5 research outputs found
High-efficiency multipartite entanglement purification of electron-spin states with charge detection
We present a high-efficiency multipartite entanglement purification protocol
(MEPP) for electron-spin systems in a Greenberger-Horne-Zeilinger state based
on their spins and their charges. Our MEPP contains two parts. The first part
is our normal MEPP with which the parties can obtain a high-fidelity N-electron
ensemble directly, similar to the MEPP with controlled-not gates. The second
one is our recycling MEPP with entanglement link from N'-electron subsystems (2
< N' < N). It is interesting to show that the N'-electron subsystems can be
obtained efficiently by measuring the electrons with potential bit-flip errors
from the instances which are useless and are just discarded in all existing
conventional MEPPs. Combining these two parts, our MEPP has the advantage of
the efficiency higher than other MEPPs largely for electron-spin systems.Comment: 15 pages, 5 figure
Optimal entanglement concentration for quantum dot and optical microcavities systems
A recent paper [Chuan Wang, Phys. Rev. A \textbf{86}, 012323 (2012)]
discussed an entanglement concentration protocol (ECP) for partially entangled
electrons using a quantum dot and microcavity coupled system. In his paper,
each two-electron spin system in a partially entangled state can be
concentrated with the assistance of an ancillary quantum dot and a single
photon. In this paper, we will present an optimal ECP for such entangled
electrons with the help of only one single photon. Compared with the protocol
of Wang, the most significant advantage is that during the whole ECP, the
single photon only needs to pass through one microcavity which will increase
the total success probability if the cavity is imperfect. The whole protocol
can be repeated to get a higher success probability. With the feasible
technology, this protocol may be useful in current long-distance quantum
communications.Comment: 6 pages, 3 figure
Atomic entanglement purification using photonic Faraday rotation
We describe an entanglement purification protocol (EPP) for atomic entangled
pair using photonic Faraday rotation. It is shown that after the two single
photons input-output process in cavity QED, the high quality entangled atomic
state can be obtained from the low quality mixed entangled atomic states.
Different from other EPPs, the two pairs of mixed states do not need to intact
directly. As the photonic Faraday rotation works on the low-Q cavities, this
EPP is useful in both quantum communication and computation.Comment: 8 pages, 3 figure
Efficient multipartite entanglement concentration of electron-spin state with charge detection
We present two entanglement concentration protocols (ECPs) for arbitrary
three-electron W state based on their charges and spins. Different from other
ECPs, in both two ECPs, with the help of the electronic polarization beam
splitter (PBS) and charge detection, the less-entangled W state can be
concentrated into a maximally entangled state only with some single charge
qubits. The second ECP is more optimal than the first one, for by constructing
the complete parity check gate, the second ECP can be used repeatedly to
further concentrate the less-entangled state and obtain a higher success
probability. Therefore, both the ECPs, especially the second one may be useful
in current quantum information processing.Comment: 8 pages, 4 figure
Multipartite entanglement purification for three-level trapped atom systems
We describe an entanglement purification protocol (EPP) for multipartite
three-level atomic entangled pair using photonic Faraday rotation. In this EPP,
the multipartite atomic entangled state can be purified with the help of some
single photons. This protocol resorts to the photonic Faraday rotation to
realize the function of the controlled-Not (CNOT) gate. The purified
multipartite atomic entangled state can be retained and to be repeated to reach
a higher fidelity.Comment: 11pages, 2 figure