A josephson parametric amplifier based on full impedance matching
By replacing the parallel-plate capacitor with a coplanar waveguide resonator in the Josephson parametric amplifier, the problems of high dielectric loss and complex manufacturing process were solved, achieving low noise temperature and efficient signal readout.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ZHEJIANG QIZHEN QUANTUM TECHNOLOGY CO LTD
- Filing Date
- 2025-07-15
- Publication Date
- 2026-06-05
AI Technical Summary
In existing impedance-matched Josephson parametric amplifiers, the parallel-plate capacitors have high dielectric loss at ultra-low temperatures, which leads to increased noise temperature and affects amplifier performance. At the same time, the manufacturing process is complex and the yield is low.
Resonators made with coplanar waveguides replace traditional parallel-plate capacitors. Impedance matching is achieved by adjusting the geometry of the coplanar waveguides, simplifying the manufacturing process and reducing dielectric loss.
The readout efficiency of superconducting quantum bit signals was optimized, noise temperature was reduced, the overall performance of the amplifier was improved, and the manufacturing process was simplified.
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Figure CN224329442U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of superconducting quantum computing technology, and in particular to a Josephson parametric amplifier based on full impedance matching. Background Technology
[0002] In the field of superconducting quantum computing, impedance-matched Josephson parametric amplifiers (IMPAs) are widely used to amplify quantum bit signals with low noise in order to meet the requirements of high-precision signal readout.
[0003] Existing IMPA typically comprises four parts: an impedance transformer, a parallel-plate capacitor, a superconducting quantum interference device (SQUID), and a pump line. The impedance transformer uses a coplanar waveguide (CPW) to achieve initial matching of the signal input impedance to the internal circuitry, reducing reflection loss. The parallel-plate capacitor and the nonlinear inductance of the SQUID form an LC resonant circuit, tuning the signal transmission and reflection impedance. The SQUID uses a nonlinear inductance to perform parametric amplification, amplifying the weak input signal. The pump line injects a pump signal through directional coupling, driving the SQUID for mixing and amplification.
[0004] However, in the above-mentioned scheme, the SiO2 or Al2O3 dielectric layer in the parallel plate capacitor still exhibits dielectric loss at ultra-low temperatures, leading to increased noise temperature and affecting the amplifier's noise performance. Furthermore, the parallel plate capacitor requires multi-layer photolithography and precise dielectric layer deposition, resulting in complex processes and low yield. Utility Model Content
[0005] This invention provides a Josephson parametric amplifier based on full impedance matching. By using a resonator made of coplanar waveguide to replace the traditional parallel plate capacitor to provide equivalent impedance, it reduces dielectric loss, simplifies the manufacturing process, and thus optimizes the readout efficiency of superconducting quantum bit signals.
[0006] This invention provides a Josephson parametric amplifier based on full impedance matching. The Josephson parametric amplifier based on full impedance matching includes a substrate and an impedance transformer, a resonator, a superconducting quantum interference device, and a pump line arranged sequentially on the substrate.
[0007] The first end of the impedance transformer is coupled to the input and output ports of the Josephson parametric amplifier, and the second end is coupled to the resonator.
[0008] The first end of the superconducting quantum interference device is coupled to the resonator, and the other end is inductively connected to the pump line.
[0009] The resonator and the superconducting quantum interference device form a resonant circuit. The resonator is used to provide the impedance required for resonance, and the superconducting quantum interference device is used to provide the nonlinear inductance required for resonance.
[0010] The impedance transformer, the resonator, and the pump line are all coplanar waveguides. The resonator and the impedance transformer together form an impedance network to provide the necessary impedance for signal amplification.
[0011] Optionally, the coplanar waveguides in the impedance transformer, the resonator, and the pump line are all made of superconducting materials.
[0012] Optionally, the resonator is either a half-wavelength coplanar waveguide or a quarter-wavelength coplanar waveguide.
[0013] Optionally, the characteristic impedance, length, and material of the resonator satisfy the impedance matching between the impedance network and the impedance transformer.
[0014] Optionally, the impedance transformer includes a quarter-wavelength coplanar waveguide and a half-wavelength coplanar waveguide coupled in sequence.
