Resonant effects in a SQUID qubit subjected to nonadiabatic changes

F. Chiarello; S. Spilla; M. G. Castellano; C. Cosmelli; A. Messina; R. Migliore; A. Napoli; G. Torrioli

doi:10.1103/PhysRevB.89.134506

← Back to search

Resonant effects in a SQUID qubit subjected to nonadiabatic changes

F. Chiarello, S. Spilla, M. G. Castellano, C. Cosmelli, A. Messina, R. Migliore, A. Napoli, G. Torrioli

DOI 10.1103/PhysRevB.89.134506 · Physical Review B

T1

Active bibliographic source — not scientific approval

Bibliographic access preserves source history; it does not approve extracted materials or validate reported claims. Review warnings on each occurrence separately.

Abstract

By quickly modifying the shape of the effective potential of a double SQUID flux qubit from a single-well to a double-well condition, we experimentally observe an anomalous behavior, namely, an alternation 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 simulation of the time evolution of the system indeed suggests that the observed anomalous behavior can be imputable to quantum coherence effects. The interplay among all these mechanisms has a practical implication for quantum computing purposes, giving a direct measurement of the limits on the sweeping rates possible for a correct manipulation of the qubit state by means of fast flux pulses, avoiding transitions to noncomputational states.