1,969 research outputs found
Efficient -particle state concentration with different parity check gates
We present an universal way to concentrate an arbitrary -particle
less-entangled state into a maximally entangled state with different
parity check gates. It comprises two protocols. The first protocol is based on
the linear optical elements say the partial parity check gate and the second
one uses the quantum nondemolition (QND) to construct the complete parity check
gate. Both of which can achieve the concentration task. These protocols have
several advantages. First, it can obtain a maximally entangled W state only
with the help of some single photons, which greatly reduces the number of
entanglement resources. Second, in the first protocol, only linear optical
elements are required which is feasible with current techniques. Third, in the
second protocol, it can be repeated to perform the concentration step and get a
higher success probability. All these advantages make it be useful in current
quantum communication and computation applications.Comment: 11pages,8figure
Efficient entanglement concentration for arbitrary less-entangled NOON state assisted with single photon
We put forward two efficient entanglement concentration protocols (ECPs) for
distilling the maximally entangled NOON state from arbitrary less-entangled
NOON state with only an auxiliary single photon. With the help of the weak
cross-Kerr nonlinearities, both the two ECPs can be used repeatedly to get a
high success probability. In the first ECP, the auxiliary single photon should
be shared by the two parties say Alice and Bob. In the second ECP, the
auxiliary single photon is only possessed by Bob, which can greatly increase
the practical success probability by avoiding the transmission loss. Moreover,
Bob can operate the whole protocol alone, which makes the protocol more simple.
Therefore, our two ECPs, especially the second ECP may be more useful and
convenient in the current quantum information processing.Comment: 10 pages, 3 figure
Efficient entanglement purification for polarization logic Bell state with the photonic Faraday rotation
Logic-qubit entanglement is a promising resource in quantum information
processing, especially in future large-scale quantum networks. In the paper, we
put forward an efficient entanglement purification protocol (EPP) for nonlocal
mixed logic entangled states with the bit-flip error in the logic qubits of the
logic Bell state, resorting to the photon-atom interaction in low-quality (Q)
cavity and atomic state measurement. Different from existing EPPs, this
protocol can also purify the logic phase-flip error, and the bit-flip error and
the phase-flip error in physic qubit. During the protocol, we only require to
measure the atom states, and it is useful for improving the entanglement of
photon systems in future large-scale quantum networks.Comment: 14 page, 6 figure
Distilling and protecting the single-photon entangled state
We propose two efficient entanglement concentration protocols (ECPs) for
arbitrary less-entangled single-photon entanglement (SPE). Different from all
the previous ECPs, these protocols not only can obtain the maximally SPE, but
also can protect the single qubit information encoded in the polarization
degree of freedom. These protocols only require one pair of less-entangled
single-photon entangled state and some auxiliary single photons, which makes
them economical. The first ECP is operated with the linear optical elements,
which can be realized in current experiment. The second ECP adopts the
cross-Kerr nonlinearities. Moreover, the second ECP can be repeated to
concentrate the discard states in some conventional ECPs, so that it can get a
high success probability. Based on above properties, our ECPs may be useful in
current and future quantum communication.Comment: 11 pages, 4 figure
The heralded amplification for the single-photon entanglement of the time-bin qubit
We put forward an effective amplification protocol for protecting the
single-photon entangled state of the time-bin qubit. The protocol only requires
one pair of the single-photon entangled state and some auxiliary single
photons. With the help of the 50:50 beam splitters, variable beam splitters
with the transmission of and the polarizing beam splitters, we can increase
the fidelity of the single-photon entangled state under .
Moreover, the encoded time-bin information can be perfectly contained. Our
protocol is quite simple and economical. More importantly, it can be realized
under current experimental condition. Based on the above features, our protocol
may be useful in current and future quantum information processing.Comment: 9 page4, 4 figure
Generalized entanglement distillation
We present a way for the entanglement distillation of genuine mixed state.
Different from the conventional mixed state in entanglement purification
protocol, each components of the mixed state in our protocol is a
less-entangled state, while it is always a maximally entangled state. With the
help of the weak cross-Kerr nonlinearity, this entanglement distillation
protocol does not require the sophisticated single-photon detectors. Moreover,
the distilled high quality entangled state can be retained to perform the
further distillation. These properties make it more convenient in practical
applications.Comment: 7 pages, 4 figure
Bell-state Analysis for Logic Qubits Entanglement
Decoherence is one of the main obstacles in long-distance quantum
communication. Recently, the theoretical work of Fr\"{o}wis and W. D\"{u}r
(Phys. Rev. Lett. \textbf{106}, 110402 (2011)) and the experiment of Lu
\emph{et al.} (Nat. Photon. \textbf{8}, 364 (2014)) both showed that the logic
qubits entanglement say the concatenated Greenberger-Horne-Zeilinger (C-GHZ)
state is more robust under decoherence. In this paper, we describe a protocol
for Bell-state analysis for this logic qubits entanglement. This protocol can
also be extended to the multipartite C-GHZ state analysis. Also, we discuss its
application in the quantum teleportation of a unknown logic qubit and in the
entanglement swapping of logic Bell states. As the logic qubits entanglement is
more robust under decoherence, our protocol shows that it is possible to
realize the long-distance quantum communication based on logic qubits
entanglement.Comment: 5 pages, 2 figure
Detection of the nonlocal atomic entanglement assisted with single photons
We present an efficient way for measuring the entanglement of the atoms.
Through the auxiliary single photons input-output process in cavity quantum
electrodynamics (QED), the concurrence of the atomic entanglement can be
obtained according to the success probability of picking up the singlet states
of the atoms. This protocol has three advantages: First, we do not require the
sophisticated controlled-not (CNOT) gates. Second, the distributed atoms are
not required to intact with each other. Third, the atomic entanglement can be
distributed nonlocally, which provides its important applications in
distributed quantum computation.Comment: 5 pages, 3 figure
The effective protection protocol of single photon state from photon loss and decoherence
We design an effect protocol for protecting the single-photon entanglement
from photon loss and decoherence. The protocol only requires some auxiliary
single photons and the linear optical elements. By operating the protocol, the
photon loss can be effectively decreased and the less entangled single photon
state can be recovered to the maximally entangled state with some probability.
Moreover, the polarization information encoded in the single photon state can
be perfectly contained. The protocol can be realized under current experimental
condition. As the single photon entanglement is quite important in quantum
communication, this protocol may be useful in current and future quantum
information processing.Comment: 9 pages,5 figures. arXiv admin note: text overlap with
arXiv:1605.0948
Deterministic polarization entanglement purification using time-bin entanglement
We present a deterministic entanglement purification protocol (EPP) working
for currently available experiment technique. In this protocol, we resort to
the robust time-bin entanglement to purify the polarization entanglement
determinately, which is quite different from the previous EPPs. After
purification, one can obtain a completely pure maximally entangled pair with
the success probability of 100%, in principle. As the maximal polarization
entanglement is of vice importance in long-distance quantum communication, this
protocol may have a wide application.Comment: 5 pages, 2 figure
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