[0015] Optionally, the superconducting quantum interference device includes two or more superconducting Josephson junctions connected in parallel.
[0016] The technical solution of this invention involves setting a substrate in a Josephson parametric amplifier based on full impedance matching, and arranging an impedance transformer, a resonator, a superconducting quantum interference device (SQU), and a pump line sequentially on the substrate. The impedance transformer is coupled at its first end to the input and output ports of the Josephson parametric amplifier, and at its second end to the resonator. This allows the impedance transformer to transform the input signal impedance to the target impedance and transmit it to the resonator. The SQU is coupled at its first end to the resonator, forming a resonant circuit. The resonator provides the impedance required for resonance, and the SQU provides the nonlinear inductance required for resonance. Since the resonator is a coplanar waveguide, which does not require a dielectric layer, impedance matching can be achieved by adjusting the geometry of the coplanar waveguide. This allows the resonator to optimize the frequency and phase of the input signal, while reducing dielectric loss and avoiding phase distortion at high frequencies. By connecting the other end of the superconducting quantum interference device (SQFID) to the pump line through mutual inductance, the pump line can inject a pump signal into the SQFID, enabling the SQFID to amplify the energy of the input signal under pump signal modulation. Furthermore, by configuring the impedance transformer, resonator, and pump line as coplanar waveguides, broadband resonance is supported, and the manufacturing process is simplified. Matching the impedance of the resonator to that of the impedance transformer minimizes reflection loss during signal transmission, improving the overall performance of the Josephson parametric amplifier and optimizing the readout efficiency of the superconducting quantum bit signal.
[0017] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of this utility model, nor is it intended to limit the scope of this utility model. Other features of this utility model will become readily apparent from the following description. Attached Figure Description
[0018] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 This is a schematic diagram of the structure of an impedance-matched Josephson parametric amplifier in the prior art;
[0020] Figure 2 This is a schematic diagram of the structure of a Josephson parametric amplifier based on full impedance matching provided in an embodiment of this utility model;
[0021] Figure 3This is a schematic flowchart illustrating a method for fabricating a Josephson parametric amplifier based on full impedance matching, as provided in an embodiment of this utility model. Detailed Implementation
[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.
[0023] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the utility model described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0024] Figure 1 This is a schematic diagram of the impedance-matched Josephson parametric amplifier in the prior art. (Example) Figure 1As shown, the impedance-matched Josephson parametric amplifier includes an impedance transformer 01, a parallel-plate capacitor 02, a superconducting quantum interference device (SQU) 03, and a pump line 04 to achieve efficient signal transmission, bandwidth expansion, and impedance matching between nonlinear parametric amplification and the transmission line. Specifically, the impedance transformer 01 can be composed of a coplanar waveguide to initially transform the impedance of the input transmission line to an intermediate value, preparing for the impedance transition of the subsequent parallel-plate capacitor 02 and SQU 03. The parallel-plate capacitor 02 and the nonlinear inductance of the SQU 03 form an LC resonant circuit for tuning the signal frequency and impedance. The parallel-plate capacitor 02 is typically an Al-SiO2-Al or Al-Al2O3-Al structure. The capacitance value of the parallel-plate capacitor 02 directly affects the resonant frequency and impedance transformation ratio to ensure conjugate matching within the target frequency band and optimize signal transmission. The impedance of the SQU 03 dynamically changes with the pump signal to transfer the energy of the pump signal to the input signal through a nonlinear mixing process, achieving low-noise amplification. When the pump is off, the superconducting quantum interference device (SQUID) 03 exhibits high impedance, matching the resonant circuit. When the pump is on, the nonlinear mixing process dynamically converts the impedance to the signal frequency band, achieving energy transfer, thus enabling efficient amplification of weak signals through the SQUID 03. The pump line 04, through a directional coupling design, injects the pump signal into the SQUID 03 to provide driving energy for parametric amplification. The coupling coefficient of the pump line 04 needs to be optimized to avoid power reflection; simultaneously, the selection of the pump frequency of the pump line 04 determines the impedance transformation ratio of the mixing process.
