Storage of quantum coherences as phase labeled local polarization using magnetic fields gradients in Solid State NMR

MARÍA BELÉN FRANZONI; ROFOLFO ACOSTA; HORACIO M. PASTAWSKI; PATRICIA R. LEVSTEIN

PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY OF LONDON SERIES A-MATHEMATICAL AND PHYSICAL SCIENCES

ROYAL SOC

Lugar: Londres; Año: 2012

0080-4614

Storage of quantum coherences as phase labeled local polarization using magnetic fields gradients in Solid State NMR B. Franzoni, R. Acosta, H. M.  Pastawski and P. R. Levstein Philosophical Transactions of the Royal Society of London Series A-Mathematical and Physical Sciences  (2011, in press)Nuclear spins are promising candidates for quantum information processing because their goodisolation from the environment precludes the rapid loss of quantum coherence. Many strategies havebeen developed to further extend their decoherence times. Some of them make use of decouplingtechniques based on the Carr–Purcell and Carr–Purcell–Meiboom–Gill pulse sequences. In manycases, when applied to inhomogeneous samples, they yield a magnetization decay much slower thanthe Hahn echo. However, we have proved that these decays cannot be associated with longerdecoherence times as coherences remain frozen. They result from coherences recovered after theirstorage as local polarization and thus they can be used as memories. We show here how thisfreezing of the coherent state, which can subsequently be recovered after times longer than thenatural decoherence time of the system, can be generated in a controlled way with the use of fieldgradients. A similar behaviour of homogeneous samples in inhomogeneous fields are demonstrated.It is emphasized that the effects of inhomogeneities in solid state NMR, independently of their origin,should not be disregarded as they play a crucial role in multipulse sequences.PACS numbers: 03.65.Yz, 76.20.+q , 76.60.Lz, 82.56.Jn