Josephson parameter amplifier and preparation method thereof

Abstract

The preparation method comprises the following steps: preparing a bottom-layer superconducting thin film on the surface of a substrate, preparing a bottom-layer superconducting circuit structure on the bottom-layer superconducting thin film, growing a bottom-layer aluminum thin film in a Josephson junction region, and taking the bottom-layer aluminum thin film as a lower polar plate of the Josephson junction; preparing an upper-layer superconducting circuit structure on the bottom-layer superconducting circuit structure; feeding into an oxidation chamber, and oxidizing in a controlled oxidation environment to obtain a corresponding oxide layer on the surface of the bottom aluminum film; after oxidation treatment, an upper-layer aluminum film is evaporated on the upper-layer superconducting circuit structure and stripped to a preset size, the upper-layer superconducting circuit structure serves as an upper polar plate of a Josephson junction, the area of an intersection area of the upper polar plate and a lower polar plate is 35-45 square micrometers, and the high-performance broadband Josephson parametric amplifier without an independent capacitor is achieved; the performance of the Josephson parametric amplifier is improved; meanwhile, the process complexity and the requirement for preparation equipment are reduced, the preparation efficiency is high, and the preparation cost is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of amplifier design and preparation, in particular to a Josephson parameter amplifier and a preparation method thereof. Background Art

[0002] Typically, a Josephson parametric amplifier consists of an output circuit, an impedance conversion circuit, an independent capacitor, and an LC resonator formed by parallel connection of a superconducting quantum interference device. All known amplifiers require the use of a complex preparation process to prepare this independent capacitor, and currently mainly use dielectric parallel plate capacitors, interdigitated capacitors, vacuum gap capacitors, and their variants. However, these capacitors have their own shortcomings when applied to Josephson parametric amplifiers. Dielectric parallel plate capacitors require redundant preparation processes, and due to defects introduced during the growth process, they usually lead to more dissipation; the excessive structural volume of the interdigitated capacitor leads to inevitable parasitic inductance, which limits the operating frequency range of the Josephson parametric amplifier; the manufacturing yield of vacuum gap capacitors is generally low, the manufacturing repeatability is also poor, and the reliability during use is low.

[0003] In order to overcome the shortcomings of using independent capacitors in existing broadband Josephson parametric amplifiers, improve the preparation yield of the amplifier, simplify the preparation process of the amplifier, and make the amplifier preparation process fully compatible with the superconducting quantum bit preparation process, it is urgent to find a new Josephson parametric amplifier and its preparation method. Summary of the invention

[0004] The purpose of the present invention is to provide a Josephson parametric amplifier and a preparation method thereof, which can effectively solve the problems existing in the above-mentioned prior art.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solution: a method for preparing a Josephson parametric amplifier, comprising the following steps:

[0006] A substrate is provided, and a bottom superconducting thin film is prepared on the surface of the substrate.

[0007] A bottom superconducting circuit structure is prepared on the bottom superconducting film, and a bottom aluminum film is grown in a preset Josephson junction region to serve as a lower electrode of the Josephson junction;

[0008] Fabricate an upper superconducting circuit structure on the lower superconducting circuit structure:

[0009] Coating a photoresist on the bottom superconducting circuit structure, and obtaining the required pattern of the upper superconducting circuit structure on the photoresist through photolithography;

[0010] Ar ion etching is used to remove the oxide layer on the surface of the bottom aluminum film;

[0011] The aluminum film is sent into an oxidation chamber and oxidized in a controlled oxidation environment to obtain a corresponding oxide layer on the surface of the bottom aluminum film;

[0012] After oxidation treatment, an upper aluminum film is evaporated, and a portion of the upper aluminum film is peeled off to obtain a grounding circuit and an upper plate of a Josephson junction of a preset size; and

[0013] The intersection area of ​​the upper electrode plate and the lower electrode plate is 35-45 square microns.

[0014] Preferably, the thickness of the bottom superconducting film is greater than its magnetic field penetration depth, generally greater than 60 nm.