[0025] While the aforementioned components play a crucial role in the impedance-matched Josephson parametric amplifier, the design of the parallel-plate capacitor 02 has significant drawbacks. The SiO2 or Al2O3 dielectric layer of the parallel-plate capacitor 02 still exhibits dielectric loss at ultra-low temperatures, leading to increased noise temperature and affecting the amplifier's noise performance, thus limiting its application in superconducting quantum computing. Furthermore, the parallel-plate capacitor 02 requires multi-layer photolithography and precise dielectric layer deposition, resulting in complex processes, low yields, and increased manufacturing costs. Alternatives to the parallel-plate capacitor 02 could include interdigital capacitors, but interdigital capacitors have small feature sizes, placing extremely high demands on photolithography equipment and easily introducing parasitic parameters that affect high-frequency performance. Another alternative to the parallel-plate capacitor 02 could be a parallel-plate vacuum capacitor. While parallel-plate vacuum capacitors can reduce dielectric loss, they require additional fabrication of pillars, increasing the manufacturing difficulty; additionally, the poor uniformity of pillar height fabrication affects the performance of the parametric amplifier. To address this, this invention proposes a Josephson parametric amplifier based on full impedance matching. By using a coplanar waveguide resonator to replace the traditional parallel-plate capacitor to provide equivalent matching impedance, the dielectric loss is reduced and the manufacturing process is simplified, thereby optimizing the amplification efficiency of superconducting quantum bit signals.
[0026] Figure 2 This is a schematic diagram of a Josephson parametric amplifier based on full impedance matching provided in an embodiment of this utility model, as shown below. Figure 2 As shown, the Josephson parametric amplifier based on full impedance matching includes a substrate and an impedance transformer 1, a resonator 2, a superconducting quantum interference device (SQU) 3, and a pump line 4 arranged sequentially on the substrate. The first terminal 11 of the impedance transformer 1 is coupled to the input and output ports of the Josephson parametric amplifier, and the second terminal 12 is coupled to the resonator 2. The first terminal of the superconducting quantum interference device 3 is coupled to the resonator 2, and the other terminal is inductively connected to the pump line 4. The resonator 2 and the superconducting quantum interference device 3 form a resonant circuit. The resonator 2 provides the impedance required for resonance, and the superconducting quantum interference device 3 provides the nonlinear inductance required for resonance. The impedance transformer 1, the resonator 2, and the pump line 4 are all coplanar waveguides. The resonator and the impedance transformer together form an impedance network to provide the impedance required for signal amplification.
[0027] Specifically, the substrate can be understood as the base material used to support and carry all functional components in the Josephson parametric amplifier. For example, the substrate may include high-resistivity silicon or high-dielectric-quality materials such as sapphire. The impedance transformer 1 can be composed of multiple levels of coplanar waveguides, for example, it may include a quarter-wavelength coplanar waveguide and a half-wavelength coplanar waveguide, or it may include a coplanar waveguide with a gradually changing width, to smoothly transform the impedance of the signal input to the Josephson parametric amplifier's input port (e.g., 50Ω) received at the first end 11 of the impedance transformer 1 to a target impedance (e.g., 20Ω) to reduce signal reflection interference. It is understood that the impedance of the coplanar waveguide can be precisely controlled by adjusting its geometry, such as the width of the center conductor and the gap, thereby forming a distributed impedance matching network.
[0028] The second terminal 12 of impedance transformer 1 is coupled to resonator 2, so that the input signal, after impedance transformation by impedance transformer 1, can be transmitted to resonator 2 through the second terminal 12 of impedance transformer 1. Resonator 2 can be composed of a coplanar waveguide resonator, and the first terminal of superconducting quantum interference device 3 is coupled to resonator 2, so that resonator 2 and superconducting quantum interference device 3 form a resonant circuit. Resonator 2 is used to provide the impedance required for resonance, thereby realizing the replacement of the parallel plate capacitor in the LC resonator by resonator 2. The impedance of resonator 2 is determined by its characteristic impedance. (L′ and C′ represent inductance and capacitance per unit length), the length of the CPW, the CPW material, and the substrate material are all determined. It is understood that the impedance of the coplanar waveguide can be adjusted by changing the width of the center conductor, the gap, and the length of the coplanar waveguide. For example, when the width of the center conductor increases, the inductance per unit length of the coplanar waveguide decreases, and the capacitance per unit length increases, thus reducing the characteristic impedance of the coplanar waveguide. When the gap of the coplanar waveguide decreases, the inductance per unit length increases, and the capacitance per unit length changes less, thus reducing the characteristic impedance of the coplanar waveguide. By adjusting the length of the coplanar waveguide, the equivalent impedance of resonator 2 at different frequencies is changed. Therefore, by adjusting the dimensions of the coplanar waveguide, impedance matching between resonator 2 and impedance transformer 1 can be achieved, thus completing impedance matching of the entire network. Coplanar waveguides do not require a dielectric layer and rely solely on the geometry of superconducting metals to define impedance, thereby reducing dielectric loss. At the same time, the single-layer coplanar waveguide structure allows for precise control of impedance, avoiding phase distortion at high frequencies. This enables the noise temperature of Josephson parametric amplifiers to be reduced to less than 300mK.
