Decoherence of multiple quantum coherences generated from a dipolar ordered state

C. E. GONZÁLEZ; H. H. SEGNORILE; R. C. ZAMAR

PHYSICAL REVIEW E

AMER PHYSICAL SOC

Año: 2010

1539-3755

Starting from the hypothesis that the decay of coherent signals observed in 1H NMR experiments is driven by quantum interference, irreversible decoherence and non-idealities in the experiment, we design an experiment to isolate and identify the irreversible attenuation of multiple quantum coherences towards quasi-equilibrium states of dipolar order in nematic liquid crystals (LC). The experiment combines the well known “magic sandwich” pulse sequence with preparation of dipolar ordered states and encoding of multiple quantum coherences. The spin system composed by the dipole coupled protons of a LC molecule provides an example of a small cluster of strongly interacting spins. We study decoherence rates under a sequence which reverses time evolution with the secular dipolar Hamiltonian to compensate coherent evolution of a closed quantum system. In this way the time scale is made evident where irreversible decoherence takes place, providing insight on the nature of the processes responsible for the attainment of quasi-equilibrium. The behavior of single and double quantum coherence amplitudes with reversion time is interpreted as an evidence of the quantum character (as oposed to stochastic character) of the processes which drive irreversible decoherence. The experimental method proposed is useful for probing the action of the environment on materials with quantum information processing potential.