Prolonged Orbital Relaxation by Locally Modified Phonon Density of States for the SiV^{-} Center in Nanodiamonds

Coherent quantum systems are a key resource for emerging quantum technology. Solid-state spin systems are of particular importance for compact and scalable devices. However, interaction with the solid-state host degrades the coherence properties. The negatively charged silicon vacancy center in diamond is such an example. While spectral properties are outstanding, with optical coherence protected by the defects symmetry, the spin coherence is susceptible to rapid orbital relaxation limiting the spin dephasing time. A prolongation of the orbital relaxation time is therefore of utmost urgency and has been tackled by operating at very low temperatures or by introducing large strain. However, both methods have significant drawbacks: the former requires use of dilution refrigerators and the latter affects intrinsic symmetries. Here, a novel method is presented to prolong the orbital relaxation with a locally modified phonon density of states in the relevant frequency range, by restricting the diamond host to below 100 nm. Subsequently measured coherent population trapping shows an extended spin dephasing time compared to the phonon-limited time in a pure bulk diamond. The method works at liquid helium temperatures of few Kelvin and in the low-strain regime.

[Androgenic function of the adrenal cortex in girl athletes with retarded sexual development]

Diurnal excretion of 17-ketosteroids and their fractions was studied in 43 girl athletes with retarded sexual development (RSD) and 22 patients who did not go in for sports. Twenty-five healthy girls with a normal menstrual cycle constituted the control group. Athletes with RSD showed relative hyperandrogeny marked by a higher proportion of more active androgenic fractions (dehydroepiandrosterone and androsterone) in total 17-ketosteroids. Excretion of neutral 17-ketosteroids in athletes examined, as compared with non-athletes with RSD, was within age-associated norms or surpassed them. It is suggested that androgens of the adrenal cortex are involved into the pathogenesis of RSD in female athletes.