424,219 research outputs found
Optimal Non-Universally Covariant Cloning
We consider non-universal cloning maps, namely cloning transformations which
are covariant under a proper subgroup G of the universal unitary group U(d),
where d is the dimension of the Hilbert space H of the system to be cloned. We
give a general method for optimizing cloning for any cost-function. Examples of
applications are given for the phase-covariant cloning (cloning of equatorial
qubits) and for the Weyl-Heisenberg group (cloning of "continuous variables").Comment: 6 page
Quantum cloning
The impossibility of perfectly copying (or cloning) an arbitrary quantum
state is one of the basic rules governing the physics of quantum systems. The
processes that perform the optimal approximate cloning have been found in many
cases. These "quantum cloning machines" are important tools for studying a wide
variety of tasks, e.g. state estimation and eavesdropping on quantum
cryptography. This paper provides a comprehensive review of quantum cloning
machines (both for discrete-dimensional and for continuous-variable quantum
systems); in addition, it presents the role of cloning in quantum cryptography,
the link between optimal cloning and light amplification via stimulated
emission, and the experimental demonstrations of optimal quantum cloning
Quantum Cloning Machines and the Applications
No-cloning theorem is fundamental for quantum mechanics and for quantum
information science that states an unknown quantum state cannot be cloned
perfectly. However, we can try to clone a quantum state approximately with the
optimal fidelity, or instead, we can try to clone it perfectly with the largest
probability. Thus various quantum cloning machines have been designed for
different quantum information protocols. Specifically, quantum cloning machines
can be designed to analyze the security of quantum key distribution protocols
such as BB84 protocol, six-state protocol, B92 protocol and their
generalizations. Some well-known quantum cloning machines include universal
quantum cloning machine, phase-covariant cloning machine, the asymmetric
quantum cloning machine and the probabilistic quantum cloning machine etc. In
the past years, much progress has been made in studying quantum cloning
machines and their applications and implementations, both theoretically and
experimentally. In this review, we will give a complete description of those
important developments about quantum cloning and some related topics. On the
other hand, this review is self-consistent, and in particular, we try to
present some detailed formulations so that further study can be taken based on
those results.Comment: 98 pages, 12 figures, 400+ references. Physics Reports (published
online
Controlled Secret Sharing Protocol using a Quantum Cloning Circuit
We demonstrate the possibility of controlling the success probability of a
secret sharing protocol using a quantum cloning circuit. The cloning circuit is
used to clone the qubits containing the encoded information and {\em en route}
to the intended receipients. The success probability of the protocol depends on
the cloning parameters used to clone the qubits. We also establish a relation
between the concurrence of initially prepared state, entanglement of the mixed
state received by the receivers after cloning scheme and the cloning parameters
of cloning machine.Comment: This is a modified version of the previous work
quant-ph/arXiv:1011.286
Attack of the Clones: Legislative Approaches to Human Cloning in the United States
The legal concerns involving the application of cloning technology to humans should be of utmost concern, as the area is extremely complex. Cloning could potentially have great benefits or disastrous effects. Lawmakers have been careful to make certain that the legislation passed is comprehensive and useful for regulation of the ever-changing field of cloning. From debates on whether reproductive or therapeutic cloning should be permitted or banned, to concerns as to who has jurisdiction over cloning, the battle to develop cloning legislation has been difficult. However, this iBrief argues that the currently-proposed federal legislation is constitutional
Quantum Cloning of Mixed States in Symmetric Subspace
Quantum cloning machine for arbitrary mixed states in symmetric subspace is
proposed. This quantum cloning machine can be used to copy part of the output
state of another quantum cloning machine and is useful in quantum computation
and quantum information. The shrinking factor of this quantum cloning achieves
the well-known upper bound. When the input is identical pure states, two
different fidelities of this cloning machine are optimal.Comment: Revtex, 4 page
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