Quantum dynamics of a dc-SQUID coupled to an asymmetric Cooper pair transistor

Aurélien Fay (1) , Wiebke Guichard (1) , Olivier Buisson (1) , Frank. W. J. Hekking (2)

1 NEEL - QuantECA - Circuits électroniques quantiques Alpes
2 LPM2C - Laboratoire de physique et modélisation des milieux condensés

We present a theoretical analysis of the quantum dynamics of a superconducting circuit based on a highly asymmetric Cooper pair transistor (ACPT) in parallel to a dc-SQUID. Starting from the full Hamiltonian we show that the circuit can be modeled as a charge qubit (ACPT) coupled to an anharmonic oscillator (dc-SQUID). Depending on the anharmonicity of the SQUID, the Hamiltonian can be reduced either to one that describes two coupled qubits or to the Jaynes-Cummings Hamiltonian. Here the dc-SQUID can be viewed as a tunable micron-size resonator. The coupling term, which is a combination of a capacitive and a Josephson coupling between the two qubits, can be tuned from the very strong- to the zero-coupling regimes. It describes very precisely the tunable coupling strength measured in this circuit and explains the 'quantronium' as well as the adiabatic quantum transfer read-out.

Domaines: Autre [cond-mat.other]

Aurélien Fay, Wiebke Guichard, Olivier Buisson, Frank. W. J. Hekking. Quantum dynamics of a dc-SQUID coupled to an asymmetric Cooper pair transistor. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2011, pp.184510. ⟨10.1103/PhysRevB.83.184510⟩. ⟨hal-00993444⟩