Issue
EPL
Volume 87, Number 2, July 2009
Article Number 28004
Number of page(s) 6
Section Interdisciplinary Physics and Related Areas of Science and Technology
DOI http://dx.doi.org/10.1209/0295-5075/87/28004
Published online 18 August 2009
EPL, 87 (2009) 28004
DOI: 10.1209/0295-5075/87/28004

Optimal control of superconducting N-level quantum systems

H. Jirari1, F. W. J. Hekking1 and O. Buisson2

1   LPMMC, CNRS - Université Joseph Fourier - BP 166, 38042 Grenoble-cedex 9, France, EU
2   Institut Néel, CNRS - Université Joseph Fourier - BP 166, 38042 Grenoble-cedex 9, France, EU


received 7 April 2009; accepted in final form 17 July 2009; published July 2009
published online 18 August 2009

Abstract
We consider a current-biased dc SQUID in the presence of an applied time-dependent bias current or magnetic flux. The phase dynamics of such a Josephson device is equivalent to that of a quantum particle trapped in a 1D anharmonic potential, subject to external time-dependent control fields, i.e. a driven multilevel quantum system. The problem of finding the required time-dependent control field that will steer the system from a given initial state to a desired final state at a specified final time is formulated in the framework of optimal-control theory. Using the spectral filter technique, we show that the selected optimal field which induces a coherent population transfer between quantum states is represented by a carrier signal having a constant frequency but which is time-varied both in amplitude and phase. The sensitivity of the optimal solution to parameter perturbations is also addressed.

PACS
85.25.Cp - Josephson devices.
02.30.Yy - Control theory.
03.67.-a - Quantum information.

© EPLA 2009