M. G. M. Moreno

Remote preparation of W states from imperfect bipartite sources

Several proposals to produce tripartiteW-type entanglement are probabilistic even if no imperfections are considered in the processes. We provide a deterministic way to remotely create W states out of an EPR source. The proposal is made viable through measurements (which can be demolitive) in an appropriate three-qubit basis. The protocol becomes probabilistic only when source flaws are considered. It turns out that, even in this situation, it is robust against imperfections in two senses: (i) It is possible, after postselection, to create a pure ensemble of W states out of an EPR source containing a systematic error; (ii) If no postselection is done, the resulting mixed state has a fidelity, with respect to a pure

Using three-partite GHZ states for partial quantum error detection in entanglement-based protocols

|W\rangle

Comment on Testing Bell's inequality with one party weak measurements

|W⟩, which is higher than that of the imperfect source in comparison with an ideal EPR source. This simultaneously amounts to entanglement concentration and lifting.

Investigation of the collapse of quantum states using entangled photons

Channels composed by Einstein–Podolsky–Rosen (EPR) pairs are capable of teleporting arbitrary multipartite states. The question arises whether EPR channels are also optimal against imperfections. In particular, the teleportation of Greenberger–Horne–Zeilinger states (GHZ) requires three EPR states as the channel and full measurements in the Bell basis. We show that, by using two GHZ states as the channel, it is possible to transport any unknown three-qubit state of the form

All bipartitions of arbitrary Dicke states

c_0|000\rangle +c_1|111\rangle

Efficient production of

c0|000⟩+c1|111⟩. The teleportation is made through measurements in the GHZ basis, and, to obtain deterministic results, in most of the investigated scenarios, four out of the eight elements of the basis need to be unambiguously distinguished. Most importantly, we show that when both systematic errors and noise are considered, the fidelity of the teleportation protocol is higher when a GHZ channel is used in comparison with that of a channel composed by EPR pairs.