Abstract: A non-linear superconducting quantum circuit having a first mode and a second mode is disclosed, wherein the first mode and the second mode have respective resonant frequencies. The circuit is configured such that the resonant frequency of the second mode is substantially 2N times the resonant frequency of the first mode when a predetermined current of a constant intensity is applied to the circuit. The circuit intrinsically performs a resonant 2N-to-1 photon exchange between respectively the first mode and the second mode, with N being a positive integer, thus improving the non-linear superconducting quantum circuit. When this circuit receives a predetermined current and when the second mode is driven appropriately, the circuit can stabilize a cat-qubit. In order to perform quantum measurements on this circuit, the drive of the second mode is turned off, thus switching to a no-drive manifold such that the quantum measurements can be performed.

Abstract: A non-linear superconducting quantum circuit having a first mode and a second mode is disclosed, wherein the first and second modes have respective resonant frequencies. The circuit is configured such that the resonant frequency of the second mode is substantially 2N times the resonant frequency of the first mode when a predetermined current of a constant intensity is applied to the circuit. The circuit intrinsically performs a resonant 2N-to-1 photon exchange between the first and second modes, with N being a positive integer, and thus improving the circuit. When this circuit receives a predetermined current and when the second mode is driven appropriately, the circuit can stabilize a cat-qubit. In a symmetrical version of this circuit, a flux line has been developed to allow RF coupling to the second mode and not to the first mode, allowing the stabilization to be turned off and quantum measurements to be performed.

Abstract: A non-linear superconducting quantum circuit comprising at least one resonant portion and an asymmetrical threaded superconducting quantum interference device connected to said at least one resonant portion galvanically, said non-linear superconducting circuit having a first mode with a first resonant frequency and a second mode with a second resonant frequency, the ratio between said first resonant frequency and said second resonant frequency being different from ½, said at least one resonant portion being configured with inductance and capacitance values of its symbolic representation which induce with said asymmetrical threaded superconducting quantum interference device said first mode and said second mode such that, said non-linear superconducting quantum circuit has zero-point fluctuations of the superconducting phase across the asymmetrical threaded superconducting quantum interference device for the first mode and the second mode which are superior or equal to 0.05 rad.

Abstract: A non-linear superconducting quantum circuit comprising at least one resonant portion and an asymmetrical threaded superconducting quantum interference device connected to said at least one resonant portion galvanically, said non-linear superconducting circuit having a first mode with a first resonant frequency and a second mode with a second resonant frequency, the ratio between said first resonant frequency and said second resonant frequency being different from ½, said at least one resonant portion being configured with inductance and capacitance values of its symbolic representation which induce with said asymmetrical threaded superconducting quantum interference device said first mode and said second mode such that, said non-linear superconducting quantum circuit has zero-point fluctuations of the superconducting phase across the asymmetrical threaded superconducting quantum interference device for the first mode and the second mode which are superior or equal to 0.05 rad.

Abstract: A non-linear superconducting quantum circuit (circuit) comprises a resonant portion and an asymmetrical threaded superconducting quantum interference device (ATS), connected galvanically, and which implements first and second modes with respective resonant frequencies, wherein the ratio between the resonant frequencies is different by 1/2. The resonant portion has a symbolic representation comprising a linear resonant portion implemented with an inductor and a capacitor, and a non-linear resonant portion implemented with a capacitor and the ATS, wherein the linear and non-linear resonant portions are connected galvanically and are arranged such that one has elements connected in series, and the other has elements connected in parallel. The resonant portion is configured with inductance and capacitance values which induce, with the ATS, the first and second modes such that the circuit has zero-point fluctuations of the superconducting phase across the ATS for the first and second modes at or above 0.05 rad.

Abstract: The disclosure notably relates to a non-linear superconducting quantum circuit having a first mode and a second mode. Each of the first mode and the second mode has a respective resonant frequency. The circuit is configured such that the resonant frequency of the second mode is substantially 2N times the resonant frequency of the first mode when a predetermined current of a constant intensity is applied to the circuit. The circuit thereby performs intrinsically a resonant 2N-to-1 photon exchange between respectively the first mode and the second mode, N being a positive integer. This forms an improved non-linear superconducting quantum circuit.

Abstract: A superconducting detection device for detecting a single microwave photon, including: —a quantum system with two energy levels of which the ground state and an excited state are controllable and detectable, the quantum system being designed to allow modulable three-wave interaction; —a buffer resonator arranged to receive an incident single microwave photon; —a highly dissipative auxiliary resonator arranged to discharge a photon; and —a reading device arranged to detect the state of the two-level quantum system; the buffer resonator and the auxiliary resonator are coupled to the quantum system; and the excited state of the quantum system and the photon of the auxiliary resonator are created in response to the reception of the incident photon in the buffer resonator and to the application of parametric pumping to the device. A method for detecting a single microwave photon implemented by a device according to the invention.

Abstract: The present invention relates to an inductive dipole element for a superconducting microwave quantum circuit. The dipole element comprises a DC-SQUID formed by a pair of Josephson junctions shunted by an inductance, wherein the Josephson junctions have equal energy, and the Josephson junctions and the inductance are arranged such that each of the junctions forms a loop with the inductance. The two loops are asymmetrically threaded with external magnetic DC fluxes ?ext1 and ?ext2, respectively, such that ?ext1=? and ?ext2=0, wherein parametric pumping is enabled by modulating the total flux ??=?ext,1+?ext,2 threading the dipole element, thereby allowing even-wave mixing between modes that participate in the dipole element with no Kerr-like interactions.

Abstract: A superconducting detection device for detecting a single microwave photon, including: —a quantum system with two energy levels of which the ground state and an excited state are controllable and detectable, the quantum system being designed to allow modulable three-wave interaction; —a buffer resonator arranged to receive an incident single microwave photon; —a highly dissipative auxiliary resonator arranged to discharge a photon; and—a reading device arranged to detect the state of the two-level quantum system; the buffer resonator and the auxiliary resonator are coupled to the quantum system; and the excited state of the quantum system and the photon of the auxiliary resonator are created in response to the reception of the incident photon in the buffer resonator and to the application of parametric pumping to the device. A method for detecting a single microwave photon implemented by a device according to the invention.

Abstract: The present invention relates to an inductive dipole element for a superconducting microwave quantum circuit. The dipole element comprises a DC-SQUID formed by a pair of Josephson junctions shunted by an inductance, wherein the Josephson junctions have equal energy, and the Josephson junctions and the inductance are arranged such that each of the junctions forms a loop with the inductance. The two loops are asymmetrically threaded with external magnetic DC fluxes ?ext1 and ?ext2, respectively, such that ?ext1=? and ?ext2=0, wherein parametric pumping is enabled by modulating the total flux ??=?ext,1+?ext,2 threading the dipole element, thereby allowing even-wave mixing between modes that participate in the dipole element with no Kerr-like interactions.