[0029] The superconducting quantum interference device 3 (SQU3) can consist of two or more Josephson junctions to provide the nonlinear inductance required for resonance. SQU3 enables parametric amplification through pump signal modulation via the nonlinear inductance, thereby amplifying the energy of the weak input signal from impedance transformer 1. The superconducting characteristics of SQU3 ensure low noise, making it suitable for amplifying superconducting quantum bit signals. The other end of SQU3 is inductively connected to pump line 4, allowing pump line 4 to inject a pump signal into SQU3 via directional coupling, providing driving energy for parametric amplification while avoiding signal crosstalk between the input and output ports of the Josephson parametric amplifier. It is also understandable that the signal input to the input port of the Josephson parametric amplifier undergoes impedance transformation via impedance transformer 1, impedance network matching via resonator 2, and parametric amplification via superconducting quantum interference device 3. It can then return to the output port of the Josephson parametric amplifier through the output path of impedance transformer 1. Impedance transformer 1 can also transform the signal from internal impedance back to impedance matching the external transmission line to ensure efficient output of the amplified signal and reduce reflection loss.
[0030] Impedance transformer 1, resonator 2, and pump line 4 are all coplanar waveguides. This distributed coplanar waveguide design supports broadband resonance and is simpler and more stable in design. Furthermore, the fact that all three components are coplanar waveguides allows for fabrication via a single UV lithography and reactive ion stripping process, eliminating the need for dielectric layer deposition and simplifying the manufacturing process. In addition, the fully coplanar waveguide design, along with impedance matching between resonator 2 and impedance transformer 1, ensures minimal reflection loss during signal transmission from impedance transformer 1 to resonator 2 and then to the superconducting quantum interference device 3, maximizing energy transfer efficiency. This improves the overall performance of the Josephson parametric amplifier and optimizes the readout efficiency of the superconducting quantum bit signal.
[0031] In this embodiment, a substrate is set within a Josephson parametric amplifier based on full impedance matching, and an impedance transformer, a resonator, a superconducting quantum interference device (SQFID), and a pump line are arranged sequentially on the substrate. The impedance transformer is coupled at its first end to the input and output ports of the Josephson parametric amplifier, and at its second end to the resonator, enabling it to transform the input impedance of the signal to the target impedance. The SQFID is coupled at its first end to the resonator, forming a resonant circuit. The resonator provides the impedance required for resonance, and the SQFID provides the nonlinear inductance required for resonance. Since the resonator is a coplanar waveguide, which does not require a dielectric layer, impedance matching can be achieved by adjusting the geometry of the coplanar waveguide, simplifying the resonator design and reducing dielectric loss while avoiding phase distortion at high frequencies. The other end of the SQFID is connected to the pump line via mutual inductance, allowing the pump line to inject a pump signal into the SQFID, thus enabling the SQFID to amplify the energy of the input signal under pump signal modulation. Furthermore, by configuring the impedance transformer, resonator, and pump line as coplanar waveguides, broadband resonance is supported, and the manufacturing process is simplified. By forming an impedance matching network with the resonator and impedance transformer, reflection loss during signal transmission is minimized, improving the overall performance of the Josephson parametric amplifier and optimizing the readout efficiency of the superconducting quantum bit signal.
