Gaussian Decoherence and Gaussian Echo from Spin Environments

• Autores: Zurek, Wojciech; Cucchietti, Fernando; Paz, Juan Pablo
• Año de publicación: 2007
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: DECOHERENCE; QUANTUM INFORMATION
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

We examine an exactly solvable model of decoherence -- a spin-system interacting with a collection of environment spins. We show that in this simple model (introduced some time ago to illustrate environment--induced superselection) generic assumptions about the coupling strengths lead to a universal (Gaussian) suppression of coherence between pointer states. We explore the regime of validity of this result and discuss its relation to spectral features of the environment. We also consider its relevance to the experiments on the so-called Loschmidt echo (which measures, in effect, the fidelity between the initial and time-reversed or "echo" signal). In particular, we show that for partial reversals (e.g., when of only a part of the total Hamiltonian changes sign) fidelity will exhibit a Gaussian dependence on the time of reversal. In such cases echo may become independent of the details of the reversal procedure or the specifics of the coupling to the environment. This puzzling behavior was observed in several NMR experiments. Natural candidates for such two environments (one of which is easily reversed, while the other is ``irreversible´´) are suggested for the experiment involving ferrocene.
Fil: Zurek, Wojciech. Los Alamos National High Magnetic Field Laboratory; Estados Unidos
Fil: Cucchietti, Fernando. Los Alamos National High Magnetic Field Laboratory; Estados Unidos
Fil: Paz, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina