75 research outputs found
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
Optical-power-dependent splitting of magnetic resonance in nitrogen-vacancy centers in diamond
Nitrogen-vacancy (NV) centers in diamonds are a powerful tool for accurate
magnetic field measurements. The key is precisely estimating the
field-dependent splitting width of the optically detected magnetic resonance
(ODMR) spectra of the NV centers. In this study, we investigate the optical
power dependence of the ODMR spectra using NV ensemble in nanodiamonds (NDs)
and a single-crystal bulk diamond. We find that the splitting width
exponentially decays and is saturated as the optical power increases.
Comparison between NDs and a bulk sample shows that while the decay amplitude
is sample-dependent, the optical power at which the decay saturates is almost
sample-independent. We propose that this unexpected phenomenon is an intrinsic
property of the NV center due to non-axisymmetry deformation or impurities. Our
finding indicates that diamonds with less deformation are advantageous for
accurate magnetic field measurements.Comment: 9 pages, 7 figure
Long Rayleigh length confocal microscope: A fast evaluation tool for obtaining quantum properties of color centers
Color centers in wide band-gap semiconductors, which have superior quantum
properties even at room temperature and atmospheric pressure, have been
actively applied to quantum sensing devices. Characterization of the quantum
properties of the color centers in the semiconductor materials and ensuring
that these properties are uniform over a wide area are key issues for
developing quantum sensing devices based on color center. In this article, we
will describe the principle and performance of a newly developed confocal
microscope system with a long Rayleigh length (LRCFM). This system can
characterize a wider area faster than the confocal microscope systems commonly
used for color center evaluation
Perfect alignment and preferential orientation of nitrogen-vacancy centers during CVD growth of diamond on (111) surfaces
Synthetic diamond production is key to the development of quantum metrology
and quantum information applications of diamond. The major quantum sensor and
qubit candidate in diamond is the nitrogen-vacancy (NV) color center. This
lattice defect comes in four different crystallographic orientations leading to
an intrinsic inhomogeneity among NV centers that is undesirable in some
applications. Here, we report a microwave plasma-assisted chemical vapor
decomposition (MPCVD) diamond growth technique on (111)-oriented substrates
that yields perfect alignment () of as-grown NV centers along a single
crystallographic direction. In addition, clear evidence is found that the
majority () of the aligned NV centers were formed by the nitrogen
being first included in the (111) growth surface and then followed by the
formation of a neighboring vacancy on top. The achieved homogeneity of the
grown NV centers will tremendously benefit quantum information and metrology
applications.Comment: 6 pages, 4 figures, changes to previous version: added
acknowledgemen
キンゾク/SiC オヨビ キンゾク/Si カイメン ノ Schottky ショウヘキ ノ ケイセイ キコウ ニカンスル ケンキュウ
筑波大学博士 (工学) 学位論文・平成10年3月23日授与 (甲第1884号
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