Quantum device, quantum computing system, and method for reading a quantum device

Abstract

This invention provides a quantum device, a quantum computing system, and a method for reading out a quantum device that can perform multiple readouts on multiple qubit circuits. [Solution] The quantum device comprises a first qubit circuit, a second qubit circuit, and a cover chip, wherein the first qubit circuit comprises a first port, a first qubit, and a first resonator coupled to the first qubit and the first port and having a first resonant frequency, the second qubit circuit comprises a second port, a second qubit, and a second resonator coupled to the second qubit and the second port and having a second resonant frequency different from the first resonant frequency, and the cover chip comprises waveguides coupled to the first port and the second port. The quantum device can be used, for example, in quantum computing.

Description

[Technical Field]

[0001] This disclosure relates to quantum devices, quantum computing systems, and methods for reading quantum devices. [Background technology]

[0002] Conventionally, quantum devices have been proposed in which multiple qubits are coupled to a readout port provided in a qubit circuit, enabling multiple readouts through a single readout port. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] U.S. Patent Application Publication No. 2021 / 342729 [Patent Document 2] U.S. Patent No. 10068181 [Patent Document 3] International Publication No. 2023-132063 [Patent Document 4] Special Publication No. 2019-532520 [Patent Document 5] Patent No. 7359476 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] There is a demand for multiple readout for multiple qubit circuits.

[0005] The purpose of this disclosure is to provide a quantum device, a quantum computing system, and a method for reading out a quantum device that can perform multiple readouts on multiple qubit circuits. [Means for solving the problem]

[0006] According to one embodiment of the present disclosure, a quantum device is provided having a first qubit circuit, a second qubit circuit, and a cover chip, wherein the first qubit circuit has a first port, a first qubit, and a first resonator coupled to the first qubit and the first port and having a first resonant frequency, the second qubit circuit has a second port, a second qubit, and a second resonator coupled to the second qubit and the second port and having a second resonant frequency different from the first resonant frequency, and the cover chip has waveguides coupled to the first port and the second port. [Effects of the Invention]

[0007] According to this disclosure, multiple readouts can be performed on multiple qubit circuits. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view (part 1) showing a quantum device according to the first embodiment. [Figure 2] This is a cross-sectional view (part 2) showing a quantum device according to the first embodiment. [Figure 3] This is a cross-sectional view (part 3) showing a quantum device according to the first embodiment. [Figure 4] This is a top view showing the first qubit circuit and the second qubit circuit in the quantum device according to the first embodiment. [Figure 5] This is a bottom view showing the cover chip in the quantum device according to the first embodiment. [Figure 6] This is a cross-sectional view (part 1) showing a first example of a method for reading out a quantum device according to the first embodiment. [Figure 7] This is a cross-sectional view (part 2) showing a first example of a method for reading out a quantum device according to the first embodiment. [Figure 8] This is a cross-sectional view (part 3) showing a first example of a method for reading out a quantum device according to the first embodiment. [Figure 9] This is a diagram (part 1) showing the characteristics of a traveling wave parametric amplifier. [Figure 10] It is a diagram (part 2) showing the characteristics of a traveling-wave parametric amplifier. [Figure 11] It is a diagram (part 3) showing the characteristics of a traveling-wave parametric amplifier. [Figure 12] It is a cross-sectional view (part 1) showing a second example of a method for reading a quantum device according to the first embodiment. [Figure 13] It is a cross-sectional view (part 2) showing a second example of a method for reading a quantum device according to the first embodiment. [Figure 14] It is a cross-sectional view (part 3) showing a second example of a method for reading a quantum device according to the first embodiment. [Figure 15] It is a cross-sectional view (part 1) showing a quantum device according to the second embodiment. [Figure 16] It is a cross-sectional view (part 2) showing a quantum device according to the second embodiment. [Figure 17] It is a cross-sectional view (part 3) showing a quantum device according to the second embodiment. [Figure 18] It is a cross-sectional view (part 1) showing a quantum device according to the third embodiment. [Figure 19] It is a cross-sectional view (part 2) showing a quantum device according to the third embodiment. [Figure 20] It is a cross-sectional view (part 3) showing a quantum device according to the third embodiment. [Figure 21] It is a cross-sectional view (part 1) showing a quantum device according to the fourth embodiment. [Figure 22] It is a cross-sectional view (part 2) showing a quantum device according to the fourth embodiment. [Figure 23] It is a cross-sectional view (part 3) showing a quantum device according to the fourth embodiment. [Figure 24] It is a cross-sectional view (part 1) showing a quantum device according to the fifth embodiment. <0OO0109>It is a cross-sectional view (part 2) showing a quantum device according to the fifth embodiment. [Figure 26] ​ [Figure 27] This is a cross-sectional view (part 1) showing a quantum device according to the sixth embodiment. [Figure 28] This is a cross-sectional view (part 2) showing a quantum device according to the sixth embodiment. [Figure 29] This is a cross-sectional view (part 3) showing a quantum device according to the sixth embodiment. [Figure 30] This is a cross-sectional view showing a quantum device according to the seventh embodiment. [Figure 31] This is a cross-sectional view showing a quantum device according to the eighth embodiment. [Figure 32] This is a cross-sectional view showing a quantum device according to the ninth embodiment. [Figure 33] This is a cross-sectional view showing a quantum device according to the 10th embodiment. [Figure 34] This is a cross-sectional view showing a quantum device according to the 11th embodiment. [Figure 35] This is a cross-sectional view showing a quantum device according to the 12th embodiment. [Figure 36] This is a bottom view showing the first modified cover tip. [Figure 37] This is a bottom view showing a second modified example of the cover chip. [Modes for carrying out the invention]

[0009] Embodiments of this disclosure will be described in detail below with reference to the attached drawings. In this specification and drawings, components having substantially the same functional configuration will be denoted by the same reference numerals to avoid redundant descriptions. In the following description, the XYZ Cartesian coordinate system will be used, but this coordinate system is defined for illustrative purposes only and is not limited to the orientation of the quantum device. Also, from any point, the +Z side may be referred to as up, upper, or top, and the -Z side may be referred to as down, lower, or bottom. Furthermore, a planar view means viewing the object from the +Z side, and a planar shape means the shape of the object as viewed from the +Z side.

