A balanced superconducting quantum interference device microwave amplifier and its fabrication method

Abstract

This invention provides a balanced superconducting quantum interference device (SQUID) microwave amplifier and its fabrication method. The balanced SQUID microwave amplifier includes a first 3dB orthogonal directional coupler, a first impedance matching network, a second impedance matching network, a first superconducting quantum interference device (SQUID), a second superconducting quantum interference device (SQUID), a third impedance matching network, a fourth impedance matching network, and a second 3dB orthogonal directional coupler. The entire circuit of the balanced SQUID microwave amplifier of this invention is SQUID-symmetric. Compared to a single-channel SQUID microwave amplifier circuit, the balanced SQUID microwave amplifier not only significantly improves input-output matching performance and expands the device's operating bandwidth, making cascading easier, but also improves amplifier saturation power and stability. The balanced SQUID microwave amplifier is fabricated using planar micro / nano fabrication technology, which is compatible with most existing superconducting device fabrication processes, and can greatly improve the integration of related cryogenic detection systems.

Description

Technical Field

[0001] This invention belongs to the field of superconducting electronics technology and relates to a balanced superconducting quantum interference device microwave amplifier and its fabrication method. Background Technology

[0002] Superconducting qubits (qubits) possess advantages such as compatibility with traditional microelectronic fabrication techniques, controllability, low loss, and scalability, and are considered one of the most promising solutions for realizing fault-tolerant quantum computers. The continuous development of large-scale superconducting qubit arrays (on the order of millions) and the improvement of qubit manipulation precision are the main trends and directions for the future development of superconducting quantum computing technology. As a key component of superconducting qubit circuits, cryogenic microwave amplifiers not only require low power consumption and low noise performance, but also need to be integrated onto superconducting qubit device chips in the future to form large-scale superconducting qubit array integrated circuits. Currently, commonly used low-noise microwave amplifiers for superconducting qubit systems include Josephson junction parametric amplifiers (JPAs), traveling-wave parametric amplifiers (TWPAs), SQUID microwave amplifiers, and HEMT cryogenic amplifiers. Among these, compared with Josephson junction parametric amplifiers (JPAs) and traveling-wave parametric amplifiers (TWPAs), SQUID microwave amplifiers not only achieve noise temperatures close to the quantum limit (90 mK @ 1 GHz) and amplification gains exceeding 20 dB, but their most prominent advantage is that they do not require a local oscillator pump signal. This will significantly reduce the required circuit complexity, which is especially important for the future development of large-scale systems. Furthermore, compared to traditional semiconductor HEMT amplifiers, it not only offers lower power consumption, noise performance, and size, but is also fully compatible with superconducting quantum bit device fabrication processes, enabling the simultaneous integration of superconducting quantum bit devices and readout amplifier circuits on the same chip. This is particularly important for future large-scale superconducting quantum bit array circuits. However, existing single-channel superconducting quantum interference device (SQUID) microwave amplifiers also face problems such as poor operational stability, narrow operating bandwidth, poor in-band flatness, low saturation power, and difficulty in cascading, making it difficult to meet the diverse application requirements of future quantum computing. Summary of the Invention

[0003] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a balanced superconducting quantum interference device microwave amplifier and its fabrication method, which solves the problems of poor working stability, narrow operating bandwidth, poor in-band flatness, low saturation power, and difficulty in cascading of existing single-channel SQUID microwave amplifiers.

[0004] To achieve the above and other related objectives, the present invention provides a balanced superconducting quantum interference device microwave amplifier, comprising:

[0005] The first 3dB orthogonal directional coupler is used to receive the input signal;

[0006] The first impedance matching network and the second impedance matching network are connected to the output of the first 3dB orthogonal directional coupler.

[0007] The first superconducting quantum interference device and the second superconducting quantum interference device are respectively connected to the output terminals of the first impedance matching network and the second impedance matching network.

[0008] The third impedance matching network and the fourth impedance matching network are respectively connected to the output terminal of the first superconducting quantum interference device and the output terminal of the second superconducting quantum interference device;

[0009] The second 3dB orthogonal directional coupler connects the output of the third impedance matching network and the output of the fourth impedance matching network, and is used to output signals.

