Optical manipulation of a single Mn spin in a CdTe-based quantum dot

A system of two coupled CdTe quantum dots, one of them containing a single Mn ion, was studied in continuous wave and modulated photoluminescence, photoluminescence excitation, and photon correlation experiments. Optical writing of information in the spin state of the Mn ion has been demonstrated, using orientation of the Mn spin by spin-polarized carriers transferred from the neighbor quantum dot. Mn spin orientation time values from 20 ns to 100 ns were measured, depending on the excitation power. Storage time of the information in the Mn spin was found to be enhanced by application of a static magnetic field of 1 T, reaching hundreds of microseconds in the dark. Simple rate equation models were found to describe correctly static and dynamical properties of the system.Comment: 4 pages, 3 figure

Single spin optical read-out in CdTe/ZnTe quantum dot studied by photon correlation spectroscopy

Spin dynamics of a single electron and an exciton confined in CdTe/ZnTe quantum dot is investigated by polarization-resolved correlation spectroscopy. Spin memory effects extending over at least a few tens of nanoseconds have been directly observed in magnetic field and described quantitatively in terms of a simple rate equation model. We demonstrate an effective (68%) all-optical read-out of the single carrier spin state through probing the degree of circular polarization of exciton emission after capture of an oppositely charged carrier. The perturbation introduced by the pulsed optical excitation serving to study the spin dynamics has been found to be the main source of the polarization loss in the read-out process. In the limit of low laser power the read-out efficiency extrapolates to a value close to 100%. The measurements allowed us as well to determine neutral exciton spin relaxation time ranging from 3.4 +/- 0.1 ns at B = 0 T to 16 +/- 3 ns at B = 5 T.Comment: to appear in Phys. Rev.

Fibre-optic delivery of time and frequency to VLBI station

The quality of Very Long Baseline Interferometry (VLBI) radio observations predominantly relies on precise and ultra-stable time and frequency (T&F) standards, usually hydrogen masers (HM), maintained locally at each VLBI station. Here, we present an operational solution in which the VLBI observations are routinely carried out without use of a local HM, but using remote synchronization via a stabilized, long-distance fibre-optic link. The T&F reference signals, traceable to international atomic timescale (TAI), are delivered to the VLBI station from a dedicated timekeeping laboratory. Moreover, we describe a proof-of-concept experiment where the VLBI station is synchronized to a remote strontium optical lattice clock during the observation.Comment: 8 pages, 8 figures, matches the version published in A&A, section Astronomical instrumentatio

Constraints to Waterfowl Hunting by Hunters and Anglers in the Central United States

Waterfowl hunting participation has been on the decline since the mid‐1980s. We used a web‐based survey to better understand waterfowl hunting constraints (i.e., factors that limit or prohibit participation and enjoyment in leisure activities) among hunters and anglers that hunted or did not hunt waterfowl in the central United States. Forty‐eight constraint items were condensed into 10 constraint factors: Rules and Regulations, Waterfowl Identification, Cost, Waterfowl Hunting Skills, Land Access and Permissions, Interference by Other Hunters, Travel, Social, Waterfowl Populations, and Views of Others. We observed significant effects of both state of residence and activity type (i.e., frequent waterfowl hunters, sporadic waterfowl hunters, dissociated waterfowl hunters, non‐waterfowl hunters, and anglers) but the effect sizes were mostly small. There were few meaningful differences between constraints based on state of residence, indicating that the perception of constraints was largely consistent among the states included in our study. However, Social, Waterfowl Identification, and Waterfowl Hunting Skills constraints had greater differences, particularly between frequent waterfowl hunters and non‐waterfowl hunters. Our assessment of waterfowl constraints did not indicate a single constraint that was inhibiting (or prohibiting) participation of waterfowl hunting among waterfowl hunters or non‐waterfowl hunters. However, there were numerous constraints that were slightly to moderately limiting across all activity groups similarly, which suggests that constraints may act collectively to create a perception of an insurmountable impediment to participation to the individual