[0010] (First Embodiment) A first embodiment will be described. The first embodiment relates to a quantum device. Figures 1, 2, and 3 are cross-sectional views showing a quantum device according to the first embodiment. Figure 4 is a top view showing the first qubit circuit and the second qubit circuit in the quantum device according to the first embodiment. Figure 5 is a bottom view showing the cover chip in the quantum device according to the first embodiment. Figure 1 corresponds to a cross-sectional view along line II in Figures 4 and 5. Figure 2 corresponds to a cross-sectional view along line II-II in Figures 4 and 5. Figure 3 corresponds to a cross-sectional view along line III-III in Figures 4 and 5. Note that Figures 1 to 5 show only a part of the quantum device, and the side edges of each figure do not represent the side edges of the quantum device. Furthermore, the quantum device can have a larger number of qubit circuits.

[0011] As shown in Figures 1 to 5, the quantum device 1 according to the first embodiment includes a first qubit circuit 100, a second qubit circuit 200, and a cover chip 300. In this embodiment, the first qubit circuit 100 and the second qubit circuit 200 are located on the same chip.

[0012] The first qubit circuit 100 includes a substrate 410, a conductive layer 430, and a conductive layer 440. The substrate 410 is, for example, a Si substrate, a sapphire substrate, or an MgO substrate. The dielectric loss of the substrate 410 is preferably 1 × 10⁻⁶. -3 The following applies, more preferably 1 × 10 -4 The following applies: The dielectric loss of the substrate 410 changes with temperature. In order to suppress the degradation of the characteristics of the first qubit circuit 100 due to the dielectric loss originating from the substrate 410, the dielectric loss is set to 1 × 10⁻¹⁰ in an extremely low temperature environment (for example, around 1 mK to 100 mK). -6 The following is preferable: The resistivity of the substrate 410 is preferably 0.1 kΩ·cm or more, and more preferably 1 kΩ·cm or more. The substrate 410 has an upper surface 411 on the +Z side and a lower surface 412 on the -Z side. Through holes 421 for input and output and a plurality of through holes 423 for grounding are formed in the substrate 410. The first qubit circuit 100 has a conductive layer 451 covering the inner wall surface of the through hole 421 and a conductive layer 453 provided in the through hole 423.

[0013] The conductive layer 430 is provided on the upper surface 411 of the substrate 410. The conductive layer 430 has a first port 110, four qubits 121, 122, 123 and 124 in the first qubit circuit 100, four resonators 131, 132, 133 and 134 in the first qubit circuit 100, a first filter 140, four inter-bit wirings 151, 152, 153 and 154, and a ground portion 160. The qubits 121 to 124 are examples of first qubits, and the resonators 131 to 134 are examples of first resonators.

[0014] The qubits 121-124 are arranged at the vertices of a square in a planar view, with the first port 110 at the center. Qubit 122 is located on the +X side of qubit 121, qubit 123 is located on the +Y side of qubit 122, qubit 124 is located on the -X side of qubit 123, and qubit 121 is located on the -Y side of qubit 124. The first port 110 is connected to the conductive layer 451.

[0015] Resonator 131 is located between qubit 121 and the first port 110. Resonator 132 is located between qubit 122 and the first port 110. Resonator 133 is located between qubit 123 and the first port 110. Resonator 134 is located between qubit 124 and the first port 110. Resonator 131 is coupled to qubit 121, resonator 132 is coupled to qubit 122, resonator 133 is coupled to qubit 123, and resonator 134 is coupled to qubit 124. Resonators 131 to 134 have different first resonant frequencies. For example, the first resonant frequencies differ by about 100 MHz each. For example, in a plan view, resonators 131 to 134 have a meander shape.

[0016] The first filter 140 is positioned between the resonators 131-134 and the first port 110, and is coupled to the resonators 131-134 and the first port 110. The resonators 131-134 are coupled to the first port 110 via the first filter 140. The first filter 140 is, for example, a parcel filter. A parcel filter may be provided for each of the resonators 131-134. In this case, the first port 110 is directly or indirectly coupled to each parcel filter. Here, indirect coupling may be capacitive coupling or inductive coupling, and may include both capacitive and inductive coupling.

[0017] Interbit wiring 151 extends parallel to the X-axis and is coupled to qubits 121 and 122. Interbit wiring 152 extends parallel to the Y-axis and is coupled to qubits 122 and 123. Interbit wiring 153 extends parallel to the X-axis and is coupled to qubits 123 and 124. Interbit wiring 154 extends parallel to the Y-axis and is coupled to qubits 124 and 121. Interbit wiring directly or indirectly connects two qubits. For example, the qubits may be capacitively coupled, inductively coupled, or both capacitive and inductive coupling may be included. Interbit wiring is also called a coupler. The strength of this coupling may be fixed or variable.

[0018] Although not shown in Figure 4, the grounding section 160 is located around the first port 110, qubits 121-124, resonators 131-134, first filter 140, and inter-bit wiring 151-154. The grounding section 160 is connected to the conductive layer 453.

[0019] The conductive layer 440 is provided on the lower surface 412 of the substrate 410. The conductive layer 440 has a read signal input / output section 441, four qubit control signal input sections 442, and a plurality of grounding sections 443.

[0020] The four qubit control signal input units 442 are each positioned on the -Z side of qubits 121 to 124 and overlap with qubits 121 to 124 in a plan view. The four qubit control signal input units 442 do not necessarily overlap with qubits 121 to 124 in a plan view. The four qubit control signal input units 442 are each coupled to qubits 121 to 124. Control signals for qubits 121 to 124 are input to the qubit control signal input units 442. The read signal input / output unit 441 is connected to the conductive layer 451. The read signal input / output unit 441 is electrically connected to the first port 110 via the conductive layer 451. The grounding unit 443 is connected to the conductive layer 453. The grounding unit 443 is electrically connected to the grounding unit 160 via the conductive layer 453.

[0021] The conductive layers 430, 440, 451, and 453 are formed from a material that becomes a superconductor at extremely low temperatures, such as Al, Nb, Ta, or TiN.

