CN-122026047-A - Compact superconducting resonator based on space filling curve, preparation method, design method and application

CN122026047ACN 122026047 ACN122026047 ACN 122026047ACN-122026047-A

Abstract

The invention discloses a compact superconducting resonator based on a space filling curve, a preparation method, a design method and application thereof, wherein the resonator comprises a space filling curve resonator main body formed by superconducting thin films, wherein the space filling curve continuously traverses a limited plane area without crossing the area; the space filling curve resonator main body and the coplanar waveguide transmission line are coupled through capacitance or inductance so as to realize signal reading. The compact superconducting resonator can be widely applied to quantum bit readout, microwave filters and low-temperature quantum microwave devices, and has high integration level, low loss and good expandability.

Inventors

SUN GUOZHU
LI BINGLIN
CAO CHUNHAI
WU PEIHENG
YANG SHIYAO
JIANG JUNLIANG
Zang Siming
Hou Ziru
SONG HAIFENG
GUO TINGTING
ZHANG KAIXUAN
ZHU JIYUAN

Assignees

南京大学
合肥国家实验室

Dates

Publication Date: 20260512
Application Date: 20260130

Claims (10)

1. A compact superconducting resonator based on a space-filling curve, comprising: A space-filling curve resonator body composed of superconducting thin films, the space-filling curve traversing a defined planar region continuously and without intersecting the region; The coplanar waveguide transmission line comprises a central conductor band and ground planes positioned on two sides of the central conductor band; The space filling curve resonator main body and the coplanar waveguide transmission line are coupled through capacitance or inductance to realize signal reading.
2. The compact superconducting resonator according to claim 1, wherein the space-filling curve is a Hilbert curve or a Peano curve, and the material of the superconducting thin film is at least one selected from tantalum, niobium nitride, titanium nitride, or aluminum.
3. The compact superconducting resonator according to claim 1 or 2, characterized in that the resonator is of a two-dimensional planar structure and comprises a substrate (101), a space-filling curve resonator body (102) arranged on the substrate (101) and a coplanar waveguide transmission line (103) coupled with the substrate, wherein the space-filling curve resonator body (102) is of an open-ended structure, and a ground plane of the coplanar waveguide transmission line (103) is arranged around the space-filling curve resonator body (102) and does not enter the interior of a traversing area where the body is arranged.
4. The compact superconducting resonator according to claim 1 or 2, characterized in that the resonator is of a three-dimensional flip-chip structure comprising an upper chip and a lower chip; The lower chip comprises a lower substrate (210), a coplanar waveguide transmission line (211) arranged on the lower substrate (210), and a plurality of metal posts (212) formed on ground planes at two sides of the coplanar waveguide transmission line (211); The upper chip comprises an upper substrate (220), a space filling curve resonator main body (221) arranged on the upper substrate (220), and a bridging superconducting film (222); The metal column (212) is connected with the bridging superconducting film (222) in a bonding way, so that the bridging superconducting film (222) and the metal column (212) jointly form a superconducting air bridge crossing a central conductor belt of the coplanar waveguide transmission line (211), and three-dimensional superconducting grounding interconnection between an upper chip and a lower chip is realized; The space-filling curve resonator body (221) and coplanar waveguide transmission line (211) are coupled by an inter-chip capacitance or an inter-chip inductance.
5. The compact superconducting resonator according to claim 4, wherein the metal posts (212) are indium posts having a diameter of 5 to 600 microns and a height of 4 to 15 microns, and the bridging superconducting thin film (222) is rectangular or square in shape.
6. A compact superconducting resonator according to claim 4 or claim 5, wherein the width of the centre conductor strip of the coplanar waveguide transmission line (211) and the spacing between it and the ground plane in the region of overlap of the space-filling curved resonator body (221) with the perpendicular projection of the coplanar waveguide transmission line (211) is not less than 2 times the corresponding dimension of the non-overlapping region.
7. A method of making a compact superconducting resonator as claimed in claim 3, comprising the steps of: patterning the superconducting thin film by an etching process or a stripping process to form a space filling curve resonator main body (102) and a coplanar waveguide transmission line (103); the etching process comprises the steps of firstly depositing a superconducting film, forming a pattern through photoetching, developing and dry or wet etching, and the stripping process comprises the steps of firstly forming the pattern through photoetching, then depositing the superconducting film and stripping to obtain the pattern.
8. A method of making a compact superconducting resonator as claimed in claim 4 or claim 5, comprising the steps of: Preparing a space-filling curve resonator body (221) and a bridging superconducting film (222) on an upper substrate (220); Preparing a coplanar waveguide transmission line (211) and a metal column (212) on a lower substrate (210); And (3) carrying out flip-chip alignment and lamination on the upper chip and the lower chip, and connecting the metal column (212) with the bridging superconducting film (222) to form a three-dimensional superconducting grounding structure.
9. A method for designing the resonant frequency of the compact superconducting resonator of any one of claims 1-6, comprising the steps of: Determining design parameters of a space filling curve resonator main body, wherein the design parameters at least comprise iteration orders of the space filling curve, conductor widths, ground intervals and side lengths of areas occupied by the resonator main body; at least one parameter of iteration order, conductor width, interval to ground and side length is adjusted to meet the design requirement of the target resonant frequency.
10. Use of a compact superconducting resonator based on a space-filling curve according to any of claims 1-6, for a superconducting qubit readout resonator, a superconducting parametric amplifier or a low temperature quantum microwave device.

