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Simple unconventional geometric scenario of one-way quantum computation with superconducting qubits inside a cavity
We propose a simple unconventional geometric scenario to achieve a kind of
nontrivial multi-qubit operations with superconducting charge qubits placed in
a microwave cavity. The proposed quantum operations are insensitive not only to
the thermal state of cavity mode but also to certain random operation errors,
and thus may lead to high-fidelity quantum information processing. Executing
the designated quantum operations, a class of highly entangled cluster states
may be generated efficiently in the present scalable solid-state system,
enabling one to achieve one-way quantum computation.Comment: Accepted version with minor amendments. To appear in Phys. Rev.
Comment on 'Secure Communication using mesoscopic coherent states', Barbosa et al, Phys Rev Lett 90, 227901 (2003)
In a recent letter, Barbosa et al [PRL 90, 227901(2003)] claim that secure
communication is possible with bright coherent pulses, by using quantum noise
to hide the data from an eavesdropper. We show here that the secrecy in the
scheme of Barbosa et al is unrelated to quantum noise, but rather derives from
the secret key that sender and receiver share beforehand
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