[0022] The second qubit circuit 200 has a substrate 510, a conductive layer 530, and a conductive layer 540. The substrate 510 is, for example, a Si substrate, a sapphire substrate, or an MgO substrate. The dielectric loss of the substrate 510 is preferably 1 × 10⁻¹⁶. -3 The following applies, more preferably 1 × 10 -4 The following applies: The dielectric loss of the substrate 510 changes with temperature. In order to suppress the degradation of the characteristics of the second qubit circuit 200 due to the dielectric loss originating from the substrate 510, the dielectric loss is set to 1 × 10 in an extremely low temperature environment (for example, around 1 mK to 100 mK). -6 The following is preferable: The resistivity of the substrate 510 is preferably 0.1 kΩ·cm or more, and more preferably 1 kΩ·cm or more. The substrate 510 has an upper surface 511 on the +Z side and a lower surface 512 on the -Z side. Through holes 521 for input and output and a plurality of through holes 523 for grounding are formed in the substrate 510. The second qubit circuit 200 has a conductive layer 551 covering the inner wall surface of the through hole 521 and a conductive layer 553 provided in the through hole 523. For example, substrates 410 and 510 are made from a single substrate.

[0023] The conductive layer 530 is provided on the upper surface 511 of the substrate 510. The conductive layer 530 has a second port 210, four qubits 221, 222, 223 and 224 in the second qubit circuit 200, four resonators 231, 232, 233 and 234 in the second qubit circuit 200, a second filter 240, four inter-bit wirings 251, 252, 253 and 254, and a ground portion 260. The qubits 221 to 224 are examples of second qubits, and the resonators 231 to 234 are examples of second resonators.

[0024] The qubits 221-224 are arranged at the vertices of a square in a plan view, with the second port 210 at the center. Qubit 222 is located on the +X side of qubit 221, qubit 223 is located on the +Y side of qubit 222, qubit 224 is located on the -X side of qubit 223, and qubit 221 is located on the -Y side of qubit 224. The second port 210 is connected to the conductive layer 551.

[0025] Resonator 231 is located between qubit 221 and the second port 210. Resonator 232 is located between qubit 222 and the second port 210. Resonator 233 is located between qubit 223 and the second port 210. Resonator 234 is located between qubit 224 and the second port 210. Resonator 231 is coupled to qubit 221, resonator 232 is coupled to qubit 222, resonator 233 is coupled to qubit 223, and resonator 234 is coupled to qubit 224. Resonators 231-234 have different second resonant frequencies. Also, the first and second resonant frequencies differ between the four resonators 131-134 and the four resonators 231-234. For example, the second resonant frequencies differ by about 100 MHz each. For example, in a plan view, resonators 231-234 have a meander shape.

[0026] The second filter 240 is positioned between the resonators 231-234 and the second port 210, and is coupled to the resonators 231-234 and the second port 210. The resonators 231-234 are coupled to the second port 210 via the second filter 240. The second filter 240 is, for example, a parcel filter. A parcel filter may be provided for each of the resonators 231-234. In this case, the second port 210 is directly or indirectly coupled to each parcel filter.

[0027] Interbit wiring 251 extends parallel to the X-axis and is connected to qubits 221 and 222. Interbit wiring 252 extends parallel to the Y-axis and is connected to qubits 222 and 223. Interbit wiring 253 extends parallel to the X-axis and is connected to qubits 223 and 224. Interbit wiring 254 extends parallel to the Y-axis and is connected to qubits 224 and 221.

[0028] Although not shown in Figure 4, there are inter-bit wirings between qubit 123 in the first qubit circuit 100 and qubit 224 in the second qubit circuit 200, and between qubit 122 in the first qubit circuit 100 and qubit 221 in the second qubit circuit 200. These inter-bit wirings directly or indirectly connect two qubits. These inter-bit wirings may be formed in the conductive layer 640 (see Figure 5).

[0029] Although not shown in Figure 4, the grounding section 260 is located around the second port 210, qubits 221-224, resonators 231-234, second filter 240, and inter-bit wiring 251-254. The grounding section 260 is connected to the conductive layer 553.

[0030] The conductive layer 540 is provided on the lower surface 512 of the substrate 510. The conductive layer 540 has a read signal input / output section 541, four qubit control signal input sections 542, and a plurality of grounding sections 543.

[0031] The four qubit control signal input units 542 are respectively arranged on the -Z sides of the qubits 221 to 224 and overlap the qubits 221 to 224 in a plan view. The four qubit control signal input units 542 may not overlap the qubits 221 to 224 in a plan view. The four qubit control signal input units 542 are respectively coupled to the qubits 221 to 224. Control signals for the qubits 221 to 224 are input to the qubit control signal input units 542. The readout signal input / output unit 541 is connected to the conductive layer 551. The readout signal input / output unit 541 is electrically connected to the second port 210 via the conductive layer 551. The grounding unit 543 is connected to the conductive layer 553. The grounding unit 543 is electrically connected to the grounding unit 260 via the conductive layer 553.

[0032] The conductive layers 530, 540, 551 and 553 are formed of a material that becomes a superconductor at extremely low temperatures, such as Al, Nb, Ta or TiN.

[0033] The cover chip 300 has a substrate 610, a shield layer 620, an insulating film 630, and a conductive layer 640. The substrate 610 is, for example, a Si substrate, a sapphire substrate or a MgO substrate. The substrate 610 may be a Si substrate with a thermal oxide film. The dielectric loss of the substrate 610 is preferably -3 below, and more preferably -4 below. The dielectric loss of the substrate 610 changes with temperature. In order to suppress the deterioration of the characteristics of the first qubit circuit 100 and the second qubit circuit 200 due to the dielectric loss derived from the substrate 610, the dielectric loss is preferably -6 below in an extremely low temperature environment (for example, in the vicinity of 1 mK to 100 mK). The specific resistance of the substrate 610 is preferably 0.1 kΩ·cm or more, and more preferably 1 kΩ·cm or more. The substrate 610 has an upper surface 611 on the +Z side and a lower surface 612 on the -Z side.

[0034] The shield layer 620 is provided on the lower surface 612 of the substrate 610, the insulating film 630 is provided on the lower surface of the shield layer 620, and the conductive layer 640 is provided on the lower surface of the insulating film 630. The insulating film 630 is provided between the shield layer 620 and the conductive layer 640. The shield layer 620 covers the first qubit circuit 100 and the second qubit circuit 200 from the +Z side.