[0010] The first 3dB orthogonal directional coupler, the second 3dB orthogonal directional coupler, the first impedance matching network, the second impedance matching network, the third impedance matching network, and the fourth impedance matching network all include a superconducting transmission line structure.

[0011] Optionally, the first 3dB orthogonal directional coupler is used to split the input microwave signal into two signals with equal power and a 90° phase difference, which are then output to the first impedance matching network and the second impedance matching network, respectively; the second 3dB orthogonal directional coupler is used to combine the two amplified microwave signals with a 90° phase difference and equal power into a single microwave signal for output.

[0012] Optionally, the first 3dB orthogonal directional coupler and the second 3dB orthogonal directional coupler respectively include one of a branch line coupler, a coupled line coupler, and a Lange coupler.

[0013] Optionally, the first impedance matching network, the second impedance matching network, the third impedance matching network, and the fourth impedance matching network all include a planar transmission line impedance transformation network, which includes one of a quarter-wavelength impedance transformation network, a high-low impedance transformation network, and an asymptote impedance transformation network.

[0014] Optionally, the superconducting transmission line structure includes at least one of superconducting microstrip lines, superconducting coplanar waveguides, superconducting striplines, and superconducting coupling lines.

[0015] Optionally, both the first superconducting quantum interference device and the second superconducting quantum interference device include a superconducting loop composed of two Josephson junctions and a superconducting wire, and include an input coupling coil and a magnetic field biasing coil located on or near the superconducting loop. The input coupling coil is used to couple incident microwave signals, and the magnetic field biasing coil is used to bias the amplifier magnetic field.

[0016] Optionally, both the first superconducting quantum interference device and the second superconducting quantum interference device adopt a zero-order gradient configuration, a first-order gradient configuration, or a multi-order gradient configuration.

[0017] This invention also provides a method for fabricating a balanced superconducting quantum interference device (SQU) microwave amplifier, used to fabricate the balanced superconducting quantum interference device microwave amplifier as described in any of the above claims, comprising the following steps:

[0018] A substrate is provided, a resistive layer is formed on the substrate, and the resistive layer is patterned;

[0019] A first insulating layer covering the resistive layer is formed on the substrate, and a first via exposing the resistive layer is formed in the first insulating layer;

[0020] A first superconducting layer, a barrier layer, and a second superconducting layer are formed sequentially from bottom to top on the first insulating layer. The first superconducting layer is also filled into the first via to connect the resistive layer.

[0021] The second superconducting layer is graphically represented to obtain the Josephson junction region;

[0022] The barrier layer is graphically represented, retaining the portion of the barrier layer located below the Josephson junction region;

[0023] The first superconducting layer is graphically represented to obtain the loop and lead structure of the superconducting quantum interference device;

[0024] A second insulating layer is formed on the first superconducting layer to cover the second superconducting layer, and a plurality of second vias are formed in the second insulating layer, wherein at least one second via exposes the second superconducting layer and at least one second via exposes the first superconducting layer;

[0025] A third superconducting layer is formed on the second insulating layer and the third superconducting layer is patterned, and the third superconducting layer fills the second via.

[0026] Optionally, the superconducting transmission line structures of the first 3dB orthogonal directional coupler, the second 3dB orthogonal directional coupler, the first impedance matching network, the second impedance matching network, the third impedance matching network, and the fourth impedance matching network are respectively obtained by graphical representation based on the first superconducting layer and / or the third superconducting layer.

[0027] Optionally, the substrate comprises a Si layer and a SiO2 layer stacked sequentially from bottom to top, or the substrate comprises one of an MgO substrate and an Al2O3 substrate; the resistive layer comprises at least one of a Mo layer, a TiPd layer, and a TiAuPd layer.

[0028] As described above, the entire circuit input and output terminals of the balanced superconducting quantum interference device microwave amplifier of the present invention are symmetrical about SQUID, i.e., they adopt a balanced symmetrical structure. Compared with a single-channel SQUID microwave amplifier circuit, the balanced SQUID microwave amplifier can not only significantly improve the input-output matching performance and expand the device's operating bandwidth, but also make cascading easier; it can also improve the amplifier's saturation power and stability. Furthermore, the balanced SQUID microwave amplifier is fabricated using planar micro-nano fabrication technology, which is compatible with most existing superconducting device fabrication processes, greatly improving the integration of related cryogenic detection systems. Attached Figure Description

[0029] Figure 1 The diagram shown is a structural block diagram of the microwave amplifier of the balanced superconducting quantum interference device of the present invention.

