Quantum devices and methods for manufacturing quantum devices

Abstract

This quantum device comprises a first quantum bit substrate, a second quantum bit substrate, and a capacitive coupling substrate. The first quantum bit substrate has a first quantum bit and a first electrode connected to the first quantum bit. The second quantum bit substrate has a second quantum bit and a second electrode connected to the second quantum bit. The capacitive coupling substrate has: a third electrode that is capacitively coupled to the first electrode and the second electrode; a shield layer that covers the first quantum bit and the second quantum bit; and an insulating film provided between the third electrode and the shield layer. The quantum device can be used in, for example, quantum computing.

Description

Technical Field

[0001] The present disclosure relates to a quantum device and a method for manufacturing a quantum device.

Background Art

[0002] In a quantum device including qubits, multi-bitization of qubits has been studied for expanding the amount of computation. Therefore, a quantum device including a plurality of qubit substrates on which qubits are formed has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] For multi-bitization of qubits, capacitive coupling is considered by using another substrate (capacitive coupling substrate) facing a plurality of substrates on which qubits are formed to connect between a plurality of qubits. Further, in a quantum device, it is required to shield external electromagnetic waves from the qubits.

[0006] The object of this disclosure is to provide a quantum device and a method for manufacturing a quantum device that can connect qubits using a capacitively coupled substrate and shield qubits from external electromagnetic waves. [Means for solving the problem]

[0007] According to one embodiment of the present disclosure, a quantum device is provided comprising a first qubit substrate, a second qubit substrate, and a capacitive coupling substrate, wherein the first qubit substrate comprises a first qubit and a first electrode connected to the first qubit, the second qubit substrate comprises a second qubit and a second electrode connected to the second qubit, and the capacitive coupling substrate comprises a third electrode capacitively coupled to the first and second electrodes, a shield layer covering the first and second qubits, and an insulating film provided between the third electrode and the shield layer. [Effects of the Invention]

[0008] According to this disclosure, it is possible to connect qubits and shield them from external electromagnetic waves. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a cross-sectional view showing a quantum device according to the first embodiment. [Figure 2] Figure 2 is a top view showing the first qubit substrate and the second qubit substrate in the quantum device according to the first embodiment. [Figure 3] Figure 3 is a bottom view showing a capacitively coupled substrate in a quantum device according to the first embodiment. [Figure 4] Figure 4 is a cross-sectional view showing a method of using the quantum device according to the first embodiment. [Figure 5] Figure 5 is a cross-sectional view showing a quantum device related to a reference example. [Figure 6] Figure 6 is a cross-sectional view (part 1) showing a first example of the method for manufacturing a capacitively coupled substrate in the first embodiment. [Figure 7] FIG. 7 is a cross-sectional view (part 2) showing a first example of a method for manufacturing a capacitive coupling substrate in the first embodiment. [Figure 8] FIG. 8 is a cross-sectional view (part 3) showing a first example of a method for manufacturing a capacitive coupling substrate in the first embodiment. [Figure 9] FIG. 9 is a cross-sectional view (part 4) showing a first example of a method for manufacturing a capacitive coupling substrate in the first embodiment. [Figure 10] FIG. 10 is a cross-sectional view (part 1) showing a second example of a method for manufacturing a capacitive coupling substrate in the first embodiment. [Figure 11] FIG. 11 is a cross-sectional view (part 2) showing a second example of a method for manufacturing a capacitive coupling substrate in the first embodiment. [Figure 12] FIG. 12 is a cross-sectional view (part 3) showing a second example of a method for manufacturing a capacitive coupling substrate in the first embodiment. [Figure 13] FIG. 13 is a bottom view showing a capacitive coupling substrate in a quantum device according to the second embodiment. [Figure 14] FIG. 14 is a cross-sectional view showing a quantum device according to the third embodiment. [Figure 15] FIG. 15 is a cross-sectional view showing a quantum device according to the fourth embodiment. [Figure 16] FIG. 16 is a cross-sectional view showing a quantum device according to the fifth embodiment. [Figure 17] FIG. 17 is a cross-sectional view showing a quantum device according to the sixth embodiment. [Figure 18] FIG. 18 is a top view showing a first qubit substrate and a second qubit substrate in a quantum device according to the sixth embodiment. [Figure 19] FIG. 19 is a cross-sectional view showing a quantum device according to the seventh embodiment.

