Traveling wave parametric amplifier and method for preparing the same

Abstract

The present invention provides a traveling wave parametric amplifier and a method for preparing the traveling wave parametric amplifier. The traveling wave parametric amplifier comprises: a substrate; a microstrip line core line, which is arranged on the substrate, and the microstrip line core line comprises a junction chain composed of at least one Josephson junction; a first capacitor, which comprises: a first superconducting metal layer, which is suitable for grounding; a second superconducting metal layer, which is suitable for connecting to one end of the Josephson junction; a dielectric layer, which is suitable for isolating the first superconducting metal layer and the second superconducting metal layer, and the inductance provided by the Josephson junction and the first capacitor determine the characteristic impedance of the traveling wave parametric amplifier; a phase matching resonance unit, which is connected to the microstrip line core line, and the phase matching resonance unit is suitable for performing phase matching between a pump signal and a read signal obtained from the outside and an idler signal generated in the traveling wave parametric amplifier, so as to improve the gain of the traveling wave parametric amplifier through phase matching.

Description

Technical Field

[0001] The present disclosure relates to the technical field of quantum computing, and more specifically, to a traveling wave parametric amplifier and a method for preparing the traveling wave parametric amplifier. Background Art

[0002] The parametric amplifier is a key device for improving the fidelity of qubit reading. It can amplify weak reading signals in extremely low temperature ranges and only add noise close to the quantum limit, thereby greatly improving the signal-to-noise ratio of the reading signal, achieving shorter reading pulse duration and weaker reading pulse level, and reducing the impact of the reading pulse on qubit performance. The use of parametric amplifiers enables single-shot reading of qubits, laying the foundation for quantum error correction.

[0003] The current development of quantum computer technology is in its early stages, and how to achieve fast and high-fidelity quantum bit state measurement is the focus of quantum computing development. Superconducting quantum chips realized by superconducting quantum bits are one of the most effective physical platforms for quantum computing. How to achieve high-fidelity information readout of large-scale superconducting quantum chips is the core technology and challenge to improve the accuracy of quantum bit reading.

[0004] The design and preparation method of the traveling wave amplifier currently proposed uses a transmission line structure based on a coplanar waveguide, and requires additional structures such as a capacitor bridge to increase the ground capacitance. This design makes the chip less compact and will bring additional capacitance and inductance to affect the impedance matching of the line. On the other hand, the current preparation process of the parametric amplifier is incompatible with the preparation process of the quantum bit chip, and there are problems such as high preparation difficulty. Summary of the invention

[0005] In order to solve at least one of the above-mentioned and other technical problems in the prior art, the present disclosure provides a traveling wave parametric amplifier and a method for preparing the traveling wave parametric amplifier, which can reduce the additional capacitance and inductance caused by the transmission line structure of the coplanar waveguide, thereby making the internal structure of the traveling wave parametric amplifier compact.

[0006] The embodiment of the present disclosure provides a traveling wave parametric amplifier, comprising: a substrate; a microstrip line core line, arranged on the above substrate, the above microstrip line core line includes a junction chain composed of at least one Josephson junction; a first capacitor, comprising: a first superconducting metal layer, suitable for grounding; a second superconducting metal layer, suitable for connecting to one end of the above Josephson junction; a dielectric layer, the above dielectric layer is suitable for isolating the above first superconducting metal layer and the above second superconducting metal layer, the inductance provided by the above Josephson junction and the above first capacitor determine the characteristic impedance of the traveling wave parametric amplifier; a phase matching resonance unit, connected to the above microstrip line core line, the above phase matching resonance unit is suitable for phase matching a pump signal and a read signal obtained from the outside with an idler signal generated in the above traveling wave parametric amplifier, and the gain of the above traveling wave parametric amplifier is improved through the above phase matching.

[0007] According to some embodiments of the present disclosure, the material of the dielectric layer is any one of the following: calcium fluoride, silicon oxide, and amorphous silicon.

[0008] According to some embodiments of the present disclosure, the first superconducting metal layer is formed on the substrate, the dielectric layer is formed on the first superconducting metal layer, and the second superconducting metal layer is formed on the dielectric layer.

[0009] According to some embodiments of the present disclosure, the second superconducting metal layer is formed on the substrate, the dielectric layer is formed on the second superconducting metal layer, and the first superconducting metal layer is formed on the dielectric layer; wherein the dielectric layer covers the second superconducting metal layer.

[0010] According to some embodiments of the present disclosure, the phase-matching resonance unit includes: a resonance cavity, one end of which is connected to the first superconducting metal layer, the resonance cavity being suitable for phase-matching a pump signal and a read signal obtained from the outside with an idler signal generated in the traveling wave parametric amplifier, so as to improve the gain of the traveling wave parametric amplifier through the phase matching; a second capacitor, one end of which is connected to the resonance cavity and the other end of which is connected to the core line of the microstrip line, the second capacitor being suitable for coupling the capacitance of the resonance cavity and the core line of the microstrip line.

