1,112 research outputs found
Quantum sensing with arbitrary frequency resolution
Quantum sensing takes advantage of well controlled quantum systems for
performing measurements with high sensitivity and precision. We have
implemented a concept for quantum sensing with arbitrary frequency resolution,
independent of the qubit probe and limited only by the stability of an external
synchronization clock. Our concept makes use of quantum lock-in detection to
continuously probe a signal of interest. Using the electronic spin of a single
nitrogen vacancy center in diamond, we demonstrate detection of oscillating
magnetic fields with a frequency resolution of 70 uHz over a MHz bandwidth. The
continuous sampling further guarantees an excellent sensitivity, reaching a
signal-to-noise ratio in excess of 10,000:1 for a 170 nT test signal measured
during a one-hour interval. Our technique has applications in magnetic
resonance spectroscopy, quantum simulation, and sensitive signal detection.Comment: Manuscript resubmitted to Science. Includes Supplementary Material
Three-dimensional nuclear spin positioning using coherent radio-frequency control
Distance measurements via the dipolar interaction are fundamental to the
application of nuclear magnetic resonance (NMR) to molecular structure
determination, but they only provide information on the absolute distance
and polar angle between spins. In this Letter, we present a protocol
to also retrieve the azimuth angle . Our method relies on measuring the
nuclear precession phase after application of a control pulse with a calibrated
external radio-frequency coil. We experimentally demonstrate three-dimensional
positioning of individual carbon-13 nuclear spins in a diamond host crystal
relative to the central electronic spin of a single nitrogen-vacancy center.
The ability to pinpoint three-dimensional nuclear locations is central for
realizing a nanoscale NMR technique that can image the structure of single
molecules with atomic resolution.Comment: 5 pages, 4 figure
High-bandwidth microcoil for fast nuclear spin control
The active manipulation of nuclear spins with radio-frequency (RF) coils is
at the heart of nuclear magnetic resonance (NMR) spectroscopy and spin-based
quantum devices. Here, we present a microcoil transmitter system designed to
generate strong RF pulses over a broad bandwidth, allowing for fast spin
rotations on arbitrary nuclear species. Our design incorporates: (i) a planar
multilayer geometry that generates a large field of 4.35 mT per unit current,
(ii) a 50 Ohm transmission circuit with a broad excitation bandwidth of
approximately 20 MHz, and (iii) an optimized thermal management for removal of
Joule heating. Using individual 13C nuclear spins in the vicinity of a diamond
nitrogen-vacancy (NV) center as a test system, we demonstrate Rabi frequencies
exceeding 70 kHz and nuclear pi/2 rotations within 3.4 us. The extrapolated
values for 1H spins are about 240 kHz and 1 us, respectively. Beyond enabling
fast nuclear spin manipulations, our microcoil system is ideally suited for the
incorporation of advanced pulse sequences into micro- and nanoscale NMR
detectors operating at low (<1 T) magnetic field.Comment: 8 pages, 5 figures. Submitted to Rev. Sci. Inst
Spurious harmonic response of multipulse quantum sensing sequences
Multipulse sequences based on Carr-Purcell decoupling are frequently used for
narrow-band signal detection in single spin magnetometry. We have analyzed the
behavior of multipulse sensing sequences under real-world conditions, including
finite pulse durations and the presence of detunings. We find that these
non-idealities introduce harmonics to the filter function, allowing additional
frequencies to pass the filter. In particular, we find that the XY family of
sequences can generate signals at the 2fac, 4fac and 8fac harmonics and their
odd subharmonics, where fac is the ac signal frequency. Consideration of the
harmonic response is especially important for diamond-based nuclear spin
sensing where the NMR frequency is used to identify the nuclear spin species,
as it leads to ambiguities when several isotopes are present.Comment: 6 pages, 7 figure
Nuclear spin relaxation induced by a mechanical resonator
We report on measurements of the spin lifetime of nuclear spins strongly
coupled to a micromechanical cantilever as used in magnetic resonance force
microscopy. We find that the rotating-frame correlation time of the statistical
nuclear polarization is set by the magneto-mechanical noise originating from
the thermal motion of the cantilever. Evidence is based on the effect of three
parameters: (1) the magnetic field gradient (the coupling strength), (2) the
Rabi frequency of the spins (the transition energy), and (3) the temperature of
the low-frequency mechanical modes. Experimental results are compared to
relaxation rates calculated from the spectral density of the magneto-mechanical
noise.Comment: 4 pages, 4 figure
Evolutionary implications of a high selfing rate in the freshwater snail Lymnaea truncatula.
Self-compatible hermaphroditic organisms that mix self-fertilization and outcrossing are of great interest for investigating the evolution of mating systems. We investigate the evolution of selfing in Lymnaea truncatula, a self-compatible hermaphroditic freshwater snail. We first analyze the consequences of selfing in terms of genetic variability within and among populations and then investigate how these consequences along with the species ecology (harshness of the habitat and parasitism) might govern the evolution of selfing. Snails from 13 localities (classified as temporary or permanent depending on their water availability) were sampled in western Switzerland and genotyped for seven microsatellite loci. F(IS) (estimated on adults) and progeny array analyses (on hatchlings) provided similar selfing rate estimates of 80%. Populations presented a low polymorphism and were highly differentiated (F(ST) = 0.58). Although the reproductive assurance hypothesis would predict higher selfing rate in temporary populations, no difference in selfing level was observed between temporary and permanent populations. However, allelic richness and gene diversity declined in temporary habitats, presumably reflecting drift. Infection levels varied but were not simply related to either estimated population selfing rate or to differences in heterozygosity. These findings and the similar selfing rates estimated for hatchlings and adults suggest that within-population inbreeding depression is low in L. truncatula
Feedback cooling of a cantilever's fundamental mode below 5 mK
We cool the fundamental mechanical mode of an ultrasoft silicon cantilever
from a base temperature of 2.2 K to 2.9 +/- 0.3 mK using active optomechanical
feedback. The lowest observed mode temperature is consistent with limits
determined by the properties of the cantilever and by the measurement noise.
For high feedback gain, the driven cantilever motion is found to suppress or
"squash" the optical interferometer intensity noise below the shot noise level.Comment: 4 pages, 6 figure
- …