Techniques related to vertical silicon-on-metal superconducting quantum interference devices and method of fabricating the same are provided. Also provided are associated flux control and biasing circuitry. A superconductor structure can comprise a silicon-on-metal substrate that can comprise a first superconducting layer, comprising a first superconducting material, between a first crystalline silicon layer and a second crystalline silicon layer. The superconducting structure can also comprise a first via comprising a first Josephson junction and a second via comprising a second Josephson junction. The first via and the second via can be formed between the first superconducting layer and a second superconducting layer, comprising a second superconducting material. An electrical loop around a defined area of the second crystalline silicon layer can comprise the first via comprising the first Josephson junction, the second via comprising the second Josephson junction, the first superconducting layer, and the second superconducting layer.

Qubit circuits having components formed deep in a substrate are described. The qubit circuits can be manufactured using existing integrated-circuit technologies. By forming components such as superconducting current loops, inductive, and/or capacitive components deep in the substrate, the footprint of the qubit circuit integrated within the substrate can be reduced. Additionally, coupling efficiency to and from the qubit can be improved and losses in the qubit circuit may be reduced.

A method for adjusting a resonance frequency of a qubit in a quantum mechanical device includes providing a substrate having a frontside and a backside, the frontside having at least one qubit formed thereon, the at least one qubit comprising capacitor pads; and removing substrate material from the backside of the substrate at an area opposite the at least one qubit to alter a capacitance around the at least one qubit so as to adjust a resonance frequency of the at least one qubit.

One example includes a superconducting current control system. The system includes an inductive coupler comprising a load inductor and a control inductor. The inductive coupler can be configured to inductively provide a control current from the control inductor to a superconducting circuit device based on a load current being provided through the load inductor. The system also includes a current control element comprising a superconducting quantum interference device (SQUID) array comprising a plurality of SQUIDs. The current control element can be coupled to the inductive coupler to control an amplitude of the load current through the load inductor, and thus to control an amplitude of the control current to the superconducting circuit device.

A parametric amplifier for amplifying an input signal includes a resonator comprising a Josephson junction. The Josephson junction comprises a first superconductor component, a second superconductor component and a semiconductor component. The semiconductor component is configured to enable coupling of the first and second superconductor components. The parametric amplifier further comprises a gate electrode configured to apply an electrostatic field to the semiconductor component of the Josephson junction for tuning the parametric amplifier. Such parametric amplifiers are useful for amplifying signals in the microwave frequency range. Tuning the junction by electrostatic gating may allow for improved scalability compared to tuning using magnetic flux. Also provided are the use of the parametric amplifier to amplify a signal; and a method of amplifying a signal.

A device includes a first substrate having a principal surface; a second substrate having a principal surface, in which the first substrate is bump-bonded to the second substrate such that the principal surface of the first substrate faces the principal surface of the second substrate; a circuit element having a microwave frequency resonance mode, in which a first portion of the circuit element is arranged on the principal surface of the first substrate and a second portion of the circuit element is arranged on the principal surface of the second substrate; and a first bump bond connected to the first portion of the circuit element and to the second portion of the circuit element, in which the first superconductor bump bond provides an electrical connection between the first portion and the second portion.

A quantum computing device includes a first chip having a first substrate and one or more qubits disposed on the first substrate. Each of the one or more qubits has an associated resonance frequency. The quantum computing device further includes a second chip having a second substrate and at least one conductive surface disposed on the second substrate opposite the one or more qubits. The at least one conductive surface has at least one dimension configured to adjust the resonance frequency associated with at least one of the one or more qubits to a determined frequency adjustment value.

Methods, devices, and systems are described for forming a superconducting qubit. An example device may comprise a substrate having a first surface and a patterned layer adjacent the substrate and comprising tantalum in an alpha phase. The patterned layer may comprise at least a part of a structure for storing a quantum state.

A hybrid quantum system performs high-fidelity quantum state transduction between a superconducting (SC) microwave qubit and the ground state spin system of a solid-state artificial atom. This transduction is mediated via an acoustic bus connected by piezoelectric transducers to the SC microwave qubit. For SC circuit qubits and diamond silicon vacancy centers in an optimized phononic cavity, the system can achieve quantum state transduction with fidelity exceeding 99% at a MHz-scale bandwidth. By combining the complementary strengths of SC circuit quantum computing and artificial atoms, the hybrid quantum system provides high-fidelity qubit gates with long-lived quantum memory, high-fidelity measurement, large qubit number, reconfigurable qubit connectivity, and high-fidelity state and gate teleportation through optical quantum networks.

A vertical Josephson junction device includes a substrate, and an epitaxial stack formed on the substrate. The vertical Josephson junction device includes a first superconducting electrode embedded in the epitaxial stack, and a second superconducting electrode embedded in the epitaxial stack, the second superconducting electrode being separated from the first superconducting electrode by a dielectric layer. In operation, the first superconducting electrode, the dielectric layer, and the second superconducting electrode form a vertical Josephson junction.