Embodiments for Carrying Out the Invention

[0010] 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 explanations. In this disclosure, the X1-X2 direction, Y1-Y2 direction, and Z1-Z2 direction are mutually orthogonal directions. A plane including the X1-X2 direction and the Y1-Y2 direction is described as the XY plane, a plane including the Y1-Y2 direction and the Z1-Z2 direction is described as the YZ plane, and a plane including the Z1-Z2 direction and the X1-X2 direction is described as the ZX plane. For convenience, the Z1-Z2 direction is considered the up and down direction, with the Z1 side being the upper side and the Z2 side being the lower side. Furthermore, a plan view means viewing the object from the Z1 side, and a planar shape means the shape of the object as viewed from the Z1 side.

[0011] In recent years, there has been a growing demand for quantum devices that enable larger-scale qubit computations, particularly those involving qubits. This requires multi-bit technology to connect multiple qubits together. One such multi-bit technology involves connecting qubit-forming substrates using opposing substrates. More specifically, this can be achieved by arranging coupling substrates opposite multiple qubit substrates and providing electrodes on the coupling substrates to facilitate coupling between qubits. The inventors have further investigated a structure that provides the coupling substrates with a shielding function to block external electromagnetic waves.

[0012] (First Embodiment) A first embodiment will be described. The first embodiment relates to a quantum device. Figure 1 is a cross-sectional view showing a quantum device according to the first embodiment. Figure 2 is a top view showing a first qubit substrate and a second qubit substrate in the quantum device according to the first embodiment. Figure 3 is a bottom view showing a capacitive coupling substrate in the quantum device according to the first embodiment.

[0013] As shown in Figures 1 and 2, the quantum device 1 according to the first embodiment includes a first qubit substrate 100, a second qubit substrate 200, and a capacitive coupling substrate 301. Note that the capacitive coupling substrate 301 is omitted in Figure 2.

[0014] The first qubit substrate 100 includes a first substrate 110, a plurality of first qubits 120, a plurality of first electrodes 130, a plurality of first readout circuits 140, a plurality of first input units 150, and a plurality of first readout units 160. The first substrate 110 is, for example, a Si substrate, a sapphire substrate, or an MgO substrate. The dielectric loss of the first substrate 110 is preferably 1 × 10⁻⁶. -3 The following applies, more preferably 1 × 10 -4 The following applies: The resistivity of the first substrate 110 is preferably 0.1 kΩ·cm or more, and more preferably 1 kΩ·cm or more. The first substrate 110 has an upper surface 111 on the Z1 side and a lower surface 112 on the Z2 side. Multiple first read-through holes 113 and multiple first grounding through holes 114 are formed in the first substrate 110. The first qubit 120, the first electrode 130 and the first read-through circuit 140 are provided on the upper surface 111, and the first input section 150 is provided on the lower surface 112. The first electrode 130 and the first read-through circuit 140 are connected to the first qubit 120. These connections may be direct or indirect, such as magnetic coupling, capacitive coupling, or galvanic coupling. In a plan view, the first input section 150 and the first qubit 120 overlap. The first readout through-hole 113 is formed such that the first readout circuit 140 is positioned between it and the first qubit 120. The first readout section 160 is provided in the first readout through-hole 113 and is indirectly connected to the first readout circuit 140 by magnetic coupling, capacitive coupling, galvanic coupling, or the like.

[0015] Each first qubit 120 is indirectly connected to other adjacent first qubits 120 via inter-bit wiring 181, using methods such as magnetic coupling, capacitive coupling, or galvanic coupling. A capacitor 182 is provided along the path of the inter-bit wiring 181. Each first qubit 120 creates a quantum entanglement state with other adjacent first qubits 120 to perform quantum operations.

[0016] The first qubit 120, the first electrode 130, the first readout circuit 140, the first input section 150, and the first readout section 160 are made of a material that becomes a superconductor at extremely low temperatures, such as Al, Nb, or TiN. A conductor layer 172 that enters into the first grounding through hole 114 is provided on the lower surface 112, and a conductor layer 171 connected to the conductor layer 172 is provided on the upper surface 111. Conductor layers 171 and 172 are also made of a material that becomes a superconductor at extremely low temperatures, such as Al, Nb, TiN, or NbN. Conductor layer 171 is an example of a first conductor layer.

