290 research outputs found
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
In situ method for power re-equalization of wavelength pulses inside of OCDMA codes
A simple in-situ method to equalize power among individual wavelengths pulses representing two-dimensional wavelength-hopping time-spreading OCDMA code originally generated by a fibre Bragg grating-based OCDMA encoder is presented. Experimental data obtained in a field-based multiuser OCDMA testbed shows that applying this method results in system performance enhancements which was demonstrated by observing improved bit error rate (BER) during the field trials
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
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
Chitosan Derivatives / Calcium Carbonate Composite Capsules Prepared by the Layer - by - Layer Deposition Method II Stabilization of the Shell by Crosslinking
The layer-by-layer deposition method is utilized to prepare rodlike core / shell capsules. Chitosan (polycation)and chitosansulfate (polyanion)were alternatively deposited on the surface of calcium carbonate whisker(rodlikeparticle). The thickness of the obtained shells ranged from 26 to 42 nm. After the deposition, the shell was treated with diisocyanate to form crosslink between the chitosan or chitosansulfate chains in order to stabilize the deposited shell. The obtained shell crosslinked rodlike capsules were successfully converted to hollow particles by immersing them into hydrochloric acid due to the enhanced shell stability, whereas from noncrosslinked shells, no hollow capsules were yielded : the shell was removed by dissolution in hydrochloric acid. It is revealed that the crosslinking reactivity is higher for 1,6-diisocyanatehexane than for tolylene 2,4-diisocyanate, suggesting that the reactivity depends on the size and flxibility of the crosslinking molecule
Quantum key distribution with an efficient countermeasure against correlated intensity fluctuations in optical pulses
Quantum key distribution (QKD) allows two distant parties to share secret
keys with the proven security even in the presence of an eavesdropper with
unbounded computational power. Recently, GHz-clock decoy QKD systems have been
realized by employing ultrafast optical communication devices. However,
security loopholes of high-speed systems have not been fully explored yet. Here
we point out a security loophole at the transmitter of the GHz-clock QKD, which
is a common problem in high-speed QKD systems using practical band-width
limited devices. We experimentally observe the inter-pulse intensity
correlation and modulation-pattern dependent intensity deviation in a practical
high-speed QKD system. Such correlation violates the assumption of most
security theories. We also provide its countermeasure which does not require
significant changes of hardware and can generate keys secure over 100 km fiber
transmission. Our countermeasure is simple, effective and applicable to wide
range of high-speed QKD systems, and thus paves the way to realize ultrafast
and security-certified commercial QKD systems
Morphology and release kinetics of protein-loaded porous poly(L-lactic acid) spheres prepared by freeze-drying technique
Freeze-drying a biodegradable polymer, poly(L-lactic acid) (PLLA) from 1,4-dioxane solutions provided very porous spherical particles of ca. 3 mm in radius with specific surface area of 8 − 13 m2 g−1. The surface of the particle was found to be less porous compared with its interior. To apply the freeze-dried PLLA (FDPLLA) to drug delivery system, its morphology and drug releasing kinetics were investigated, bovine serum albumin (BSA) being used as a model drug compound. Immersion of FDPLLA into a BSA aqueous solution gave BSA-loaded FDPLLA, where mass fraction of the adsorbed BSA reached up to 79%. Time-dependent release profile of BSA in water suggested a two-step mechanism: (1) very rapid release of BSA deposited on and near the particle surface, which results in an initial burst, and (2) leaching of BSA from the interior of the particle by the diffusion process. It was suggested that the latter process is largely governed by the surface porosity. The porosity of both the interior and surface was found to decrease remarkably as the concentration of the original PLLA / 1,4-dioxane solution increases, C0. Thus, C0 is a key parameter that controls the loading and releasing of BSA
7-Chloro-1,2-dihydrofuro[2,3-c]isoquinolin-5-amine
In the title compound, C11H9ClN2O, the fused-ring system is essentially planar, with a maximum deviation of 0.0323 (16) Å. In the crystal, molecules are connected by N—H⋯O hydrogen bonds forming a zigzag chain along the c axis. Molecules are further stacked along the a axis through weak π–π interactions, the shortest distance between ring centroids being 3.6476 (8) Å
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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