Qubit device, method for manufacturing a qubit device, and method for measuring a qubit device

Abstract

This quantum bit device comprises: a substrate; a quantum bit provided on the substrate; signal wiring provided on the substrate and electrically connected to the quantum bit; and a semiconductor film provided in contact with a portion of the signal wiring, and having a width wider than the width of the signal wiring. The quantum bit device makes it possible to measure the characteristics of the signal wiring without affecting the quantum bit, by applying a measurement terminal to the semiconductor film in a normal temperature environment and measuring the characteristics of the signal wiring.

Description

Technical Field

[0001] The present invention relates to a qubit device, a method for manufacturing a qubit device, and a method for measuring a qubit device.

Background Art

[0002] There is known a qubit device in which qubits and signal wirings electrically connected to the qubits are provided on a substrate. For example, it is known to make the signal wiring a two-layer structure of a superconductor material (for example, Patent Documents 1 and 2), or to make it a two-layer structure of a superconductor layer and a normal-conducting metal layer (for example, Patent Document 3). It is also known to configure the signal wiring with a superconductor layer and an antiferromagnetic insulator layer covering the surface of the superconductor layer (for example, Patent Document 4).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, a qubit device is measured for its characteristics in an extremely low temperature state of several tens of millikelvin (mK). In this case, there are problems such as the need for a long time to cool to the extremely low temperature and the difficulty of replacing the measurement terminals in the cooling device.

[0005] Therefore, it is desirable to measure the characteristics of signal wiring in a room temperature environment. However, because signal wiring is narrow, it is difficult to measure its characteristics by directly contacting the measurement terminal with the signal wiring. Furthermore, even if one attempts to measure the characteristics of signal wiring via a qubit, the DC resistance of the qubit becomes very high at room temperature (several thousand ohms), making it difficult to measure the characteristics of the signal wiring.

[0006] One aspect of this is the ability to measure the characteristics of signal wiring in a room temperature environment. [Means for solving the problem]

[0007] In one embodiment, the qubit device comprises a substrate, a qubit provided on the substrate, signal wiring provided on the substrate and electrically connected to the qubit, and a semiconductor film provided overlapping a portion of the signal wiring and having a width wider than the width of the signal wiring.

[0008] In one embodiment, the method for manufacturing a qubit device comprises the steps of: forming signal wiring on a substrate; forming a semiconductor film that overlaps with a portion of the signal wiring and has a width wider than the width of the signal wiring; and forming a qubit on the substrate that is electrically connected to the signal wiring.

[0009] In one embodiment, a method for measuring a qubit device is provided on a substrate, comprising a qubit and signal wiring electrically connected to the qubit, and a semiconductor film overlapping a portion of the signal wiring and having a width wider than the width of the signal wiring, wherein a measurement terminal is applied to the semiconductor film to measure the characteristics of the signal wiring. [Effects of the Invention]

[0010] One aspect of this is that it becomes possible to measure the characteristics of signal wiring in a room temperature environment. [Brief explanation of the drawing]

[0011] [Figure 1] Fig. 1(a) is a plan view of the qubit device according to Example 1, and Fig. 1(b) is a plan view with an enlarged view near the resonator. [Figure 2] Fig. 2(a) is a plan view near the end of the signal wiring of the qubit device according to Example 1, and Fig. 2(b) is a cross-sectional view taken along the line A-A of Fig. 2(a). [Figure 3] Figs. 3(a) to 3(d) are cross-sectional views (Part 1) showing the manufacturing method of the qubit device according to Example 1. [Figure 4] Figs. 4(a) and 4(b) are cross-sectional views (Part 2) showing the manufacturing method of the qubit device according to Example 1. [Figure 5] Figs. 5(a) and 5(b) are a cross-sectional view and a plan view showing a method for measuring the DC resistance of the signal wiring in Example 1. [Figure 6] Figs. 6(a) and 6(b) are a cross-sectional view and a plan view showing a method for measuring the high-frequency characteristics of the signal wiring in Example 1. [Figure 7] Fig. 7 is a circuit schematic diagram of the qubit device according to Example 1. [Figure 8] Figs. 8(a) to 8(c) are diagrams (Part 1) showing the simulation results of the resonance waveform of the signal wiring in Example 1. <​​​​​​​​​​​​FIG. 13(a) is a cross-sectional view showing a method for measuring the DC resistance of the signal wiring in Example 2, and FIG. 13(b) is a cross-sectional view showing a method for measuring the high-frequency characteristics. [Figure 14] FIG. 14 is a cross-sectional view near the end of the signal wiring of the quantum bit device according to Example 3. [Figure 15] FIGS. 15(a) to 15(c) are cross-sectional views showing a method for manufacturing the quantum bit device according to Example 3. [Figure 16] FIG. 16 is a cross-sectional view near the end of the signal wiring of the quantum bit device according to Example 4. [Figure 17] FIG. 17(a) is a plan view of the quantum bit device according to Example 5, and FIG. 17(b) is an enlarged plan view near the resonator and the band-pass filter. [Figure 18] FIG. 18(a) is a plan view near the end of the signal wiring of the quantum bit device according to Example 5, and FIG. 18(b) is a cross-sectional view taken along the line A-A of FIG. 18(a).