[0017] The second qubit substrate 200 includes a second substrate 210, a plurality of second qubits 220, a plurality of second electrodes 230, a plurality of second readout circuits 240, a plurality of second input units 250, and a plurality of second readout units 260. The second substrate 210 is, for example, a Si substrate, a sapphire substrate, or an MgO substrate. The dielectric loss of the second substrate 210 is preferably 1 × 10⁻⁶. -3 The following applies, more preferably 1 × 10 -4The following applies: The resistivity of the second substrate 210 is preferably 0.1 kΩ·cm or more, and more preferably 1 kΩ·cm or more. The second substrate 210 has an upper surface 211 on the Z1 side and a lower surface 212 on the Z2 side. Multiple second read-through holes 213 and multiple second grounding through holes 214 are formed in the second substrate 210. The second qubit 220, the second electrode 230 and the second read-through circuit 240 are provided on the upper surface 211, and the second input section 250 is provided on the lower surface 212. The second electrode 230 and the second read-through circuit 240 are connected to the second qubit 220. These connections may be direct or indirect, such as magnetic coupling, capacitive coupling, or galvanic coupling. In a plan view, the second input section 250 and the second qubit 220 overlap. The second readout through-hole 213 is formed such that the second readout circuit 240 is positioned between it and the second qubit 220. The second readout section 260 is provided in the second readout through-hole 213 and is indirectly connected to the second readout circuit 240 by magnetic coupling, capacitive coupling, galvanic coupling, or the like.

[0018] Each second qubit 220 is indirectly connected to other adjacent second qubits 220 via inter-bit wiring 281 by magnetic coupling, capacitive coupling, galvanic coupling, etc. A capacitor 282 is provided along the path of the inter-bit wiring 281. Each second qubit 220 creates a quantum entanglement state with other adjacent second qubits 220 to perform quantum operations.

[0019] The second qubit 220, the second electrode 230, the second readout circuit 240, the second input section 250, and the second readout section 260 are made of a material that becomes a superconductor at extremely low temperatures, such as Al, Nb, or TiN. A conductive layer 272 that enters into the second grounding through hole 214 is provided on the lower surface 212, and a conductive layer 271 connected to the conductive layer 272 is provided on the upper surface 211. Conductive layers 271 and 272 are also made of a material that becomes a superconductor at extremely low temperatures, such as Al, Nb, TiN, or NbN. Conductive layer 271 is an example of a second conductive layer.

[0020] The capacitive coupling substrate 301 includes a third substrate 310, a shield layer 320, an insulating film 330, a third electrode 340, and a shield layer 350. The third substrate 310 may be a Si substrate with a thermal oxide film. More preferably, the dielectric loss of the third substrate 310 is low, for example, a Si substrate, a sapphire substrate, or an MgO substrate. The dielectric loss of the third substrate 310 is preferably 1 × 10⁻⁶ -3 The following applies, more preferably 1 × 10 -4 The following applies: The resistivity of the third substrate 310 is preferably 0.1 kΩ·cm or more, and more preferably 1 kΩ·cm or more. The third substrate 310 has an upper surface 311 on the Z1 side and a lower surface 312 on the Z2 side. The shield layer 320 is provided on the lower surface 312, the insulating film 330 is provided on the lower surface of the shield layer 320, and the third electrode 340 and the shield layer 350 are provided on the lower surface of the insulating film 330. The insulating film 330 is provided between the shield layer 320 and the third electrode 340 and the shield layer 350. The shield layer 320 covers the first qubit 120 and the second qubit 220 from the Z1 side. The shield layer 320, the third electrode 340 and the shield layer 350 are made of a material that becomes a superconductor at cryogenic temperatures, which are the operating temperatures of the first qubit 120 and the second qubit 220, such as Al, TiN, or NbN. The insulating film 330 is composed of, for example, an oxide of the material of the shield layer 320, i.e., aluminum oxide, or a nitride, such as aluminum nitride. The shield layer 350 is an example of a third conductive layer.

[0021] The third electrodes 340 are arranged in an island-like configuration and are electrically insulated from the shield layers 320 and 350. The potential of the third electrodes 340 is, for example, the floating potential. The third electrodes 340 have a rectangular planar shape, and the dimensions (width) of the third electrodes 340 in the Y1-Y2 direction are constant. In plan view, each third electrode 340 overlaps with one first electrode 130 and one second electrode 230, and the shield layers 350 overlap at least partially with the conductor layers 171 and 271. The third electrodes 340 are capacitively coupled to the first electrodes 130 and 230. The first electrodes 130 and 230 face the third electrodes 340, and the first qubit 120 and 220 face the insulating film 330.

