Superconducting circuit and method for protecting the same

Abstract

The application discloses a superconducting circuit and a protection method thereof. The protection method comprises the following steps: providing a substrate on the surface of which a superconducting circuit is formed; and forming a germanium protection layer covering the superconducting circuit on the substrate, so as to reduce or avoid the contact between the surface of the superconducting circuit and the outside world. Since the germanium has high thermal conductivity, good microwave transmission and strong mechanical property, the germanium can not only play an isolation role on the superconducting circuit, but also will not affect the performance of the superconducting circuit, so that the superconducting circuit can be isolated from the outside world without affecting the performance.

Description

Technical Field

[0001] This invention relates to the field of superconducting circuits, and in particular to a superconducting circuit and a method for protecting it. Background Technology

[0002] Superconducting circuits are circuits made using superconducting materials, primarily used in superconducting quantum chips. Superconducting materials are those that exhibit zero resistance and complete reflection of magnetic fields at low temperatures. In superconducting materials, electron pairs are coupled in the form of Cooper pairs, resulting in zero resistance. However, superconducting materials also have certain disadvantages:

[0003] 1. Magnetic field sensitivity: Sensitive to external magnetic fields, which may lead to changes or degradation in circuit performance;

[0004] 2. Stability: It is chemically reactive, readily undergoes reactions, and is easily affected by environmental factors.

[0005] The performance of superconducting circuits can be adversely affected by environmental factors such as electromagnetic interference, thermal fluctuations, and chemical contamination. Therefore, how to avoid these adverse effects on the performance of superconducting circuits is an urgent problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a superconducting circuit and its protection method to solve the problem that the performance of superconducting circuits in the prior art is easily affected by environmental factors, and to isolate the superconducting circuit from the outside world without affecting its performance.

[0007] To solve the above-mentioned technical problems, the present invention provides a protection method for superconducting circuits, characterized in that it includes:

[0008] Provide a substrate with a superconducting circuit formed on its surface;

[0009] A germanium protective layer is formed on the substrate to cover the superconducting circuit, thereby reducing or preventing the surface of the superconducting circuit from contacting the outside environment.

[0010] Preferably, the germanium protective layer is formed in a vacuum environment.

[0011] Preferably, the germanium protective layer is formed using physical vapor deposition, chemical vapor deposition, or molecular beam epitaxy.

[0012] Preferably, when the germanium protective layer is formed using a physical vapor deposition process, the formation process is carried out at room temperature or below room temperature.

[0013] Preferably, prior to the step of forming a germanium protective layer covering the superconducting circuit on the substrate, the method further includes:

[0014] Remove the natural oxide film from the surface of the superconducting circuit.

[0015] Preferably, prior to the step of forming a germanium protective layer covering the superconducting circuit on the substrate, the method further includes:

[0016] The surface of the superconducting circuit is roughened.

[0017] Preferably, the protection method further includes:

[0018] The germanium protective layer is patterned to expose the superconducting circuitry in a predetermined area.

[0019] Preferably, the thickness of the germanium protective layer is more than 10 times the thickness of the superconducting circuit.

[0020] Preferably, the superconducting conductor is formed of aluminum, niobium, titanium, tantalum, or titanium nitride.

[0021] To solve the above-mentioned technical problems, the present invention also provides a superconducting circuit obtained according to the protection method described in any of the foregoing claims.

[0022] Unlike existing technologies, the method for protecting superconducting circuits provided by this invention forms a germanium protective layer on a substrate. The germanium protective layer covers the superconducting circuit on the substrate, reducing or preventing the surface of the superconducting circuit from contacting the outside world. Because germanium has high thermal conductivity, good microwave transmittance, and strong mechanical properties, it can isolate the superconducting circuit without affecting its performance, thus isolating the superconducting circuit from the outside world without affecting its performance.