[0032] Optionally, the coplanar waveguides in impedance transformer 1, resonator 2, and pump line 4 are all made of superconducting materials.
[0033] Specifically, the coplanar waveguides in impedance transformer 1, resonator 2, and pump line 4 are all fabricated using superconducting materials. For example, the superconducting material may include at least one of aluminum, niobium, tantalum, or titanium titanide. Superconducting quantum computing systems typically operate in ultra-low temperature environments. Below ultra-low temperatures, the resistance of the superconducting material is zero, thereby minimizing ohmic losses during signal transmission from impedance transformer 1 to resonator 2 and from pump line 4 to superconducting quantum interference device 3, maximizing energy transfer efficiency, and meeting the broadband transmission requirements of superconducting quantum bit signals. This optimizes the readout efficiency of superconducting quantum bit signals and reduces the noise temperature of the Josephson parametric amplifier.
[0034] Optionally, the resonator 2 can be either a half-wavelength coplanar waveguide or a quarter-wavelength coplanar waveguide.
[0035] Specifically, resonator 2 can be either a half-wavelength coplanar waveguide or a quarter-wavelength coplanar waveguide, allowing it to form a standing wave along its length (half or a quarter of the signal wavelength) and generate either high or low impedance. This enables resonator 2 to form a resonant circuit with the superconducting quantum interference device 3, precisely tuning the input signal to the target frequency band. The choice of either coplanar waveguide for resonator 2 allows the Josephson parametric amplifier to flexibly adjust its performance based on the frequency and impedance requirements of the input signal, enhancing its flexibility and adaptability. Furthermore, the coplanar waveguide eliminates the need for a dielectric layer, relying solely on the geometry of the superconducting metal to define the impedance. This reduces dielectric loss, simplifies manufacturing processes, supports broadband resonance, and optimizes the readout efficiency of superconducting quantum bit signals.
[0036] Resonator 2 is coupled to impedance transformer 1 and superconducting quantum interference device 3 on its two sides, respectively. Specifically, resonator 2 can have a symmetrical structure, resulting in a more uniform distribution of electric and magnetic fields within it, reducing local electromagnetic interference and ensuring high signal transmission efficiency. Furthermore, the symmetrical structure of resonator 2 allows for coupling to impedance transformer 1 and superconducting quantum interference device 3 on either side of its central region. This ensures the stability of the impedance matching between resonator 2 and impedance transformer 1, as well as the stability of the resonant circuit formed by resonator 2 and superconducting quantum interference device 3, reducing reflection loss and making it suitable for the broadband transmission requirements of superconducting quantum bit signals. This optimizes the readout efficiency of superconducting quantum bit signals and reduces the noise temperature of the Josephson parametric amplifier.
[0037] Optional, continue to refer to Figure 2The impedance transformer 1 includes a quarter-wavelength coplanar waveguide 101 and a half-wavelength coplanar waveguide 102 coupled in sequence; the impedance of the quarter-wavelength coplanar waveguide 101 is matched with the impedance of the half-wavelength coplanar waveguide 102, and the impedance of the half-wavelength coplanar waveguide 102 is matched with the impedance of the resonator 2.
[0038] Specifically, impedance transformer 1 includes a quarter-wavelength coplanar waveguide 101 and a half-wavelength coplanar waveguide 102 coupled sequentially. This allows impedance transformer 1 to initially transform the impedance of the signal input to the Josephson parametric amplifier's input port to an intermediate value through the quarter-wavelength coplanar waveguide 101. The impedance of the quarter-wavelength coplanar waveguide 101 is matched with that of the half-wavelength coplanar waveguide 102, enabling the half-wavelength coplanar waveguide 102 to further tune the impedance of the input signal, after transformation by the quarter-wavelength coplanar waveguide 101, to the impedance of the resonator 2. This achieves a transition of the input signal's impedance from the input impedance to the target impedance, reducing signal reflection loss and maximizing signal transmission efficiency. The impedance matching network formed by the impedance transformer and the resonator meets the broadband requirements of superconducting quantum computing.
