Non-linear coupling between the two oscillation modes of a dc-SQUID

Florent Lecocq (1) , Julien Claudon (2) , Olivier Buisson (1) , Pérola Milman (3, 4)

1 NEEL - QuantECA - Circuits électroniques quantiques Alpes
2 INAC - Institut Nanosciences et Cryogénie
3 MPQ (UMR_7162) - Laboratoire Matériaux et Phénomènes Quantiques
4 ISMO - Institut des Sciences Moléculaires d'Orsay

We make a detailed theoretical description of the two-dimensional nature of a dc-SQUID, analyzing the coupling between its two orthogonal phase oscillation modes. While it has been shown that the mode defined as ''longitudinal" can be initialized, manipulated and measured, so as to encode a quantum bit of information, the mode defined as ''transverse" is usually repelled at high frequency and does not interfere in the dynamics. We show that, using typical parameters of existing devices, the transverse mode energy can be made of the order of the longitudinal one. In this regime, we can observe a strong coupling between these modes, described by an Hamiltonian providing a wide range of interesting effects, such as conditional quantum operations and entanglement. This coupling also creates an atomic-like structure for the combined two mode states, with a V-like scheme.

Mots clés: SQUID; superconducting qubit; non-linear coupling

Domaines: Systèmes mésoscopiques et effet Hall quantique [cond-mat.mes-hall]

Florent Lecocq, Julien Claudon, Olivier Buisson, Pérola Milman. Non-linear coupling between the two oscillation modes of a dc-SQUID. Physical Review Letters, 2011, 107 (19), pp.197002. ⟨10.1103/PhysRevLett.107.197002⟩. ⟨hal-00621266v2⟩