[0023] The superconducting circuit provided by this invention is obtained according to the protection method described above, and therefore has the same beneficial effects, which will not be repeated here. Attached Figure Description

[0024] Figure 1 A schematic flowchart of a method for protecting superconducting circuits provided in an embodiment of the present invention. Detailed Implementation

[0025] The specific embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0026] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0028] Please refer to Figure 1 This invention provides a protection method for superconducting circuits. The protection method includes the following steps:

[0029] S1: Provides a substrate with superconducting circuits formed on its surface.

[0030] The superconducting circuit includes superconducting devices such as Josephson junctions, resonators, and bit capacitors, as well as superconducting transmission lines electrically connecting these devices. The superconducting circuit can exhibit superconducting properties at approximately 10-100 millikelvin (mK) or approximately 4K. In this embodiment, the superconducting circuit is formed from superconducting materials such as aluminum, niobium, titanium, tantalum, or titanium nitride. These superconducting materials can be deposited using deposition processes such as chemical vapor deposition, physical vapor deposition (e.g., evaporation or sputtering), epitaxial techniques, and other deposition processes, exemplarily including ion beam assisted deposition (IBAD), vacuum evaporation, molecular beam epitaxy (MBE), pulsed laser deposition (PLD), chemical vapor deposition (CVD), sol-gel deposition, and magnetron sputtering.

[0031] S2: A germanium protective layer is formed on the substrate to cover the superconducting circuit, so as to reduce or avoid the surface of the superconducting circuit from contacting the outside world.

[0032] In this embodiment, the thickness of the germanium protective layer is more than 10 times the thickness of the superconducting circuit. In some specific applications, the thickness of the superconducting circuit is on the order of hundreds of nanometers, while the thickness of the germanium protective layer is on the order of micrometers. Germanium is a microwave material with the following characteristics:

[0033] 1. High thermal conductivity: Germanium has a higher thermal conductivity than ordinary metal materials, which can effectively conduct heat;

[0034] 2. Good microwave transmission: Germanium has excellent transmission performance for electromagnetic waves in the microwave band, and has low loss in high-frequency applications, especially in the millimeter wave and submillimeter wave bands, which can ensure that the transmission of microwave signals is unimpeded.

[0035] 3. High mechanical properties: Germanium has high hardness and wear resistance.

[0036] Because the superconducting circuit is covered with a germanium protective layer, it is isolated from the external environment, minimizing or eliminating contact with it. This makes it less susceptible to chemical reactions caused by moisture and oxygen in the environment, and the germanium protective layer also dissipates the heat generated by the superconducting circuit. Furthermore, although the germanium protective layer isolates the surface of the superconducting circuit from the external environment, it exhibits low loss tangent at microwave frequencies, minimizing microwave signal absorption and ensuring efficient transmission and operation of microwave signals within the superconducting circuit without affecting its performance. In addition, the germanium protective layer strengthens the mechanical properties of the superconducting circuit, protecting its surface from mechanical damage during storage and use, thus maintaining its performance.

[0037] In the above manner, the superconducting circuit protection method of this embodiment forms a germanium protective layer to cover the superconducting circuit on the substrate, thereby reducing or avoiding contact between the surface of the superconducting circuit and the outside world. Since germanium has high thermal conductivity, good microwave transmittance and strong mechanical properties, it can not only isolate the superconducting circuit, but also not affect the performance of the superconducting circuit, thus isolating the superconducting circuit from the outside world without affecting its performance.

[0038] In some embodiments of this application, the germanium protective layer is formed in a vacuum environment. The vacuum environment prevents the superconducting material on the surface of the superconducting circuit from being oxidized before the germanium protective layer is formed.

[0039] In some embodiments of this application, the germanium protective layer can be formed using physical vapor deposition (PVD), chemical vapor deposition (CVD), or molecular beam epitaxy (MBE). In particular, physical vapor deposition is preferred. Furthermore, when the germanium protective layer is formed using physical vapor deposition, the formation process is performed at room temperature or below. Performing physical vapor deposition at room temperature or below minimizes the impact on temperature-sensitive superconducting circuits.