[0039] Furthermore, the quarter-wavelength coplanar waveguide 101 and the half-wavelength coplanar waveguide 102 can be extended in a serpentine manner to extend the length of the coplanar waveguide within a limited substrate area, thereby meeting the specific length requirements of the quarter-wavelength coplanar waveguide 101 and the half-wavelength coplanar waveguide 102.
[0040] Optionally, the superconducting quantum interference device 3 includes two or more superconducting Josephson junctions connected in parallel.
[0041] Specifically, the superconducting quantum interference device 3 may include two or more superconducting Josephson junctions connected in parallel. These parallel Josephson junctions provide flux-tunable nonlinear inductance, enabling parametric amplification of the input signal via three-wave mixing, achieving a gain of up to 20 dB to meet the amplification requirements of superconducting quantum bit signals. Furthermore, the Josephson junctions can employ an Al / AlOx / Al structure, using aluminum and alumina as insulating layers, resulting in zero resistance at extremely low temperatures, thus reducing the noise temperature of the Josephson parametric amplifier. In addition, the parallel Josephson junctions can share current, increasing the amplifier's saturation power and making it suitable for simultaneous amplification and readout of multi-bit signals.
[0042] Based on the same technical concept, this utility model embodiment also provides a method for fabricating a Josephson parametric amplifier based on full impedance matching, which is used to fabricate a Josephson parametric amplifier based on full impedance matching in any embodiment of this utility model. Figure 3This is a schematic flowchart illustrating a method for fabricating a Josephson parametric amplifier based on full impedance matching, as provided in an embodiment of this utility model. Figure 3 As shown, the fabrication method of the Josephson parametric amplifier based on full impedance matching includes:
[0043] S101. Prepare a metal layer on the substrate.
[0044] Specifically, the substrate can be understood as the base material used to support and carry all functional components in the Josephson parametric amplifier. For example, the substrate may include high-resistivity silicon or high-dielectric-quality materials such as sapphire. Specifically, a metal layer can be prepared on the substrate using methods such as magnetron sputtering, thermal evaporation, electron beam evaporation, or chemical vapor deposition to lay the foundation for subsequent formation of impedance transformers, resonators, and pump lines.
[0045] Optionally, a metal layer is prepared on the substrate, including: using a superconducting metal material to prepare a superconducting metal layer of a predetermined thickness on the substrate.
[0046] Specifically, superconducting metal materials can be deposited on a substrate using methods such as magnetron sputtering, thermal evaporation, electron beam evaporation, or chemical vapor deposition to fabricate a superconducting metal layer of a predetermined thickness. For example, the predetermined thickness can be 200 nm, and the superconducting metal material can include at least one of aluminum, niobium, tantalum, or titanium titanide. By fabricating a superconducting metal layer of a predetermined thickness on the substrate, the coplanar waveguides in the subsequently formed impedance transformer, resonator, and pump line are all made of superconducting material. This minimizes ohmic losses during signal transmission from the impedance transformer to the resonator to the superconducting quantum interference device, maximizing energy transfer efficiency and meeting the broadband transmission requirements of superconducting quantum bit signals. This optimizes the readout efficiency of the superconducting quantum bit signal and reduces the noise temperature of the Josephson parametric amplifier.
[0047] S102. Pattern the metal layer and fabricate coplanar waveguides at three preset positions arranged in sequence, thereby forming an impedance transformer, a resonator, and a pump line.
[0048] The first end of the impedance transformer is coupled to the input and output ports of the Josephson parametric amplifier, and the second end is coupled to the resonator.
[0049] Specifically, after forming the metal layer, the geometric patterns of the coplanar waveguide structure corresponding to the impedance transformer, resonator, and pump line can be precisely etched at three predetermined positions on the metal layer using photolithography and reactive ion etching processes, thus realizing the fabrication of the impedance transformer, resonator, and pump line. The three predetermined positions are arranged sequentially on the substrate to ensure that the first end of the impedance transformer is coupled to the input and output ports of the Josephson parametric amplifier, and the second end is coupled to the resonator. This allows the impedance transformer to receive the signal input from the Josephson parametric amplifier's input port through the first end and smoothly transform the impedance of the input signal to the target impedance, reducing signal reflection interference. Simultaneously, the impedance-transformed input signal can be transmitted to the resonator through the second end of the impedance transformer, allowing the resonator to optimize the frequency and phase of the signal input to the impedance transformer. Furthermore, the impedance of the resonator is matched with the impedance of the impedance transformer to ensure that reflection loss is minimized during signal transmission from the impedance transformer to the resonator, maximizing energy transfer efficiency and thus improving the overall performance of the Josephson parametric amplifier and optimizing the readout efficiency of the superconducting quantum bit signal.
