Spin and Time Reversal

R. Winkler, Ulrich Zülicke

Serge Lacelle

The behavior of multiple spin dynamics under time-reversal excitation is investigated in strongly dipolar coupled spin networks. It is demonstrated that the typical physical intuition that NMR spectroscopists have of time-reversal in such systems is erroneous. By studying the equation of motion of the spin system in an infinite one-dimensional quantum spin chain with nearest-neighbor dipolar interactions and evolving under time-reversal excitation, a more appropriate physical picture emerges. Implications of these new findings are briefly discussed in the context of error propagation and teleportation in NMR quantum information processing.Key words: time-reversal, NMR, nuclear spin dynamic, quantum information processing.

Philip H. Butler

G. Morpurgo, B. F. Touschek, Luigi A. Radicati

Ion I. Geru

In this chapter we discuss the properties of the time-reversal operator (introduced into quantum mechanics by Wigner in 1932) for particles without spin, as well as taking into account the spin. There are given Wigner criteria ( a ), ( b ), and ( c ) concerning the absence or presence of an additional degeneracy of energy levels due to the symmetry with respect to time reversal, both in the case when the spin of particles that form the quantum system is taken into account and in the case it is not. Wigner corepresentations of symmetry groups associated with the presence of time-reversal symmetry are also discussed.

Marko Horbatsch