[0030] Figure 2 The diagram shows a basic structure of a branch-line coupler based on a superconducting microstrip line.

[0031] Figure 3 This is a basic configuration diagram of SQUID as a second-order gradient configuration.

[0032] Figure 4 The diagram shows the structure after the resistive layer is formed and visualized.

[0033] Figure 5 The diagram shows the structure after the first insulating layer and the first via have been formed.

[0034] Figure 6 The diagram shows the structure formed from bottom to top, consisting of the first superconducting layer, the barrier layer, and the second superconducting layer.

[0035] Figure 7 The diagram shows the structure after graphically representing the second superconducting layer.

[0036] Figure 8 The diagram shows the structure of the barrier layer after it has been graphically rendered.

[0037] Figure 9 The diagram shows the structure of the first superconducting layer after it has been graphically visualized.

[0038] Figure 10The diagram shows the structure after the formation of the second insulating layer and multiple second vias.

[0039] Figure 11 This is a schematic diagram of the structure after the formation of the third superconducting layer and its graphical representation.

[0040] Component designation explanation

[0041] 100 First 3dB Orthogonal Directional Coupler

[0042] 201 First Impedance Matching Network

[0043] 202 Second Impedance Matching Network

[0044] 301 First Superconducting Quantum Interference Device

[0045] 302 Second Superconducting Quantum Interference Device

[0046] 401 Third Impedance Matching Network

[0047] 402 Fourth Impedance Matching Network

[0048] 500 Second 3dB Orthogonal Directional Coupler

[0049] 601 Input Port

[0050] 602 and 603 output ports

[0051] 604 Isolation Port

[0052] 701 First Josephson knot

[0053] 702 Second Josephson knot

[0054] 703 First Resistive Layer

[0055] 704 Second Resistive Layer

[0056] 801 substrate

[0057] 802 resistive layer

[0058] 803 First Insulation Layer

[0059] 804 First Through Hole

[0060] 805 First Superconducting Layer

[0061] 806 Barrier Layer

[0062] 807 Second Superconducting Layer

[0063] 807' Josephson knot region

[0064] 808 Second Insulation Layer

[0065] 809 Second Through Hole

[0066] 810 Third superconducting layer Detailed Implementation

[0067] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0068] Please see Figures 1 to 11 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0069] Example 1

[0070] This invention provides a balanced superconducting quantum interference device microwave amplifier. Please refer to [link to relevant documentation]. Figure 1The diagram shows the structural block diagram of the balanced superconducting quantum interference device (SQU) microwave amplifier, including a first 3dB orthogonal directional coupler 100, a first impedance matching network 201, a second impedance matching network 202, a first superconducting quantum interference device (SQU) 301, a second superconducting quantum interference device (SQU) 302, a third impedance matching network 401, a fourth impedance matching network 402, and a second 3dB orthogonal directional coupler 500. The first 3dB orthogonal directional coupler 100 is used to receive the input signal; the first impedance matching network 201 and the second impedance matching network 202 are connected to the output terminals of the first 3dB orthogonal directional coupler 100; the first superconducting quantum interference device (SQU) 301 and the second superconducting quantum interference device (SQU) 302 are respectively connected to the first impedance matching network. The output terminal of the first superconducting quantum interference device 301 is connected to the output terminal of the second impedance matching network 202; the third impedance matching network 401 and the fourth impedance matching network 402 are respectively connected to the output terminals of the first superconducting quantum interference device 301 and the second superconducting quantum interference device 302; the second 3dB orthogonal directional coupler 500 is connected to the output terminals of the third impedance matching network 401 and the fourth impedance matching network 402, and is used to output signals; the first 3dB orthogonal directional coupler 100, the second 3dB orthogonal directional coupler 500, the first impedance matching network 201, the second impedance matching network 202, the third impedance matching network 401 and the fourth impedance matching network 402 all include a superconducting transmission line structure.