BEST MODE FOR CARRYING OUT THE INVENTION

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

EXAMPLE

[0013] FIG. 1(a) is a plan view of the quantum bit device 100 according to Example 1, and FIG. 1(b) is an enlarged plan view near the resonator 40. In FIGS. 1(a) and 1(b), for clarity of the drawing, the superconducting film and the semiconductor film provided on the substrate 10 are hatched. Also, for clarity of the drawing, in FIG. 1(a), the illustration of the ground layer 44 shown in FIG. 1(b) is omitted, and in FIGS. 1(a) and 1(b), the illustration of the insulating film 46 shown in FIGS. 2(a) and 2(b) is omitted.

[0014] As shown in Figures 1(a) and 1(b), the qubit device 100 according to Embodiment 1 has a plurality of qubits 20, a plurality of resonators 40, a plurality of coupling connections 60, and a readout terminal 62 provided on a substrate 10. The qubit device 100 is used, for example, in a quantum computer that operates in a superconducting state at extremely low temperatures of several tens of millikelvins (mK).

[0015] Each of the multiple resonators 40 is electrostatically coupled to each of the multiple qubits 20. Furthermore, the multiple resonators 40 are electrostatically coupled to a single readout terminal 62. The resonators 40 interact with the qubits 20 to read out their states. The read-out states of the qubits 20 are retrieved externally via the readout terminal 62. The resonators 40 are, for example, lumped-parameter circuits such as LC resonators, distributed-parameter circuits such as λ / 2 resonators, or distributed-parameter circuits such as λ / 4 resonators. The coupling wiring 60 is electrostatically coupled to the qubits 20 and connects adjacent qubits 20. The connections between the qubits 20 and the resonators 40, between the resonators 40 and the readout terminal 62, and between the qubits 20 and the coupling wiring 60 are high-frequency connections.

[0016] The qubit 20 includes a Josephson junction element 26 joined between a central electrode 22 and an outer electrode 24, and a capacitor 28 formed by the opposing central electrode 22 and outer electrode 24. The Josephson junction element 26 is connected between the central electrode 22 and the outer electrode 24 by a superconducting film 30 connected to the central electrode 22 and a superconducting film 32 connected to the outer electrode 24. In the region where the superconducting film 30 and the superconducting film 32 intersect, an insulating film (not shown) is provided between the superconducting film 30 and the superconducting film 32.

[0017] The resonator 40 has a meander structure coplanar line in which the signal wiring 42 is sandwiched between ground layers 44. A high-frequency signal for readout, for example in the gigahertz band (e.g., 2 GHz to 10 GHz), propagates through the signal wiring 42. A semiconductor film 50 is provided overlapping both ends of the signal wiring 42. The semiconductor film 50 is not provided anywhere other than the ends of the signal wiring 42. The semiconductor film 50 is provided in contact with each end of the signal wiring 42. The semiconductor film 50 is provided away from the qubit 20 and is not in contact with the outer electrodes 24, etc., that constitute the qubit 20. In Figure 1(b), an example is shown in which a ground layer 44 is also provided between the qubit 20 and the resonator 40, but it is also possible that there is no ground layer 44 between the qubit 20 and the resonator 40.

[0018] Figure 2(a) is a plan view of the vicinity of the end of the signal wiring 42 of the qubit device 100 according to Example 1, and Figure 2(b) is a cross-sectional view of AA in Figure 2(a). In Figure 2(a), hatching is applied to the signal wiring 42, ground layer 44, insulating film 46, and semiconductor film 50 for clarity. As shown in Figures 2(a) and 2(b), the semiconductor film 50 has a width greater than the width of the signal wiring 42 and covers the entire width of the signal wiring 42. The width X of the signal wiring 42 is, for example, 10 μm to 30 μm. The semiconductor film 50 has, for example, a rectangular shape in plan view, and the width Y1 in the width direction of the signal wiring 42 and the width Y2 in the direction perpendicular to the width direction of the signal wiring 42 are greater than the width of the signal wiring 42, ranging from 50 μm to 500 μm. Thus, the semiconductor film 50 has an outer shape greater than the width of the signal wiring 42.

[0019] The upper surface of the signal wiring 42 is left exposed and uncovered, and an insulating film 46 is provided from above the ground layer 44 to the gap between the signal wiring 42 and the ground layer 44. The semiconductor film 50 is in contact with the upper surface of the signal wiring 42 and is provided from above the signal wiring 42 to the insulating film 46. Therefore, the semiconductor film 50 is not in contact with the ground layer 44. The signal wiring 42 and the ground layer 44 have the same thickness T1, which is, for example, 0.01 μm to 20 μm. The thickness T2 of the insulating film 46 is, for example, 1 μm to 20 μm. The thickness T3 of the semiconductor film 50 is, for example, 5 μm to 30 μm.