[0011] According to some embodiments of the present disclosure, the above-mentioned resonant cavity is a distributed structure, and a half-wavelength or quarter-wavelength resonant cavity is constructed by adjusting the length of the above-mentioned microstrip line core line. The characteristic frequency of the above-mentioned resonant cavity is the characteristic frequency corresponding to the half-wavelength or quarter-wavelength.

[0012] According to some embodiments of the present disclosure, the resonant cavity is composed of a lumped inductor and a lumped capacitor connected in parallel.

[0013] Another aspect of the present disclosure provides a method for preparing the above-mentioned traveling wave parametric amplifier, comprising: depositing a first superconducting metal layer on a pretreated substrate by any one of thermal evaporation, electron beam evaporation, magnetron sputtering or molecular beam epitaxy; performing graphic definition by electron beam exposure equipment or optical exposure equipment, and etching the first superconducting metal layer by wet etching equipment or dry etching equipment; depositing a dielectric layer on the first superconducting metal layer by any one of thermal evaporation, electron beam evaporation or chemical vapor deposition, and etching the dielectric layer; performing graphic definition by electron beam exposure equipment or optical exposure equipment, and depositing a second superconducting metal layer on the dielectric layer by any one of thermal evaporation, electron beam evaporation or magnetron sputtering, and etching the second superconducting metal layer; preparing a Josephson junction on the second superconducting metal layer.

[0014] According to some embodiments of the present disclosure, the preparation of the Josephson junction on the second superconducting metal layer includes: using electron beam exposure equipment to define the pattern of the Josephson junction, and using a dual-angle evaporation process and a lift-off process to prepare the Josephson junction.

[0015] Another aspect of the present disclosure provides a method for preparing the above-mentioned traveling wave parametric amplifier, comprising: depositing a second superconducting metal layer on a pretreated substrate by any one of thermal evaporation, electron beam evaporation, magnetron sputtering or molecular beam epitaxy; performing graphic definition by electron beam exposure equipment or optical exposure equipment, and etching the second superconducting metal layer by wet etching equipment or dry etching equipment; defining the pattern of the Josephson junction by electron beam exposure equipment, and preparing the Josephson junction on the second superconducting metal layer by dual-angle evaporation process and lift-off process; depositing a dielectric layer on the second superconducting metal layer by any one of thermal evaporation, electron beam evaporation or chemical vapor deposition, and etching the pattern of the dielectric layer; performing graphic definition by electron beam exposure equipment or optical exposure equipment, and depositing a first superconducting metal layer on the dielectric layer by any one of thermal evaporation, electron beam evaporation or magnetron sputtering, and etching the pattern of the first superconducting metal layer.

[0016] According to a traveling wave parametric amplifier and a method for preparing the traveling wave parametric amplifier provided by the present disclosure, a microstrip line core is arranged on a substrate, the microstrip line core includes a junction chain composed of at least one Josephson junction, a first superconducting metal layer of a first capacitor is grounded, a second superconducting metal layer of the first capacitor is connected to one end of the Josephson junction, a dielectric layer is arranged between the first superconducting metal layer and the second superconducting metal layer, the dielectric layer is suitable for isolating the first superconducting metal layer and the second superconducting metal layer, the inductance provided by the Josephson junction and the first capacitor determine the characteristic impedance of the traveling wave parametric amplifier, the additional capacitance and inductance caused by the transmission line structure of the coplanar waveguide can be reduced, so that the internal structure of the traveling wave parametric amplifier is compact, and the microstrip line core is connected through a phase matching resonance unit, the phase matching resonance unit phase matches the pump signal and the read signal obtained from the outside with the idler signal generated in the traveling wave parametric amplifier, and the gain of the traveling wave parametric amplifier is improved through phase matching. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a lumped element topology diagram of a traveling wave parametric amplifier according to an exemplary embodiment of the present disclosure;

[0018] Figure 2 is a top view of a microstrip line core according to an exemplary embodiment of the present disclosure;

[0019] Figure 3 is a cross-sectional view of a traveling wave parametric amplifier according to an exemplary embodiment of the present disclosure;

[0020] Figure 4 is a top view of a microstrip line core according to another exemplary embodiment of the present disclosure;

[0021] Figure 5 is a cross-sectional view of a traveling wave parametric amplifier according to another exemplary embodiment of the present disclosure;

[0022] Figure 6 is a flow chart of a method for preparing a traveling wave parametric amplifier according to an illustrative embodiment of the present disclosure;

[0023] Figure 7 is a flow chart of a method for preparing a traveling wave parametric amplifier according to another exemplary embodiment of the present disclosure; and

[0024] Figure 8 is a graph showing the gain and bandwidth performance of a traveling wave parametric amplifier according to an exemplary embodiment of the present disclosure.

