232 research outputs found
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
Force-detected nuclear double resonance between statistical spin polarizations
We demonstrate nuclear double resonance for nanometer-scale volumes of spins
where random fluctuations rather than Boltzmann polarization dominate. When the
Hartmann-Hahn condition is met in a cross-polarization experiment, flip-flops
occur between two species of spins and their fluctuations become coupled. We
use magnetic resonance force microscopy to measure this effect between 1H and
13C spins in 13C-enriched stearic acid. The development of a cross-polarization
technique for statistical ensembles adds an important tool for generating
chemical contrast in nanometer-scale magnetic resonance.Comment: 14 pages, 4 figure
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
Harnessing nuclear spin polarization fluctuations in a semiconductor nanowire
Soon after the first measurements of nuclear magnetic resonance (NMR) in a
condensed matter system, Bloch predicted the presence of statistical
fluctuations proportional to in the polarization of an ensemble of
spins. First observed by Sleator et al., so-called "spin noise" has
recently emerged as a critical ingredient in nanometer-scale magnetic resonance
imaging (nanoMRI). This prominence is a direct result of MRI resolution
improving to better than 100 nm^3, a size-scale in which statistical spin
fluctuations begin to dominate the polarization dynamics. We demonstrate a
technique that creates spin order in nanometer-scale ensembles of nuclear spins
by harnessing these fluctuations to produce polarizations both larger and
narrower than the natural thermal distribution. We focus on ensembles
containing ~10^6 phosphorus and hydrogen spins associated with single InP and
GaP nanowires (NWs) and their hydrogen-containing adsorbate layers. We monitor,
control, and capture fluctuations in the ensemble's spin polarization in
real-time and store them for extended periods. This selective capture of large
polarization fluctuations may provide a route for enhancing the weak magnetic
signals produced by nanometer-scale volumes of nuclear spins. The scheme may
also prove useful for initializing the nuclear hyperfine field of electron spin
qubits in the solid-state.Comment: 18 pages, 5 figure
Pengaruh Lembar Kerja Peserta Didik (LKPD) Berbasis Guided Discovery Terhadap Keterampilan Proses Sains (KPS) dan Hasil Belajar Peserta Didik Kelas VIII
Penelitian ini bertujuan untuk mengetahui 1) tingkat keterampilan proses sains dan hasil belajar peserta didik setelah diajarkan dengan menggunakan LKPD
berbasis guided discovery, 2) tingkat keterampilan proses sains dan hasil belajar peserta didik setelah diajarkan menggunakan LKPD konvensional, dan 3)
pengaruh LKPD berbasis guided discovery terhadap keterampilan proses sains dan hasil belajar IPA. Jenis penelitian ini adalah penelitian quasi experiment dan
desain penelitian Nonequivalent Control Group Design dengan populasi seluruh peserta didik kelas VIII SMP Negeri 4 Makassar yang terdiri dari 10 kelas
dengan jumlah peserta didik sebanyak 335 orang dipilih secara purposive sampling yaitu kelas eksperimen 14 orang dan kelas kontrol 13 orang. Keterampilan
proses sains peserta didik diperoleh nilai rerata pada kelas eksperimen 70,22 kategori kurang dan kelas kontrol 67,61 kategori kurang. Hasil belajar peserta
didik diperoleh skor rerata pada kelas eksperimen 13,9 kategori sedang dan kelas kontrol 13,2 tergolong kategori sedang. Berdasarkan hasil analisis inferensial
menggunakan uji-t keterampilan proses sains dan hasil belajar diperoleh <. Demikian disimpulkan bahwa tidak terdapat pengaruh LKPD berbasis guided
discovery terhadap keterampilan proses sains dan hasil belajar IPA peserta didik kelas VIII SMP Negeri 4 Makassar
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