12 research outputs found
High-fidelity quantum driving
The ability to accurately control a quantum system is a fundamental
requirement in many areas of modern science such as quantum information
processing and the coherent manipulation of molecular systems. It is usually
necessary to realize these quantum manipulations in the shortest possible time
in order to minimize decoherence, and with a large stability against
fluctuations of the control parameters. While optimizing a protocol for speed
leads to a natural lower bound in the form of the quantum speed limit rooted in
the Heisenberg uncertainty principle, stability against parameter variations
typically requires adiabatic following of the system. The ultimate goal in
quantum control is to prepare a desired state with 100% fidelity. Here we
experimentally implement optimal control schemes that achieve nearly perfect
fidelity for a two-level quantum system realized with Bose-Einstein condensates
in optical lattices. By suitably tailoring the time-dependence of the system's
parameters, we transform an initial quantum state into a desired final state
through a short-cut protocol reaching the maximum speed compatible with the
laws of quantum mechanics. In the opposite limit we implement the recently
proposed transitionless superadiabatic protocols, in which the system perfectly
follows the instantaneous adiabatic ground state. We demonstrate that
superadiabatic protocols are extremely robust against parameter variations,
making them useful for practical applications.Comment: 17 pages, 4 figure
The Effects of Handling and Anesthetic Agents on the Stress Response and Carbohydrate Metabolism in Northern Elephant Seals
Free-ranging animals often cope with fluctuating environmental conditions such as weather, food availability, predation risk, the requirements of breeding, and the influence of anthropogenic factors. Consequently, researchers are increasingly measuring stress markers, especially glucocorticoids, to understand stress, disturbance, and population health. Studying free-ranging animals, however, comes with numerous difficulties posed by environmental conditions and the particular characteristics of study species. Performing measurements under either physical restraint or chemical sedation may affect the physiological variable under investigation and lead to values that may not reflect the standard functional state of the animal. This study measured the stress response resulting from different handling conditions in northern elephant seals and any ensuing influences on carbohydrate metabolism. Endogenous glucose production (EGP) was measured using [6-3H]glucose and plasma cortisol concentration was measured from blood samples drawn during three-hour measurement intervals. These measurements were conducted in weanlings and yearlings with and without the use of chemical sedatives—under chemical sedation, physical restraint, or unrestrained. We compared these findings with measurements in adult seals sedated in the field. The method of handling had a significant influence on the stress response and carbohydrate metabolism. Physically restrained weanlings and yearlings transported to the lab had increased concentrations of circulating cortisol (F11, 46 = 25.2, p<0.01) and epinephrine (F3, 12 = 5.8, p = 0.01). Physical restraint led to increased EGP (t = 3.1, p = 0.04) and elevated plasma glucose levels (t = 8.2, p<0.01). Animals chemically sedated in the field typically did not exhibit a cortisol stress response. The combination of anesthetic agents (Telazol, ketamine, and diazepam) used in this study appeared to alleviate a cortisol stress response due to handling in the field without altering carbohydrate metabolism. Measures of hormone concentrations and metabolism made under these conditions are more likely to reflect basal values