[0071] Specifically, the first 3dB orthogonal directional coupler 100 is used to split the input microwave signal into two signals with equal power and a 90° phase difference, which are then output to the first impedance matching network 201 and the second impedance matching network 202, respectively. The first impedance matching network 201 and the second impedance matching network 202 are used to achieve impedance matching between the first 3dB orthogonal directional coupler 100 and the first superconducting quantum interference device 301 and the second superconducting quantum interference device 302, respectively, to achieve maximum power transmission efficiency. The first superconducting quantum interference device 301 is used to amplify the transmission of the first impedance matching network 201 and the second impedance matching network 202. The signal is amplified and output to the third impedance matching network 401. The second superconducting quantum interference device 302 is used to amplify the signal transmitted by the second impedance matching network 202 and output it to the fourth impedance matching network 402. The third impedance matching network 401 and the fourth impedance matching network 402 are used to achieve impedance matching between the first superconducting quantum interference device 301, the second superconducting quantum interference device 302 and the second 3dB orthogonal directional coupler 500 to achieve maximum power transmission efficiency. The second 3dB orthogonal directional coupler 500 is used to combine two amplified microwave signals with a 90° phase difference and equal power into one microwave signal for output.

[0072] Specifically, both the first 3dB orthogonal directional coupler 100 and the second 3dB orthogonal directional coupler 500 are realized based on a superconducting transmission line structure fabricated using planar micro-nano technology. The superconducting transmission line structure includes at least one of superconducting microstrip lines, superconducting coplanar waveguides, superconducting striplines, and superconducting coupling lines, or other suitable forms.

[0073] As an example, the first 3dB orthogonal directional coupler 100 and the second 3dB orthogonal directional coupler 500 respectively include one of the following configurations: branch line coupler, coupled line coupler, and Lange coupler, or other suitable configurations.

[0074] For example, please refer to Figure 2 The diagram shows a basic structure of a branch-line coupler based on a superconducting microstrip line, including an input port 601, an output port 602, an output port 603, and an isolation port 604. The corresponding S-parameters are as follows:

[0075]

[0076] As can be seen from the S-parameters, all ports of the 3dB orthogonal directional coupler are mutually matched. The input signal power of input port 601 is equally distributed to output ports 602 and 603 with a phase difference of 90°, and no power is coupled to the isolation port 604. The branch line coupler exhibits high symmetry; any port can be used as an input port, and the output port is always on the opposite side of the network's input ports. The isolation port is the remaining port on the same side as the input port. Based on existing branch line coupler design theory, the characteristic impedance and electrical length of each transmission line segment are already... Figure 1 The superconducting transmission line structure is implemented using a superconducting microstrip line, with a characteristic impedance Z0 set to 50Ω. λ represents the center frequency wavelength. The characteristic impedance and wavelength of the superconducting microstrip line can be calculated and extracted using software.

[0077] Specifically, both the first superconducting quantum interference device 301 and the second superconducting quantum interference device 302 include a superconducting loop composed of two Josephson junctions and a superconducting wire, and include an input coupling coil and a magnetic field bias coil located on or near the superconducting loop. The input coupling coil is used to couple incident microwave signals, and the magnetic field bias coil is used to bias the amplifier magnetic field. In this embodiment, both the first superconducting quantum interference device 301 and the second superconducting quantum interference device 302 also include a DC bias lead.

[0078] Specifically, the SQUID is the core unit of a balanced superconducting quantum interference device (SQUID) microwave amplifier. Its design, besides adhering to basic SQUID device design principles, must also consider the specific requirements of its use as a microwave amplifier. Gain, as one of the most important performance parameters of a microwave amplifier, is related to the flux-voltage conversion factor V of the SQUID. φ The coupling efficiency is positively correlated with the input microwave signal. This is to improve the flux-to-voltage conversion coefficient V. φ Within the limits of process fabrication capabilities, the size of the Josephson junction needs to be minimized as much as possible.