[0015] Wherein, when the bottom superconducting film is a bottom aluminum film, the preparation method based on the bottom aluminum film is as follows:

[0016] Preparing a bottom layer superconducting circuit structure on the bottom layer aluminum film;

[0017] Fabricate an upper superconducting circuit structure on the lower superconducting circuit structure:

[0018] Coating a photoresist on the bottom superconducting circuit structure, and obtaining the required pattern of the upper superconducting circuit structure on the photoresist through photolithography;

[0019] Ar ion etching is used to remove the oxide layer on the surface of the bottom aluminum film;

[0020] The aluminum film is sent into an oxidation chamber and oxidized in a controlled oxidation environment to obtain a corresponding oxide layer on the surface of the bottom aluminum film;

[0021] After oxidation treatment, an upper aluminum film is evaporated, and part of the upper aluminum film is peeled off to obtain a grounding circuit and an upper plate of a Josephson junction of a preset size.

[0022] Preferably, the bottom superconducting film is formed by an aluminum film deposited by electron beam evaporation;

[0023] Preferably, a bottom layer superconducting circuit structure is prepared on the bottom layer aluminum film by photolithography and etching processes;

[0024] Preferably, a photoresist suitable for the lift-off process is spin-coated on the prepared bottom superconducting circuit structure, and a required pattern of the upper superconducting circuit structure is obtained on the photoresist through photolithography and corresponding development;

[0025] Preferably, the aluminum film is placed in an ultra-high vacuum multi-chamber electron beam evaporation system and Ar ion etching is used to remove the oxide layer on the surface of the bottom aluminum film;

[0026] When a superconducting film that is more difficult to oxidize than aluminum is used as the underlying superconducting film, such as a niobium film or a tantalum film, magnetron sputtering or other thin film deposition methods are used to grow the niobium film, the tantalum film or other superconducting film.

[0027] When the bottom superconducting film is a bottom niobium film or a bottom tantalum film, and the preparation method based on the bottom niobium film or the bottom tantalum film is as follows:

[0028] Preparing a bottom superconducting circuit structure on the bottom niobium film or the bottom tantalum film;

[0029] Coating a photoresist on the underlying superconducting circuit structure, and obtaining the required pattern of the Josephson junction region on the photoresist by photolithography;

[0030] Using Ar ion etching to remove the oxide layer on the surface of the bottom niobium film or the bottom tantalum film;

[0031] Vapor-depositing a layer of bottom aluminum film on the bottom superconducting circuit structure, and obtaining the bottom aluminum film in the Josephson junction region by a lift-off process;

[0032] Fabricate an upper superconducting circuit structure on the lower superconducting circuit structure:

[0033] Coating a photoresist on the bottom superconducting circuit structure, and obtaining the required pattern of the upper superconducting circuit structure on the photoresist through photolithography;

[0034] Ar ion etching is used to remove the oxide layer on the surface of the bottom aluminum film;

[0035] The aluminum film is sent into an oxidation chamber and oxidized in a controlled oxidation environment to obtain a corresponding oxide layer on the surface of the bottom aluminum film;

[0036] After oxidation treatment, an upper aluminum film is evaporated, and part of the upper aluminum film is peeled off to obtain a grounding circuit and an upper plate of a Josephson junction of a preset size.

[0037] Based on the above, in each Josephson parametric amplifier preparation method, there are two Josephson junction regions, and each Josephson junction region is prepared with a bottom aluminum film as the lower electrode of the Josephson junction, and an upper aluminum film as the upper electrode of the Josephson junction.

[0038] Preferably, the exposure line widths of the lower plate and the upper plate are both greater than 2 microns.

[0039] Preferably, the thickness of the upper aluminum film and the bottom aluminum film are both greater than 60 nm, and the thickness of the upper aluminum film is greater than the sum of the thickness of the bottom superconducting film and the bottom aluminum film.

[0040] Preferably, the bottom superconducting circuit structure includes a signal input and output line, a ground plane, an impedance conversion circuit, a pump signal line, and a lower electrode; the upper superconducting circuit structure includes a ground circuit and an upper electrode; the signal input and output line is located at one end of the substrate surface; the signal input and output line is connected to the input port of the impedance conversion circuit; the output port of the impedance conversion circuit is connected to the lower electrode, the lower electrode is connected to the upper electrode through the intermediate barrier layer of the Josephson junction, the upper electrode is connected to the ground circuit, the ground circuit is connected to the ground plane, the pump signal line is located at the other end of the substrate surface, one end of the pump signal line is connected to the ground plane, and the other end of the pump signal line is a pump signal input port for feeding the pump signal.

