Inhibiting decoherence via ancilla processes

General conditions are derived for preventing the decoherence of a single two-state quantum system (qubit) in a thermal bath. The employed auxiliary systems required for this purpose are merely assumed to be weak for the general condition while various examples such as extra qubits and extra classical fields are studied for applications in quantum information processing. The general condition is confirmed with well known approaches towards inhibiting decoherence. A novel approach for decoherence-free quantum memories and quantum operations is presented by placing the qubit into the center of a sphere with extra qubits on its surface.Comment: pages 8, Revtex

Environment-Induced Decoherence and the Transition From Quantum to Classical

We study dynamics of quantum open systems, paying special attention to those aspects of their evolution which are relevant to the transition from quantum to classical. We begin with a discussion of the conditional dynamics of simple systems. The resulting models are straightforward but suffice to illustrate basic physical ideas behind quantum measurements and decoherence. To discuss decoherence and environment-induced superselection einselection in a more general setting, we sketch perturbative as well as exact derivations of several master equations valid for various systems. Using these equations we study einselection employing the general strategy of the predictability sieve. Assumptions that are usually made in the discussion of decoherence are critically reexamined along with the ``standard lore'' to which they lead. Restoration of quantum-classical correspondence in systems that are classically chaotic is discussed. The dynamical second law -it is shown- can be traced to the same phenomena that allow for the restoration of the correspondence principle in decohering chaotic systems (where it is otherwise lost on a very short time-scale). Quantum error correction is discussed as an example of an anti-decoherence strategy. Implications of decoherence and einselection for the interpretation of quantum theory are briefly pointed out.Comment: 80 pages, 7 figures included, Lectures given by both authors at the 72nd Les Houches Summer School on "Coherent Matter Waves", July-August 199

Performance of the Contact Stabilization Process

Federal Water Pollution Control Administration Demonstration Grant No. WPRD 178-01-68Center for Water and the Environmen

CONCURRENT MEASUREMENTS OF THE INHIBITION OF ATP SYNTHESIS AND ALANINE TRANSPORT IN INTACT-CELLS OF RHODOBACTER-CAPSULATUS

AbstractMyxothiazol, antimycin A and carboxylcyanide-m-chlorophenylhydrazone (CCCP) all had a more pronounced inhibitory effect on the rate of ATP synthesis than on the rate of alanine transport during illumination of intact cells of Rhodobacter capsulatus. CCCP had the most potent effect and antimycin A the least. The data suggest that the energy-input requirement for alanine transport is lower than that for ATP synthesis. A new test for direct interactions between the electron transport system and the ATP synthase and alanine transporter is applied to the data. Subject to reservations about the accuracy of rate measurement in intact bacterial cells and about the specificity of inhibition, the test reveals that the proton motive force is not the sole determinant of the rate of ATP synthesis and the rate of alanine transport