Selective darkening of degenerate transitions demonstrated with two superconducting quantum bits

Controlled manipulation of quantum states is central to studying natural and artificial quantum systems. If a quantum system consists of interacting subunits, the nature of the coupling may lead to quantum levels with degenerate energy differences. This degeneracy makes frequency-selective quantum o...

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Bibliographic Details
Published in:Nature physics 2010-10, Vol.6 (10), p.763-766
Main Authors: Lupa cu, A, Schouten, R. N, de Groot, P. C, Lisenfeld, J, Ashhab, S, Harmans, C. J. P. M, Mooij, J. E
Format: Article
Language:English
Subjects:
Atomic
Classical and Continuum Physics
Coherence
Complex Systems
Condensed Matter Physics
Darkening
Driving
Energy
Flux
Joining
letter
Mathematical and Computational Physics
Molecular
Optical and Plasma Physics
Physics
Physics and Astronomy
Quantum physics
Quantum theory
Qubits (quantum computing)
Research methodology
Superconductivity
Theoretical
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Summary:Controlled manipulation of quantum states is central to studying natural and artificial quantum systems. If a quantum system consists of interacting subunits, the nature of the coupling may lead to quantum levels with degenerate energy differences. This degeneracy makes frequency-selective quantum operations impossible. For the prominent group of transversely coupled two-level systems, that is, qubits, we introduce a method to selectively suppress one transition of a degenerate pair while coherently exciting the other, effectively creating artificial selection rules. It requires driving two qubits simultaneously with the same frequency and specified relative amplitude and phase. We demonstrate our method on a pair of superconducting flux qubits. It can directly be applied to the other superconducting qubits, and to any other qubit type that allows for individual driving. Our results provide a single-pulse controlled-NOT gate for the class of transversely coupled qubits.
ISSN:1745-2473
1745-2481
DOI:10.1038/nphys1733