160 research outputs found
A comparative study of protocols for secure quantum communication under noisy environment: single-qubit-based protocols versus entangled-state-based protocols
The effect of noise on various protocols of secure quantum communication has
been studied. Specifically, we have investigated the effect of amplitude
damping, phase damping, squeezed generalized amplitude damping, Pauli type as
well as various collective noise models on the protocols of quantum key
distribution, quantum key agreement,quantum secure direct quantum communication
and quantum dialogue. From each type of protocol of secure quantum
communication, we have chosen two protocols for our comparative study; one
based on single qubit states and the other one on entangled states. The
comparative study reported here has revealed that single-qubit-based schemes
are generally found to perform better in the presence of amplitude damping,
phase damping, squeezed generalized amplitude damping noises, while
entanglement-based protocols turn out to be preferable in the presence of
collective noises. It is also observed that the effect of noise entirely
depends upon the number of rounds of quantum communication involved in a scheme
of quantum communication. Further, it is observed that squeezing, a completely
quantum mechanical resource present in the squeezed generalized amplitude
channel, can be used in a beneficial way as it may yield higher fidelity
compared to the corresponding zero squeezing case.Comment: 23 pages 7 figure
Which verification qubits perform best for secure communication in noisy channel?
In secure quantum communication protocols, a set of single qubits prepared
using 2 or more mutually unbiased bases or a set of -qubit ()
entangled states of a particular form are usually used to form a verification
string which is subsequently used to detect traces of eavesdropping. The qubits
that form a verification string are referred to as decoy qubits, and there
exists a large set of different quantum states that can be used as decoy
qubits. In the absence of noise, any choice of decoy qubits provides equivalent
security. In this paper, we examine such equivalence for noisy environment
(e.g., in amplitude damping, phase damping, collective dephasing and collective
rotation noise channels) by comparing the decoy-qubit assisted schemes of
secure quantum communication that use single qubit states as decoy qubits with
the schemes that use entangled states as decoy qubits. Our study reveals that
the single qubit assisted scheme perform better in some noisy environments,
while some entangled qubits assisted schemes perform better in other noisy
environments. Specifically, single qubits assisted schemes perform better in
amplitude damping and phase damping noisy channels, whereas a few
Bell-state-based decoy schemes are found to perform better in the presence of
the collective noise. Thus, if the kind of noise present in a communication
channel (i.e., the characteristics of the channel) is known or measured, then
the present study can provide the best choice of decoy qubits required for
implementation of schemes of secure quantum communication through that channel.Comment: 11 pages, 4 figure
Hierarchical Joint Remote State Preparation in Noisy Environment
A novel scheme for quantum communication having substantial applications in
practical life is designed and analyzed. Specifically, we have proposed a
hierarchical counterpart of the joint remote state preparation (JRSP) protocol,
where two senders can jointly and remotely prepare a quantum state. One sender
has the information regarding amplitude, while the other one has the phase
information of a quantum state to be jointly prepared at the receiver's port.
However, there exists a hierarchy among the receivers, as far as powers to
reconstruct the quantum state is concerned. A 5-qubit cluster state has been
used here to perform the task. Further, it is established that the proposed
scheme for hierarchical JRSP (HJRSP) is of enormous practical importance in
critical situations involving defense and other sectors, where it is essential
to ensure that an important decision/order that can severely affect a society
or an organization is not taken by a single person, and once the order is
issued all the receivers don't possess an equal right to implement it. Further,
the effect of different noise models (e.g., amplitude damping (AD), phase
damping (PD), collective noise and Pauli noise models) on the HJRSP protocol
proposed here is investigated. It is found that in AD and PD noise models a
higher power agent can reconstruct the quantum state to be remotely prepared
with higher fidelity than that done by the lower power agent(s). In contrast,
the opposite may happen in the presence of collective noise models. We have
also proposed a scheme for probabilistic HJRSP using a non-maximally entangled
5-qubit cluster state.Comment: 24 pages, 6 figure
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