[0020] The substrate 10 is an insulating substrate such as a silicon substrate or a sapphire substrate. The signal wiring 42 and ground layer 44 are formed of a superconducting material, for example, aluminum (Al), titanium nitride (TiN), niobium (Nb), or tantalum (Ta). The insulating film 46 is formed of a resin material or an inorganic insulating material, for example, a solder resist. The semiconductor film 50 has an electrical resistivity of 10 at an extremely low temperature of 20 millikelvin (mK). 4 It is formed from a semiconductor material having insulating properties of Ω·m or greater. For example, the semiconductor film 50 is formed from an oxide semiconductor such as amorphous silicon, indium oxide (In2O3), titanium oxide (TiO2), or zinc oxide (ZnO), a III-V compound semiconductor such as gallium arsenide (GaAs) or indium phosphide (InP), or a II-VI compound semiconductor such as cadmium telluride (CdTe) or cadmium sulfide (CdS). The semiconductor film 50 may also be doped with materials such as phosphorus (P) and boron (B).

[0021] [Manufacturing method] Figures 3(a) to 4(b) are cross-sectional views showing a method for manufacturing a qubit device 100 according to Example 1. As shown in Figure 3(a), a superconducting film 80 is formed on a substrate 10 using, for example, a sputtering method or a vapor deposition method.

[0022] As shown in Figure 3(b), the superconducting film 80 is patterned using, for example, photolithography and etching. This forms the signal wiring 42 and ground layer 44 that constitute the resonator 40. Also, as shown in Figure 4(a), the central electrode 22 and outer electrode 24 are formed. Although not shown in the figure, coupling wiring 60 and readout terminal 62 are also formed.

[0023] As shown in Figure 3(c), an insulating film 46 is deposited on the substrate 10 by, for example, printing, sputtering, vapor deposition, or CVD (Chemical Vapor Deposition). Subsequently, the insulating film 46 is patterned by, for example, photolithography and etching. This forms an insulating film 46 that extends from the ground layer 44 to the gap between the ground layer 44 and the signal wiring 42, exposing the upper surface of the signal wiring 42.

[0024] As shown in Figure 3(d), a semiconductor film 50 is formed on the substrate 10 using, for example, sputtering, vapor deposition, or CVD. Then, the semiconductor film 50 is patterned using, for example, photolithography and etching. As a result, a semiconductor film 50 is formed on both ends of the signal wiring 42, in contact with the upper surface of the signal wiring 42 and covering the signal wiring 42. The semiconductor film 50 is formed from above the signal wiring 42 to above the insulating film 46.

[0025] As shown in Figure 4(a), a superconducting film 30 is formed to connect to the central electrode 22. The superconducting film 30 is formed, for example, by oblique deposition and lift-off methods. Subsequently, the surface of the superconducting film 30 is oxidized to form an insulating film 34 on the surface of the superconducting film 30.

[0026] As shown in Figure 4(b), a superconducting film 32 is formed to connect to the outer electrode 24. The superconducting film 32 is formed, for example, by oblique deposition and lift-off methods. This forms a Josephson junction element 26 having a Josephson junction, which is a region where the superconducting film 30 and the superconducting film 32 overlap via an insulating film 34.

[0027] [Measurement method] Figures 5(a) and 5(b) are a cross-sectional view and a plan view showing a method for measuring the DC resistance of the signal wiring 42 in Example 1. In Figure 5(b), for clarity, the signal wiring 42 is shown as a straight line, and the insulating film 46 is omitted from the illustration. The DC resistance may be measured in an environment at room temperature (e.g., 20°C ± 15°C) before forming the Josephson junction element 26, or after forming the Josephson junction element 26. As shown in Figures 5(a) and 5(b), the DC resistance of the signal wiring 42 is measured by bringing a measuring terminal 82 into contact with the semiconductor film 50 provided on the end of the signal wiring 42. For example, a semiconductor parameter may be used as a measuring device for measuring the DC resistance. For example, if there is an open circuit in the signal wiring 42, the DC resistance value will be infinite, and if there is a short circuit in the signal wiring 42, the DC resistance value will be such that the resistance value of the semiconductor film 50 is dominant.

[0028] As an example, suppose the width X of the signal wiring 42 is 30 μm, the widths Y1 and Y2 of the semiconductor film 50 are 100 μm, the thickness T3 of the semiconductor film 50 is 10 μm, and the conductivity of the semiconductor film 50 is 20 S / m (see Figures 2(a) and 2(b) for width X, Y1, Y2, and thickness T3). In this case, the resistance R in the semiconductor film 50 of the current flowing between the measurement terminal 82 and the signal wiring 42 is R = (10 × 10 -6 ) / 20×(100×10 -6 )×(50×10 -6 It can be calculated as (10 × 10) and will be approximately 100Ω. Note that in the above formula, (10 × 10 -6 ) is the thickness of the semiconductor film 50. 20 is the conductivity of the semiconductor film 50. (100 × 10 -6 ) is the length of the overlap between the signal wiring 42 and the semiconductor film 50. (50 × 10 -6 ) represents the approximate width of the current that converges on the 30 μm wide signal wiring 42.