[0041] The present invention also discloses a Josephson parametric amplifier, which is prepared based on the Josephson parametric amplifier preparation method. The amplifier comprises:

[0042] substrate;

[0043] A signal input and output line is formed at one end of the substrate surface;

[0044] An impedance conversion circuit is formed on the surface of the substrate, and the signal input and output lines are connected to the impedance conversion circuit;

[0045] A lower electrode plate is formed on the surface of the substrate, and the output port of the impedance conversion circuit is connected to the lower electrode plate;

[0046] An upper electrode plate is formed on the surface of the intermediate barrier layer obtained after oxidation of the lower electrode plate, the upper electrode plate is connected to a ground circuit, and the other end of the ground circuit is connected to a ground plane;

[0047] A pump signal line is formed at the other end of the substrate surface, and the pump signal line is connected to the ground plane.

[0048] Preferably, the Josephson junction region and the superconducting loop connecting the upper plate and the lower plate of the Josephson junction region form a superconducting quantum interference device, and the superconducting quantum interference device is located in the gap between the impedance conversion circuit, the pump signal line and the ground plane.

[0049] Beneficial effects: The method for preparing a Josephson parametric amplifier of the present invention uses a large-area Josephson junction and cooperates with the required oxidation conditions to obtain the required intermediate barrier layer, thereby realizing a high-performance broadband Josephson parametric amplifier that does not require an independent capacitor; the above-mentioned preparation method can avoid the use of independent capacitors, thereby effectively avoiding the shortcomings of various independent capacitors and improving the performance of the Josephson parametric amplifier; at the same time, the process complexity and the requirements for preparation equipment are reduced, and the stability of the obtained device is improved; no independent capacitor is prepared, and the equipment required for preparing independent capacitors is omitted, so that the method for preparing a Josephson parametric amplifier of the present invention is compatible with the superconducting quantum bit preparation process; the use of a large-junction-area Josephson junction makes high-precision exposure equipment (such as electron beam exposure equipment) no longer necessary; the thickening of the intermediate oxide layer improves the antistatic ability of the Josephson parametric amplifier; the preparation efficiency is high and the preparation cost is greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0051] In the attached picture:

[0052] Figure 1 It is a schematic diagram of the structure of the Josephson parametric amplifier of the present invention;

[0053] Numbers in the figure: 101, substrate; 102, bottom superconducting film; 103, signal input and output lines; 104, ground plane; 105, impedance transformation circuit; 106, lower electrode plate; 107, upper electrode plate; 108, ground circuit; 109, pump signal line. DETAILED DESCRIPTION

[0054] The embodiments of the present invention are described below in conjunction with the drawings in the embodiments of the present invention. The terms used in the implementation mode of the present invention are only used to explain the specific embodiments of the present invention, and are not intended to limit the present invention. The embodiments of the present application are described below in conjunction with the drawings.

[0055] Embodiment 1:

[0056] The bottom superconducting film 102 is a bottom aluminum film, and the preparation method based on the bottom aluminum film is as follows:

[0057] Providing a substrate 101;

[0058] Wherein, the substrate 101 may be a high-resistance intrinsic silicon wafer or a sapphire substrate;

[0059] For the pretreatment of substrate 101:

[0060] The substrate 101 is cleaned to remove impurities on the surface of the substrate 101 and improve the quality of the underlying superconducting film 102 prepared subsequently. Specifically, for high-resistance intrinsic silicon wafers, they are cleaned in acetone, ethanol, and deionized water solutions for 10 minutes each, and then cleaned with a slow-release hydrofluoric acid solution to remove the surface oxide layer. For sapphire substrates, piranha solution can be used for cleaning, and then acetone, ethanol, and deionized water can be used for cleaning for 10 minutes each.

[0061] A bottom superconducting film 102, i.e., a bottom aluminum film, is prepared on the surface of the substrate 101;

[0062] The bottom superconducting film 102 is formed by an aluminum film deposited by electron beam evaporation; the thickness of the bottom superconducting film 102 is greater than the penetration depth of its magnetic field, generally greater than 100 nm.