[0050] Optionally, the metal layer is photolithographically patterned to fabricate coplanar waveguides at three sequentially arranged preset positions, corresponding to the formation of an impedance transformer, a resonator, and a pump line. This includes: using a single ultraviolet photolithography process and a reactive ion etching process to pattern the metal layer, and fabricating coplanar waveguides at three sequentially arranged preset positions, corresponding to the formation of an impedance transformer, a resonator, and a pump line.
[0051] Specifically, the steps for patterning a metal layer to form an impedance transformer, resonator, and pump line can be as follows: First, a layer of photoresist is uniformly coated onto the surface of the metal layer. The photoresist serves as a mask material, providing protection and selective etching areas for patterning. After coating the photoresist, a pre-fabricated mask is placed on top of the photoresist. The mask has pre-fabricated geometric patterns corresponding to the coplanar waveguide structures of the impedance transformer, resonator, and pump line, i.e., three predetermined positions arranged sequentially. Then, an ultraviolet light source is used to irradiate the sample through the mask, allowing for a single ultraviolet lithography process to expose the three predetermined positions on the same mask in one step. After exposure, the sample is immersed in a developer and cleaned to dissolve the photoresist in the exposed areas, retaining the photoresist mask that matches the geometric patterns corresponding to the coplanar waveguide structures of the impedance transformer, resonator, and pump line. After photolithography using an ultraviolet light source, the metal layer not protected by the photoresist needs to be removed by reactive ion etching. This allows coplanar waveguides to be formed at three predetermined locations within the metal layer, corresponding to the impedance transformer, resonator, and pump line. By forming the impedance transformer, resonator, and pump line in a single ultraviolet photolithography process and reactive ion etching, the pattern definition is completed in one step without the need for dielectric layer deposition, simplifying the manufacturing process.
[0052] S103. Fabricate a superconducting quantum interference device between the resonator and the pump line.
[0053] The first end of the superconducting quantum interference device (SQU) is coupled to the resonator, and the other end is inductively connected to the pump line. The resonator and the SQU form a resonant circuit, with the resonator providing the impedance required for resonance and the SQU providing the nonlinear inductance required for resonance.
[0054] Specifically, after forming the impedance transformer, resonator, and pump line, a superconducting quantum interference device (SQI) can be fabricated using electron beam lithography, cantilever bridging (or shadow evaporation) techniques, and between the resonator and pump line. The first end of the SQI is coupled to the resonator, forming a resonant circuit. The resonator provides the impedance required for resonance, thus replacing the parallel-plate capacitor in an LC resonator. Impedance matching between the resonator and the impedance transformer can be achieved by adjusting the dimensions of the resonator's coplanar waveguide, eliminating the need for a dielectric layer and reducing dielectric loss. Furthermore, the single-layer coplanar waveguide structure has lower requirements for lithographic precision, reducing fabrication difficulty. The SQI provides the nonlinear inductance required for resonance. The SQI can achieve parametric amplification through the nonlinear inductance modulated by the pump signal, thereby amplifying the energy of the input signal. The other end of the superconducting quantum interference device is inductively connected to the pump line so that the pump line can inject a pump signal into the superconducting quantum interference device through directional coupling, thereby providing driving energy for the parametric amplifier and avoiding signal crosstalk between the input and output ports of the Josephson parametric amplifier.
[0055] Optionally, a superconducting quantum interference device can be fabricated between the resonator and the pump line, including: using cantilever bridge technology or shadow evaporation technology to fabricate two or more A-superconducting Josephson junctions connected in parallel between the resonator and the pump line to form a superconducting quantum interference device.