[0029] Figures 6(a) and 6(b) are cross-sectional and plan views, respectively, illustrating a method for measuring the high-frequency characteristics of the signal wiring 42 in Example 1. In Figure 6(b), for clarity, the signal wiring 42 is shown as a straight line, and the insulating film 46 is omitted from the illustration. The measurement of high-frequency characteristics, like the measurement of DC resistance, may be performed at room temperature (e.g., 20°C ± 15°C) before forming the Josephson junction element 26, or after forming the Josephson junction element 26. As shown in Figures 6(a) and 6(b), the measurement terminal 82 is brought into contact with the semiconductor film 50 and the ground layers 44 on both sides of the signal wiring 42, which are provided on the end of the signal wiring 42, to measure the high-frequency characteristics of the signal wiring 42. In measuring the high-frequency characteristics, the measurement terminal 82 may be brought into contact with the semiconductor film 50 and the ground layers 44 on both sides at both ends of the signal wiring 42, or it may be brought into contact with the semiconductor film 50 and the ground layers 44 on both sides at only one end. As high-frequency characteristics, for example, a resonant waveform or a TDR (Time Domain Reflectometry) waveform is measured. For measuring the resonant waveform, for example, a vector network analyzer can be used. For measuring the TDR waveform, for example, a TDR oscilloscope or the TDR conversion of a vector network analyzer can be used.

[0030] Figure 7 is a schematic circuit diagram of the qubit device 100 according to Embodiment 1. As shown in Figure 7, the qubit 20 and the resonator 40 are coupled via a capacitor 74. Measuring the characteristics of the signal wiring 42 by bringing the measurement terminal 82 into contact with the semiconductor film 50 provided at the end of the signal wiring 42 is equivalent to measuring the characteristics of the signal wiring 42 by bringing the measurement terminal 82 into contact with the location indicated by arrow A. Therefore, the characteristics of the signal wiring 42 can be measured without being affected by the qubit 20 coupled via the capacitor 74.

[0031] For example, if the resonator 40 is a distributed-parameter circuit resonator, the signal wiring 42 becomes thin and long, so the DC resistance of the signal wiring 42 becomes high, for example, it may reach several hundred ohms. In such cases, it is desirable to measure the DC resistance as a characteristic of the signal wiring 42. If the resonator 40 is a lumped-parameter circuit resonator, the signal wiring 42 becomes short, so the DC resistance becomes small. In such cases, it is desirable to measure the high-frequency characteristics such as the resonant waveform and / or TDR waveform as a characteristic of the signal wiring 42.

[0032] Figures 8(a) to 9(b) show the simulation results of the resonant waveform of the signal wiring 42 in Example 1. In Figures 8(a) to 9(b), the horizontal axis represents frequency in GHz, and the vertical axis represents the reflection characteristic |S11| in dB. In Figures 8(a) to 9(b), the waveform when the total DC resistance of the signal wiring 42 and the semiconductor film 50 provided at both ends of the signal wiring 42 is 0 Ω is shown by a dotted line, and the waveforms for 1 Ω, 10 Ω, 30 Ω, 100 Ω, and 300 Ω are shown by solid lines. The resistance value of the semiconductor film 50 was determined as described in paragraph 0028. The simulation conditions are as follows. Substrate 10: Silicon substrate Signal wiring 42 and ground layer 44: Aluminum layer Insulating film 46: Solder resist Semiconductor film 50: Amorphous silicon Average relative permittivity of air and silicon substrate: 6.25 Signal wire length 42: 6mm Signal cable width 42: 0.02mm Resonance frequency: 10GHz

[0033] As shown in Figures 8(a) to 9(b), resonance was observed up to a total DC resistance of 30Ω for the signal wiring 42 and semiconductor film 50, but not at 100Ω or higher. From these results, it can be seen that resonance can be observed when the total DC resistance of the signal wiring 42 and semiconductor film 50 is less than 100Ω, and that 30Ω or less is preferable.

[0034] Figures 10(a) to 10(c) show the simulation results of the resonant waveform when the resonant frequency is varied in the signal wiring 42 in Example 1. In Figures 10(a) to 10(c), the horizontal axis represents frequency in GHz, and the vertical axis represents the reflection characteristic |S11| in dB. Also, in Figures 10(a) to 10(c), the waveform when the total DC resistance of the signal wiring 42 and semiconductor film 50 is 0 Ω is shown by a dotted line, and the waveform when it is 30 Ω is shown by a solid line. The simulation conditions in Figure 10(a) are the same as in paragraph 0032. The simulation conditions in Figure 10(b) are the same as in paragraph 0032, except that the average relative permittivity of air and silicon substrate is 6.25, the length of the signal wiring 42 is 7 mm, and the resonant frequency is 8.33 GHz. The simulation conditions in Figure 10(c) are the same as those in paragraph 0032, except that the average relative permittivity of air and silicon substrate is set to 6.25, the length of signal wiring 42 is set to 5 mm, and the resonant frequency is set to 11.67 GHz.