[0063] The bottom superconducting circuit structure is prepared on the bottom aluminum film by photolithography and etching processes; the bottom superconducting circuit pattern is defined by photolithography technology, and the superconducting film not protected by the photoresist is removed by etching;

[0064] The bottom superconducting circuit structure includes a signal input and output line 103, a ground plane 104, an impedance conversion circuit 105, a pump signal line 109, and a bottom electrode 106, wherein the bottom aluminum film grown in the preset Josephson junction area serves as the bottom electrode 106 of the Josephson junction;

[0065] An upper superconducting circuit structure is prepared on the bottom superconducting circuit structure, wherein the upper superconducting circuit structure includes an upper electrode plate 107 and a grounding circuit 108. The preparation of the upper superconducting circuit structure specifically includes:

[0066] Spin-coat a photoresist suitable for a lift-off process on the prepared bottom superconducting circuit structure, and obtain the required pattern of the upper superconducting circuit structure on the photoresist through photolithography and corresponding development. The required pattern of the upper superconducting circuit structure includes the pattern of the upper electrode plate 107 of the Josephson junction and the pattern of the grounding circuit 108;

[0067] In this embodiment, a double-layer photolithography process is used to facilitate stripping; specifically, the double-layer photolithography process is LOR5B and S1813 photolithography in sequence, LOR5B 500rpm 5s+2500rpm 1min+heat baking at 180℃ 3min; S1813 500rpm 5s+3000rpm 1min+heat baking at 115℃ 2min;

[0068] In this embodiment, exposure is performed using a laser direct writing exposure device; other exposure devices may also be used, such as a contact exposure machine, a stepping exposure machine, and other exposure devices; if a double-layer electron beam photoresist is used, electron beam exposure may also be used; correspondingly, development is performed using a developer corresponding to the photoresist.

[0069] The above was placed in an ultra-high vacuum multi-chamber electron beam evaporation system, and Ar ion etching was used to remove the oxide layer on the surface of the bottom aluminum film;

[0070] Ar ion etching can be performed using a plasma source such as a Kaufman source or a Hall source, with the purpose of completely removing the oxide layer formed in the air on the bottom superconducting film 102 of the Josephson junction region;

[0071] During the ion etching process, etching can be performed facing the ion source or at a certain angle; etching can be performed from several different angles or by continuous rotation; no matter which method is used to etch, in order to ensure that the expected Josephson junction critical current and capacitance are obtained, it is necessary to ensure that the etching process is the same as the etching process used for test junction preparation.

[0072] After the above treatment, the aluminum film is sent to an oxidation chamber for oxidation in a controlled oxidation environment to obtain a corresponding oxide layer on the surface of the bottom aluminum film; the aluminum film is sent to an oxidation chamber for oxidation in a controlled oxidation environment to obtain a corresponding oxide layer on the surface of the bottom aluminum film;

[0073] After oxidation treatment, an upper aluminum film is evaporated, and a part of the upper aluminum film is peeled off to obtain a ground circuit 108 and an upper electrode plate 107 of a Josephson junction of a preset size; wherein the upper aluminum film in the graphic area of ​​the upper electrode plate 107 of the Josephson junction is used as the upper electrode plate 107 of the Josephson junction;

[0074] Among them, the thickness of the upper aluminum film is greater than that of the bottom aluminum film, ensuring the connectivity of the overlapping area of ​​the two aluminum films to improve the device preparation yield; the thickness of the bottom aluminum film is 60-100nm, and the thickness of the upper aluminum film is 80-160nm.

[0075] The exposure line widths of the lower electrode plate 106 and the upper electrode plate 107 are both greater than or much greater than 2 micrometers.