[0035] The conductive layer 640 has a first port coupling section 311 facing the first port 110 and coupled to the first port 110, a second port coupling section 312 facing the second port 210 and coupled to the second port 210, a waveguide 350, and a ground section 360. The waveguide 350 is, for example, a coplanar line. The first port 110 and the first port coupling section 311 are capacitively coupled to each other. The second port 210 and the second port coupling section 312 are capacitively coupled to each other. The waveguide 350 is connected to the first port coupling section 311 and the second port coupling section 312. The waveguide 350 is capacitively coupled to the first port 110 and the second port 210. The waveguide 350 may have a third resonator 330. If the waveguide 350 has a third resonator 330, the third resonator 330 has a third resonant frequency. The grounding section 360 is provided around the waveguide 350. Grounding section 160 and grounding section 360 are joined to each other by conductive bumps 701, and grounding section 260 and grounding section 360 are joined to each other by conductive bumps 702. When the waveguide 350 has a third resonator 330, the third resonator 330 has a meander shape in plan view. Preferably, the third resonator 330 is a λ / 2 resonator whose third resonant frequency is the average value fave, where fave is the average value of the first resonant frequencies of resonators 131 to 134 and the second resonant frequencies of resonators 231 to 234. Considering manufacturing tolerances, the third resonant frequency may be between fave × 0.7 and fave × 1.3. Preferably, the capacitive coupling between the third resonator 330 and the first port 110 and the second port 210 is sufficiently large. When the maximum value of the first and second resonant frequencies is denoted by fmax and the minimum value by fmin, the external linewidth of the third resonator includes the range from fmin to fmax, thereby obtaining a more suitable signal response when multiplexing and reading out the states of the first qubit circuit 100 and the second qubit circuit 200. Note that if the waveguide 350 has a third resonator 330, the third resonator 330 may be a parcel filter.

[0036] Furthermore, in the conductive layer 640, recesses are formed that are indented toward the +Z side in the portions that overlap with qubits 121-124, qubits 221-224, resonators 131-134, resonators 231-234, or inter-bit wirings 151-154 or inter-bit wirings 251-254 when viewed in plan.

[0037] The shield layer 620 and the conductive layer 640 are formed of a material that becomes a superconductor at cryogenic temperatures, which are the operating temperatures of qubits 121-124 and qubits 221-224, such as Al, TiN, Ta, or Nb. The insulating film 630 is formed of an oxide of the material of the shield layer 620, i.e., aluminum oxide, or a nitride, such as aluminum nitride. The conductive bumps 701 and 702 are formed of, for example, In.

[0038] The quantum device 1 is used, for example, in contact with a probe pin. Figures 6 to 8 are cross-sectional views showing a first example of a method for reading out the quantum device 1 according to the first embodiment.

[0039] As shown in Figures 6 to 8, the probe card 800 includes a circuit board 810, a read signal input probe 821, a read signal output probe 822, eight control signal input probes 830, and a plurality of grounding probes 840. The read signal input probes 821, read signal output probes 822, control signal input probes 830, and grounding probes 840 may be fixed to the circuit board 810 or they may be detachable. For example, the read signal input probes 821, read signal output probes 822, control signal input probes 830, and grounding probes 840 are coaxial pins and have a mechanism for the pins to mechanically extend and retract. For example, the read signal input probe 821 is brought into contact with the read signal input / output unit 441, and the read signal output probe 822 is brought into contact with the read signal input / output unit 541. A control signal input probe 830 is brought into contact with a qubit control signal input section 442 or 542, and a grounding probe 840 is brought into contact with a grounding section 443 or 543. Instead of the probe card 800, a package structure capable of holding the probes may be used.

[0040] A microwave signal source 851 is connected to the readout signal input probe 821, and an amplifier, such as a traveling wave parametric amplifier (TWPA) 852, is connected to the readout signal output probe 822. The amplifier may be a parametric amplifier using a Josephson junction or an amplifier utilizing kinetic inductance. A qubit control device is connected to the control signal input probe 830, and the ground probe 840 is grounded. In this way, the quantum computing system is configured.

[0041] Here, we will describe the TWPA852. Figures 9 to 11 show the characteristics of the TWPA852. The TWPA852 has a gain of 20 dB or more and a constant amplification bandwidth, as shown in Figure 9, preferably includes all four first resonant frequencies and four second resonant frequencies. In Figure 9, for clarity, the group of first resonant frequencies is grouped at a low frequency, but the combination of first and second resonant frequencies is not limited to this. The frequency assignment can be freely determined within the range in which all resonant frequencies fall within the bandwidth of the TWPA852. However, as shown in Figure 10, even if some of the first resonant frequencies and some of the second resonant frequencies fall outside the amplification bandwidth, the problems that this disclosure aims to solve can still be solved. Also, as shown in Figure 11, even if some of the second resonant frequencies fall outside the amplification bandwidth, the problems that this disclosure aims to solve can still be solved. Although not shown in the figures, even if some of the first resonant frequencies fall outside the amplification bandwidth, the problems that this disclosure aims to solve can still be solved.

[0042] During the readout of quantum device 1, signals to control the states of qubits 121-124 and qubits 221-224 are supplied from each control signal input probe 830 to qubits 121-124 and qubits 221-224. In addition, a microwave signal is input as a readout signal from signal source 851 to the first port 110 via signal input / output unit 441. The frequency of the readout signal is input by frequency multiplexing signals corresponding to the eight resonant frequencies of resonators 131-134 and resonators 231-234. When the readout signal is supplied, in the first qubit circuit 100, a readout signal in which four state signals indicating the states of qubits 121-124 are superimposed is transmitted from the first port 110 to the first port coupling unit 311. Then, in the second qubit circuit 200, four state signals indicating the states of qubits 221 to 224 are superimposed and output from the second port 210 to the TWPA852 via the readout signal input / output unit 541. At this time, the four state signals are superimposed at the second port 210 via the waveguide 350 and the second port coupling unit 312. The waveguide 350 may have a third resonator 330. The TWPA852 amplifies the readout signal with the eight state signals superimposed. The amplified signal is then measured by a signal processing device or the like provided in the quantum computing system. In this way, the states of the four qubits 121 to 124 in the first qubit circuit 100 and the four qubits 221 to 224 in the second qubit circuit 200 can be read out.

[0043] Alternatively, the read signal input probe 821 may be brought into contact with the read signal input / output unit 541, and the read signal output probe 822 may be brought into contact with the read signal input / output unit 441, so that the signals propagate in the reverse direction.

[0044] An interposer may be used instead of the probe card 800. Figures 12 to 14 are cross-sectional views showing a second example of a readout method for the quantum device 1 according to the first embodiment.