[0035] As shown in Figure 10(a), when the resonant frequency is 10 GHz when the combined DC resistance of the signal wiring 42 and semiconductor film 50 is 0 Ω, the resonant frequency shifts to 12.3 GHz when the DC resistance is 30 Ω. As shown in Figure 10(b), when the resonant frequency is 9 GHz when the DC resistance is 0 Ω, the resonant frequency shifts to 10.7 GHz when the DC resistance is 30 Ω. As shown in Figure 10(c), when the resonant frequency is 11 GHz when the DC resistance is 0 Ω, the resonant frequency shifts to 14.4 GHz when the DC resistance is 30 Ω. Thus, even when the resonant frequency at 0 Ω is different, the resonant frequency at 30 Ω is higher than the resonant frequency at 0 Ω. From this, it can be seen that if the combined DC resistance of the signal wiring 42 and semiconductor film 50 is known, it is possible to check whether the resonant frequency at 0 Ω is shifted to a lower frequency or a higher frequency relative to the desired frequency.

[0036] Figures 11(a) to 11(d) show the simulation results of the TDR waveform of the signal wiring 42 in Example 1. In Figures 11(a) to 11(d), the horizontal axis represents time in ns and the vertical axis represents impedance in ohms. In Figures 11(a) to 11(d), the waveform when the total DC resistance of the signal wiring 42 and the semiconductor film 50 is 0 Ω is shown by a dotted line, and the waveforms for 10 Ω, 30 Ω, 100 Ω, and 300 Ω are shown by solid lines. The simulation conditions are the same as in paragraph 0032. TDR measurement reveals the high and low characteristic impedance at each position of the signal wiring 42. For example, the characteristic impedance decreases as the signal wiring 42 becomes thicker, and increases as it becomes thinner.

[0037] As shown in Figures 11(a) to 11(d), when the combined DC resistance of the signal wiring 42 and the semiconductor film 50 is 0Ω, the impedance becomes low around 0.05ns and high around 0.15ns. When the DC resistance is 10Ω and 30Ω, similar to the 0Ω case, the impedance becomes low around 0.05ns and high around 0.15ns. However, when the DC resistance is 100Ω and 300Ω, it was not possible to distinguish between high and low impedance. From these results, it can be seen that, in TDR measurements, for the distinction between high and low impedance to be confirmed, the combined DC resistance of the signal wiring 42 and the semiconductor film 50 must be less than 100Ω, and preferably 30Ω or less.

[0038] From the above simulation results, high-frequency characteristics can be measured when the combined DC resistance of the signal wiring 42 and the semiconductor film 50 is less than 100 Ω, preferably 80 Ω or less, more preferably 50 Ω or less, and even more preferably 30 Ω or less. The DC resistance of a single semiconductor film 50 is preferably 30 Ω or less, more preferably 20 Ω or less, and even more preferably 10 Ω or less.

[0039] As described above, according to Example 1, as shown in Figures 1(a) to 2(b), a semiconductor film 50 having a width wider than the signal wiring 42 is provided overlapping a portion of the signal wiring 42 electrically connected to the qubit 20. This allows the characteristics of the signal wiring 42 to be measured by placing the measurement terminal 82 on the semiconductor film 50, as shown in Figures 5(a) to 6(b). Therefore, as shown in Figure 7, the characteristics of the signal wiring 42 can be measured without being affected by the qubit 20, and the characteristics of the signal wiring 42 can be measured in a room temperature environment. Here, generally, the electrical resistance of a semiconductor increases as the temperature decreases. Therefore, even when the semiconductor film 50 is provided overlapping the signal wiring 42, at extremely low temperatures of tens of mK or less, when the qubit device 100 is in operation, the semiconductor film 50 has high electrical resistance and functions as an insulator. Thus, the influence on the characteristics of the qubit device 100 can be suppressed.

[0040] Furthermore, in Example 1, as shown in Figures 1(a) and 1(b), the semiconductor film 50 is provided overlapping both ends of the signal wiring 42. This makes it possible to measure the overall characteristics of the signal wiring 42. When measuring the high-frequency characteristics of the signal wiring 42, the measurement terminal 82 can be applied to only one end of the signal wiring 42 for measurement. In such a case, the semiconductor film 50 only needs to overlap one end of the signal wiring 42. Therefore, the semiconductor film 50 only needs to overlap at least one end of the signal wiring 42.

[0041] Furthermore, in Example 1, as shown in Figures 1(a) and 1(b), the signal wiring 42 constitutes a resonator 40 that is electrically connected to the qubit 20. This allows the characteristics of the resonator 40 to be measured by measuring the characteristics of the signal wiring 42.

[0042] Furthermore, in Example 1, as shown in Figures 2(a) and 2(b), the semiconductor film 50 is provided on the substrate 10 in contact with a portion of the signal wiring 42. This allows the semiconductor film 50 to be made thinner compared to Example 3, which will be described later, and thus the total DC resistance of the signal wiring 42 and the semiconductor film 50 can be kept low.

