RESUMEN
An intuitive model of classical guitar intonation is presented that includes the effects of the resonant length of the fretted string, linear mass density, tension, and bending stiffness. An expression is derived for the vibration frequencies of a stiff string using asymmetric boundary conditions at the saddle and the fret. Based on logarithmic frequency differences ("cents") that decouple these physical effects, Taylor series expansions are introduced that exhibit clearly the origins of frequency deviations of fretted notes from the corresponding 12-tone equal temperament (12-TET) values. A simple in situ technique is demonstrated for measurement of the changes in frequency of open strings arising from small adjustments in length, and a simple procedure is proposed that any interested guitarist can use to estimate the corresponding frequency shifts due to tension and bending stiffness for their own guitars and string sets. Based on these results, a least-squares fit method is employed to select values of saddle and nut setbacks that map fretted frequencies-for a particular string set and guitar-almost perfectly onto their 12-TET targets. A general approach to tempering an "off-the-shelf" guitar is shown to further reduce the tonal errors inherent in any fretted musical instrument.
RESUMEN
We use electromagnetically induced transparency (EIT) to probe the narrow electron-spin resonance of nitrogen-vacancy centers in diamond. Working with a multipass diamond chip at temperatures 6-30 K, the zero-phonon absorption line (637 nm) exhibits an optical depth of 6 and inhomogeneous linewidth of ~30 GHz FWHM. Simultaneous optical excitation at two frequencies separated by the ground-state zero-field splitting (2.88 GHz) reveals EIT resonances with a contrast exceeding 6% and FWHM down to 0.4 MHz. The resonances provide an all-optical probe of external electric and magnetic fields with a projected photon-shot-noise-limited sensitivity of 0.2 V/cm/â[Hz] and 0.1 nT/â[Hz], respectively. Operation of a prototype diamond-EIT magnetometer measures a noise floor of ~/<1 nT/â[Hz] for frequencies above 10 Hz and Allan deviation of 1.3±1.1 nT for 100 s intervals. The results demonstrate the potential of diamond-EIT devices for applications ranging from quantum-optical memory to precision measurement and tests of fundamental physics.
RESUMEN
We report electrical tuning by the Stark effect of the excited-state structure of single nitrogen-vacancy (NV) centers located â²100 nm from the diamond surface. The zero-phonon line (ZPL) emission frequency is controllably varied over a range of 300 GHz. Using high-resolution emission spectroscopy, we observe electrical tuning of the strengths of both cycling and spin-altering transitions. Under resonant excitation, we apply dynamic feedback to stabilize the ZPL frequency. The transition is locked over several minutes and drifts of the peak position on timescales â³100 ms are reduced to a fraction of the single-scan linewidth, with standard deviation as low as 16 MHz (obtained for an NV in bulk, ultrapure diamond). These techniques should improve the entanglement success probability in quantum communications protocols.
RESUMEN
Optical microcavities and waveguides coupled to diamond are needed to enable efficient communication between quantum systems such as nitrogen-vacancy centers which are known already to have long electron spin coherence lifetimes. This paper describes recent progress in realizing microcavities with low loss and small mode volume in two hybrid systems: silica microdisks coupled to diamond nanoparticles, and gallium phosphide microdisks coupled to single-crystal diamond. A theoretical proposal for a gallium phosphide nanowire photonic crystal cavity coupled to diamond is also discussed. Comparing the two material systems, silica microdisks are easier to fabricate and test. However, at low temperature, nitrogen-vacancy centers in bulk diamond are spectrally more stable, and we expect that in the long term the bulk diamond approach will be better suited for on-chip integration of a photonic network.
RESUMEN
We report the observation of low-light level optical interactions in a tapered optical nanofiber (TNF) embedded in a hot rubidium vapor. The small optical mode area plays a significant role in the optical properties of the hot vapor Rb-TNF system, allowing nonlinear optical interactions with nW level powers even in the presence of transit-time dephasing rates much larger than the intrinsic linewidth. We demonstrate nonlinear absorption and V-type electromagnetically induced transparency with cw powers below 10 nW, comparable to the best results in any Rb-optical waveguide system. The good performance and flexibility of the Rb-TNF system makes it a very promising candidate for ultralow power resonant nonlinear optical applications.
RESUMEN
The field enhancement in the gap between two Si microdisks is theoretically investigated using the finite difference time domain method. We show that the electric field within this gap increases as the distance between the two disks decreases, and it can be enhanced by as much as two orders of magnitude. By perturbing the Si microdisks to force the field leakage into an ever smaller volume, the field enhancement can reach a value as high as 238 with a deep sub-wavelength mode volume. This behavior is comparable to what can be observed in gap plasmons between metal nanoparticles, but is produced here in purely dielectric structures.
RESUMEN
We place direct upper limits on the amplitude of gravitational waves from 28 isolated radio pulsars by a coherent multidetector analysis of the data collected during the second science run of the LIGO interferometric detectors. These are the first direct upper limits for 26 of the 28 pulsars. We use coordinated radio observations for the first time to build radio-guided phase templates for the expected gravitational-wave signals. The unprecedented sensitivity of the detectors allows us to set strain upper limits as low as a few times 10(-24). These strain limits translate into limits on the equatorial ellipticities of the pulsars, which are smaller than 10(-5) for the four closest pulsars.
RESUMEN
Using a simple semiclassical model, we explore ultrahigh-resolution optical two-photon spectroscopy of cold neutral atoms falling freely in a fountain. Considering atoms that interact with the same standing-wave laser field twice on their parabolic trajectories, and averaging over a Maxwellian velocity distribution, we predict a nearly Lorentzian line shape with just the natural linewidth. First-order Doppler shifts cancel even if the counterpropagating beams are slightly misaligned, and sub-Hertz resolution appears feasible with a fountain of modest dimensions.