Techniques for creating an offset embedded ground plane cutout for a qubit device to facilitate frequency tuning of the qubit device are presented. A qubit device can comprise a first substrate and second substrate in a flip-chip assembly. The qubit chip assembly can comprise a qubit component fabricated on the first substrate. The qubit component can comprise a Josephson junction (JJ) circuit that can be offset from a center point of the qubit component. The qubit chip assembly can comprise an embedded ground plane situated on a surface of the qubit chip assembly. A cutout section can be formed in the ground plane and positioned over the JJ circuit. The cutout section can enable access of an optical signal or magnetic flux to the JJ circuit. A frequency of the qubit component can be tuned based on application of the optical signal or magnetic flux to the JJ circuit.

Devices, systems, methods, computer-implemented methods, apparatus, and/or computer program products that can facilitate an epitaxial Josephson junction transmon device are provided. According to an embodiment, a device can comprise a substrate. The device can further comprise an epitaxial Josephson junction transmon device coupled to the substrate. According to an embodiment, a device can comprise an epitaxial Josephson junction transmon device coupled to a substrate. The device can further comprise a tuning gate coupled to the substrate and formed across the epitaxial Josephson junction transmon device. According to an embodiment, a device can comprise a first superconducting region and a second superconducting region formed on a substrate. The device can further comprise an epitaxial Josephson junction tunneling channel coupled to the first superconducting region and the second superconducting region.

A device includes a first substrate formed of a first material that exhibits a threshold level of thermal conductivity. The threshold level of thermal conductivity is achieved at a cryogenic temperature range in which a quantum circuit operates. In an embodiment, the device also includes a second substrate disposed in a recess of the first substrate, the second substrate formed of a second material that exhibits a second threshold level of thermal conductivity. The second threshold level of thermal conductivity is achieved at a cryogenic temperature range in which a quantum circuit operates. In an embodiment, at least one qubit is disposed on the second substrate. In an embodiment, the device also includes a transmission line configured to carry a microwave signal between the first substrate and the second substrate.

The present disclosure relates to routing superconducting wires in superconducting circuits and in particular to efficiently routing superconducting wires that meet inductance requirements. The superconducting wire routing technique involves modeling the target location not only as a physical location, but as a physical location (e.g., x, y, and z dimensions) combined with inductance (e.g., a target inductance range). One or more other constraints may also be included in the modeling, such as a number of wires that would need to be moved/lifted, a number of circuit-vias allowing passage through layers of the circuit, an amount of cross-coupling with other inductors, and a number of wire segments.

The subject disclosure is directed towards layered substrate structures with aligned optical access to electrical devices formed thereon for laser processing and electrical device tuning. According to an embodiment, a layered substrate structure is provided that comprises an optical substrate having a first surface and a second surface and a patterned bonding layer formed on the second surface that comprises a bonding region and an open region, wherein the open region exposes a portion of the second surface. The layered substrate structure further comprises a device chip bonded to the patterned bonding layer via the bonding region and comprising at least one electrical component aligned with the optical substrate and the open region. The at least one electrical component can include for example, a thin film wire, an air bridge, a qubit, an electrode, a capacitor or a resonator.

A system includes a quantum processor includes a plurality of qubits. For each qubit, there is a circulator operative to receive a control signal and an output signal from the qubit. An isolator is coupled to an output of the circulator. A quantum-limited amplifier is coupled to an output of the isolator and configured to provide an output of the qubit. A multiplexor (MUX) is configured to frequency multiplex the outputs of at least two of the plurality of qubits as a single output of the quantum processor.

A method of producing a quantum circuit includes forming a mask on a substrate to cover a first portion of the substrate, implanting a second portion of the substrate with ions, and removing the mask, thereby providing a nanowire. The method further includes forming a first lead and a second lead, the first lead and the second lead each partially overlapping the nanowire. In operation, a portion of the nanowire between the first and second leads forms a quantum dot, thereby providing a quantum dot Josephson junction. The method further includes forming a third lead and a fourth lead, one of the third and fourth leads partially overlapping the nanowire, wherein the third lead is separated from the fourth lead by a dielectric layer, thereby providing a Dolan bridge Josephson junction. The nanowire is configured to connect the quantum dot Josephson junction and the Dolan bridge Josephson junction in series.

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.

An aspect includes one or more board layers. A first chip cavity is formed within the one or more board layers, wherein a first Josephson amplifier or Josephson mixer is disposed within the first chip cavity. The first Josephson amplifier or Josephson mixer comprises at least one port, each port connected to at least one connector disposed on at least one of the one or more board layers, wherein at least one of the one or more board layers comprises a circuit trace formed on the at least one of the one or more board layers.

A flux-biasing device includes a set of magnetic flux generating members. A first magnetic flux generating member is configured to magnetically interact with a first qubit from a set of qubits of a quantum processor such that a first magnetic flux of the first member causes a first change in a first resonance frequency of the first qubit by a first frequency shift value. Each non-corresponding magnetic flux generating member of the set is well separated from qubits corresponding to other magnetic flux generating members of the set such that qubits corresponding to other members exhibit less than a threshold value of resonance frequency shift as a result of a magnetic flux of a non-corresponding member.