[0043] Furthermore, in Example 1, as shown in Figures 2(a) and 2(b), ground layers 44 are provided on both sides of the signal wiring 42, and an insulating film 46 is provided from above the ground layer 44 to the gap between the ground layer 44 and the signal wiring 42. The semiconductor film 50 is provided from above the signal wiring 42 to above the insulating film 46. This makes it easier to obtain a semiconductor film 50 of sufficient size to make contact with the measurement terminal 82. From the standpoint of securing the area for contact with the measurement terminal 82, the widths Y1 and Y2 of the semiconductor film 50 (see Figure 2(a) for widths Y1 and Y2) are preferably 50 μm or more and 500 μm or less. Considering the point of securing the contact area for the measurement terminal 82 and the impact on other parts due to the provision of the semiconductor film 50, the widths Y1 and Y2 of the semiconductor film 50 may be 80 μm or more and 300 μm or less, or 100 μm or more and 200 μm or less.

[0044] Furthermore, in Example 1, the semiconductor film 50 is formed from a semiconductor material that is insulating at a temperature of 20 millikelvin (mK). This increases the electrical resistance of the semiconductor film 50 at the extremely low temperatures in which the qubit device 100 operates, thus minimizing the impact on the characteristics of the qubit device 100 even when the semiconductor film 50 is provided. Here, insulating means that the electrical resistivity is 10 4 This refers to cases where the density is Ω·m or greater. Examples of such semiconductor films 50 include semiconductor films formed from amorphous silicon, indium oxide, titanium oxide, zinc oxide, etc.

[0045] Furthermore, in Example 1, as shown in Figure 1(a), the qubit 20 includes a Josephson junction element 26. As shown in Figure 4(b), the Josephson junction element 26 has a structure in which an insulating film 34 is provided between a superconducting film 30 and a superconducting film 32, so its DC resistance tends to be high, for example, several thousand ohms. However, even when such a qubit 20 is provided, in Example 1, as shown in Figure 7, the characteristics of the signal wiring 42 can be measured without being affected by the qubit 20, so the characteristics of the signal wiring 42 can be measured with high accuracy.

[0046] Furthermore, in Example 1, the semiconductor film 50 is not in contact with the qubit 20, but is provided at a distance from the qubit 20. A high Q-factor is required for the qubit 20, but if the semiconductor film 50 is in contact with the qubit 20, the Q-factor of the qubit 20 will decrease. By providing the semiconductor film 50 at a distance from the qubit 20, the decrease in the Q-factor of the qubit 20 can be suppressed.

[0047] In Example 1, when measuring the characteristics of the signal wiring 42 by applying the measurement terminal 82 to the semiconductor film 50, the measurement may be performed while shining light on the semiconductor film 50, or while heating the substrate 10 to, for example, about 50°C. This makes it possible to lower the total DC resistance of the signal wiring 42 and the semiconductor film 50. [Examples]

[0048] Figure 12(a) is a plan view of the vicinity of the end of the signal wiring 42 of the qubit device 200 according to Example 2, and Figure 12(b) is a cross-sectional view of AA in Figure 12(a). As shown in Figures 12(a) and 12(b), in Example 2, a metal film 52 is provided in contact with and covering the semiconductor film 50. The metal film 52 is a single-layer film or a multilayer film thereof, such as a copper film, aluminum film, or gold film. The other configurations are the same as in Example 1, so their description is omitted.

[0049] Figure 13(a) is a cross-sectional view showing a method for measuring the DC resistance of the signal wiring 42 in Example 2, and Figure 13(b) is a cross-sectional view showing a method for measuring the high-frequency characteristics. As shown in Figures 13(a) and 13(b), in Example 2, the characteristics of the signal wiring 42 are measured by bringing the measurement terminal 82 into contact with the metal film 52.

[0050] According to Example 2, a metal film 52 is provided that is in contact with and overlaps the semiconductor film 50. As a result, when the measurement terminal 82 is placed on the semiconductor film 50 to measure the characteristics of the signal wiring 42, the measurement terminal 82 is in contact with the metal film 52, so the current spreads in the in-plane direction across the metal film 52 and flows into the semiconductor film 50. Therefore, when the metal film 52 is provided, the DC resistance value of the current flowing between the measurement terminal 82 and the signal wiring 42 is smaller than when the metal film 52 is not provided. [Examples]

[0051] Figure 14 is a cross-sectional view of the vicinity of the end of the signal wiring 42 of the qubit device 300 according to Embodiment 3. As shown in Figure 14, in Embodiment 3, the insulating film 46 and semiconductor film 50 are not provided on the substrate 10, and the semiconductor film 50a is embedded in the substrate 10. The upper surface of the semiconductor film 50a is exposed from the upper surface of the substrate 10 and in contact with the signal wiring 42, and the lower surface is exposed from the lower surface of the substrate 10. An insulating film 54 embedded in the substrate 10 is provided between the substrate 10 and the ground layer 44 and the semiconductor film 50a. The semiconductor film 50a, like the semiconductor film 50, has a rectangular shape in plan view and a width greater than the width of the signal wiring 42. The other configurations are the same as in Embodiment 1, so their description is omitted.