Description

Compact superconducting resonator based on space filling curve, preparation method, design method and application Technical Field The invention relates to the technical field of superconducting quantum chip integration, in particular to a compact superconducting resonator based on a space filling curve, a preparation method, a design method and application. Background The superconducting quantum chip is a basic element for realizing quantum computing and quantum information processing, and a core circuit of the superconducting quantum chip generally comprises superconducting qubits, a readout resonator, a coupling line, control wiring and the like. In superconducting circuits, microwave resonators are used as qubit readout and quantum state measurement elements, whose performance can affect readout fidelity and quantum coherence time. Existing superconducting resonators mostly employ lumped LC parametric structures or distributed parametric structures, such as quarter-wavelength resonators (λ/4 resonator), half-wavelength resonators (λ/2 resonator), and variants thereof. These structures are typically implemented in coplanar waveguide (CPW) form, with the resonant frequency being determined by the equivalent electrical length of the transmission line. At typical operating frequency bands (about 4-8 GHz), the physical dimensions of such resonators typically reach hundreds of microns to several millimeters, one of the highest area-on-chip components. This large space occupation severely limits the integration level and multi-bit expansion capability of the quantum chip. Therefore, on the premise of not changing the working frequency band and the electrical performance of the resonator, how to realize longer equivalent electrical length in a limited chip area, thereby reducing the occupied size of the resonator, and becoming a key problem to be solved in the design of the superconducting quantum circuit. The improvement of the space utilization of the resonator circuit in a limited area from the geometric structure level becomes one of the important ways to achieve the miniaturization of the resonator. Space-filling curves (Space-filling curves) are a type of geometric path capable of traversing the entire plane continuously and without crossing in a limited two-dimensional area, and have high Space utilization and extensible iteration characteristics. Typical representations include Hilbert curves, peano curves, and the like. The superconducting resonator constructed based on the space filling curve can remarkably reduce the occupied area under the condition of keeping the equivalent electric length or not changing the resonant frequency, thereby realizing compact layout and high-density integration. On the other hand, with the increase of the complexity of quantum circuits, the requirement of multi-node interconnection and electromagnetic isolation cannot be met by relying on single-chip planar wiring alone. The Flip-chip (Flip-chip) structure is used as a three-dimensional integration mode, and vertical interconnection can be realized through metal columns (such as indium columns) between the upper chip and the lower chip, so that a signal path is shortened, parasitic modes are restrained, and circuit stability is improved. However, the existing flip-chip structure generally has the problems of complex process, high alignment precision, non-superconducting phase formation of an interface and the like, and causes uneven grounding and additional microwave loss at low temperature. Therefore, it is needed to provide a compact superconducting resonator structure based on a space filling curve and a preparation method thereof, wherein the compact superconducting resonator structure can realize long electric length resonance characteristics in a limited area, and can realize high space utilization rate through controllable geometric iteration of the space filling curve by adopting a two-dimensional plane grounding or three-dimensional flip-chip grounding mode, so that the device area can be further reduced under the condition of keeping the resonance frequency unchanged. The invention provides an improvement scheme aiming at the problems, and a space filling curve (such as a Hilbert curve or a Peano curve) is applied to the design of a two-dimensional and three-dimensional integrated superconducting resonator to form a multi-layer superconducting microwave device framework with the characteristics of miniaturization, high reliable grounding and flexible coupling. Disclosure of Invention The invention aims to provide a compact superconducting resonator based on a space filling curve, a preparation method, a design method and application thereof, so as to solve the problems of large volume, limited integration, complex three-dimensional interconnection, uneven grounding and the like of the traditional superconducting resonator. The technical scheme for realizing the purpose of the invention is that the compact super