Pairing entangled states

Bao‐Sen Shi, Yun-Kun Jiang, Guang‐Can Guo

It is known that entanglement swapping can be used to realize entanglement purification. In this way, two particles belonging to different nonmaximally entangled pairs can be projected probabilistically to a maximally entangled state or to a less entangled state. In this paper, we show, when the less entangled state is obtained, then a maximally entangled state can be obtained probabilistically from this less entangled state if a unitary transformation is introduced locally. The probability of success of our scheme is equal to the entanglement of a single pair purification (if two original pairs are in the same nonmaximally entangled states) or to the smaller entanglement of a single pair purification of these two pairs (if two original pairs are not in the same nonmaximally entangled states). The advantage of our scheme is that no continuous indefinite iterative procedure is needed to achieve optimal purification.

Willi-Hans Steeb, Yorick Hardy

Hai-Woong Lee

We present a setup for a direct, total teleportation of a single-particle entangled state. Our scheme consists of a parametric downconversion source, which emits a pair of entangled photons, and a dual Bell measurement system with two beam splitters and two pairs of detectors. An entangled state shared by a pair of beams can be directly transferred to another pair of beams with a 50% probability of success. By a straightforward generalization of the scheme, total teleportation of a multiparticle entangled state can also be performed.

Bipin R. Desai

Alireza Dehghani, Ahmad Akhound, Forough Panahyazdan

Ryo Namiki

We consider the probability that a bipartite quantum state contains phase-conjugate-state (PCS) pairs and/or identical-state pairs as signatures of quantum entanglement. While the fraction of the PCS pairs directly indicates the property of a maximally entangled state, the fraction of the identical-state pairs negatively determines antisymmetric entangled states such as singlet states. We also consider the physical limits of these probabilities. This imposes fundamental restrictions on the pair appearance of the states with respect to the local access of the physical system. For continuous-variable system, we investigate similar relations by employing the pairs of phase-conjugate coherent states. We also address the role of the PCS pairs for quantum teleportation in both discrete-variable and continuous-variable systems.