[0076] Embodiment 2:

[0077] Compared with the above embodiment, a superconducting film that is more difficult to oxidize than aluminum is used as the bottom superconducting film 102; for example, a niobium film, a tantalum film or other superconducting film is grown by magnetron sputtering; taking a niobium film or a tantalum film as an example:

[0078] Preparing a bottom superconducting circuit structure on the bottom niobium film or the bottom tantalum film by photolithography and etching processes;

[0079] Coating a photoresist on the above-mentioned bottom superconducting circuit structure, and obtaining the required pattern of the Josephson junction region on the photoresist by photolithography;

[0080] After the above treatment, the substrate is placed in an ultra-high vacuum multi-chamber electron beam evaporation system, and Ar ion etching is used to remove the oxide layer on the surface of the bottom superconducting film 102;

[0081] A layer of aluminum film is evaporated on the bottom superconducting circuit structure, and an aluminum film of the junction region is obtained by a lift-off process; the aluminum film here serves as the lower electrode 106 of the Josephson junction;

[0082] An upper superconducting circuit structure is prepared on the bottom superconducting circuit structure, wherein the upper superconducting circuit structure includes an upper electrode plate 107 and a grounding circuit 108. The preparation of the upper superconducting circuit structure specifically includes:

[0083] Coating a photoresist on the bottom superconducting circuit structure, and obtaining the required pattern of the upper superconducting circuit structure on the photoresist through photolithography;

[0084] After the above treatment, the film was placed in an ultra-high vacuum multi-chamber electron beam evaporation system, and Ar ion etching was used to remove the oxide layer on the surface of the bottom aluminum film;

[0085] After removing the oxide layer, the aluminum film is sent to an oxidation chamber for oxidation in a controlled oxidation environment; a corresponding oxide layer is obtained on the surface of the aluminum film, thereby obtaining a suitable Josephson junction intermediate barrier layer;

[0086] After oxidation treatment, an upper aluminum film is evaporated, and part of the upper aluminum film is peeled off to obtain a ground circuit 108 and an upper electrode plate 107 of a Josephson junction of a preset size; wherein the upper aluminum film in the graphic area of ​​the upper electrode plate 107 of the Josephson junction is used as the upper electrode plate 107 of the Josephson junction.

[0087] In each Josephson parametric amplifier preparation method, there are two Josephson junction regions, and each Josephson junction region is prepared with a bottom aluminum film as the lower electrode 106 of the Josephson junction, and an upper aluminum film as the upper electrode 107 of the Josephson junction.

[0088] Based on Example 1 and Example 2, the present invention also provides a method for testing the critical current and capacitance of Josephson junctions with different junction areas under a specific oxidation environment, which specifically includes:

[0089] Based on the same method as in Example 1 or Example 2, prepare the bottom electrode of the test junction (Josephson junction for testing) and the test connection circuit structure;

[0090] Coating photoresist on the bottom layer circuit, and obtaining the required pattern of the upper layer circuit of the test junction with different junction areas on the photoresist through photolithography;

[0091] The above sample was placed in an ultra-high vacuum multi-chamber electron beam evaporation system, and Ar ion etching was used to remove the surface oxide layer of the bottom aluminum film;

[0092] The circuit with the oxide layer removed is sent into an oxidation chamber for oxidation in a controlled oxidation environment;

[0093] Vapor-depositing an upper aluminum film on the circuit, and obtaining the required test junction and connection circuit through a peeling process;

[0094] Test the room temperature resistance and capacitance of test junctions with different junction areas;

[0095] Through the Ambegaokar-Baratoff relationship The critical current of Josephson junctions of different areas under specific oxidation conditions is estimated, where Δ is the energy gap of the superconducting material, i.e., the aluminum film in the present invention, e is the basic charge, and R n is the room temperature resistance;

[0096] In the process of preparing the amplifier, suitable oxidation conditions and junction area are selected according to the required critical current and capacitance of the superconducting quantum interference device.

[0097] For example, when the aluminum film is oxidized for 1 hour under an oxygen pressure of 100 Torr, the critical current density of the Josephson junction with different junction areas is about 75nA / μm 2 ; Capacitance density is about 45-50fF / μm 2 .

