Discord and information deficit in the XX chain

L. CILIBERTI; R. ROSSIGNOLI; N. CANOSA

PHYSICAL REVIEW A - ATOMIC, MOLECULAR AND OPTICAL PHYSICS

AMER PHYSICAL SOC

Lugar: New York; Año: 2013 vol. 88 p. 121191 - 1211911

1050-2947

We examine the quantum discord between two spins in the exact ground state of finite spin-1/2 arrays with anisotropic XY couplings in a transverse field B. It is shown that in the vicinity of the factorizing field Bs , the discord approaches a common finite non-negligible limit which is independent of the pair separation and the coupling range. An analytic expression of this limit is provided. The discord of a mixture of aligned pairs in two different directions, crucial for the previous results, is analyzed in detail, including the evaluation of coherence effects, relevant in small samples and responsible for a parity splitting at Bs . Exact results for finite chains with first-neighbor and full-range couplings and their interpretation in terms of such mixtures are provided.