A fluxonium-based artificial molecule with a tunable magnetic moment
Authors:
A. Kou,
W. C. Smith,
U. Vool,
R. T. Brierley,
H. Meier,
L. Frunzio,
S. M. Girvin,
L. I. Glazman,
M. H. Devoret
Abstract:
Engineered quantum systems allow us to observe phenomena that are not easily accessible naturally. The LEGO-like nature of superconducting circuits makes them particularly suited for building and coupling artificial atoms. Here, we introduce an artificial molecule, composed of two strongly coupled fluxonium atoms, which possesses a tunable magnetic moment. Using an applied external flux, one can t…
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Engineered quantum systems allow us to observe phenomena that are not easily accessible naturally. The LEGO-like nature of superconducting circuits makes them particularly suited for building and coupling artificial atoms. Here, we introduce an artificial molecule, composed of two strongly coupled fluxonium atoms, which possesses a tunable magnetic moment. Using an applied external flux, one can tune the molecule between two regimes: one in which the ground-excited state manifold has a magnetic dipole moment and one in which the ground-excited state manifold has only a magnetic quadrupole moment. By varying the applied external flux, we find the coherence of the molecule to be limited by local flux noise. The ability to engineer and control artificial molecules paves the way for building more complex circuits for protected qubits and quantum simulation.
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Submitted 4 December, 2016; v1 submitted 4 October, 2016;
originally announced October 2016.
Signatures of quantum phase transitions in the dynamic response of fluxonium qubit chains
Authors:
Hendrik Meier,
R. T. Brierley,
Angela Kou,
S. M. Girvin,
Leonid I. Glazman
Abstract:
We evaluate the microwave admittance of a one-dimensional chain of fluxonium qubits coupled by shared inductors. Despite its simplicity, this system exhibits a rich phase diagram. A critical applied magnetic flux separates a homogeneous ground state from a phase with a ground state exhibiting inhomogeneous persistent currents. Depending on the parameters of the array, the phase transition may be a…
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We evaluate the microwave admittance of a one-dimensional chain of fluxonium qubits coupled by shared inductors. Despite its simplicity, this system exhibits a rich phase diagram. A critical applied magnetic flux separates a homogeneous ground state from a phase with a ground state exhibiting inhomogeneous persistent currents. Depending on the parameters of the array, the phase transition may be a conventional continuous one, or of a commensurate-incommensurate nature. Furthermore, quantum fluctuations affect the transition and possibly lead to the presence of gapless "floating phases". The signatures of the soft modes accompanying the transitions appear as a characteristic frequency dependence of the dissipative part of admittance.
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Submitted 24 August, 2015; v1 submitted 22 July, 2015;
originally announced July 2015.