[0079] As an example, the first superconducting quantum interference device 301 and the second superconducting quantum interference device 302 adopt the same structural design, and can both adopt a zero-order gradient configuration, a first-order gradient configuration, or a multi-order gradient configuration. In this embodiment, in order to improve the coupling efficiency of the input microwave signal and thus increase the gain of the amplifier, the first superconducting quantum interference device 301 and the second superconducting quantum interference device 302 preferably adopt a second-order gradient configuration design. This configuration can not only effectively improve the coupling efficiency of the input signal, but also effectively suppress common-mode noise introduced by the environment, thereby improving the performance of the microwave amplifier.

[0080] For example, please refer to Figure 3The diagram shows a basic configuration of a SQUID with a second-order gradient configuration, including a first Josephson junction 701, a second Josephson junction 702, a first resistive layer 703, a second resistive layer 704, a superconducting self-inductance loop, an input coupling coil, a magnetic field bias coil, and a lead structure. The first Josephson junction 701 and the second Josephson junction 702 are connected in parallel through the superconducting self-inductance loop and the lead structure to form a superconducting loop. The input coupling coil and the magnetic field bias coil are located within the superconducting loop. It should be noted that the intersections of some superconducting wires in the diagram are staggered in the vertical direction, i.e., located in different superconducting layers. In other embodiments, the specific layout of the superconducting self-inductance loop, the input coupling coil, the magnetic field bias coil, and the lead structure can be adjusted as needed.

[0081] Specifically, the impedance matching network is a crucial unit for maximizing power transfer between the 3dB orthogonal directional coupler and the SQUID. In this embodiment, the output impedance of the 3dB orthogonal directional coupler is 50Ω, which is inherently mismatched with the input impedance of the SQUID device. The input impedance of the SQUID can be simulated and extracted using high-frequency simulation software such as Sonnet. The Josephson junction portion can be equivalently represented using the RCSJ model. Other parts of the simulation circuit are modeled based on specific process parameters.

[0082] As an example, the first impedance matching network 201, the second impedance matching network 202, the third impedance matching network 401 and the fourth impedance matching network 402 are all realized based on a superconducting transmission line structure fabricated by planar micro-nano technology. The superconducting transmission line structure includes at least one of superconducting microstrip lines, superconducting coplanar waveguides, superconducting striplines and superconducting coupling lines or other suitable forms.

[0083] As an example, the first impedance matching network 201, the second impedance matching network 202, the third impedance matching network 401, and the fourth impedance matching network 402 all include planar transmission line impedance transformation networks. These planar transmission line impedance transformation networks include one of the following: quarter-wavelength impedance transformation networks, high-low impedance transformation networks, and asymptotic impedance transformation networks, or other commonly used planar transmission line impedance transformation networks. In this embodiment, the first impedance matching network 201, the second impedance matching network 202, the third impedance matching network 401, and the fourth impedance matching network 402 are preferably all based on a quarter-wavelength impedance transformer using a superconducting microstrip line, which has a simple structure and a simpler design method.

[0084] In this embodiment, the entire circuit of the balanced superconducting quantum interference device microwave amplifier is symmetrical about SQUID. Compared with a single-channel SQUID microwave amplifier circuit, the balanced symmetrical structure of the SQUID microwave amplifier can not only significantly improve the input-output matching performance and expand the device's operating bandwidth, but also make it easier to cascade; it can also improve the amplifier's saturation power and stability.

[0085] Example 2

[0086] This embodiment provides a method for fabricating a balanced superconducting quantum interference device (SQU) microwave amplifier, used to fabricate the balanced superconducting quantum interference device microwave amplifier described in Embodiment 1, comprising the following steps:

[0087] S1: Provide a substrate, form a resistive layer on the substrate, and pattern the resistive layer;

[0088] S2: A first insulating layer covering the resistive layer is formed on the substrate, and a first via exposing the resistive layer is formed in the first insulating layer;

[0089] S3: A first superconducting layer, a barrier layer and a second superconducting layer are formed sequentially from bottom to top on the first insulating layer. The first superconducting layer is also filled into the first via to connect the resistive layer.

