Exploiting Non-Markovianity of the Environment for Quantum Control

When the environment of an open quantum system is non-Markovian, amplitude and phase flow not only from the system into the environment but also back. Here we show that this feature can be exploited to carry out quantum control tasks that could not be realized if the system was isolated. Inspired by recent experiments on superconducting phase circuits, we consider an anharmonic ladder with resonant amplitude control only. This restricts realizable operations to SO(N). The ladder is immersed in an environment of two-level systems. Strongly coupled two-level systems lead to non-Markovian effects, whereas the weakly coupled ones result in single-exponential decay. Presence of the environment allows for implementing diagonal unitaries that, together with SO(N), yield the full group SU(N). Using optimal control theory, we obtain errors that are solely $T_1$-limited

The DRAO 26-m Large Scale Polarization Survey at 1.41 GHz

The Effelsberg telescope as well as the DRAO synthesis telescope are currently surveying the Galactic polarized emission at 21 cm in detail. These new surveys reveal an unexpected richness of small-scale structures in the polarized sky. However, observations made with synthesis or single-dish telescopes are not on absolute intensity scales and therefore lack information about the large-scale distribution of polarized emission to a different degree. Until now, absolutely calibrated polarization data from the Leiden/Dwingeloo polarization surveys are used to recover the missing spatial information. However, these surveys cannot meet the requirements of the recent survey projects regarding sampling and noise and new polarization observation were initiated to complement the Leiden/Dwingeloo Survey. In this paper we will outline the observation and report on the progress for a new polarization survey of the northern sky with the 26-m telescope of the DRAO.Comment: 5 pages, 6 figure