[0025] In the drawings, the meanings of the reference numerals are as follows:

[0026] 1. Substrate;

[0027] 2. Microstrip line core wire;

[0028] 3. The first capacitor;

[0029] 4. Phase matching resonance unit;

[0030] 5. Josephson knot;

[0031] 6. A first superconducting metal layer;

[0032] 7. A second superconducting metal layer;

[0033] 8. Dielectric layer;

[0034] 9. Resonant cavity;

[0035] 10. The second capacitor. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0037] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0038] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification, and should not be interpreted in an idealized or overly rigid manner.

[0039] When using expressions such as "at least one of A, B, and C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, and C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc. When using expressions such as "at least one of A, B, or C, etc.", it should generally be interpreted as the meaning of the expression generally understood by those skilled in the art. For example, "a system having at least one of A, B, or C" should include but not be limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.

[0040] According to the concept of one aspect of the present disclosure, for the design and preparation method of the currently proposed traveling wave amplifier, in order to solve the problem that the transmission line structure based on the coplanar waveguide needs to additionally design a capacitor bridge and other structures to increase the capacitance to the ground, this design makes the chip not compact enough and will bring about the problem that the additional capacitance and inductance affect the impedance matching of the line, the present disclosure arranges a microstrip line core line on a substrate, the microstrip line core line includes a junction chain composed of at least one Josephson junction, the first superconducting metal layer of the first capacitor is grounded, the second superconducting metal layer of the first capacitor is connected to one end of the Josephson junction, and the first superconducting metal layer and the second superconducting metal layer are connected. A dielectric layer is arranged between the metal layers, and the dielectric layer is suitable for isolating the first superconducting metal layer and the second superconducting metal layer. The inductance provided by the Josephson junction and the first capacitor determine the characteristic impedance of the traveling wave parametric amplifier, which can reduce the additional capacitance and inductance caused by the transmission line structure of the coplanar waveguide, so that the internal structure of the traveling wave parametric amplifier is compact. It is connected to the microstrip line core wire through a phase matching resonance unit. The phase matching resonance unit phase-matches the pump signal and the read signal obtained from the outside with the idler signal generated in the traveling wave parametric amplifier, and the gain of the traveling wave parametric amplifier is improved through phase matching.

[0041] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0042] Figure 1 is a lumped element topology diagram of a traveling wave parametric amplifier according to an illustrative embodiment of the present disclosure.

[0043] According to an embodiment of the present disclosure, a traveling wave parametric amplifier includes a substrate 1, a microstrip line core 2, a first capacitor 3 and a phase matching resonance unit 4. Figure 1 As shown, the microstrip core 2 is arranged on the substrate 1, and the microstrip core 2 includes a junction chain composed of at least one Josephson junction 5. The first capacitor 3 includes a first superconducting metal layer 6, a second superconducting metal layer 7 and a dielectric layer 8. The first superconducting metal layer 6 is suitable for grounding. The second superconducting metal layer 7 is suitable for connecting to one end of the Josephson junction 5. The dielectric layer 8 is suitable for isolating the first superconducting metal layer 6 and the second superconducting metal layer 7, and the inductance provided by the Josephson junction 5 and the first capacitor 3 determine the characteristic impedance of the traveling wave parametric amplifier. The phase matching resonance unit 4 is connected to the microstrip core 2, and the phase matching resonance unit 4 is suitable for phase matching the pump signal and the read signal obtained from the outside with the idler signal generated in the traveling wave parametric amplifier, so as to improve the gain of the traveling wave parametric amplifier through phase matching.

[0044] According to the embodiments of the present disclosure, Figure 1 As shown, the complete traveling wave parametric amplifier consists of hundreds of Figure 1The unit composition shown in the figure, each unit includes a number of sub-units a and a phase matching resonance unit 4.

[0045] According to an embodiment of the present disclosure, the material of the substrate 1 may be a sapphire substrate or a high-resistance silicon substrate.

[0046] According to the embodiment of the present disclosure, the first superconducting metal layer 6 and the second superconducting metal layer 7 of the first capacitor 3 may be any shape of equal area that meets the design requirements, such as a rectangle or a circle.

[0047] According to an embodiment of the present disclosure, the second superconducting metal layer 7 is composed of a superconducting metal block of the microstrip line core 2 .