[0022] The quantum device 1 includes a conductive bonding material 361 that joins the conductive layer 171 and the shield layer 350, and a conductive bonding material 362 that joins the conductive layer 271 and the shield layer 350. The material of the conductive bonding materials 361 and 362 is, for example, In if it is a superconducting material, and for example, Au or Cu if it is a normal conducting material. The conductive bonding materials 361 and 362 may be made of only superconducting materials, only normal conducting materials, or both.

[0023] Quantum device 1 is used, for example, with a probe substrate attached. Figure 4 is a cross-sectional view showing a method of using quantum device 1 according to the first embodiment.

[0024] As shown in Figure 4, the probe substrate 400 includes a base material 410, a plurality of first input probes 421, a plurality of second input probes 422, a plurality of first read probes 431, a plurality of second read probes 432, a plurality of first ground probes 441, and a plurality of second ground probes 442. The first input probes 421, second input probes 422, first read probes 431, second read probes 432, first ground probes 441, and second ground probes 442 may be fixed to the base material 410. For example, the first input probes 421, second input probes 422, first read probes 431, and second read probes 432 may be coaxial pins and may have a mechanism for the pins to mechanically extend and retract. Each first input probe 421 contacts one first input section 150, and each second input probe 422 contacts one second input section 250. Each first read probe 431 contacts one first read unit 160, and each second read probe 432 contacts one second read unit 260. Each first ground probe 441 contacts the conductor layer 172, and each second ground probe 442 contacts the conductor layer 272.

[0025] Ground potential is supplied to the conductor layers 171, 172, 271, and 272 and the shield layer 350 from the first ground probe 441 and the second ground probe 442. A signal to change the state of the first qubit 120 is supplied to the first input unit 150 from the first input probe 421, and a signal to change the state of the second qubit 220 is supplied to the second input unit 250 from the second input probe 422. The state of the first qubit 120 is read out from the first read probe 431, and the state of the second qubit 220 is read out from the second read probe 432.

[0026] Next, the effects of the first embodiment will be described in comparison with the reference example. Figure 5 is a cross-sectional view showing a quantum device according to the reference example.

[0027] The quantum device 1X in the reference example has a capacitive coupling substrate 301X instead of the capacitive coupling substrate 301. The capacitive coupling substrate 301X does not have a shield layer 320 and an insulating film 330, and the third electrode 340 and the shield layer 350 are provided on the lower surface 312 of the third substrate 310. The other configurations are the same as in the first embodiment.

[0028] In both quantum devices 1 and 1X, the third electrode 340 is capacitively coupled to the first electrode 130 and the second electrode 230. Therefore, the first electrode 130 and the second electrode 230 are capacitively coupled via the third electrode 340. For example, the strength of the capacitive coupling between the first electrode 130 and the second electrode 230 is equal to the strength of the capacitive coupling between adjacent first qubits 120 in the first qubit substrate 100, and the strength of the capacitive coupling between adjacent second qubits 220 in the second qubit substrate 200.

[0029] However, in quantum device 1, a shielding layer 320 exists above the first qubit 120 and the first readout circuit 140, whereas in quantum device 1X, the shielding layer 320 does not exist above the first qubit 120 and the first readout circuit 140. Therefore, quantum device 1 can obtain a good shielding effect against electromagnetic waves coming from above toward the first qubit 120 and the first readout circuit 140, but in quantum device 1X, electromagnetic waves coming from above can easily reach the first qubit 120 and the first readout circuit 140. Similarly, quantum device 1 can obtain a good shielding effect against electromagnetic waves coming from above toward the second qubit 220 and the second readout circuit 240, but in quantum device 1X, electromagnetic waves coming from above can easily reach the second qubit 220 and the second readout circuit 240.

[0030] Furthermore, in quantum device 1, the dielectric loss of the third substrate 310 does not significantly affect the first qubit 120 and the first readout circuit 140 due to the presence of the shield layer 320, whereas in quantum device 1X, the dielectric loss of the third substrate 310 is more likely to affect the first qubit 120 and the first readout circuit 140. Similarly, in quantum device 1, the dielectric loss of the third substrate 310 does not significantly affect the second qubit 220 and the second readout circuit 240, whereas in quantum device 1X, the dielectric loss of the third substrate 310 is more likely to affect the second qubit 220 and the second readout circuit 240.

