By quickly modifying the shape of the effective potential of a double SQUID flux qubit from asingle well to a double well condition, we experimentally observe an anomalous behavior, namely an alternance of resonance peaks, in the probability to find the qubit in a given flux state. The occurrence of Landau-Zener transitions as well as resonant tunneling between degenerate levels in the two wells may be invoked to partially justify the experimental results. A quantum simulationof the time evolution of the system indeed suggests that the observed anomalous behavior can beimputable to quantum coherence effects. The interplay among all these mechanisms has a practicalimplication for quantum computing purposes, giving a direct measurement of the limits on thesweeping rates possible for a correct manipulation of the qubit state by means of fast flux pulses,avoiding transitions to non-computational states.
|Numero di pagine||7|
|Rivista||PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS|
|Stato di pubblicazione||Published - 2014|
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