Lower order and higher order entanglement in 87Rb87Rb 5S−5P−5D5S-5P-5D hyperfine manifold modeled as a four-wave mixing process

Possibilities of generation of lower order and higher order intermodal entanglement in 87Rb 5S-5P-5D hyperfine manifold are rigorously investigated using Sen-Mandal perturbative technique by showing the equivalence of the system with the four-wave mixing (FWM) process. The investigation has revealed that for a set of experimentally realizable/relevant parameters we can observe lower order and higher order intermodal entanglement between pump and signal modes, signal and idler modes, and idler and pump modes in a FWM process associated with the 87Rb 5S-5P-5D hyperfine manifold. In addition, trimodal entanglement involving pump, signal and idler modes is also reported.Comment: 12 pages, 5 figure

Spektroskopska mjerenja prijelaza D2 Rb u ovisnosti o temperaturi i snazi sa i bez Dopplerovog efekta

An external-cavity diode-laser spectrometer has been set up for high-resolution measurement of line shapes of the RbD2 transitions. Temperature-dependent fine-structure measurements are carried out in a free-running temperature condition by using frequency ramps for repetitive current tuning over a region of 17 GHz, encompassing all of the four Doppler broadened transitions of the two isotopes in an almost collision-free region. The Doppler broadened widths extracted from temperature-dependent line shapes, on least squares fitting to observed data, lead to an estimation of root-means-square velocities of vapour atoms under varying temperature conditions. Saturated-absorption spectroscopic measurements show complete resolution of the hyperfine Lamb dips and crossover resonance dips of one 87RbD2 transition. Data recorded from power-dependent measurement of one of unresolved 85RbD2 transitions are analyzed to obtain the saturation parameter and power broadening coefficient. The linewidths of different fully resolved Lamb dips of the hyperfine and crossover-resonance components are not the same, suggesting differences in their natural linewidths.Pomoću diodnog lasera s vanjskim rezonatorom načinili smo mjerenja oblika linija prijelaza D2 Rb. Mjerenja temperaturne ovisnosti fine strukture izveli smo u uvjetima slobodno promjenljive temperature, upotrebom frekventne rampe za ponavljanje struje, podešene za područje 17 GHz koje obuhvaća sva četiri Dopplerovim efektom proširena prijelaza dvaju izotopa Rb u uvjetima gotovo bez sudara. Širenje linija Dopplerovim efektom u ovisnosti o temperaturi, utvrđeno metodom najmanjih kvadrata, daje korijene iz srednjih kvadrata brzina atoma u parama. Spektroskopska mjerenja sa zasićenom apsorpcijom pokazuju potpuno razlučivanje hiperfinih Lambovih i preskočnih rezonantnih minimuma prijelaza D2 87Rb. Podatke iz mjerenja ovisnosti o snazi za nerazlučeni prijelaz D2 85Rb smo analizirali radi dobivanja parametara zasićenja i koeficijenta širenja sa snagom. Širine potpuno razlučenih linija hiperfinih Lambovih i preskočnih rezonantnih minimuma nisu jednake, što ukazuje na različitost njihovih prirodnih širina

Spektroskopska mjerenja prijelaza D2 Rb u ovisnosti o temperaturi i snazi sa i bez Dopplerovog efekta

An external-cavity diode-laser spectrometer has been set up for high-resolution measurement of line shapes of the RbD2 transitions. Temperature-dependent fine-structure measurements are carried out in a free-running temperature condition by using frequency ramps for repetitive current tuning over a region of 17 GHz, encompassing all of the four Doppler broadened transitions of the two isotopes in an almost collision-free region. The Doppler broadened widths extracted from temperature-dependent line shapes, on least squares fitting to observed data, lead to an estimation of root-means-square velocities of vapour atoms under varying temperature conditions. Saturated-absorption spectroscopic measurements show complete resolution of the hyperfine Lamb dips and crossover resonance dips of one 87RbD2 transition. Data recorded from power-dependent measurement of one of unresolved 85RbD2 transitions are analyzed to obtain the saturation parameter and power broadening coefficient. The linewidths of different fully resolved Lamb dips of the hyperfine and crossover-resonance components are not the same, suggesting differences in their natural linewidths.Pomoću diodnog lasera s vanjskim rezonatorom načinili smo mjerenja oblika linija prijelaza D2 Rb. Mjerenja temperaturne ovisnosti fine strukture izveli smo u uvjetima slobodno promjenljive temperature, upotrebom frekventne rampe za ponavljanje struje, podešene za područje 17 GHz koje obuhvaća sva četiri Dopplerovim efektom proširena prijelaza dvaju izotopa Rb u uvjetima gotovo bez sudara. Širenje linija Dopplerovim efektom u ovisnosti o temperaturi, utvrđeno metodom najmanjih kvadrata, daje korijene iz srednjih kvadrata brzina atoma u parama. Spektroskopska mjerenja sa zasićenom apsorpcijom pokazuju potpuno razlučivanje hiperfinih Lambovih i preskočnih rezonantnih minimuma prijelaza D2 87Rb. Podatke iz mjerenja ovisnosti o snazi za nerazlučeni prijelaz D2 85Rb smo analizirali radi dobivanja parametara zasićenja i koeficijenta širenja sa snagom. Širine potpuno razlučenih linija hiperfinih Lambovih i preskočnih rezonantnih minimuma nisu jednake, što ukazuje na različitost njihovih prirodnih širina

Performance of a spacecraft DC-DC converter breadboard modified for low temperature operation

A 1OW 3OV/5.OV push-pull dc-dc converter breadboard, designed by the Jet Propulsion Laboratory (JPL) with a +50 C to +5 C operating range for the Cassini space probe, was characterized for lower operating temperatures. The breadboard converter which failed to operate for temperatures below -125 C was then modified to operate at temperatures approaching that of liquid nitrogen (LN2). Associated with this low operating temperature range (greater than -196 C) was a variety of performance problems such as significant change in output voltage, converter switching instability, and failure to restart at temperatures below -154 C. An investigation into these problems yielded additional modifications to the converter which improved low temperature performance even further

Low-temperature operation of a Buck DC/DC converter

Low-temperature (77 K) operation of a 42/28 V, 175 W, 50 kHz PWM Buck DC/DC converter designed with commercially available components is reported. Overall, the converter losses decreased at 77 K compared to room temperature operation. A full-load efficiency of 97 percent was recorded at liquid-nitrogen temperature, compared to 95.8 percent at room temperature. Power MOSFET operation improved significantly where as the output rectifier operation deteriorated at low-temperature. The performance of the output filter inductor and capacitor did not change significantly at 77 K compared to room temperature performance. It is possible to achieve high-density and high efficiency power conversion at low-temperatures due to improved electronic, electrical and thermal properties of materials