From Large to Small Spin Systems: Exploring Many-body Effects in NMR

M Mehring, Elmar K. Wolff, Michael E. Stoll

Paola Cappellaro, Joseph Emerson, Nicolas Boulant +3 more

We propose a new approach to the measurement of a single spin state, based on nuclear magnetic resonance (NMR) techniques and inspired by the coherent control over many-body systems envisaged by quantum information processing. A single target spin is coupled via the magnetic dipolar interaction to a large ensemble of spins. Applying radio frequency pulses, we can control the evolution so that the spin ensemble reaches one of two orthogonal states whose collective properties differ depending on the state of the target spin and are easily measured. We first describe this measurement process using quantum gates; then we show how equivalent schemes can be defined in terms of the Hamiltonian and thus implemented under conditions of real control, using well established NMR techniques. We demonstrate this method with a proof of principle experiment in ensemble liquid state NMR and simulations for small spin systems.

Edward B. Fel’dman

Tarek A. Elsayed, Boris V. Fine

We investigate the sensitivity of nonintegrable large-spin quantum lattices to small perturbations with a particular focus on the time reversal experiments known in statistical physics as 'Loschmidt echoes' and in nuclear magnetic resonance (NMR) as 'magic echoes.' Our numerical simulations of quantum spin- clusters indicate that there is a regime where Loschmidt echoes exhibit nearly exponential sensitivity to small perturbations with characteristic constant approximately equal to twice the value of the largest Lyapunov exponent of the corresponding classical spin clusters. The above theoretical results are verifiable by NMR experiments on solids containing large-spin nuclei.

真治 松本

Serge I. Doronin, Edward B. Fel’dman, Serge Lacelle