[0090] S4: Pattern the second superconducting layer to obtain the Josephson junction region;

[0091] S5: Graphicalize the barrier layer, retaining the portion of the barrier layer located below the Josephson junction region;

[0092] S6: Graph the first superconducting layer to obtain the loop and lead structure of the superconducting quantum interference device;

[0093] S7: A second insulating layer covering the second superconducting layer is formed on the first superconducting layer, and a plurality of second vias are formed in the second insulating layer, wherein at least one second via exposes the second superconducting layer and at least one second via exposes the first superconducting layer;

[0094] S8: A third superconducting layer is formed on the second insulating layer, and the third superconducting layer is patterned, the third superconducting layer filling the second via.

[0095] Please refer to the following first. Figure 4 Perform step S1: Provide a substrate 801, form a resistive layer 802 on the substrate 801, and pattern the resistive layer 802.

[0096] As an example, the substrate 801 includes a Si layer and a SiO2 layer stacked sequentially from bottom to top, and the resistive layer 802 is fabricated on the SiO2 layer. In other embodiments, the substrate 801 may also include an MgO substrate, an Al2O3 substrate, or other suitable substrates.

[0097] As an example, the resistive layer 802 includes at least one of a Mo layer, a TiPd layer, and a TiAuPd layer, or other suitable metal material layers. The resistive layer 802 can be formed by sputtering and metal etching processes, or by metal lift-off processes.

[0098] Then please see Figure 5 Step S2 is performed: a first insulating layer 803 covering the resistive layer 802 is formed on the substrate 801, and a first via 804 exposing the resistive layer 802 is formed in the first insulating layer 803.

[0099] As an example, the first insulating layer 803 is formed by chemical vapor deposition, physical vapor deposition or other suitable methods, and the first insulating layer 803 may include any one of SiO2 layer, SiO layer or MgO layer or other suitable insulating material layer.

[0100] As an example, the first via 804 is formed by photolithography and etching processes, wherein the etching process includes dry etching and / or wet etching.

[0101] Please refer to the following: Figure 6 Step S3 is performed: a first superconducting layer 805, a barrier layer 806, and a second superconducting layer 807 are formed sequentially from bottom to top on the first insulating layer 803. The first superconducting layer 805 is also filled into the first via 804 to connect the resistive layer 802.

[0102] As an example, the first superconducting layer 805 may be made of Nb, NbN, Al, Ti, Mo, or other suitable superconducting materials; the barrier layer 806 may be made of suitable insulating materials such as alumina or aluminum nitride; and the second superconducting layer 807 may be made of Nb, NbN, Al, Ti, Mo, or other suitable superconducting materials. For example, the first superconducting layer / barrier layer / second superconducting layer may adopt any one of the following structures: Nb / Al-AlOx / Nb, NbN / Al-AlOx / NbN, and NbN / AlN / NbN. Here, Al-AlOx refers to the barrier layer being obtained by first growing an aluminum layer and then oxidizing it; different oxygen composition x values ​​represent different degrees of oxidation. In other embodiments, the first superconducting layer / barrier layer / second superconducting layer may also adopt other suitable material combinations.

[0103] Please see again Figure 7 Perform step S4: Graphicalize the second superconducting layer 807 to obtain the Josephson junction region 807'.

[0104] As an example, the second superconducting layer 807 can be patterned by reactive ion etching, ion beam etching, stripping, chemical etching or other suitable processes to obtain the Josephson junction region 807'.

[0105] Please see again Figure 8 Perform step S5: graphically visualize the barrier layer 806, retaining the portion of the barrier layer 806 located below the Josephson junction region 807'.

[0106] As an example, the barrier layer 806 can be patterned using reactive ion etching, ion beam etching, stripping, chemical etching, or other suitable processes.

[0107] Please see again Figure 9 Then, perform step S6: graphically visualize the first superconducting layer 805 to obtain the loop and lead structure of the superconducting quantum interference device.

[0108] As an example, the first superconducting layer 805 can be patterned by reactive ion etching, ion beam etching, stripping, chemical etching or other suitable processes.

[0109] Please see again Figure 10 Step S7 is performed: a second insulating layer 808 is formed on the first superconducting layer 805 covering the second superconducting layer 807, and a plurality of second vias 809 are formed in the second insulating layer 808. At least one second via 809 exposes the second superconducting layer 807 to lead out the top electrode of the Josephson junction, and at least one second via 809 exposes the first superconducting layer 805 to indirectly lead out the resistive layer 802.