[0056] Specifically, the steps for fabricating a superconducting quantum interference device (QID) between the resonator and the pump line using the cantilever bridge technique (or shadow evaporation technique) can be as follows: First, an electron beam resist is spin-coated onto a substrate, and a superconducting Josephson junction pattern is formed by exposure and development. Next, a first layer of aluminum is deposited to form a bottom electrode pattern. Then, in-situ oxidation is performed on the exposed aluminum surface to generate an aluminum oxide tunneling barrier. A second layer of aluminum is then evaporated at different angles to form a top electrode, connecting two or more parallel Al / AlOx / Al Josephson junctions. Finally, the electron beam resist is removed, thus fabricating a superconducting QID that is mutually inductively coupled to both the resonator and the pump line.
[0057] Understandably, superconducting quantum interference devices (SQUs) consist of two or more superconducting Josephson junctions connected in parallel. These parallel Josephson junctions provide a larger nonlinear inductance, thereby increasing the amplifier's saturation power and improving the readout efficiency of superconducting qubit signals, thus meeting the requirement for simultaneous amplification of multiple superconducting qubit signals. The Josephson junction employs an Al / AlOx / Al structure, using alumina as the insulating layer, resulting in zero resistance at extremely low temperatures, thereby reducing the noise temperature of the Josephson parametric amplifier.
[0058] The above-described method for fabricating a Josephson parametric amplifier based on full impedance matching can be used to fabricate the Josephson parametric amplifier based on full impedance matching provided in any embodiment of this utility model, possessing the corresponding functions and beneficial effects of a Josephson parametric amplifier based on full impedance matching. Technical details not described in detail in this embodiment can be found in the Josephson parametric amplifier based on full impedance matching provided in any embodiment of this utility model.
[0059] Since the fabrication method of the Josephson parametric amplifier based on full impedance matching described above can be used to fabricate the Josephson parametric amplifier based on full impedance matching in this embodiment of the present invention, those skilled in the art can understand the specific implementation method and various variations of the fabrication method of the Josephson parametric amplifier based on full impedance matching in this embodiment of the present invention based on the Josephson parametric amplifier based on full impedance matching described in this embodiment of the present invention. Therefore, how the fabrication method of the Josephson parametric amplifier based on full impedance matching in this embodiment of the present invention is fabricated will not be described in detail here. Anyone skilled in the art who implements the method for fabricating the Josephson parametric amplifier based on full impedance matching in this embodiment of the present invention falls within the scope of protection of this application.
[0060] It should be understood that the various forms of processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in this utility model can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this utility model can be achieved, and no limitation is imposed herein.
[0061] The specific embodiments described above do not constitute a limitation on the scope of protection of this utility model. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.
Claims
1. A Josephson parametric amplifier based on full impedance matching, characterized in that, It includes a substrate and an impedance transformer, a resonator, a superconducting quantum interference device, and a pump line arranged sequentially on the substrate; The first end of the impedance transformer is coupled to the input and output ports of the Josephson parametric amplifier, and the second end is coupled to the resonator. The first end of the superconducting quantum interference device is coupled to the resonator, and the other end is inductively connected to the pump line. The resonator and the superconducting quantum interference device form a resonant circuit. The resonator is used to provide the impedance required for resonance, and the superconducting quantum interference device is used to provide the nonlinear inductance required for resonance. The impedance transformer, the resonator, and the pump line are all coplanar waveguides. The resonator and the impedance transformer together form an impedance network to provide the necessary impedance for signal amplification.
2. The Josephson parametric amplifier according to claim 1, characterized in that, The impedance transformer, the resonator, and the coplanar waveguides in the pump line are all made of superconducting materials.
3. The Josephson parametric amplifier according to claim 1, characterized in that, The resonator is either a half-wavelength coplanar waveguide or a quarter-wavelength coplanar waveguide.
4. The Josephson parametric amplifier according to claim 1, characterized in that, The characteristic impedance, length, and material of the resonator satisfy the impedance matching between the impedance in the impedance network and the impedance of the impedance transformer.
5. The Josephson parametric amplifier according to claim 1, characterized in that, The impedance transformer comprises a quarter-wavelength coplanar waveguide and a half-wavelength coplanar waveguide coupled in sequence.
6. The Josephson parametric amplifier according to claim 1, characterized in that, The superconducting quantum interference device includes two or more superconducting Josephson junctions connected in parallel.