Hot entanglement in a simple dynamical model
Abstract
How mixed can one component of a bipartite system be initially and still become entangled through interaction with a thermalized partner? We address this question here. In particular, we consider the question of how mixed a twolevel system and a field mode may be such that free entanglement arises in the course of the time evolution according to a JaynesCummings type interaction. We investigate the situation for which the twolevel system is initially in mixed state taken from a oneparameter set, whereas the field has been prepared in an arbitrary thermal state. Depending on the particular choice for the initial state and the initial temperature of the quantised field mode, three cases can be distinguished: (i) free entanglement will be created immediately, (ii) free entanglement will be generated, but only at a later time different from zero, (iii) the partial transpose of the joint state remains positive at all times. It will be demonstrated that increasing the initial temperature of the field mode may cause the joint state to become distillable during the time evolution, in contrast to a nondistillable state at lower initial temperatures. We further assess the generated entanglement quantitatively, by evaluating the logarithmic negativity numerically, and by providing an analytical upper bound.
 Publication:

Journal of Modern Optics
 Pub Date:
 June 2003
 DOI:
 10.1080/09500340308234538
 arXiv:
 arXiv:quantph/0207120
 Bibcode:
 2003JMOp...50..881S
 Keywords:

 Quantum Physics
 EPrint:
 5 pages, 2 figures. Contribution to the proceedings of the 'International Conference on Quantum Information', Oviedo, July 1318, 2002. Discusses sudden changes of entanglement properties in a dynamical quantum model