[0110] As an example, the second insulating layer 808 is formed by chemical vapor deposition, physical vapor deposition or other suitable methods, and the second insulating layer 808 may include any one of SiO2 layer, SiO layer or MgO layer or other suitable insulating material layer.

[0111] As an example, the second via 809 is formed by photolithography and etching processes, the etching processes including dry etching and / or wet etching.

[0112] Please see again Figure 11 Step S8 is performed: a third superconducting layer 810 is formed on the second insulating layer 808, and the third superconducting layer 810 is patterned, and the third superconducting layer 810 is filled into the second via 809.

[0113] As an example, the third superconducting layer 810 can be patterned using reactive ion etching, ion beam etching, stripping, chemical etching, or other suitable processes.

[0114] As an example, the superconducting transmission line structures of the first 3dB orthogonal oriented coupler 100, the second 3dB orthogonal oriented coupler 500, the first impedance matching network 201, the second impedance matching network 202, the third impedance matching network 401, and the fourth impedance matching network 402 are respectively obtained based on the patterning of the first superconducting layer 805 and / or the third superconducting layer 810. For example, the superconducting transmission line structure of the first 3dB orthogonal oriented coupler 100 can be obtained by patterning only the first superconducting layer 805 or the third superconducting layer 810, or it can be partially obtained by patterning the first superconducting layer 805 and partially obtained by patterning the third superconducting layer 810. The portions of the first 3dB orthogonal oriented coupler 100 located in different superconducting layers can be connected through vias. Similarly, the superconducting transmission line structures of the second 3dB orthogonal directional coupler 500, the first impedance matching network 201, the second impedance matching network 202, the third impedance matching network 401, and the fourth impedance matching network 402 are also the same, and will not be described in detail here.

[0115] The fabrication method of the balanced superconducting quantum interference device microwave amplifier in this embodiment uses planar micro-nano fabrication technology to fabricate the first 3dB orthogonal directional coupler 100, the first impedance matching network 201, the second impedance matching network 202, the first superconducting quantum interference device 301, the second superconducting quantum interference device 302, the third impedance matching network 401, the fourth impedance matching network 402, and the second 3dB orthogonal directional coupler 500. It is compatible with most existing superconducting device fabrication processes and can greatly improve the integration of related cryogenic detection systems.

[0116] In summary, the entire circuit of the balanced superconducting quantum interference device microwave amplifier of this invention is SQUID symmetrical about its input and output terminals, i.e., it adopts a balanced symmetrical structure. Compared with a single-channel SQUID microwave amplifier circuit, the balanced SQUID microwave amplifier not only significantly improves input-output matching performance and expands the device's operating bandwidth, but also makes cascading easier; it also improves amplifier saturation power and stability. Furthermore, the balanced SQUID microwave amplifier is fabricated using planar micro-nano fabrication technology, which is compatible with most existing superconducting device fabrication processes, greatly improving the integration of related cryogenic detection systems. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial application value.