[0048] According to an embodiment of the present disclosure, the materials of the first superconducting metal layer 6 and the second superconducting metal layer 7 may be superconducting aluminum metal, superconducting niobium metal, titanium nitride or the like.

[0049] According to the embodiment of the present disclosure, when designing the traveling wave parametric amplifier, the characteristic impedance of the microstrip line core 2 needs to be matched with the characteristic impedance of the peripheral line to avoid reflection. The characteristic impedance is, for example, 50Ω. The characteristic impedance Z of the microstrip line core 2 of the traveling wave parametric amplifier is char It is expressed by the following formula (1):

[0050]

[0051] Among them, L l Expressed as the inductance per unit length of the microstrip line core 2, C l It is represented as the value of the first capacitance 3 per unit length of the microstrip line core 2.

[0052] According to an embodiment of the present disclosure, the inductance value is determined by the nonlinear inductance provided by the Josephson junction 5. The nonlinear inductance L provided by the Josephson junction 5 is expressed by the following formula (2):

[0053]

[0054] Among them, Φ0 represents the magnetic flux quantum, I c It represents the critical current of the Josephson junction 5, and I represents the current value flowing through the Josephson junction 5 in the working state, and I is generally 0.5I c ~0.8I c .

[0055] According to an embodiment of the present disclosure, the determination of the value of the first capacitor 3 includes parallel plate capacitance value estimation and microwave simulation. The parallel plate capacitance value C estimation is expressed by the following formula (3):

[0056]

[0057] Among them, ε0 represents the vacuum dielectric constant, ε r represents the relative dielectric constant of the material of the dielectric layer 8 , S represents the area of ​​the first superconducting metal layer 6 and the second superconducting metal layer 7 facing each other, and d represents the thickness of the dielectric layer 8 .

[0058] According to the embodiments of the present disclosure, the difference between the value of the first capacitor 3 per unit length estimated by using the parallel plate capacitance value and the actual capacitance value is within 10%. At this time, a more accurate capacitance value result can be obtained by using the finite element method or the moment method through microwave simulation software for correction.

[0059] According to an embodiment of the present disclosure, a pump signal and a read signal are inputted externally into a traveling wave parametric amplifier, and an idler signal is generated by a physical process of nonlinear parametric amplification inside the traveling wave parametric amplifier.

[0060] According to an embodiment of the present disclosure, a microstrip core line 2 is arranged on a substrate 1, the microstrip core line 2 includes a junction chain composed of at least one Josephson junction 5, a first superconducting metal layer 6 of a first capacitor 3 is grounded, a second superconducting metal layer 7 of the first capacitor 3 is connected to one end of the Josephson junction 5, a dielectric layer 8 is arranged between the first superconducting metal layer 6 and the second superconducting metal layer 7, and the dielectric layer 8 is suitable for isolating the first superconducting metal layer 6 and the microstrip core line 2. Compared with a transmission line structure of a coplanar waveguide composed of grounded metal layers on both sides and a core line located between the grounded metal layers on both sides, the present disclosure has a structure in which the first superconducting metal layer 6 and the second superconducting metal layer 7 are connected. A dielectric layer 8 is arranged between the superconducting metal layers 7. The inductance provided by the Josephson junction 5 and the first capacitor 3 are used to determine the characteristic impedance of the traveling wave parametric amplifier, which is matched with the characteristic impedance of the peripheral line to avoid reflection. This can reduce the additional capacitance and inductance caused by the transmission line structure of the coplanar waveguide, so that the internal structure of the traveling wave parametric amplifier is compact. The traveling wave parametric amplifier is connected to the microstrip line core line 2 through a phase matching resonance unit 4. The phase matching resonance unit 4 phase-matches the pump signal and the read signal obtained from the outside with the idler signal generated in the traveling wave parametric amplifier, so as to improve the gain of the traveling wave parametric amplifier through phase matching.

[0061] According to an embodiment of the present disclosure, the material of the dielectric layer 8 is any one of the following: calcium fluoride, silicon oxide, and amorphous silicon.

[0062] According to the embodiments of the present disclosure, the dielectric constant of the air medium is only 1. If any one of calcium fluoride, silicon oxide, and amorphous silicon is used as the material of the dielectric layer 8, the dielectric constant of the dielectric layer 8 is much larger than 1, and a larger capacitance value can be provided under the same thickness of the dielectric layer 8 and the same area of ​​the first superconducting metal layer 6 and the second superconducting metal layer 7 facing each other. The large capacitance value of the first capacitor 3 and the small number of capacitors 3 can realize the compact setting of the microstrip line inside the traveling wave parametric amplifier.

[0063] Figure 2 is a top view of a microstrip line core line 2 according to an exemplary embodiment of the present disclosure. Figure 3 is a cross-sectional view of a traveling wave parametric amplifier according to an exemplary embodiment of the present disclosure.

