title: Flux qubits with long coherence times for hybrid quantum circuits.
abstract: We present measurements of superconducting flux qubits embedded in a three dimensional copper cavity. The qubits are fabricated on a sapphire substrate and are measured by coupling them inductively to an on-chip superconducting resonator located in the middle of the cavity. At their flux-insensitive point, all measured qubits reach an intrinsic energy relaxation time in the 6-20  μs range and a pure dephasing time comprised between 3 and 10  μs. This significant improvement over previous works opens the way to the coherent coupling of a flux qubit to individual spins.
authors.affiliation: Quantronics Group, SPEC, IRAMIS, DSM, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: M
authors.initials: M
authors.lastname: Stern
authors.affiliation: Forschungszentrum Jülich, Peter Grünberg Institut (PGI-2), 52425 Jülich, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Catelani
authors.affiliation: Quantronics Group, SPEC, IRAMIS, DSM, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Kubo
authors.affiliation: Quantronics Group, SPEC, IRAMIS, DSM, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: C
authors.initials: C
authors.lastname: Grezes
authors.affiliation: Quantronics Group, SPEC, IRAMIS, DSM, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: A
authors.initials: A
authors.lastname: Bienfait
authors.affiliation: Quantronics Group, SPEC, IRAMIS, DSM, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: D
authors.initials: D
authors.lastname: Vion
authors.affiliation: Quantronics Group, SPEC, IRAMIS, DSM, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: D
authors.initials: D
authors.lastname: Esteve
authors.affiliation: Quantronics Group, SPEC, IRAMIS, DSM, CEA Saclay, 91191 Gif-sur-Yvette, France.
authors.forename: P
authors.initials: P
authors.lastname: Bertet