INSTITUTO DE FISICA LA PLATA
Unidad Ejecutora - UE
congresos y reuniones científicas
Entanglement between distant qubits in XXZ spin chains
N. CANOSA; R. ROSSIGNOLI
Workshop; II QUANTUM INFORMATION SCHOOL AND WORKSHOP.; 2009
CNPq - Institute for Quantum Computing
We evaluate the exact concurrence between any two spins in cyclic XXZ chains placed in a uniform transverse magnetic field, both at zero and finite temperature, by means of the Jordan-Wigner transformation plus a parity projected statistics. It is shown that while at T=0 there is always entanglement between any two spins in a narrow field interval before the transition to the aligned state, at low but non-zero temperatures the entanglement remains non-zero for arbitrarily high fields, for any pair separation L, although its magnitude decreases exponentially with the field. It is also demonstrated that all associated limit temperatures approach a constant non-zero value in this limit, which decreases as 1/L^2 for L << n but exhibit special finite size effects for distant qubits. Comparison with the behavior of the thermal pairwise entanglement in fully connected XXZ chains is also discussed.