arXiv subjects

Sonia G Schirmer

Publications and source records attributed to Sonia G Schirmer.

5 recordsLinked to original sources

arXiv2008

Comparative Analysis of Control Strategies

Different ways of modelling quantum control systems, formulating control problems and solving the resulting problems are considered and compared. In particular, we compare the performance of geometric and optimal control, as well as iterative techniques for optimal control design versus local gradient optimization using a Lyapunov-type potential function for two problems of general interest: global control of qubits and entanglement generation in the form of Bell state preparation.

quant-ph↗

arXiv2006

Hamiltonian engineering for quantum systems

We describe different strategies for using a semi-classical controller to engineer quantum Hamiltonians to solve control problems such as quantum state or process engineering or optimization of observables.

quant-ph↗

arXiv2005

Controllability of multi-partite quantum systems and selective excitation of quantum dots

We consider the degrees of controllability of multi-partite quantum systems as well as necessary and sufficient criteria for each case. The results are applied to the problem of simultaneous control of an ensemble of quantum dots with a single laser pulse. Finally, we apply optimal control techniques to demonstrate selective excitation of individual dots for a simultaneously controllable ensemble.

quant-ph↗

arXiv2004

Constraints on relaxation rates for N-level quantum systems

We study the constraints imposed on the population and phase relaxation rates by the physical requirement of completely positive evolution for open N-level systems. The Lindblad operators that govern the evolution of the system are expressed in terms of observable relaxation rates, explicit formulas for the decoherence rates due to population relaxation are derived, and it is shown that there are additional, non-trivial constraints on the pure dephasing rates for N>2. Explicit experimentally testable inequality constraints for the decoherence rates are derived for three and four-level systems, and the implications of the results are discussed for generic ladder-, Lambda- and V-systems, and transitions between degenerate energy levels.

quant-ph↗

arXiv2004

Dissipative Quantum Control

Nature, in the form of dissipation, inevitably intervenes in our efforts to control a quantum system. In this talk we show that although we cannot, in general, compensate for dissipation by coherent control of the system, such effects are not always counterproductive; for example, the transformation from a thermal (mixed) state to a cold condensed (pure state) can only be achieved by non-unitary effects such as population and phase relaxation.

quant-ph↗