2,499 research outputs found
Controlled and secure direct communication using GHZ state and teleportation
A theoretical scheme for controlled and secure direct communication is
proposed. The communication is based on GHZ state and controlled quantum
teleportation. After insuring the security of the quantum channel (a set of
qubits in the GHZ state), Alice encodes the secret message directly on a
sequence of particle states and transmits them to Bob supervised by Charlie
using controlled quantum teleportation. Bob can read out the encoded messages
directly by the measurement on his qubits. In this scheme, the controlled
quantum teleportation transmits Alice's message without revealing any
information to a potential eavesdropper. Because there is not a transmission of
the qubit carrying the secret messages between Alice and Bob in the public
channel, it is completely secure for controlled and direct secret communication
if perfect quantum channel is used. The feature of this scheme is that the
communication between two sides depends on the agreement of the third side.Comment: 4 pages, no figur
Controlled quantum teleportation and secure direct communication
We present a controlled quantum teleportation protocol. In the protocol,
quantum information of an unknown state of a 2-level particle is faithfully
transmitted from a sender (Alice) to a remote receiver (Bob) via an initially
shared triplet of entangled particles under the control of the supervisor
Charlie. The distributed entangled particles shared by Alice, Bob and Charlie
function as a quantum information channel for faithful transmission. We also
propose a controlled and secure direct communication scheme by means of this
teleportation. After insuring the security of the quantum channel, Alice
encodes the secret message directly on a sequence of particle states and
transmits them to Bob supervised by Charlie using this controlled quantum
teleportation. Bob can read out the encoded message directly by the measurement
on his qubit. In this scheme, the controlled quantum teleportation transmits
Alice's message without revealing any information to a potential eavesdropper.
Because there is not a transmission of the qubit carrying the secret message
between Alice and Bob in the public channel, it is completely secure for
controlled and direct secret communication if perfect quantum channel is used.
The feature of this scheme is that the communication between two sides depends
on the agreement of the third side.Comment: 4 page
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
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
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
Symmetric multiparty-controlled teleportation of an arbitrary two-particle entanglement
We present a way for symmetric multiparty-controlled teleportation of an
arbitrary two-particle entangled state based on Bell-basis measurements by
using two Greenberger-Horne-Zeilinger states, i.e., a sender transmits an
arbitrary two-particle entangled state to a distant receiver, an arbitrary one
of the agents via the control of the others in a network. It will be
shown that the outcomes in the cases that is odd or it is even are
different in principle as the receiver has to perform a controlled-not
operation on his particles for reconstructing the original arbitrary entangled
state in addition to some local unitary operations in the former. Also we
discuss the applications of this controlled teleporation for quantum secret
sharing of classical and quantum information. As all the instances can be used
to carry useful information, its efficiency for qubits approaches the maximal
value.Comment: 9 pages, 3 figures; the revised version published in Physical Review
A 72, 022338 (2005). The detail for setting up a GHZ-state quantum channel is
adde
A simple proof of the unconditional security of quantum key distribution
Quantum key distribution is the most well-known application of quantum
cryptography. Previous proposed proofs of security of quantum key distribution
contain various technical subtleties. Here, a conceptually simpler proof of
security of quantum key distribution is presented. The new insight is the
invariance of the error rate of a teleportation channel: We show that the error
rate of a teleportation channel is independent of the signals being
transmitted. This is because the non-trivial error patterns are permuted under
teleportation. This new insight is combined with the recently proposed quantum
to classical reduction theorem. Our result shows that assuming that Alice and
Bob have fault-tolerant quantum computers, quantum key distribution can be made
unconditionally secure over arbitrarily long distances even against the most
general type of eavesdropping attacks and in the presence of all types of
noises.Comment: 13 pages, extended abstract. Comments will be appreciate
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