[0045] As shown in Figures 12 to 14, the structure 900 having an interposer includes a substrate 910, an input wiring 921, a read wiring 922, eight control wirings 930, and a plurality of ground wirings 940. The input wiring 921, read wiring 922, control wiring 930, and ground wiring 940 are provided within the substrate 910. For example, the substrate 910 is a Si substrate, and the input wiring 921, read wiring 922, control wiring 930, and ground wiring 940 are through silicon vias (TSVs). For example, the input wiring 921 is electrically connected to the read signal input / output section 441 by a conductive bump 961, and the read wiring 922 is electrically connected to the read signal input / output section 541 by a conductive bump 962. The control wiring 930 is electrically connected to the qubit control signal input section 442 or 542 by a conductive bump 963, and the ground wiring 940 is electrically connected to the ground section 443 or 543 by a conductive bump 964. Instead of the structure 900 having an interposer, a package structure holding a substrate having an interposer may be used.

[0046] A microwave signal source 951 is connected to input wiring 921, and an amplifier, such as TWPA 952, is connected to readout wiring 922. A qubit control device is connected to control wiring 930, and ground wiring 940 is grounded. In this way, the quantum computing system is configured.

[0047] The quantum device 1 can be read out even when using structure 900 having an interposer with this configuration.

[0048] Alternatively, the input wiring 921 may be electrically connected to the read signal input / output unit 541, and the read wiring 922 may be electrically connected to the read signal input / output unit 441, so that the signal propagates in the reverse direction.

[0049] The input wiring 921, read wiring 922, control wiring, and ground wiring 940 do not need to be TSVs, and the structure 900 having an interposer may have multilayer wiring including wiring parallel to the main plane. The structure 900 having an interposer may be used in combination with a multilayer wiring board. Alternatively, the probe card 800 may be used in combination with the structure 900 having an interposer. Furthermore, a probe having a coaxial pin with a mechanism for mechanically extending and retracting the pins in the first example may be used in combination with the structure having an interposer.

[0050] Thus, the quantum device 1 enables multiple readouts of the first qubit circuit 100 and the second qubit circuit. The number of qubits included in the first qubit circuit 100 and the number of qubits included in the second qubit circuit 200 are not limited and may be 1, 2, 3, or 5 or more.

[0051] If the waveguide 350 has a third resonator 330, by making the third resonator 330 a λ / 2 resonator, antinodes of standing waves are located at the first port coupling 311 and the second port coupling 312, allowing signals to propagate between the first port 110 and the second port 210 with high efficiency. Furthermore, by adjusting the impedance of the third resonator 330, the impedance between the first qubit circuit 100 and the second qubit circuit 200 can be matched.

[0052] (Second Embodiment) A second embodiment will now be described. The second embodiment differs from the first embodiment mainly in the configuration of the conductive layer 640. Figures 15, 16, and 17 are cross-sectional views showing a quantum device according to the second embodiment.

[0053] As shown in Figures 15 to 17, in the quantum device 2 according to the second embodiment, the conductive layer 640 does not include any portion that overlaps with the qubits 121 to 124, qubits 221 to 224, resonators 131 to 134, resonators 231 to 234, or inter-bit wirings 151 to 154 or inter-bit wirings 251 to 254 in a plan view. The insulating film 630 is exposed on the +Z side of the qubits 121 to 124, qubits 221 to 224, resonators 131 to 134, resonators 231 to 234, or inter-bit wirings 151 to 154 or inter-bit wirings 251 to 254. Thus, quantum device 2 differs from quantum device 1 mainly in the configuration of the conductive layer 640.

[0054] The other configurations of quantum device 2 are the same as those of quantum device 1. The same effects can be obtained with quantum device 2 as with quantum device 1. Similar to the first embodiment, a quantum computing system can also be constructed using quantum device 2.

[0055] (Third embodiment) A third embodiment will now be described. The third embodiment differs from the first embodiment mainly in the configuration of the first qubit circuit and the second qubit circuit. Figures 18, 19, and 20 are cross-sectional views showing the quantum device according to the third embodiment.

[0056] As shown in Figures 18 to 20, in the quantum device 3 according to the third embodiment, through holes 421 formed in the substrate 410 are blocked by a conductive layer 451, and through holes 521 formed in the substrate 510 are blocked by a conductive layer 551. Thus, quantum device 3 differs from quantum device 1 mainly in the configuration of the first qubit circuit 100 and the second qubit circuit 200.

[0057] The other configurations of quantum device 3 are the same as those of quantum device 1. Quantum device 3 can also achieve the same effects as quantum device 1. Similar to the first embodiment, a quantum computing system can also be constructed using quantum device 3.

[0058] (Fourth Embodiment) A fourth embodiment will now be described. The fourth embodiment differs from the third embodiment mainly in the configuration of the conductive layer 640. Figures 21, 22, and 23 are cross-sectional views showing the quantum device according to the fourth embodiment.

[0059] As shown in Figures 21 to 23, in the quantum device 4 according to the fourth embodiment, the conductive layer 640 does not include any portion that overlaps with the qubits 121 to 124, qubits 221 to 224, resonators 131 to 134, resonators 231 to 234, or inter-bit wirings 151 to 154 or inter-bit wirings 251 to 254 in a plan view. The insulating film 630 is exposed on the +Z side of the qubits 121 to 124, qubits 221 to 224, resonators 131 to 134, resonators 231 to 234, or inter-bit wirings 151 to 154 or inter-bit wirings 251 to 254. Thus, the quantum device 4 differs from the quantum device 3 mainly in the configuration of the conductive layer 640.

[0060] The other configurations of quantum device 4 are the same as those of quantum device 3. The same effects can be obtained with quantum device 4 as with quantum device 3. Similar to the first embodiment, a quantum computing system can also be constructed using quantum device 4.

[0061] (Fifth embodiment) A fifth embodiment will now be described. The fifth embodiment differs from the third embodiment mainly in the configuration of the first qubit circuit and the second qubit circuit. Figures 24, 25, and 26 are cross-sectional views showing the quantum device according to the fifth embodiment.

[0062] As shown in Figures 24 to 26, in the quantum device 5 according to the fifth embodiment, the substrate 410 does not have through holes 421, and the first qubit circuit 100 does not have a conductive layer 451. Also, the substrate 510 does not have through holes 521, and the second qubit circuit 200 does not have a conductive layer 551. In the first qubit circuit 100, the first port 110 and the signal input / output unit 441 are capacitively coupled to each other, and in the second qubit circuit 200, the second port 210 and the read signal input / output unit 541 are capacitively coupled to each other. Thus, quantum device 5 differs from quantum device 3 mainly in the configuration of the first qubit circuit 100 and the second qubit circuit 200.

