Direct measurement of the systemenvironment coupling as a tool for understanding decoherence and dynamical decoupling
Abstract
Decoherence is a major obstacle to any practical implementation of quantum information processing. One of the leading strategies to reduce decoherence is dynamical decoupling—the use of an external field to average out the effect of the environment. The decoherence rate under any control field can be calculated if the spectrum of the coupling to the environment is known. We present a direct measurement of the bathcoupling spectrum in an ensemble of optically trapped ultracold atoms, by applying a spectrally narrowband control field. The measured spectrum follows a Lorentzian shape at low frequencies but exhibits nonmonotonic features at higher frequencies due to the oscillatory motion of the atoms in the trap. These features agree with our analytical models and numerical Monte Carlo simulations of the collisional bath. From the inferred bathcoupling spectrum, we predict the performance of some wellknown dynamical decoupling sequences. We then apply these sequences in experiment and compare the results to predictions, finding good agreement in the weakcoupling limit. Thus, our work establishes experimentally the validity of the overlap integral formalism and is an important step towards the implementation of an optimal dynamical decoupling sequence for a given measured bath spectrum.
 Publication:

Journal of Physics B Atomic Molecular Physics
 Pub Date:
 August 2011
 DOI:
 10.1088/09534075/44/15/154006
 arXiv:
 arXiv:1103.1104
 Bibcode:
 2011JPhB...44o4006A
 Keywords:

 Quantum Physics;
 Condensed Matter  Statistical Mechanics
 EPrint:
 9 pages, 6 figures