[0098] Embodiment 3:

[0099] The present invention also discloses a Josephson parametric amplifier, which is prepared based on the method of the above-mentioned embodiment 1 or embodiment 2; Figure 1 As shown, the Josephson parametric amplifier includes:

[0100] Substrate 101;

[0101] A signal input / output line 103 is formed at one end of the surface of the substrate 101;

[0102] The impedance conversion circuit 105 is formed on the surface of the substrate 101, and the signal input and output line 103 is connected to the impedance conversion circuit 105;

[0103] The impedance transformation circuit 105 can be implemented in different forms, including a coplanar waveguide impedance mutation circuit, a coplanar waveguide impedance gradient circuit, an impedance gradient circuit using an air bridge, an impedance gradient circuit using a dielectric bridge, and a fishbone line impedance transformation circuit 105;

[0104] A lower electrode plate 106 is formed on the surface of the substrate 101, and the output port of the impedance conversion circuit 105 is connected to the lower electrode plate;

[0105] An upper electrode plate 107 is formed on the surface of the intermediate barrier layer obtained after oxidation of the lower electrode plate 106. The upper electrode plate 107 is connected to a ground circuit 108, and the other end of the ground circuit 108 is connected to the ground plane 104;

[0106] A pump signal line 109 is formed at the other end of the surface of the substrate 101 , one end of the pump signal line 109 is connected to the ground plane 104 , and the other end of the pump signal line 109 is a pump signal input port for feeding the pump signal;

[0107] Among them, the Josephson junction region and the superconducting loop connecting the upper plate 107 and the lower plate 106 of the Josephson junction region form a superconducting quantum interference device, which is located in the gap between the impedance conversion circuit 105, the pump signal line 109 and the ground plane 104; and is respectively connected to the output port of the impedance conversion circuit 105 and the ground plane 104. By using the large-area Josephson junction preparation technology, the superconducting quantum interference device has the required critical current and the required capacitance, and the preparation of a high-performance broadband Josephson parametric amplifier can be realized by combining with the corresponding impedance conversion circuit 105; the use of independent capacitors can be effectively avoided, thereby completely avoiding the defects of various independent capacitors, and the performance of the Josephson parametric amplifier can be improved, while also reducing the process complexity and the requirements for preparation equipment, improving the preparation efficiency, and greatly reducing the preparation cost.

[0108] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. For ordinary technicians in this technical field, after knowing the contents recorded in the present invention, they can make several equivalent changes and substitutions without departing from the principle of the present invention. These equivalent changes and substitutions should also be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for preparing a Josephson parametric amplifier, characterized in that: The steps include: Providing a substrate, and preparing a bottom superconducting thin film on the surface of the substrate; A bottom superconducting circuit structure is prepared on the bottom superconducting film, and a bottom aluminum film is grown in a preset Josephson junction region to serve as a lower electrode of the Josephson junction; Fabricate an upper superconducting circuit structure on the lower superconducting circuit structure: Coating a photoresist on the bottom superconducting circuit structure, and obtaining the required pattern of the upper superconducting circuit structure on the photoresist through photolithography; Ar ion etching is used to remove the oxide layer on the surface of the bottom aluminum film; The aluminum film is sent into an oxidation chamber and oxidized in a controlled oxidation environment to obtain a corresponding oxide layer on the surface of the bottom aluminum film; After oxidation treatment, an upper aluminum film is evaporated, and a portion of the upper aluminum film is peeled off to obtain a grounding circuit and an upper plate of a Josephson junction of a preset size; as well as The intersection area of ​​the upper electrode plate and the lower electrode plate is 35-45 square microns.

2. The method for preparing a Josephson parametric amplifier according to claim 1, characterized in that: The thickness of the bottom superconducting film is greater than its magnetic field penetration depth.

3. The method for preparing a Josephson parametric amplifier according to claim 1, characterized in that: The bottom superconducting film is a bottom aluminum film, and the preparation method based on the bottom aluminum film is as follows: Preparing a bottom layer superconducting circuit structure on the bottom layer aluminum film; Fabricate an upper superconducting circuit structure on the lower superconducting circuit structure: Coating a photoresist on the bottom superconducting circuit structure, and obtaining the required pattern of the upper superconducting circuit structure on the photoresist through photolithography; Ar ion etching is used to remove the oxide layer on the surface of the bottom aluminum film; The aluminum film is sent into an oxidation chamber and oxidized in a controlled oxidation environment to obtain a corresponding oxide layer on the surface of the bottom aluminum film; After oxidation treatment, an upper aluminum film is evaporated, and part of the upper aluminum film is peeled off to obtain a grounding circuit and an upper plate of a Josephson junction of a preset size.

