8,434 research outputs found
Control power in perfect controlled teleportation via partially entangled channels
We analyze and evaluate perfect controlled teleportation via three-qubit
entangled channels from the point of view of the controller. The key idea in
controlled teleportation is that the teleportation is performed only with the
participation of the controller. We calculate a quantitative measure of the
controller's power and establish a lower bound on the control power required
for controlled teleportation. We show that the maximally entangled GHZ state is
a suitable channel for controlled teleportation of arbitrary single qubits -
the controller's power meets the bound and the teleportation fidelity without
the controller's permission is no better than the fidelity of a classical
channel. We also construct partially entangled channels that exceed the bound
for controlled teleportation of a restricted set of states called the
equatorial states. We calculate the minimum entanglement required in these
channels to exceed the bound. Moreover, we find that in these restricted
controlled teleportation schemes, the partially entangled channels can
outperform maximally entangled channels with respect to the controller's power.
Our results provide a new perspective on controlled teleportation schemes and
are of practical interest since we propose useful partially entangled channels.Comment: 5 page, Physical Review A 201
Analysis of N-qubit Perfect Controlled Teleportation Schemes from the Controller\u27s Point of View
We quantitatively analyze and evaluate the controller\u27s power in N-qubit controlled teleportation schemes. We calculate the minimum control power required to ensure the controller\u27s authority such that the teleportation fidelity without the controller\u27s permission is no more than the classical bound. We revisit several typical controlled teleportation schemes from the controller\u27s point of view and evaluate the control power in these schemes. We find that for teleporting arbitrary N-qubit states, each controller should control at least N bits of useful information to ensure his or her authority over the protocol. We also discuss the general rules that must be satisfied by controlled teleportation schemes to ensure both teleportation fidelity and control power
Optimal Controlled Teleportation
We give the analytic expressions of maximal probabilities of successfully
controlled teleportating an unknown qubit via every kind of tripartite states.
Besides, another kind of localizable entanglement is also determined.
Furthermore, we give the sufficient and necessary condition that a three-qubit
state can be collapsed to an EPR pair by a measurement on one qubit, and
characterize the three-qubit states that can be used as quantum channel for
controlled teleporting a qubit of unknown information with unit probability and
with unit fidelity.Comment: 4 page
Quantum logic networks for probabilistic and controlled teleportation of unknown quantum states
We present simplification schemes for probabilistic and controlled
teleportation of the unknown quantum states of both one-particle and
two-particle and construct efficient quantum logic networks for implementing
the new schemes by means of the primitive operations consisting of single-qubit
gates, two-qubit controlled-not gates, Von Neumann measurement and classically
controlled operations. In these schemes the teleportation are not always
successful but with certain probability.Comment: 9 pages, 5 figure
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
Quantum Logic Network for Probabilistic Teleportation of Two-Particle State of General Form
A simplification scheme of probabilistic teleportation of two-particle state
of general form is given. By means of the primitive operations consisting of
single-qubit gates, two-qubit controlled-not gates,
Von Neumann measurement and classically controlled operations, we construct
an efficient quantum logical network for implementing the new scheme of
probabilistic teleportation of a two-particle state of general form.Comment: 9 pages, 2 figure
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
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