[0064] According to the embodiments of the present disclosure, Figure 2 and Figure 3 As shown, a first superconducting metal layer 6 is formed on a substrate 1 , a dielectric layer 8 is formed on the first superconducting metal layer 6 , and a second superconducting metal layer 7 is formed on the dielectric layer 8 .

[0065] According to the embodiments of the present disclosure, Figure 2 and Figure 3 As shown, Figure 3 for Figure 2 In the cross-sectional view along the AA direction, the microstrip line core 2 is non-buried, the first superconducting metal layer 6 serves as the grounding layer of the traveling wave parametric amplifier, the second superconducting metal layer 7 serves as the non-grounding layer of the traveling wave parametric amplifier, and is also the preparation layer for the junction chain composed of the Josephson junction 5, and the dielectric layer 8 separates the microstrip line core 2 and the grounding layer.

[0066] According to an optional embodiment of the present disclosure, Figure 2 As shown, the Josephson junction 5 connected between the two second superconducting metal layers 7 can be connected to the center position of the side of the second superconducting metal layer 7, and can also be connected to the end position of the side of the second superconducting metal layer 7.

[0067] According to an embodiment of the present disclosure, compared with a coplanar waveguide without a dielectric layer 8, the coplanar waveguide is composed of a transmission line structure of grounded metal layers on both sides and a core line located between the grounded metal layers on both sides, while the present disclosure sets a dielectric layer 8 between the microstrip line core line 2 and the ground layer, which can reduce the additional capacitance and inductance caused by the transmission line structure of the coplanar waveguide, thereby making the internal structure of the traveling wave parametric amplifier compact.

[0068] Figure 4 is a top view of a microstrip line core line 2 according to another exemplary embodiment of the present disclosure. Figure 5 is a cross-sectional view of a traveling wave parametric amplifier according to another exemplary embodiment of the present disclosure.

[0069] According to the embodiments of the present disclosure, Figure 4 and Figure 5 As shown, the second superconducting metal layer 7 is formed on the substrate 1, the dielectric layer 8 is formed on the second superconducting metal layer 7, and the first superconducting metal layer 6 is on the dielectric layer 8. The dielectric layer 8 covers the second superconducting metal layer 7.

[0070] According to the embodiments of the present disclosure, Figure 4 and Figure 5As shown, Figure 5 for Figure 4 In the cross-sectional view along the AA direction, the microstrip line core 2 is buried, the dielectric layer 8 covers the second superconducting metal layer 7, the first superconducting metal layer 6 covers the dielectric layer 8, the first superconducting metal layer 6 serves as the grounding layer of the traveling wave parametric amplifier, the second superconducting metal layer 7 serves as the non-grounding layer of the traveling wave parametric amplifier, and is also the preparation layer for the junction chain composed of the Josephson junction 5. The junction chain composed of the Josephson junction 5 is also covered by the dielectric layer 8 and the first superconducting metal layer 6. The dielectric layer 8 isolates the microstrip line core 2 from the grounding layer.

[0071] According to the embodiments of the present disclosure, compared with the coplanar waveguide without the dielectric layer 8, the present disclosure sets a dielectric layer 8 between the microstrip line core 2 and the ground layer. When the microstrip line core 2 is buried, the dielectric layer 8 is used to cover the second superconducting metal layer 7 to isolate the microstrip line core 2 and the ground layer, which can reduce the additional capacitance and inductance caused by the transmission line structure of the coplanar waveguide, thereby making the internal structure of the traveling wave parametric amplifier compact.

[0072] According to an embodiment of the present disclosure, the phase matching resonant unit 4 includes a resonant cavity 9 and a second capacitor 10. One end of the resonant cavity 9 is connected to the first superconducting metal layer 6, and the resonant cavity 9 is suitable for phase matching the pump signal and the read signal obtained from the outside with the idler signal generated in the traveling wave parametric amplifier, so as to improve the gain of the traveling wave parametric amplifier through phase matching. One end of the second capacitor 10 is connected to the resonant cavity 9, and the other end is connected to the microstrip line core 2, and the second capacitor 10 is suitable for coupling the capacitance of the resonant cavity 9 and the microstrip line core 2.

[0073] According to the embodiments of the present disclosure, Figure 2 , Figure 3 , Figure 4 and Figure 5 As shown, one end of the resonant cavity 9 is connected to the first superconducting metal layer 6 , and the other end is connected to one end of the second capacitor 10 .