4. The method for preparing a Josephson parametric amplifier according to claim 1, characterized in that: The bottom superconducting film is a bottom niobium film or a bottom tantalum film, and the preparation method based on the bottom niobium film or the bottom tantalum film is as follows: Preparing a bottom superconducting circuit structure on the bottom niobium film or the bottom tantalum film; Coating a photoresist on the underlying superconducting circuit structure, and obtaining the required pattern of the Josephson junction region on the photoresist by photolithography; Using Ar ion etching to remove the oxide layer on the surface of the bottom niobium film or the bottom tantalum film; Vapor-depositing a layer of bottom aluminum film on the bottom superconducting circuit structure, and obtaining the bottom aluminum film in the Josephson junction region by a lift-off process; Fabricate an upper superconducting circuit structure on the lower superconducting circuit structure: Coating a photoresist on the bottom superconducting circuit structure, and obtaining the required pattern of the upper superconducting circuit structure on the photoresist through photolithography; Ar ion etching is used to remove the oxide layer on the surface of the bottom aluminum film; The aluminum film is sent into an oxidation chamber and oxidized in a controlled oxidation environment to obtain a corresponding oxide layer on the surface of the bottom aluminum film; After oxidation treatment, an upper aluminum film is evaporated, and part of the upper aluminum film is peeled off to obtain a grounding circuit and an upper plate of a Josephson junction of a preset size.

5. A method for preparing a Josephson parametric amplifier according to claim 3 or 4, characterized in that: There are two Josephson junction regions, and in each Josephson junction region, a bottom aluminum film is prepared as a lower electrode plate of the Josephson junction, and an upper aluminum film is prepared as an upper electrode plate of the Josephson junction.

6. The method for preparing a Josephson parametric amplifier according to claim 5, characterized in that: The exposure line widths of the lower electrode plate and the upper electrode plate are both greater than 2 microns.

7. The method for preparing a Josephson parametric amplifier according to claim 5, characterized in that: The thickness of the upper aluminum film and the bottom aluminum film are both greater than 60nm, and the thickness of the upper aluminum film is greater than the sum of the thickness of the bottom superconducting film and the bottom aluminum film.

8. The method for preparing a Josephson parametric amplifier according to claim 5, characterized in that: The bottom superconducting circuit structure includes a signal input / output line, a ground plane, an impedance conversion circuit, a pump signal line, and a lower electrode; the upper superconducting circuit structure includes a ground circuit and an upper electrode; the signal input / output line is located at one end of the substrate surface; the signal input / output line is connected to the input port of the impedance conversion circuit; the output port of the impedance conversion circuit is connected to the lower electrode, the lower electrode is connected to the upper electrode through the intermediate barrier layer of the Josephson junction, the upper electrode is connected to the ground circuit, the ground circuit is connected to the ground plane, the pump signal line is located at the other end of the substrate surface, one end of the pump signal line is connected to the ground plane, and the other end of the pump signal line is a pump signal input port for feeding the pump signal.

9. A Josephson parametric amplifier, characterized in that: The Josephson parametric amplifier is prepared based on the preparation method of any one of claims 6 to 8, and the amplifier comprises: substrate; A signal input and output line is formed at one end of the substrate surface; An impedance conversion circuit is formed on the surface of the substrate, and the signal input and output lines are connected to the impedance conversion circuit; A lower electrode plate is formed on the surface of the substrate, and the output port of the impedance conversion circuit is connected to the lower electrode plate; An upper electrode plate is formed on the surface of the intermediate barrier layer obtained after oxidation of the lower electrode plate, the upper electrode plate is connected to a ground circuit, and the other end of the ground circuit is connected to a ground plane; A pump signal line is formed at the other end of the substrate surface, and the pump signal line is connected to the ground plane.

10. A Josephson parametric amplifier according to claim 9, characterized in that: The Josephson junction region and the superconducting loop connecting the upper plate and the lower plate of the Josephson junction region form a superconducting quantum interference device, and the superconducting quantum interference device is located in the gap between the impedance conversion circuit, the pump signal line and the ground plane.

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