[0052] Figures 15(a) to 15(c) are cross-sectional views showing a method for manufacturing a qubit device 300 according to Example 3. As shown in Figure 15(a), after forming through holes 11 in the substrate 10, an insulating film 54 and a semiconductor film 50a are embedded in the through holes 11. The through holes 11 are formed, for example, by etching or laser processing. The insulating film 54 and the semiconductor film 50a are formed, for example, by deposition or CVD, and then unwanted portions formed on the upper surface of the substrate 10 are removed by polishing or the like.

[0053] As shown in Figure 15(b), a superconducting film 80 is formed on the substrate 10 using, for example, a sputtering method or a vapor deposition method.

[0054] As shown in Figure 15(c), the superconducting film 80 is patterned using, for example, photolithography and etching. This forms the signal wiring 42 and ground layer 44 that constitute the resonator 40. The semiconductor film 50a is positioned to touch and overlap both ends of the signal wiring 42. Although not shown in the figure, the central electrode 22, outer electrode 24, coupling wiring 60, and readout terminal 62 are also formed. Subsequently, the Josephson junction element 26 is formed using the same method as in Figures 4(a) and 4(b) of Example 1.

[0055] In Example 3, the characteristics of the signal wiring 42 are measured by applying the measurement terminal 82 to the semiconductor film 50a from the lower side of the substrate 10.

[0056] According to Example 3, a semiconductor film 50a is provided that overlaps a portion of the signal wiring 42 and has a width wider than the width of the signal wiring 42. As a result, similar to Example 1, the characteristics of the signal wiring 42 can be measured without being affected by the qubit 20, and the characteristics of the signal wiring 42 can be measured in a room temperature environment.

[0057] In Example 3, the semiconductor film 50a is embedded in the substrate 10 and positioned in contact with a portion of the signal wiring 42. This allows the measurement terminal 82 to be placed on the semiconductor film 50 from the underside of the substrate 10 to measure the characteristics of the signal wiring 42. [Examples]

[0058] Figure 16 is a cross-sectional view of the vicinity of the end of the signal wiring 42 of the qubit device 400 according to Example 4. As shown in Figure 16, in Example 4, similar to Example 3, a semiconductor film 50a that contacts the signal wiring 42 and an insulating film 54 that electrically isolates the semiconductor film 50a from the substrate 10 and the ground layer 44 are embedded in the substrate 10. Unlike Example 3, a metal film 52a is provided that overlaps the semiconductor film 50a and is in contact with the side of the semiconductor film 50a opposite to the signal wiring 42. The other configurations are the same as in Example 1, so their description is omitted.

[0059] In Example 4, the characteristics of the signal wiring 42 are measured by applying the measurement terminal 82 to the metal film 52a from the lower side of the substrate 10.

[0060] In Example 4, a metal film 52a is provided that is in contact with and overlaps the semiconductor film 50a. As a result, when measuring the characteristics of the signal wiring 42 by placing the measurement terminal 82 on the semiconductor film 50a, as in Example 2, the measurement terminal 82 is in contact with the metal film 52a, so the current spreads in the in-plane direction through the metal film 52a and flows into the semiconductor film 50a. Therefore, the DC resistance value of the current flowing between the measurement terminal 82 and the signal wiring 42 becomes small. [Examples]

[0061] Figure 17(a) is a plan view of the qubit device 500 according to Example 5, and Figure 17(b) is an enlarged plan view of the vicinity of the resonator 40 and the band-pass filter 70. In Figures 17(a) and 17(b), hatching is applied to the superconducting film and semiconductor film provided on the substrate 10 for clarity. Also, for clarity, the ground layer 44 shown in Figure 17(b) is omitted from Figure 17(a), and the insulating film 46 shown in Figures 18(a) and 18(b) is omitted from Figures 17(a) and 17(b).

[0062] As shown in Figures 17(a) and 17(b), in Embodiment 5, in addition to multiple qubits 20, multiple resonators 40, multiple coupling wirings 60, and readout terminals 62, multiple band-pass filters 70 are provided on the substrate 10. Each of the multiple band-pass filters 70 is electrostatically coupled to each of the multiple resonators 40. Furthermore, the multiple band-pass filters 70 are electrostatically coupled to one readout terminal 62. In this way, the band-pass filters 70 are connected between the resonators 40 and the readout terminals 62. The connections between the resonators 40 and the band-pass filters 70, and between the band-pass filters 70 and the readout terminals 62, are high-frequency connections.

[0063] The band-pass filter 70, like the resonator 40, has a meander structure coplanar line in which the signal wiring 72 is sandwiched between ground layers 44. A high-frequency signal for readout, for example in the gigahertz band (e.g., 2 GHz to 10 GHz), propagates through the signal wiring 72. The signal wiring 72, like the signal wiring 42, is formed from a superconducting material, such as aluminum (Al), titanium nitride (TiN), niobium (Nb), or tantalum (Ta). The semiconductor film 50 is provided on both ends of the signal wiring 42 of the resonator 40, as well as on both ends of the signal wiring 72 of the band-pass filter 70. The semiconductor film 50 is not provided on any parts of the signal wiring 42 other than the ends, nor on any parts of the signal wiring 72 other than the ends. The other configurations are the same as in Example 1, so their description is omitted.

