Controllable coupling of superconducting flux qubits

Abstract

We have realized controllable coupling between two three-junction flux qubits by inserting an additional coupler loop between them, containing three Josephson junctions. Two of these are shared with the qubit loops, providing strong qubit--coupler interaction. The third junction gives the coupler a nontrivial current--flux relation; its derivative (i.e., the susceptibility) determines the coupling strength J, which thus is tunable in situ via the coupler's flux bias. In the qubit regime, J was varied from ~45 (antiferromagnetic) to ~ -55 mK (ferromagnetic); in particular, J vanishes for an intermediate coupler bias. Measurements on a second sample illuminate the relation between two-qubit tunable coupling and three-qubit behavior.

REVTeX4, 4pp., 6 figs, 10 EPS figure files; N.B.: "Alec" is my first, and "Maassen van den Brink" my family name. v2: included discussion of a 2nd sample with sign-tunability v3:rewritten for publication

References in corpus (8)

• Spectroscopy on two coupled flux qubits
• Tunable coupling scheme for flux qubits at the optimal point
• Four-qubit device with mixed couplings
• Switchable resonant coupling of flux qubits
• Direct Josephson coupling between superconducting flux qubits
• Mediated tunable coupling of flux qubits
• Possible implementation of adiabatic quantum algorithm with superconducting flux qubits
• Realization of a classical counterpart of a scalable design for adiabatic quantum computation

Cited by in corpus (16)

• Coupling Superconducting Qubits via a Cavity Bus
• Using Sideband Transitions for Two-Qubit Operations in Superconducting Circuits
• Tuning the Gap of a Superconducting Flux Qubit
• Generation of squeezed states of microwave radiation in a superconducting resonant circuit
• Interqubit coupling mediated by a high-excitation-energy quantum object
• Large-amplitude driving of a superconducting artificial atom: Interferometry, cooling, and amplitude spectroscopy
• Long-range coupling and scalable architecture for superconducting flux qubits
• Coupling superconducting flux qubits at optimal point via dynamic decoupling with the quantum bus
• Protecting entanglement in superconducting qubits
• Strong tunable coupling between a superconducting charge and phase qubit
• Spectroscopy of superconducting charge qubits coupled by a Josephson inductance
• Switchable coupling for superconducting qubits using double resonance in the presence of crosstalk
• Two-dimensional Ising model with competing interactions and its application to clusters and arrays of $\pi$-rings and adiabatic quantum computing
• Quantum theory of the low-frequency linear susceptibility of interferometer-type superconducting qubits
• Entanglement and Bell States in Superconducting Flux Qubits
• Stability of longitudinal coupling for Josephson charge qubits