[0031] Thus, according to the first embodiment, a shielding effect can be obtained while connecting qubits, and the reduction in coherence due to dielectric loss can be suppressed.

[0032] Furthermore, in the regions of the capacitive coupling substrate 301 facing the first qubit 120 and the second qubit 220, no conductive material is provided between the insulating film 330 and the first qubit 120, and between the insulating film 330 and the second qubit 220. Therefore, parasitic stray capacitance in the first qubit 120 and the second qubit 220 can be suppressed.

[0033] Furthermore, when using the quantum device 1, the space between the first qubit substrate 100 and the second qubit substrate 200 and the capacitive coupling substrate 301 may be sealed by creating a vacuum or by filling this space with an inert gas. In this case, the first qubit 120 and the second qubit 220 can be operated more stably.

[0034] Next, a method for manufacturing the capacitive coupling substrate 301 will be described. Figures 6 to 9 are cross-sectional views showing a first example of the method for manufacturing the capacitive coupling substrate 301, and Figures 10 to 12 are cross-sectional views showing a second example of the method for manufacturing the capacitive coupling substrate 301.

[0035] In the first example, as shown in Figure 6, a first layer 320A, which will be the shield layer 320, is first formed on the surface that will become the lower surface 312 of the third substrate 310. The first layer 320A can be formed, for example, by a vapor deposition method. The first layer 320A is made of, for example, Al or TiN.

[0036] Next, as shown in Figure 7, the surface of the first layer 320A is oxidized to form an insulating film 330. The remaining portion of the first layer 320A becomes the shield layer 320. The insulating film 330 can be formed, for example, by forced oxidation or natural oxidation. Note that if the first layer 320A is an Al film, this step may be a nitriding step in which the first layer 320A is nitrided.

[0037] Subsequently, as shown in Figure 8, a second layer 340A, which will serve as the third electrode 340 and the shield layer 350, is formed on the insulating film 330. The second layer 340A can be formed, for example, by vapor deposition. The second layer 340A is made of, for example, Al or TiN.

[0038] Next, as shown in Figure 9, the second layer 340A is processed, for example, by etching, to form the third electrode 340 and the shield layer 350. In this way, the capacitive coupling substrate 301 can be manufactured.

[0039] In the second example, the process up to the formation of the insulating film 330 is carried out in the same manner as in the first example. Next, a resist pattern 380 is formed as shown in Figure 10. The resist pattern 380 has openings in the portion where the third electrode 340 is formed and in the portion where the shield layer 350 is formed.

[0040] Subsequently, as shown in Figure 11, a third layer 340B, which will serve as the third electrode 340 and shield layer 350, is formed on the insulating film 330 and the resist pattern 380. The third layer 340B can be formed, for example, by vapor deposition. The third layer 340B is made of, for example, Al or TiN.

[0041] Next, as shown in Figure 12, the resist pattern 380 is removed. Along with the removal of the resist pattern 380, the third layer 340B formed on top of the resist pattern 380 is also removed. As a result, the third electrode 340 and the shield layer 350 are formed. In this way, the capacitive coupling substrate 301 can be manufactured.

[0042] To manufacture quantum device 1, a first qubit substrate 100 and a second qubit substrate 200 are prepared, and a capacitive coupling substrate 301 is prepared using the method described above. Then, the first qubit substrate 100 and the second qubit substrate 200 are bonded to the capacitive coupling substrate 301. Conductive bonding materials 361 and 362 are used for this bonding. In this way, quantum device 1 can be manufactured.

[0043] The potential of the shield layer 320 is not limited and may be, for example, the floating potential or the ground potential. However, it is preferable that the potential of the shield layer 320 be the floating potential rather than the ground potential. This is because setting the potential of the shield layer 320 to the floating potential reduces the rate at which external electromagnetic fields pass through the shield layer 320, making it easier to stabilize the ground potential of the conductor layers 171 and 271 and the shield layer 350.

[0044] (Second Embodiment) Next, a second embodiment will be described. The second embodiment differs from the first embodiment mainly in the planar shape of the third electrode. Figure 13 is a bottom view showing a capacitively coupled substrate in the quantum device according to the second embodiment.

