Mixed qubits cannot be universally broadcast

Journal Article · Fri Jun 15 04:00:00 EDT 2007 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.75.062322· OSTI ID:20991107

Lin, Chen; Yixin, Chen ^[1]

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1. Zhejiang Insitute of Modern Physics, Zhejiang University, Hangzhou 310027 (China)

We show that no universal quantum cloning machine exists that can broadcast an arbitrary mixed qubit with a constant fidelity. Based on this result, we investigate the dependent quantum cloner in the sense that some parameter of the input qubit {rho}{sub s}({theta},{omega},{lambda}) is regarded as constant in the fidelity. For the case of constant {omega}, we establish the 1{yields}2 optimal symmetric dependent cloner with a fidelity 1/2. It is also shown that the 1{yields}M optimal quantum cloning machine for pure qubits is also optimal for mixed qubits, when {lambda} is the unique parameter in the fidelity. For general N{yields}M broadcasting of mixed qubits, the situation is very different.

• OSTI ID: 20991107
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 6 Vol. 75; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COMMUNICATIONS
MIXED STATE
QUANTUM COMPUTERS
QUANTUM MECHANICS
QUBITS