473 research outputs found
A General Method for Selecting Quantum Channel for Bidirectional Controlled State Teleportation and Other Schemes of Controlled Quantum Communication
Recently, a large number of protocols for bidirectional controlled state
teleportation (BCST) have been proposed using -qubit entangled states
() as quantum channel. Here, we propose a general method of
selecting multi-qubit quantum channels suitable for BCST and show that
all the channels used in the existing protocols of BCST can be obtained using
the proposed method. Further, it is shown that the quantum channels used in the
existing protocols of BCST forms only a negligibly small subset of the set of
all the quantum channels that can be constructed using the proposed method to
implement BCST. It is also noted that all these quantum channels are also
suitable for controlled bidirectional remote state preparation (CBRSP).
Following the same logic, methods for selecting quantum channels for other
controlled quantum communication tasks, such as controlled bidirectional joint
remote state preparation (CJBRSP) and controlled quantum dialogue, are also
provided.Comment: 8 pages, no figur
Controlled bidirectional remote state preparation in noisy environment: A generalized view
It is shown that a realistic, controlled bidirectional remote state
preparation is possible using a large class of entangled quantum states having
a particular structure. Existing protocols of probabilistic, deterministic and
joint remote state preparation are generalized to obtain the corresponding
protocols of controlled bidirectional remote state preparation (CBRSP). A
general way of incorporating the effects of two well known noise processes, the
amplitude-damping and phase-damping noise, on the probabilistic CBRSP process
is studied in detail by considering that noise only affects the travel qubits
of the quantum channel used for the probabilistic CBRSP process. Also indicated
is how to account for the effect of these noise channels on deterministic and
joint remote state CBRSP protocols.Comment: 11 pages, 2 figure
Design and experimental realization of an optimal scheme for teleportion of an -qubit quantum state
An explicit scheme (quantum circuit) is designed for the teleportation of an
-qubit quantum state. It is established that the proposed scheme requires an
optimal amount of quantum resources, whereas larger amount of quantum resources
has been used in a large number of recently reported teleportation schemes for
the quantum states which can be viewed as special cases of the general
-qubit state considered here. A trade off between our knowledge about the
quantum state to be teleported and the amount of quantum resources required for
the same is observed. A proof of principle experimental realization of the
proposed scheme (for a 2-qubit state) is also performed using 5-qubit
superconductivity-based IBM quantum computer. Experimental results show that
the state has been teleported with high fidelity. Relevance of the proposed
teleportation scheme has also been discussed in the context of controlled,
bidirectional, and bidirectional-controlled state teleportation.Comment: 11 pages 4 figure
Applications of quantum cryptographic switch: Various tasks related to controlled quantum communication can be performed using Bell states and permutation of particles
Recently, several aspects of controlled quantum communication (e.g.,
bidirectional controlled state teleportation, controlled quantum secure direct
communication, controlled quantum dialogue, etc.) have been studied using
-qubit () entanglement. Specially, a large number of schemes for
bidirectional controlled state teleportation are proposed using -qubit
entanglement (). Here, we propose a set of protocols to
illustrate that it is possible to realize all these tasks related to controlled
quantum communication using only Bell states and permutation of particles
(PoP). As the generation and maintenance of a Bell state is much easier than a
multi-partite entanglement, the proposed strategy has a clear advantage over
the existing proposals. Further, it is shown that all the schemes proposed here
may be viewed as applications of the concept of quantum cryptographic switch
which was recently introduced by some of us. The performances of the proposed
protocols as subjected to the amplitude damping and phase damping noise on the
channels are also discussed.Comment: 12 pages, 3 figure
Remote operations and interactions for systems of arbitrary dimensional Hilbert space: a state-operator approach
We present a systematic simple method for constructing deterministic remote
operations on single and multiple systems of arbitrary discrete dimensionality.
These operations include remote rotations, remote interactions and
measurements. The resources needed for an operation on a two-level system are
one ebit and a bidirectional communication of two cbits, and for an n-level
system, a pair of entangled n-level particles and two classical ``nits''. In
the latter case, there are possible distinct operations per one n-level
entangled pair. Similar results apply for generating interaction between a pair
of remote systems and for remote measurements. We further consider remote
operations on spatially distributed systems, and show that the number of
possible distinct operations increases here exponentially, with the available
number of entangled pairs that are initial distributed between the systems. Our
results follow from the properties of a hybrid state-operator object
(``stator''), which describes quantum correlations between states and
operations.Comment: 18 pages, 3 figures, typo correction
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
Controlled cyclic remote state preparation of arbitrary qubit states
Quantum secure communications could securely transmit quantum information by using quantum resource. Recently, novel applications such as bidirectional and asymmetric quantum protocols have been developed.
In this paper, we propose a new method for generating entanglement which is highly useful for multiparty quantum communications such as teleportation and Remote State Preparation (RSP). As one of its applications, we propose a new type of quantum secure communications, i.e. cyclic RSP protocols. Starting from a four-party controlled cyclic RSP protocol of one-qubit states, we show that this cyclic protocol can be generalized to a multiparty controlled cyclic RSP protocol for preparation of arbitrary qubit states. We point out that previous bidirectional and asymmetric protocols can be regarded as a simpler form of our cyclic RSP protocols
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
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