Entanglement Capacity of Two-Qubit Unitary Operator with the Help of Auxiliary System

Yao-Min Di, Li Liu

Anthony Chefles

Baolin Hu, Yao-Min Di

The entanglement capacity of general two-qubit unitary operators is studied when auxiliary systems are allowed, and the analytical results based on linear entropy when input states are disentangled are given. From the results the condition for perfect entangler, α 1 = α 2 = π/4, is obtained. Contrary to the case without auxiliary system, the parameter α 3 may play active role to the entanglement capacity when auxiliary systems are allowed.

Matthew Leifer, Leah Henderson, Noah Linden

We consider how much entanglement can be produced by a nonlocal two-qubit unitary operation, ${U}_{\mathrm{AB}}$---the entangling capacity of ${U}_{\mathrm{AB}}.$ For a single application of ${U}_{\mathrm{AB}},$ with no ancillas, we find the entangling capacity and show that it generally helps to act with ${U}_{\mathrm{AB}}$ on an entangled state. Allowing ancillas, we present numerical results from which we can conclude, quite generally, that allowing initial entanglement typically increases the optimal capacity in this case as well. Next, we show that allowing collective processing does not increase the entangling capacity if initial entanglement is allowed.

Chengzhi Wang, Chun-Xian Li, Guang‐Can Guo

Hui-Zhi Xia, Chao Li, Qing Yang +2 more