[0063] The other configurations of quantum device 5 are the same as those of quantum device 3. The same effects can be obtained with quantum device 5 as with quantum device 3. Similar to the first embodiment, a quantum computing system can also be constructed using quantum device 5.

[0064] (Sixth Embodiment) A sixth embodiment will now be described. The sixth embodiment differs from the fifth embodiment mainly in the configuration of the conductive layer 640. Figures 27, 28, and 29 are cross-sectional views showing the quantum device according to the sixth embodiment.

[0065] As shown in Figures 27 to 29, in the quantum device 6 according to the sixth embodiment, the conductive layer 640 does not include any portion that overlaps with the qubits 121 to 124, qubits 221 to 224, resonators 131 to 134, resonators 231 to 234, or inter-bit wirings 151 to 154 or inter-bit wirings 251 to 254 in a plan view. The insulating film 630 is exposed on the +Z side of the qubits 121 to 124, qubits 221 to 224, resonators 131 to 134, resonators 231 to 234, or inter-bit wirings 151 to 154 or inter-bit wirings 251 to 254. Thus, the quantum device 6 differs from the quantum device 5 mainly in the configuration of the conductive layer 640.

[0066] The other configurations of quantum device 6 are the same as those of quantum device 5. The same effects can be obtained with quantum device 6 as with quantum device 5. Similar to the first embodiment, a quantum computing system can also be constructed using quantum device 6.

[0067] (Seventh Embodiment) A seventh embodiment will now be described. The seventh embodiment differs from the first embodiment mainly in the coupling between the first port 110 and the first port coupling 311, and between the second port 210 and the second port coupling 312. Figure 30 is a cross-sectional view showing the quantum device according to the seventh embodiment.

[0068] As shown in Figure 30, the quantum device 7 according to the seventh embodiment has a conductive bump 711 that connects the first port 110 and the first port coupling portion 311, and a conductive bump 712 that connects the second port 210 and the second port coupling portion 312. The first port 110 and the first port coupling portion 311 are galvanically coupled, i.e., directly coupled to each other. The second port 210 and the second port coupling portion 312 are galvanically coupled, i.e., directly coupled to each other. The waveguide 350 is directly coupled to the first port 110 and the second port 210. The conductive bumps 711 and 712 are formed of, for example, In. The waveguide 350 may be, for example, a coplanar waveguide. The waveguide 350 may also have a λ / 2 resonator as the third resonator 330, having the average value of the first resonant frequencies of resonators 131-134 and the second resonant frequencies of resonators 231-234 as the third resonant frequency. Thus, quantum device 7 differs from quantum device 1 primarily in the coupling between the first port 110 and the first port coupling part 311, and between the second port 210 and the second port coupling part 312.

[0069] The other configurations of quantum device 7 are the same as those of quantum device 1. The same effects can be obtained with quantum device 7 as with quantum device 1. Similar to the first embodiment, a quantum computing system can also be constructed using quantum device 7.

[0070] (Eighth embodiment) The eighth embodiment will now be described. The eighth embodiment differs from the second embodiment mainly in the coupling between the first port 110 and the first port coupling 311, and between the second port 210 and the second port coupling 312. Figure 31 is a cross-sectional view showing the quantum device according to the eighth embodiment.

[0071] As shown in Figure 31, the quantum device 8 according to the eighth embodiment has a conductive bump 711 that connects the first port 110 and the first port coupling 311, and a conductive bump 712 that connects the second port 210 and the second port coupling 312. The first port 110 and the first port coupling 311 are galvanically coupled, i.e., directly coupled, to each other. The second port 210 and the second port coupling 312 are galvanically coupled, i.e., directly coupled, to each other. The waveguide 350 is directly coupled to the first port 110 and the second port 210. The waveguide 350 may be, for example, a coplanar waveguide. The waveguide 350 may also have a λ / 2 resonator as the third resonator 330, having the average value of the first resonant frequencies of resonators 131-134 and the second resonant frequencies of resonators 231-234 as the third resonant frequency. Thus, quantum device 8 differs from quantum device 2 primarily in the coupling between the first port 110 and the first port coupling part 311, and between the second port 210 and the second port coupling part 312.

[0072] The other configurations of quantum device 8 are the same as those of quantum device 2. The same effects can be obtained with quantum device 8 as with quantum device 2. Similar to the first embodiment, a quantum computing system can also be constructed using quantum device 8.

[0073] (Ninth Embodiment) The ninth embodiment will now be described. The ninth embodiment differs from the third embodiment mainly in the coupling between the first port 110 and the first port coupling 311, and between the second port 210 and the second port coupling 312. Figure 32 is a cross-sectional view showing the quantum device according to the ninth embodiment.

[0074] As shown in Figure 32, the quantum device 9 according to the ninth embodiment has a conductive bump 711 that connects the first port 110 and the first port coupling portion 311, and a conductive bump 712 that connects the second port 210 and the second port coupling portion 312. The first port 110 and the first port coupling portion 311 are galvanically coupled, i.e., directly coupled, to each other. The second port 210 and the second port coupling portion 312 are galvanically coupled, i.e., directly coupled, to each other. The waveguide 350 is directly coupled to the first port 110 and the second port 210. The waveguide 350 may be, for example, a coplanar waveguide. The waveguide 350 may also have a λ / 2 resonator as the third resonator 330, having the average value of the first resonant frequencies of resonators 131-134 and the second resonant frequencies of resonators 231-234 as the third resonant frequency. Thus, quantum device 9 differs from quantum device 3 primarily in the coupling between the first port 110 and the first port coupling part 311, and between the second port 210 and the second port coupling part 312.

[0075] The other configurations of quantum device 9 are the same as those of quantum device 3. The same effects can be obtained with quantum device 9 as with quantum device 3. Similar to the first embodiment, a quantum computing system can also be constructed using quantum device 9.

[0076] (Tenth embodiment) A tenth embodiment will now be described. The tenth embodiment differs from the fourth embodiment mainly in the coupling between the first port 110 and the first port coupling 311, and between the second port 210 and the second port coupling 312. Figure 33 is a cross-sectional view showing the quantum device according to the tenth embodiment.