[0074] According to an embodiment of the present disclosure, the second capacitor 10 is suitable for coupling the capacitance of the resonant cavity 9 and the microstrip core 2. The second capacitor 10 can be a parallel plate capacitor, which is formed by the metal island isolated from the microstrip core 2 and the grounded metal layer. The capacitance value of this second capacitor 10 is determined by the above formula (3). The second capacitor 10 can also be a finger capacitor, which is formed by drawing a part of metal from the microstrip core 2 to form metal strips that are interlaced with another metal block, and the capacitance formed between the metal strips is used as a coupling capacitor. The capacitance value of this second capacitor 10 is determined by using the finite element method or the moment method through simulation software.

[0075] According to an embodiment of the present disclosure, the phase matching resonance unit 4 performs phase matching on the pump signal and the read signal obtained from the outside with the idler signal generated in the traveling wave parametric amplifier, so as to improve the gain of the traveling wave parametric amplifier through phase matching.

[0076] According to an embodiment of the present disclosure, the resonant cavity 9 is a distributed structure. By adjusting the length of the microstrip line core 2, a half-wavelength or quarter-wavelength resonant cavity 9 is constructed, and the characteristic frequency of the resonant cavity 9 is the characteristic frequency corresponding to the half-wavelength or quarter-wavelength.

[0077] According to an embodiment of the present disclosure, when the resonant cavity 9 is a distributed structure, a coplanar waveguide or microstrip line structure is patterned on the metal film on the substrate 1, and a half-wavelength or quarter-wavelength resonant cavity 9 is constructed by adjusting the overall length of the coplanar waveguide structure or the microstrip line core 2, and the characteristic frequency of the resonant cavity 9 is the characteristic frequency corresponding to the half-wavelength or quarter-wavelength.

[0078] According to an embodiment of the present disclosure, the resonant cavity 9 is formed by a lumped inductor and a lumped capacitor connected in parallel.

[0079] According to the embodiments of the present disclosure, the lumped inductor can be realized by patterning a thin and long metal film strip on the metal film on the substrate 1, and the lumped capacitor can be realized by using the same parallel plate capacitor as the traveling wave parametric amplifier microstrip line.

[0080] According to an embodiment of the present disclosure, the resonant cavity 9 is adapted to phase-match a pump signal and a read signal obtained from the outside with an idler signal generated in the traveling wave parametric amplifier, so as to improve the gain of the traveling wave parametric amplifier through phase matching.

[0081] Figure 6 It is a flow chart of a method for preparing a traveling wave parametric amplifier according to an illustrative embodiment of the present disclosure.

[0082] According to the embodiments of the present disclosure, Figure 6 As shown, a method for preparing the above-mentioned traveling wave parametric amplifier includes the following steps S1-S5:

[0083] Step S1: depositing a first superconducting metal layer 6 on the pre-treated substrate 1 by any one of thermal evaporation, electron beam evaporation, magnetron sputtering or molecular beam epitaxy.

[0084] Step S2: Use electron beam exposure equipment or optical exposure equipment to perform graphic definition, and use wet etching equipment or dry etching equipment to etch the first superconducting metal layer 6 into a graphic form.

[0085] Step S3: Depositing a dielectric layer 8 on the first superconducting metal layer 6 by any one of thermal evaporation, electron beam evaporation or chemical vapor deposition, and etching the dielectric layer 8 into a pattern.

[0086] According to an embodiment of the present disclosure, the dielectric layer 8 may be patterned using a lift-off process or an etching process.

[0087] Step S4: Use electron beam exposure equipment or optical exposure equipment to perform graphic definition, and use any method of thermal evaporation, electron beam evaporation or magnetron sputtering to deposit the second superconducting metal layer 7 on the dielectric layer 8, and etch the second superconducting metal layer 7 into a graphic form.

[0088] According to an embodiment of the present disclosure, the second superconducting metal layer 7 may be patterned using a lift-off process.

[0089] Step S5: preparing a Josephson junction 5 on the second superconducting metal layer 7 .

[0090] According to an embodiment of the present disclosure, after completing the above steps S1-S5, the traveling wave parametric amplifier is packaged, and the prepared traveling wave parametric amplifier is packaged in a sample box using wire binding means.

[0091] According to the embodiments of the present disclosure, the method for preparing a traveling wave parametric amplifier is compatible with the preparation process of a superconducting quantum bit chip. On this process platform, a traveling wave parametric amplifier for quantum bit reading can be prepared to improve the signal-to-noise ratio of the quantum bit reading signal.

[0092] According to an embodiment of the present disclosure, preparing the Josephson junction 5 on the second superconducting metal layer 7 includes: using electron beam exposure equipment to define the pattern of the Josephson junction 5, and using a dual-angle evaporation process and a lift-off process to prepare the Josephson junction 5.

[0093] According to the embodiments of the present disclosure, the preparation of the Josephson junction 5 can provide nonlinear inductance for the traveling wave parametric amplifier.

