6 research outputs found
Maximal entanglement concentration for -qubit states
We propose two schemes for concentration of -qubit entangled states
that can be written in the form of
where and are mutually orthogonal
-qubit states. The importance of this general form is that the entangled
states like Bell, cat, GHZ, GHZ-like, , ,
4-qubit cluster states and specific states from the 9 SLOCC-nonequivalent
families of 4-qubit entangled states can be expressed in this form. The
proposed entanglement concentration protocol is based on the local operations
and classical communications (LOCC). It is shown that the maximum success
probability for ECP using quantum nondemolition (QND) technique is
for -qubit states of the prescribed form. It is shown that the proposed
schemes can be implemented optically. Further it is also noted that the
proposed schemes can be implemented using quantum dot and microcavity systems
Measurement of arbitrary two-photon entanglement state with the photonic Faraday rotation
We propose an efficient protocol for measuring the concurrence of arbitrary
two-photon pure entangled state with the help of the photonic Faraday rotation.
In the protocol, the concurrence of the photonic entangled state can be
conversed into the total success probability for picking up the odd-parity
photonic state. For completing the measurement task, we require some auxiliary
three-level atoms, which are trapped in the low-quality cavities. Our protocol
can be well realized under current experimental conditions. Moreover, under
practical imperfect atom state detection and photonic Faraday rotation
conditions, our protocol can also work well. Based on these features, our
protocol may be useful in current quantum information processing.Comment: 15 pages, 2 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
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
Linear optics based entanglement concentration protocols for Cluster-type entangled coherent state
We proposed two linear optics based entanglement concentration protocols
(ECPs) to obtain maximally entangled 4-mode Cluster-type entangled coherent
state (ECS) from less (partially) entangled Cluster-type ECS. The first ECP is
designed using a superposition of single-mode coherent state with two unknown
parameters, whereas the second ECP is obtained using a superposition of
single-mode coherent state and a superposition of two-mode coherent state with
four unknown parameters. The success probabilities have been calculated for
both the ECPs. Necessary quantum circuits enabling future experimental
realizations of the proposed ECPs are provided using linear optical elements.
Further, the benefit of the proposed schemes is established in the context of
long distance quantum communication where photon loss is an obstruction.Comment: 11 pages, 3 figure
Entanglement concentration protocols for GHZ-type entangled coherent state based on linear optics
We proposed two entanglement concentration protocols (ECPs) to obtain
maximally entangled Greenberger-Horne-Zeilinger (GHZ)-type entangled coherent
state (ECS) from the corresponding partially entangled GHZ-type ECSs. We
obtained the first ECP using a partially entangled GHZ-type ECS assisted with a
superposition of single-mode coherent state, however the second ECP is designed
using two copies of partially entangled GHZ-type ECSs. The success
probabilities have also been calculated and discussed for both the ECPs. We
have further compared the success probabilities of our first ECP for 3-mode
GHZ-type ECS with an ECP of 3-mode W-type ECS and found that our ECP is more
efficient (maximal success probabilities) for larger value (\beta=0.7) of state
parameter. For the physical realization, two optical circuits (for two ECPs)
using linear optical elements, viz 50:50 beam splitter, phase shifter, and
photon detectors are provided, which support the future experimental
implementation possible with the present technology.Comment: 9 pages, 5 figure