BACKGROUND

The currently claimed embodiments of the present invention relate to superconducting quantum processors, and more specifically, to a modular superconducting quantum processor and a quantum computer using the same and methods for making the modular superconducting quantum processor.

Quantum computation is based on the reliable control of quantum bits (referred to herein throughout as qubits). The fundamental operations required to realize quantum algorithms are a set of single-qubit operations and two-qubit operations which establish correlations between two separate quantum bits. The realization of high fidelity two-qubit operations may be desirable both for reaching the error threshold for quantum computation, and for reaching reliable quantum simulations.

The superconducting quantum processor (or superconducting qubit) includes superconducting metals (e.g., Al, Nb, etc.) on an insulating substrate (e.g., Si or high resistivity Si, Al2O3, etc.). The quantum processor is typically a planar two-dimensional lattice structure of individual qubits linked by a coupler in various lattice symmetry (for example, square, hexagonal, etc.), and a readout structure located on a flip-chip. The couplers can be made of a capacitor, a resonator, a coil or any microwave component that provides a coupling between qubits.

In order to connect input/out signal cables or lines, the quantum processor is packaged in a substrate (e.g., a printed circuit board (PCB)). The materials for the PCB can be, for example, FR4 laminate, ceramic, etc. FR4 is a versatile glass-reinforced epoxy laminate material. FR4 is a composite material having woven fiberglass cloth with an epoxy resin binder. The designation FR4 is created by the National Electrical Manufacturers Association (NEMA).

When the quantum process scales up, as future quantum computers may use a large number of qubits (hundreds to thousands, or more), it may be desirable to address many issues or problems that may occur due to the scaling factor. The various issues that may occur include spurious resonant modes that may be associated with the size of chip, frequency arrangement between qubits to cause cross-talk, and limited fabrication technologies to process growing chip sizes with a large number.

Conventional flipchip technology can be used with qubit chips. However, conventional flipchip methods do not provide frequency flexibility in connecting qubits. Therefore, a need remains for improved quantum processors and methods of producing or assembling the quantum processors.

SUMMARY

An aspect of the present invention is to provide a modular superconducting quantum processor. The modular superconducting quantum processor includes a first superconducting chip comprising a first plurality of qubits each having substantially a first resonance frequency and a second plurality of qubits each having substantially a second resonance frequency, the first resonance frequency being different from the second resonance frequency; a second superconducting chip comprising a third plurality of qubits each having substantially the first resonance frequency and a fourth plurality of qubits each having substantially the second resonance frequency; and an interposer chip connected to said first superconducting chip and to said second superconducting chip, wherein the interposer chip comprises interposer coupler elements configured to couple the second plurality of qubits having substantially the second resonance frequency to the fourth plurality of qubits having substantially the second resonance frequency.

Another aspect of the present invention is to provide a method of making a modular superconducting quantum processor. The method includes providing a first superconducting chip, the first superconducting chip comprising a first plurality of qubits each having substantially a first resonance frequency and a second plurality of qubits each having substantially a second resonance frequency, the first resonance frequency being different from the second resonance frequency; providing a second superconducting chip, the second superconducting chip comprising a third plurality of qubits each having substantially the first resonance frequency and a fourth plurality of qubits each having substantially the second resonance frequency; providing an interposer chip comprising interposer coupler elements configured to couple the second plurality of qubits having substantially the second resonance frequency to the fourth plurality of qubits having substantially the second resonance frequency; mounting the first superconducting chip and the second superconducting chip on a substrate; and mounting the interposer chip on at least a portion of the first superconducting chip, on at least a portion of the second superconducting chip, and on at least a portion of the substrate such that the first plurality of qubits, the second plurality of qubits, the third plurality of qubits and the fourth plurality of qubits are accessible from a side opposite to a side facing the substrate.

A further aspect of the present invention is to provide a quantum computer comprising a modular superconducting quantum processor. The modular superconducting quantum processor includes a first superconducting chip comprising a first plurality of qubits each having substantially a first resonance frequency and a second plurality of qubits each having substantially a second resonance frequency, the first resonance frequency being different from the second resonance frequency; a second superconducting chip comprising a third plurality of qubits each having substantially the first resonance frequency and a fourth plurality of qubits each having substantially the second resonance frequency; and an interposer chip connected to said first superconducting chip and to said second superconducting chip, wherein the interposer chip comprises interposer coupler elements configured to couple the second plurality of qubits having substantially the second resonance frequency to the fourth plurality of qubits having substantially the second resonance frequency.

