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.

Resonant effects in a SQUID qubit subjected to nonadiabatic changes / Chiarello, Fabio; S., Spilla; M. G., Castellano; Cosmelli, Carlo; Messina, Andrea; R., Migliore; A., Napoli; Torrioli, Guido. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - STAMPA. - 89:13(2014), pp. 134506.1-134506.6. [10.1103/physrevb.89.134506]

Resonant effects in a SQUID qubit subjected to nonadiabatic changes

CHIARELLO, FABIO;COSMELLI, Carlo;MESSINA, Andrea;TORRIOLI, GUIDO
2014

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.
2014
qubit; supeconductvity; squid
01 Pubblicazione su rivista::01a Articolo in rivista
Resonant effects in a SQUID qubit subjected to nonadiabatic changes / Chiarello, Fabio; S., Spilla; M. G., Castellano; Cosmelli, Carlo; Messina, Andrea; R., Migliore; A., Napoli; Torrioli, Guido. - In: PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS. - ISSN 1098-0121. - STAMPA. - 89:13(2014), pp. 134506.1-134506.6. [10.1103/physrevb.89.134506]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/559143
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