[0077] As shown in Figure 33, the quantum device 10 according to the tenth embodiment has a conductive bump 711 that connects the first port 110 and the first port coupling 311, and a conductive bump 712 that connects the second port 210 and the second port coupling 312. The first port 110 and the first port coupling 311 are galvanically coupled, i.e., directly coupled to each other. The second port 210 and the second port coupling 312 are galvanically coupled, i.e., directly coupled to each other. The waveguide 350 is directly coupled to the first port 110 and the second port 210. The waveguide 350 may be, for example, a coplanar waveguide. The waveguide 350 may also have a λ / 2 resonator as the third resonator 330, having the average value of the first resonant frequencies of resonators 131-134 and the second resonant frequencies of resonators 231-234 as the third resonant frequency. Thus, quantum device 10 differs from quantum device 4 primarily in the coupling between the first port 110 and the first port coupling part 311, and between the second port 210 and the second port coupling part 312.

[0078] The other configurations of quantum device 10 are the same as those of quantum device 4. The same effects can be obtained with quantum device 10 as with quantum device 4. Similar to the first embodiment, a quantum computing system can also be constructed using quantum device 10.

[0079] (11th embodiment) The 11th embodiment will now be described. The 11th embodiment differs from the 5th embodiment mainly in the coupling between the first port 110 and the first port coupling 311, and between the second port 210 and the second port coupling 312. Figure 34 is a cross-sectional view showing the quantum device according to the 11th embodiment.

[0080] As shown in Figure 34, the quantum device 11 according to the 11th embodiment has a conductive bump 711 that connects the first port 110 and the first port coupling 311, and a conductive bump 712 that connects the second port 210 and the second port coupling 312. The first port 110 and the first port coupling 311 are galvanically coupled, i.e., directly coupled to each other. The second port 210 and the second port coupling 312 are galvanically coupled, i.e., directly coupled to each other. The waveguide 350 is directly coupled to the first port 110 and the second port 210. The waveguide 350 may be, for example, a coplanar waveguide. The waveguide 350 may also have a λ / 2 resonator as the third resonator 330, having the average value of the first resonant frequencies of resonators 131-134 and the second resonant frequencies of resonators 231-234 as the third resonant frequency. Thus, quantum device 11 differs from quantum device 5 primarily in the coupling between the first port 110 and the first port coupling part 311, and between the second port 210 and the second port coupling part 312.

[0081] The other configurations of quantum device 11 are the same as those of quantum device 5. The same effects as those of quantum device 5 can be obtained with quantum device 11. Similar to the first embodiment, a quantum computing system can also be constructed using quantum device 11.

[0082] (12th embodiment) A twelfth embodiment will now be described. The twelfth embodiment differs from the sixth embodiment mainly in the coupling between the first port 110 and the first port coupling 311, and between the second port 210 and the second port coupling 312. Figure 35 is a cross-sectional view showing the quantum device according to the twelfth embodiment.

[0083] As shown in Figure 35, the quantum device 12 according to the twelfth embodiment has a conductive bump 711 that connects the first port 110 and the first port coupling 311, and a conductive bump 712 that connects the second port 210 and the second port coupling 312. The first port 110 and the first port coupling 311 are galvanically coupled, i.e., directly coupled to each other. The second port 210 and the second port coupling 312 are galvanically coupled, i.e., directly coupled to each other. The waveguide 350 is directly coupled to the first port 110 and the second port 210. The waveguide 350 may be, for example, a coplanar waveguide. The waveguide 350 may also have a λ / 2 resonator as the third resonator 330, having the average value of the first resonant frequencies of resonators 131-134 and the second resonant frequencies of resonators 231-234 as the third resonant frequency. Thus, quantum device 12 differs from quantum device 6 primarily in the coupling between the first port 110 and the first port coupling 311, and between the second port 210 and the second port coupling 312.

[0084] The other configurations of quantum device 12 are the same as those of quantum device 6. The same effects can be obtained with quantum device 12 as with quantum device 6. Similar to the first embodiment, a quantum computing system can also be constructed using quantum device 12.

[0085] In any embodiment, as shown in Figure 36, there may be regions around the waveguide 350 where the grounding portion 360 is not locally provided. This allows for a layout arrangement that matches the structure of the first qubit circuit 100 and the second qubit circuit 200. For example, by shaping it to match the coupler that connects the qubits, electromagnetic field radiation can be prevented. Also, the characteristic impedance of the waveguide 350 may be less than 50Ω. By designing the structure with a layout that matches the first qubit circuit 100 and the second qubit circuit 200, electromagnetic field radiation can be prevented. The impedance can be adjusted by changing the width of the waveguide 350. Figure 36 is a bottom view showing a first modified example of the cover chip.

[0086] In any embodiment, the third resonator 330 may be divided into multiple parts. For example, as shown in Figure 37, the third resonator 330 may have a fourth resonator 331 and a fifth resonator 332. For example, in a plan view, the fourth resonator 331 may be closer to the first port 110 than the inter-bit wiring 152 of the first qubit circuit 100, and the fifth resonator 332 may be closer to the second port 210 than the inter-bit wiring 254 of the second qubit circuit 200. Figure 37 is a bottom view showing a second modified example of the cover chip.

[0087] In any embodiment, in the structure made by processing the conductive layer 640 or by depositing or sputtering additional superconducting material, there may be a difference in the thickness of the superconducting material with respect to the Z-axis direction. For example, the thickness of the superconducting material in the first port coupling portion 311 and the second port coupling portion 312 of the conductive layer 640 may be greater than the thickness in the waveguide 350. In this case, by increasing the distance of the waveguide 350 from the first qubit circuit 100 and the second qubit circuit 200, while decreasing the distance of the first port coupling portion 311 and the second port coupling portion 312 from the first port 110 and the second port 210, it becomes easier to create a structure that increases the magnitude of capacitive coupling while confining radiation from the first qubit circuit 100 and the second qubit circuit 200. Furthermore, when the connection between the first port 110 and the first port coupling part 311, and the connection between the second port 210 and the second port coupling part 312 are galvanic connections, the height of the bump when connecting the two with the conductive bump 711 can be reduced, thereby enabling the creation of a stable galvanic connection.