[0064] Figure 18(a) is a plan view of the vicinity of the ends of the signal wirings 42 and 72 of the qubit device 500 according to Example 5, and Figure 18(b) is a cross-sectional view AA of Figure 18(a). As shown in Figures 18(a) and 18(b), the semiconductor film 50 has a width greater than the width of the signal wirings 42 and 72 and is provided covering the entire width direction of the signal wirings 42 and 72. The width of the signal wirings 72 is about the same as the width of the signal wirings 42, for example, 10 μm to 30 μm. The upper surfaces of the signal wirings 42 and 72 are exposed without being covered, and an insulating film 46 is provided from above the ground layer 44 to cover the gap between the signal wirings 42 and 72 and the ground layer 44. The semiconductor film 50 is in contact with the upper surfaces of the signal wirings 42 and 72 and is provided from above the signal wirings 42 and 72 to above the insulating film 46.

[0065] According to Example 5, a semiconductor film 50 is provided that overlaps a portion of the signal wirings 42 and 72 and has a width wider than the signal wirings 42 and 72. This allows the measurement terminal 82 to be placed on the semiconductor film 50 to measure the characteristics of the signal wirings 42 and 72. Therefore, the characteristics of the signal wirings 42 and 72 can be measured without being affected by the qubit 20, and the characteristics of the signal wirings 42 and 72 can be measured in a room temperature environment.

[0066] In Example 5, the signal wiring 42 constitutes a resonator 40 electrically connected to the qubit 20, and the signal wiring 72 constitutes a band-pass filter 70 electrically connected to the qubit 20. As a result, by measuring the characteristics of the signal wirings 42 and 72, the characteristics of the resonator 40 and the band-pass filter 70 can be measured.

[0067] In Example 5, the semiconductor film 50 is shown as an example where it is provided on the substrate 10 and in contact with the end of the signal wiring 72. However, as in Example 3, the semiconductor film 50a may be embedded in the substrate 10 and in contact with the end of the signal wiring 72. In this case, as in Example 4, the metal film 52a may be provided overlapping the semiconductor film 50a.

[0068] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of symbols]

[0069] 10 circuit boards 20 qubits 22 Central electrode 24 Outer electrode 26 Josephson junction element 28 Capacitors 30, 32 Superconducting film 34 Insulating Film 40 resonator 42 Signal Wiring 44 Ground Layer 46 Insulating film 50, 50a semiconductor film 52, 52a Metal film 54 Insulating film 60 Combined wiring 62 Read terminal 70 Bandpass Filter 72 Signal Wiring 80 Superconducting Film 82 Measurement terminals 100, 200, 300, 400, 500 qubit devices

Claims

1. circuit board and A qubit provided on the substrate, A signal wiring provided on the substrate and electrically connected to the qubit, A qubit device comprising: a semiconductor film provided overlapping a portion of the signal wiring and having a width wider than the width of the signal wiring.

2. The qubit device according to claim 1, wherein the portion of the signal wiring is at least one of the two ends of the signal wiring.

3. The qubit device according to claim 1 or 2, further comprising a metal film in contact with and overlapping the semiconductor film.

4. The qubit device according to claim 1 or 2, wherein the signal wiring includes a resonator or band-pass filter electrically connected to the qubit.

5. The qubit device according to claim 1 or 2, wherein the semiconductor film is provided on the substrate in contact with the portion of the signal wiring.

6. A ground layer is provided on the substrate on both sides of the signal wiring, The system comprises an insulating film provided from the ground layer to the gap between the ground layer and the signal wiring, The qubit device according to claim 5, wherein the semiconductor film is provided extending from the signal wiring to the insulating film.

7. The qubit device according to claim 1 or 2, wherein the semiconductor film is embedded in the substrate and provided in contact with the portion of the signal wiring.

8. The qubit device according to claim 1 or 2, wherein the semiconductor film is formed of a semiconductor material that is insulating at a temperature of 20 millikelvin.

9. The qubit device according to claim 1 or 2, wherein the semiconductor film is formed from amorphous silicon, indium oxide, titanium oxide, zinc oxide, gallium arsenide, indium phosphide, cadmium telluride, or cadmium sulfide.

10. The qubit device according to claim 1 or 2, wherein the qubit includes a Josephson junction element.

11. The qubit device according to claim 1 or 2, wherein the signal wiring is formed of a superconducting material.

12. The process of forming signal wiring on a substrate, A step of forming a semiconductor film that overlaps with a portion of the signal wiring and has a width wider than the width of the signal wiring, A method for manufacturing a qubit device, comprising the steps of forming a qubit on the substrate that is electrically connected to the signal wiring.

13. A method for measuring a qubit device, wherein a qubit and signal wiring electrically connected to the qubit are provided on a substrate, and a semiconductor film overlapping a portion of the signal wiring and having a width wider than the width of the signal wiring is provided, A method for measuring a qubit device, comprising applying a measurement terminal to the semiconductor film to measure the characteristics of the signal wiring.

14. A method for measuring a qubit device according to claim 13, wherein the characteristics of the signal wiring are measured in a room temperature environment.

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