[0094] Figure 7 It is a flow chart of a method for preparing a traveling wave parametric amplifier according to another exemplary embodiment of the present disclosure.

[0095] According to the embodiments of the present disclosure, Figure 7 As shown, a method for preparing the above-mentioned traveling wave parametric amplifier includes the following steps S10-S50:

[0096] Step S10: Depositing a second superconducting metal layer 7 on the pretreated substrate 1 by any one of thermal evaporation, electron beam evaporation, magnetron sputtering or molecular beam epitaxy.

[0097] Step S20: Use electron beam exposure equipment or optical exposure equipment to perform graphic definition, and use wet etching equipment or dry etching equipment to etch the second superconducting metal layer 7 into a graphic form.

[0098] Step S30: using an electron beam exposure device to define the pattern of the Josephson junction 5, and using a double-angle evaporation process and a lift-off process to prepare the Josephson junction 5 on the second superconducting metal layer 7.

[0099] Step S40: Depositing a dielectric layer 8 on the second superconducting metal layer 7 by any one of thermal evaporation, electron beam evaporation or chemical vapor deposition, and etching the dielectric layer 8 into a pattern.

[0100] According to an embodiment of the present disclosure, the dielectric layer 8 may be patterned using a lift-off process or an etching process.

[0101] Step S50: Use electron beam exposure equipment or optical exposure equipment to perform graphic definition, and use any method of thermal evaporation, electron beam evaporation or magnetron sputtering to deposit the first superconducting metal layer 6 on the dielectric layer 8, and etch the first superconducting metal layer 6 into a graphic form.

[0102] According to an embodiment of the present disclosure, the first superconducting metal layer 6 may be patterned using a lift-off process.

[0103] According to an embodiment of the present disclosure, after completing the above steps S10-S50, the traveling wave parametric amplifier is packaged, and the prepared traveling wave parametric amplifier is packaged in a sample box using wire binding means.

[0104] According to the embodiments of the present disclosure, the method for preparing a traveling wave parametric amplifier is compatible with the preparation process of a superconducting quantum bit chip. On this process platform, a traveling wave parametric amplifier for quantum bit reading can be prepared to improve the signal-to-noise ratio of the quantum bit reading signal.

[0105] Figure 8 is a graph showing the gain and bandwidth performance of a traveling wave parametric amplifier according to an exemplary embodiment of the present disclosure.

[0106] According to the embodiments of the present disclosure, Figure 8 As shown, taking the traveling wave parametric amplifier prepared by using buried microstrip line core 2 as an example, Figure 8 The graph shows the typical performance results of the traveling wave parametric amplifier, with the horizontal axis representing the signal frequency and the vertical axis representing the gain. It can be seen that this type of traveling wave parametric amplifier can achieve a gain of more than 15dB in the 5GHz-7GHz frequency band and a bandwidth of more than 2GHz. This type of traveling wave parametric amplifier can better realize the amplification of the read signal of multiple quantum bits in quantum computing.

[0107] It should also be noted that the directional terms mentioned in the embodiments, such as "upper", "lower", "front", "back", "left", "right", etc., are only reference directions of the drawings and are not intended to limit the scope of protection of the present disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present disclosure, and the shapes and sizes of the components in the drawings do not reflect the actual size and proportion, but only illustrate the contents of the embodiments of the present disclosure.

[0108] Unless otherwise indicated, the numerical parameters in this specification and the appended claims are approximate values ​​and can vary according to the desired properties obtained through the content of the present disclosure. Specifically, all numbers used in the specification and claims to express the content of the composition, reaction conditions, etc., should be understood to be modified by the term "about" in all cases. In general, the meaning of the expression is to include a variation of ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, and ±0.5% in some embodiments by a specific number.

[0109] The ordinal numbers used in the specification and claims, such as "first", "second", "third", etc., to modify the corresponding elements, do not themselves mean that the elements have any ordinal numbers, nor do they represent the order of one element and another element, or the order in the manufacturing method. The use of these ordinal numbers is only used to clearly distinguish a component with a certain name from another component with the same name.

[0110] In addition, unless the steps are specifically described or must occur in sequence, the order of the above steps is not limited to the above list, and can be changed or rearranged according to the required design. And the above embodiments can be mixed and matched with each other or with other embodiments based on design and reliability considerations, that is, the technical features in different embodiments can be freely combined to form more embodiments.