[0088] Furthermore, in the first to sixth embodiments, it is preferable that the thickness of the superconducting material in the first port coupling portion 311 and the second port coupling portion 312 of the conductive layer 640 is smaller than the thickness of the material in the ground portion 360. In this case, it is easier to electrically connect the ground portion 360 to the ground portions 160 and 260 while capacitively coupling the first port coupling portion 311 and the second port coupling portion 312 to the first port 110 and the second port 210. In the seventh to twelfth embodiments, since the first port coupling portion 311 and the second port coupling portion 312 are electrically connected to the first port 110 and the second port 210, the thickness of the first port coupling portion 311 and the second port coupling portion 312 may be equal to the thickness of the ground portion 360.

[0089] In any embodiment, the cover chip 300 does not have to include the shield layer 620 and the insulating film 630. Also, the waveguide 350 may be a microstrip line. That is, a shield layer may be provided on the upper surface 611. In this case, it is preferable that a shield layer is also provided on the side surface of the substrate 610 to prevent radiation to the outside.

[0090] In any embodiment, the first qubit circuit 100 and the second qubit circuit 200 are not limited to being on the same chip. For example, the first qubit circuit 100, which includes a first port 110, and the second qubit circuit 200, which includes a second port 210, may be on different chips, and the first port 110 and the second port 210 may be directly or indirectly coupled via a cover chip 300. In this case, a coupler may be provided between qubits 121-124 and qubits 221-224.

[0091] The quantum device, quantum computing system, and quantum device readout method relating to this disclosure can be used, for example, in quantum computing.

[0092] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims.

[0093] The various aspects of this disclosure are summarized below as an appendix.

[0094] (Note 1) The first qubit circuit and The second qubit circuit and Cover chip and, It has, The first qubit circuit is, Port 1 and, The first qubit and, A first resonator having a first resonant frequency is coupled to the first qubit and the first port, It has, The aforementioned second qubit circuit is, Port 2 and, The second qubit and The second qubit and the second port are coupled to a second resonator having a second resonant frequency different from the first resonant frequency, It has, The cover chip is a quantum device having waveguides coupled to the first port and the second port. (Note 2) The first qubit circuit comprises multiple sets of the first qubit and the first resonator, The second qubit circuit comprises multiple sets of the second qubit and the second resonator. The quantum device according to Appendix 1, wherein the first resonant frequency and the second resonant frequency differ among the plurality of first resonators and the plurality of second resonators. (Note 3) The waveguide is a quantum device according to Appendix 1 or 2, having a third resonator having a third resonant frequency. (Note 4) The quantum device described in Appendix 3, wherein, when the average value of the first and second resonant frequencies is fave, the third resonant frequency is between fave × 0.7 and fave × 1.3. (Note 5) The third resonator is a quantum device according to Appendix 3 or 4, having a meander shape in plan view. (Note 6) The first qubit circuit has a first filter coupled between the first port and the first resonator, The quantum device according to any one of appendices 1 to 5, wherein the second qubit circuit has a second filter coupled between the second port and the second resonator. (Note 7) The cover chip has a substrate and an insulating film, A quantum device according to any one of appendices 1 to 6, wherein the insulating film is located between the substrate and the waveguide. (Note 8) A quantum device according to any one of the appendices 1 to 7, wherein the first port and the second port are capacitively coupled to the waveguide. (Note 9) A quantum device according to any one of the appendices 1 to 7, wherein the first port and the second port are galvanically coupled to the waveguide. (Note 10) A quantum device described in any one of the appendices 1 to 9, A traveling wave parametric amplifier coupled to either the first port or the second port, A quantum computing system having [a certain feature]. (Note 11) A step of inputting a microwave signal to the first port of the quantum device described in any one of Appendix 1 to 9, A step of measuring the signal output from the second port, A method for reading out a quantum device having [a certain characteristic]. (Note 12) A method for reading out a quantum device according to Appendix 11, comprising a step of amplifying the signal output from the second port with a traveling wave parametric amplifier between the step of inputting the microwave signal and the step of measuring the signal. [Explanation of Symbols]

[0095] 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12: Quantum devices 100 First Qubit Circuit 110 Port 1 121, 122, 123, 124 qubits 131, 132, 133, 134 resonator 140 First filter 200 Second Qubit Circuit 210 Port 2 221, 222, 223, 224 qubits 231, 232, 233, 234 resonator 240 Second filter 300 cover tips 311 First port connection 312 Second port connection 330 Third resonator 610 circuit board 620 Shield Layer 630 Insulating film 640 Conductive layer 851, 951 signal source 852, 952 Traveling Wave Parametric Amplifier

Claims

1. The first qubit circuit and The second qubit circuit and Cover chip and, It has, The first qubit circuit is, Port 1 and, The first qubit and A first resonator coupled to the first qubit and the first port, having a first resonant frequency, It has, The aforementioned second qubit circuit is, Port 2 and, The second qubit and A second resonator coupled to the second qubit and the second port, having a second resonant frequency different from the first resonant frequency, It has, The cover chip is a quantum device having waveguides coupled to the first port and the second port.

2. The first qubit circuit has multiple sets of the first qubit and the first resonator, The second qubit circuit comprises multiple sets of the second qubit and the second resonator, The quantum device according to claim 1, wherein the first resonant frequency and the second resonant frequency are different among the plurality of first resonators and the plurality of second resonators.

3. The quantum device according to claim 1 or 2, wherein the waveguide has a third resonator having a third resonant frequency.

4. The quantum device according to claim 3, wherein when the average value of the first and second resonant frequencies is fave, the third resonant frequency is between fave × 0.7 and fave × 1.

3.

5. The first qubit circuit has a first filter coupled between the first port and the first resonator, The quantum device according to claim 1 or 2, wherein the second qubit circuit has a second filter coupled between the second port and the second resonator.

6. The cover chip has a substrate and an insulating film, The quantum device according to claim 1 or 2, wherein the insulating film is located between the substrate and the waveguide.

7. A quantum device according to claim 1 or 2, A traveling wave parametric amplifier coupled to either the first port or the second port, A quantum computing system having [a certain feature].

8. A step of inputting a microwave signal to the first port of the quantum device according to claim 1 or 2, A step of measuring the signal output from the second port, A method for reading out a quantum device having [a certain characteristic].

9. The method for reading out a quantum device according to claim 8, further comprising the step of amplifying the signal output from the second port with a traveling wave parametric amplifier between the step of inputting the microwave signal and the step of measuring the signal.

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