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Optimal universal quantum cloning and state estimation

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arxiv quant-ph/9712019 v3 pith:UZRTOBUS submitted 1997-12-09 quant-ph

classification quant-ph
keywords quantumclonerestimationstatecloningoptimalqubitssubspace
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We 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.

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Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Cloning Quantum Channels

    quant-ph 2025-09 conditional novelty 7.0 of 10

    The paper unifies state and channel cloning, proves that a channel family can super-replicate only when a certain generator β(x) is nonzero, and exhibits noisy phase gates as the first non-unitary examples.

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