[0111] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. The scope of the present disclosure is defined by the attached claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A traveling wave parametric amplifier, comprising: substrate; A microstrip line core wire is arranged on the substrate, and the microstrip line core wire includes a knot chain composed of at least one Josephson junction; The first capacitor includes: A first superconducting metal layer suitable for grounding; a second superconducting metal layer, adapted to be connected to one end of the Josephson junction; A dielectric layer, wherein the dielectric layer is suitable for isolating the first superconducting metal layer and the second superconducting metal layer, and the inductance provided by the Josephson junction and the first capacitor determine the characteristic impedance of the traveling wave parametric amplifier; Wherein, the dielectric layer is suitable for isolating the first superconducting metal layer and the microstrip line core wire; A phase matching resonance unit connected to the core line of the microstrip line, wherein the phase matching resonance unit is adapted to phase-match a pump signal and a read signal obtained from the outside with an idler signal generated in the traveling wave parametric amplifier, so as to improve the gain of the traveling wave parametric amplifier through the phase matching; Among them, the phase matching resonance unit includes a resonance cavity, which is a distributed structure. By adjusting the length of the microstrip line core, a half-wavelength or quarter-wavelength resonance cavity is constructed, and the characteristic frequency of the resonance cavity is the characteristic frequency corresponding to the half-wavelength or quarter-wavelength.

2. The traveling wave parametric amplifier according to claim 1, wherein: The material of the dielectric layer is any one of the following: calcium fluoride, silicon oxide, and amorphous silicon.

3. The traveling wave parametric amplifier according to claim 1, wherein: The first superconducting metal layer is formed on the substrate, the dielectric layer is formed on the first superconducting metal layer, and the second superconducting metal layer is formed on the dielectric layer.

4. The traveling wave parametric amplifier according to claim 1, wherein: The second superconducting metal layer is formed on the substrate, the dielectric layer is formed on the second superconducting metal layer, and the first superconducting metal layer is formed on the dielectric layer; Wherein, the dielectric layer covers the second superconducting metal layer.

5. The traveling wave parametric amplifier according to claim 1, wherein: The phase matching resonance unit comprises: A resonant cavity, one end of which is connected to the first superconducting metal layer, the resonant cavity being adapted to phase-match a pump signal and a read signal obtained from the outside with an idler signal generated in the traveling wave parametric amplifier, so as to improve the gain of the traveling wave parametric amplifier through the phase matching; A second capacitor has one end connected to the resonant cavity and the other end connected to the microstrip line core line, and the second capacitor is suitable for coupling the capacitance of the resonant cavity and the microstrip line core line.

6. The traveling wave parametric amplifier according to claim 5, wherein: The resonant cavity is formed by connecting a lumped inductor and a lumped capacitor in parallel.

7. A method for preparing a traveling wave parametric amplifier as claimed in any one of claims 1 to 6, comprising: Depositing a first superconducting metal layer on the pretreated substrate by any one of thermal evaporation, electron beam evaporation, magnetron sputtering or molecular beam epitaxy; Using electron beam exposure equipment or optical exposure equipment to perform graphic definition, and using wet etching equipment or dry etching equipment to perform graphic etching on the first superconducting metal layer; Depositing a dielectric layer on the first superconducting metal layer by any one of thermal evaporation, electron beam evaporation or chemical vapor deposition, and etching the dielectric layer into a pattern; Using an electron beam exposure device or an optical exposure device to perform graphic definition, and using any one of thermal evaporation, electron beam evaporation or magnetron sputtering to deposit a second superconducting metal layer on the dielectric layer, and etching the second superconducting metal layer; A Josephson junction is prepared on the second superconducting metal layer.

8. The preparation method according to claim 7, wherein: The step of preparing a Josephson junction on the second superconducting metal layer comprises: The pattern of the Josephson junction is defined by using an electron beam exposure device, and the Josephson junction is prepared by using a double-angle evaporation process and a lift-off process.

9. A method for preparing a traveling wave parametric amplifier as claimed in any one of claims 1 to 6, comprising: Depositing a second superconducting metal layer on the pretreated substrate by any one of thermal evaporation, electron beam evaporation, magnetron sputtering or molecular beam epitaxy; Using electron beam exposure equipment or optical exposure equipment to perform graphic definition, and using wet etching equipment or dry etching equipment to perform graphic etching on the second superconducting metal layer; Using an electron beam exposure device to define the pattern of the Josephson junction, and using a double-angle evaporation process and a lift-off process to prepare the Josephson junction on the second superconducting metal layer; Depositing a dielectric layer on the second superconducting metal layer by any one of thermal evaporation, electron beam evaporation or chemical vapor deposition, and etching the dielectric layer into a pattern; An electron beam exposure device or an optical exposure device is used for graphic definition, and a first superconducting metal layer is deposited on the dielectric layer by any one of thermal evaporation, electron beam evaporation or magnetron sputtering, and the first superconducting metal layer is etched into a graphic form.

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