[0117] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A balanced superconducting quantum interference device microwave amplifier, characterized in that, include: The first 3dB orthogonal directional coupler is used to receive the input signal; The first impedance matching network and the second impedance matching network are connected to the output of the first 3dB orthogonal directional coupler. The first superconducting quantum interference device and the second superconducting quantum interference device are respectively connected to the output terminals of the first impedance matching network and the second impedance matching network; The third impedance matching network and the fourth impedance matching network are respectively connected to the output terminal of the first superconducting quantum interference device and the output terminal of the second superconducting quantum interference device; The second 3dB orthogonal directional coupler connects the output of the third impedance matching network and the output of the fourth impedance matching network, and is used to output signals. The first 3dB orthogonal directional coupler, the second 3dB orthogonal directional coupler, the first impedance matching network, the second impedance matching network, the third impedance matching network, and the fourth impedance matching network all include a superconducting transmission line structure. The entire circuit of the microwave amplifier of the balanced superconducting quantum interference device is symmetrical about SQUID and adopts a balanced symmetrical structure. The first 3dB orthogonal directional coupler is used to split the input microwave signal into two signals with equal power and a 90° phase difference, and output them to the first impedance matching network and the second impedance matching network respectively; the second 3dB orthogonal directional coupler is used to combine the two amplified microwave signals with a 90° phase difference and equal power into one microwave signal for output. Both the first and second superconducting quantum interference devices include a superconducting loop composed of two Josephson junctions and a superconducting wire, and include an input coupling coil and a magnetic field biasing coil located on or near the superconducting loop. The input coupling coil is used to couple incident microwave signals, and the magnetic field biasing coil is used to bias the amplifier magnetic field. Both the first superconducting quantum interference device and the second superconducting quantum interference device include a DC bias lead; The loop and lead structure of the first superconducting quantum interference device and the second superconducting quantum interference device are obtained based on the patterning of the first superconducting layer. The Josephson junction region of the first superconducting quantum interference device and the second superconducting quantum interference device is obtained based on the patterning of the second superconducting layer. The patterned third superconducting layer is located above the second superconducting layer. A portion of the third superconducting layer is filled with vias to connect with the first superconducting layer, and another portion of the third superconducting layer is filled with vias to connect with the second superconducting layer. The superconducting transmission line structures of the first 3dB orthogonal directional coupler, the second 3dB orthogonal directional coupler, the first impedance matching network, the second impedance matching network, the third impedance matching network, and the fourth impedance matching network are respectively obtained by graphical representation based on the first superconducting layer and / or the third superconducting layer.

2. The balanced superconducting quantum interference device microwave amplifier according to claim 1, characterized in that: The first 3dB orthogonal directional coupler and the second 3dB orthogonal directional coupler respectively include one of a branch line coupler, a coupled line coupler, and a Lange coupler.

3. The balanced superconducting quantum interference device microwave amplifier according to claim 1, characterized in that: The first impedance matching network, the second impedance matching network, the third impedance matching network, and the fourth impedance matching network all include a planar transmission line impedance transformation network, which includes one of a quarter-wavelength impedance transformation network, a high-low impedance transformation network, and an asymptote impedance transformation network.

4. The balanced superconducting quantum interference device microwave amplifier according to claim 1, characterized in that: The superconducting transmission line structure includes at least one of superconducting microstrip lines, superconducting coplanar waveguides, superconducting striplines, and superconducting coupling lines.

5. The balanced superconducting quantum interference device microwave amplifier according to claim 1, characterized in that: Both the first superconducting quantum interference device and the second superconducting quantum interference device adopt a zero-order gradient configuration, a first-order gradient configuration, or a multi-order gradient configuration.

6. A method for fabricating a balanced superconducting quantum interference device (SQU) microwave amplifier, used to fabricate the balanced superconducting quantum interference device microwave amplifier as described in any one of claims 1-5, characterized in that, Includes the following steps: A substrate is provided, a resistive layer is formed on the substrate, and the resistive layer is patterned; A first insulating layer covering the resistive layer is formed on the substrate, and a first via exposing the resistive layer is formed in the first insulating layer; A first superconducting layer, a barrier layer, and a second superconducting layer are formed sequentially from bottom to top on the first insulating layer. The first superconducting layer is also filled into the first via to connect the resistive layer. The second superconducting layer is graphically represented to obtain the Josephson junction region; The barrier layer is graphically represented, retaining the portion of the barrier layer located below the Josephson junction region; The first superconducting layer is graphically represented to obtain the loop and lead structure of the superconducting quantum interference device; A second insulating layer is formed on the first superconducting layer to cover the second superconducting layer, and a plurality of second vias are formed in the second insulating layer, wherein at least one second via exposes the second superconducting layer and at least one second via exposes the first superconducting layer; A third superconducting layer is formed on the second insulating layer and the third superconducting layer is patterned, and the third superconducting layer fills the second via.

7. The method for fabricating a balanced superconducting quantum interference device microwave amplifier according to claim 6, characterized in that: The substrate comprises a Si layer and a SiO2 layer stacked sequentially from bottom to top, or the substrate comprises one of a MgO substrate and an Al2O3 substrate; the resistive layer comprises at least one of a Mo layer, a TiPd layer, and a TiAuPd layer.

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