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 $1/\sqrt{N}$ in the polarization of an ensemble of $N$ 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