[0040] In some embodiments of this application, before the step of forming a germanium protective layer covering the superconducting circuit on the substrate, i.e., step S2, the protection method further includes: removing the natural oxide film on the surface of the superconducting circuit.

[0041] Because superconducting materials, especially aluminum, are chemically reactive and easily oxidized, removing the natural oxide film on the surface of superconducting circuits before applying a germanium protective layer can prevent oxidation from affecting the circuit's performance. The natural oxide film can be removed using ion beam etching (IBE).

[0042] In some embodiments of this application, before the step of forming a germanium protective layer covering the superconducting circuit on the substrate, i.e., step S2, the protection method further includes: roughening the surface of the superconducting circuit.

[0043] Because germanium differs significantly in atomic radius from most superconducting materials, especially aluminum, their crystal structures are not perfectly matched, resulting in a lattice mismatch. Roughening the surface of the superconducting circuit can enhance the adhesion between the germanium protective layer and the circuit. In some applications, controlling the fabrication temperature and rate of the germanium protective layer can also improve the adhesion between the layer and the circuit.

[0044] In some embodiments of this application, the method further includes: patterning a germanium protective layer to expose a superconducting circuit in a predetermined area.

[0045] In operation, the quantum chip needs to connect to external devices, requiring the connection of some superconducting devices or transmission lines on the superconducting circuitry. This necessitates exposing these locations. The location of the predetermined area can be determined based on the required exposure points in the superconducting circuitry. The patterning of the germanium protective layer can be achieved through etching.

[0046] This invention also provides a superconducting circuit obtained according to the protection method of the foregoing embodiments. Because the surface of the superconducting circuit is covered with a germanium protective layer, the superconducting circuit of this embodiment has the following advantages:

[0047] (1) Good heat dissipation: Germanium has high thermal conductivity, which enables it to dissipate the heat generated by the superconducting circuit without affecting the superconducting performance of the superconducting circuit.

[0048] (2) Strong microwave transmittance: Germanium has low loss tangent at microwave frequencies, which can minimize the absorption of microwave signals.

[0049] (3) High chemical stability: Germanium has stable chemical properties and can protect superconducting circuits from chemical contamination.

[0050] (4) High mechanical strength: Germanium has high mechanical strength, which can prevent superconducting circuits from being mechanically damaged.

[0051] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," or "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0052] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A protection method for a superconducting circuit, characterized in that, include: Provide a substrate with a superconducting circuit formed on its surface; The surface of the superconducting circuit is roughened. A germanium protective layer is formed on the substrate to cover the superconducting circuit, thereby reducing or preventing the surface of the superconducting circuit from contacting the outside world, making the superconducting circuit less susceptible to chemical reactions caused by water vapor and oxygen in the environment, and making the surface less susceptible to mechanical damage during storage and use.

2. The protection method according to claim 1, characterized in that, The germanium protective layer is formed in a vacuum environment.

3. The protection method according to claim 1, characterized in that, The germanium protective layer is formed using physical vapor deposition, chemical vapor deposition, or molecular beam epitaxy.

4. The protection method according to claim 3, characterized in that, When the germanium protective layer is formed using a physical vapor deposition process, the formation process is carried out at room temperature or below room temperature.

5. The protection method according to claim 1, characterized in that, Prior to the step of forming a germanium protective layer covering the superconducting circuit on the substrate, the method further includes: Remove the natural oxide film from the surface of the superconducting circuit.

6. The protection method according to claim 1, characterized in that, The protection method further includes: The germanium protective layer is patterned to expose the superconducting circuitry in a predetermined area.

7. The protection method according to claim 1, characterized in that, The thickness of the germanium protective layer is more than 10 times the thickness of the superconducting circuit.

8. The protection method according to claim 1, characterized in that, The superconducting circuit is formed from aluminum, niobium, titanium, tantalum, or titanium nitride.

9. A superconducting circuit obtained by the protection method according to any one of claims 1 to 8.

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