Spin in a time-dependent magnetic field

杨进 YANG Jin, Lin Nengjie, 张德培 ZHANG De-pei +1 more

Michele Cini

Shun-Jin Wang, Jia Cheng-Long, Jun‐Hong An +1 more

A spin particle subjected to any time-dependent magnetic field is investigated in detail at different magnetic field configurations. Spin flip probability, spin alignment, cyclic and noncyclic nonadiabatic geometric phases are calculated exactly and their analytical expressions are presented. Our theoretical study shows that a spin particle controlled by a resonant time-dependent magnetic field can be used as efficient controllable devices of spin switch or qubit register.

Zhen Huang, Sabre Kais

We study the dynamics of entanglement for the XY-model, one-dimensional spin systems coupled through the nearest neighbor exchange interaction and subject to an external time-dependent magnetic field. Using the two-site density matrix, we calculate the time-dependent entanglement of formation between nearest neighbor qubits. We investigate the effect of varying the temperature, the anisotropy parameter and the external time-dependent magnetic field on the entanglement. We have found that the entanglement can be localized between nearest neighbor qubits for certain values of the external time-dependent magnetic field. Moreover, as known for the magnetization of this model, the entanglement shows nonergodic behavior, it does not approach its equilibrium value at the infinite time limit.

V. L. Pokrovsky, N. L. Sinitsyn

We study the transition between Zeeman levels of an arbitrary spin placed into a regular time-dependent magnetic field and a random field with the Gaussian distribution. One component of the regular field changes its sign at some moment of time, whereas another component does not change substantially. The noise is assumed to be fast. In this assumption we find analytically the ensemble average of the spin density matrix and its fluctuations.

Emilio d’Emilio, Luigi E. Picasso