Spectroscopy of a driven solidstate qubit coupled to a structured environment
Abstract
We study the asymptotic dynamics of a driven spinboson system where the environment is formed by a broadened localized mode. Upon exploiting an exact mapping, an equivalent formulation of the problem in terms of a quantum twostate system (qubit) coupled to a harmonic oscillator which is itself Ohmically damped, is found. We calculate the asymptotic population difference of the two states in two complementary parameter regimes. For weak damping and low temperature, a perturbative FloquetBornMarkovian master equation for the qubitoscillator system can be solved. We find multiphoton resonances corresponding to transitions in the coupled quantum system and calculate their lineshape analytically. In the complementary parameter regime of strong damping and/or high temperatures, nonperturbative realtime path integral techniques yield analytic results for the resonance line shape. In both regimes, we find very good agreement with exact results obtained from a numerical realtime pathintegral approach. Finally, we show for the case of strong detuning between qubit and oscillator that the width of the nphoton resonance scales with the nth Bessel function of the driving strength in the weakdamping regime.
 Publication:

European Physical Journal B
 Pub Date:
 June 2005
 DOI:
 10.1140/epjb/e2005001925
 arXiv:
 arXiv:condmat/0412194
 Bibcode:
 2005EPJB...45..405G
 Keywords:

 03.65.Yz;
 03.67.Lx;
 74.50.+r;
 42.50.Hz;
 Decoherence;
 open systems;
 quantum statistical methods;
 Quantum computation;
 Tunneling phenomena;
 point contacts weak links Josephson effects;
 Strongfield excitation of optical transitions in quantum systems;
 multiphoton processes;
 dynamic Stark shift;
 Condensed Matter  Mesoscopic Systems and Quantum Hall Effect;
 Condensed Matter  Superconductivity
 EPrint:
 13 pages, 5 figures