Abstract: Systems and methods are provided for a tunable transmon qubit. The qubit includes a first Josephson junction on a first path between a transmission line and a circuit ground and second and third Josephson junctions arranged in parallel with one another on a second path between the transmission line and the circuit ground to form a direct current superconducting quantum interference device (DC SQUID). The DC SQUID is in parallel with the first Josephson junction. A capacitor is arranged in parallel with the first Josephson junction and the DC SQUID on a third path between the transmission line and the circuit ground as to form, in combination with the first path, an outer loop of the tunable transmon qubit. A bias circuit is configured to provide a constant bias flux to one of the DC SQUID and the outer loop of the tunable transmon qubit.

Abstract: A superconducting system is provided that includes a coplanar superconducting circuit. The coplanar superconducting circuit includes a first ground plane region, a second ground plane region electrically isolated from the first ground plane region by portions of the coplanar superconducting circuit, and a tunable coupler having a first port and a second port. The tunable coupler comprises a variable inductance coupling element coupled between the first port and the second port, a first termination inductor having a first end coupled between a first end of the variable inductance element and a second end coupled to the first ground plane region, and a second termination inductor having a first end coupled between a second end of the variable inductance element and a second end coupled to the second ground plane region.

Abstract: Quantum systems are provided, including a qubit and a transmission line resonator having an associated resonant wavelength. A coupling capacitor is configured to capacitively couple the qubit to the transmission line resonator. A transformer is configured to inductively couple the qubit to the transmission line resonator. A selected one of an associated capacitance of the coupling capacitor and an associated mutual inductance of the transformer is a function of a location of the qubit along the transmission line resonator.

Abstract: Quantum systems are provided, including a qubit and a transmission line resonator having an associated resonant wavelength. A coupling capacitor is configured to capacitively couple the qubit to the transmission line resonator. A transformer is configured to inductively couple the qubit to the transmission line resonator. A selected one of an associated capacitance of the coupling capacitor and an associated mutual inductance of the transformer is a function of a location of the qubit along the transmission line resonator.

Abstract: Systems and methods are provided for a tunable transmon qubit. The qubit includes a first Josephson junction on a first path between a transmission line and a circuit ground and second and third Josephson junctions arranged in parallel with one another on a second path between the transmission line and the circuit ground to form a direct current superconducting quantum interference device (DC SQUID). The DC SQUID is in parallel with the first Josephson junction. A capacitor is arranged in parallel with the first Josephson junction and the DC SQUID on a third path between the transmission line and the circuit ground as to form, in combination with the first path, an outer loop of the tunable transmon qubit. A bias circuit is configured to provide a constant bias flux to one of the DC SQUID and the outer loop of the tunable transmon qubit.