Deterministic polarization-entanglement purification using spatial entanglement

We present an efficient entanglement purification protocol with hyperentanglement in which additional spatial entanglement is utilized to purify the two-particle polarization-entangled state. The bit-flip error and phase-flip error can be corrected and eliminated in one step. Two remote parties can obtainmaximally entangled polarization states deterministically and only passive linear optics are employed. We also discuss the protocol with practical quantum source and noisy channel.Comment: 4pages,1 figur

Analysis of N-qubit Perfect Controlled Teleportation Schemes from the Controller\u27s Point of View

We quantitatively analyze and evaluate the controller\u27s power in N-qubit controlled teleportation schemes. We calculate the minimum control power required to ensure the controller\u27s authority such that the teleportation fidelity without the controller\u27s permission is no more than the classical bound. We revisit several typical controlled teleportation schemes from the controller\u27s point of view and evaluate the control power in these schemes. We find that for teleporting arbitrary N-qubit states, each controller should control at least N bits of useful information to ensure his or her authority over the protocol. We also discuss the general rules that must be satisfied by controlled teleportation schemes to ensure both teleportation fidelity and control power