1,721,016 research outputs found
Data security and quantum mechanics
No full textProc. XXXIst Rencontres de Moriond, Dark Matter in Cosmology,
Quantum Measurements, Experimental Gravitation ed. da R. Ansari,
Y. Giraud-Heraud e J. Tran Thahn Van, Editions Frontier
Restoration of quantum states after measurements
No full textWe discuss possibilities of protecting quantum states against disturbances introduced by quantum measurements. We specify conditions under which it is possible to restore an unknown state of a combined quantum system after measurements which were performed on some (but not on all) of its components
Against Quantum Noise
No full textThis is a brief description of how to protect quantum states from dissipation and decoherence that arise due to uncontrolled interactions with the environment. We discuss recoherence and stabilisation of quantum states based on two techniques known as "symmetrisation" and "quantum error correction". We illustrate our considerations with the most popular quantum-optical model of the system-environment interaction, commonly used to describe spontaneous emission, and show the benefits of quantum error correction in this case
Quantum Error Correction for Communication.
No full textWe show how procedures which can correct phase and amplitude errors are in themselves sufficient to correct errors due to quantum entanglement, generalizing earlier results. We specify general criteria for quantum error correction, introduce quantum versions of the Hamming and the Gilbert-Varshamov bounds, and comment on the practical implementations of quantum codes
Quantum computation: From the sequential approach to simulated annealing
No full textThis is a brief outline of some essential features of quantum computation. We describe sequential quantum data processing and speculate on new modes of quantum computation such as quantum annealing
Optimal universal quantum cloning and state estimation
Full text linkWe derive a tight upper bound for the fidelity of a universal N to M qubit cloner, valid for any M \geq N, where the output of the cloner is required to be supported on the symmetric subspace. Our proof is based on the concatenation of two cloners and the connection between quantum cloning and quantum state estimation. We generalise the operation of a quantum cloner to mixed and/or entangled input qubits described by a density matrix supported on the symmetric subspace of the constituent qubits. We also extend the validity of optimal state estimation methods to inputs of this kind
Optimal purification of single qubits
No full textWe introduce a new decomposition of the multiqubit states of the form and employ it to construct the optimal single qubit purification procedure. The same decomposition allows us to study optimal quantum cloning and state estimation of mixed states
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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