quantum technologies
Demonstration of highly-sensitive wideband microwave sensing using ensemble nitrogen-vacancy centers
Microwave magnetometry is essential for the advancement of microwave
technologies. We demonstrate a broadband microwave sensing protocol using the
AC Zeeman effect with ensemble nitrogen-vacancy (NV) centers in diamond. A
widefield microscope can visualize the frequency characteristics of the
microwave resonator and the spatial distribution of off-resonant microwave
amplitude. Furthermore, by combining this method with dynamical decoupling, we
achieve the microwave amplitude sensitivity of , which is 7.7 times better than obtained using the protocol in previous research over a
sensing volume of . Our achievement is a concrete step in adapting ensemble NV
centers for wideband and widefield microwave imaging.Comment: 6 pages, 4 figures, and supplementary material
Demonstration of geometric diabatic control of quantum states
Geometric effects can play a pivotal role in streamlining quantum
manipulation. We demonstrate a geometric diabatic control, that is, perfect
tunneling between spin states in a diamond by a quadratic sweep of a driving
field. The field sweep speed for the perfect tunneling is determined by the
geometric amplitude factor and can be tuned arbitrarily. Our results are
obtained by testing a quadratic version of Berry's twisted Landau-Zener model.
This geometric tuning is robust over a wide parameter range. Our work provides
a basis for quantum control in various systems, including condensed matter
physics, quantum computation, and nuclear magnetic resonance
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