[0045] As shown in Figure 13, the quantum device according to the second embodiment has a capacitive coupling substrate 302 instead of the capacitive coupling substrate 301. In the capacitive coupling substrate 302, the third electrode 340 has a first region 341, a second region 342, and a third region 343. The first region 341 faces the first electrode 130, and the second region 342 faces the second electrode 230. The third region 343 is connected to the first region 341 and the second region 342 and is located between the first region 341 and the second region 342. The dimensions of the third electrode 340 in the Y1-Y2 direction (second direction) are smaller in the third region 343 than those of the first region 341 and the second region 342. The Y1-Y2 direction is perpendicular in a plan view to the X1-X2 direction (first direction) where the first electrode 130 and the second electrode 230 are aligned.

[0046] Other configurations of the second embodiment are the same as those of the first embodiment.

[0047] The same effects as the first embodiment can be obtained with the second embodiment. Furthermore, in the second embodiment, since the dimensions of the third electrode 340 in the Y1-Y2 direction are smaller in the third region 343 than in the first region 341 and the second region 342, it is possible to make it less likely for magnetic flux quantum trapping to occur in the third electrode 340.

[0048] (Third embodiment) Next, a third embodiment will be described. The third embodiment differs from the first embodiment mainly in the configuration of the first qubit substrate and the second qubit substrate. Figure 14 is a cross-sectional view showing a quantum device according to the third embodiment.

[0049] As shown in Figure 14, in the quantum device 3 according to the third embodiment, the first grounding through-hole 114 is filled with a conductor layer 172, and the second grounding through-hole 214 is filled with a conductor layer 272.

[0050] Other configurations of the third embodiment are the same as those of the first embodiment.

[0051] The same effects as those of the first embodiment can be obtained with the third embodiment as well.

[0052] (Fourth Embodiment) Next, a fourth embodiment will be described. The fourth embodiment differs from the first embodiment mainly in the configuration of the capacitively coupled substrate. Figure 15 is a cross-sectional view showing the quantum device according to the fourth embodiment.

[0053] As shown in Figure 15, the quantum device 4 according to the fourth embodiment has a capacitive coupling substrate 304 instead of the capacitive coupling substrate 301. In the capacitive coupling substrate 304, the insulating film 330 is formed only between the third electrode 340 and the shield layer 320, and between the shield layer 350 and the shield layer 320, and in a plan view, the insulating film 330 is not formed between the third electrode 340 and the shield layer 350. Therefore, the lower surface of the shield layer 320 is exposed from the insulating film 330.

[0054] Other configurations of the fourth embodiment are the same as those of the first embodiment.

[0055] The same effects as those of the first embodiment can be obtained with the fourth embodiment as well.

[0056] (Fifth embodiment) Next, a fifth embodiment will be described. The fifth embodiment differs from the first embodiment mainly in the configuration of the capacitively coupled substrate. Figure 16 is a cross-sectional view showing a quantum device according to the fifth embodiment.

[0057] As shown in Figure 16, the quantum device 5 according to the fifth embodiment has a capacitive coupling substrate 305 instead of the capacitive coupling substrate 301. The capacitive coupling substrate 305 has a conductive layer 390 formed on the insulating film 330. The conductive layer 390 includes a third electrode 340 and a shield layer 350. Furthermore, the conductive layer 390 is formed to be thinner than the region of the third electrode 340 and the shield layer 350, at least in the region facing the first qubit 120 and the second qubit 220. For example, as shown in Figures 8 and 9, the third electrode 340 and the shield layer 350 are formed by etching the second layer 340A on the insulating film 330. Similarly in this embodiment, when the conductive member formed on the insulating film 330 is partially removed by etching to form the third electrode 340 and the shield layer 350, the conductive member on the insulating film 330 is not completely removed and remains between the third electrode 340 and the shield layer 350, thereby forming the conductive layer 390.

[0058] Other configurations of the fifth embodiment are the same as those of the first embodiment.

[0059] In the fifth embodiment, as in the first embodiment, a good shielding effect can be obtained, and the reduction in coherence due to dielectric loss can be suppressed. Furthermore, because the thickness of the conductive layer 390 is thinner in the region of the capacitive coupling substrate 305 facing at least the first qubit 120 and the second qubit 220 compared to other regions, the generation of parasitic stray capacitance in the first qubit 120 and the second qubit 220 can be suppressed.

[0060] (Sixth Embodiment) Next, a sixth embodiment will be described. The sixth embodiment differs from the first embodiment mainly in the configuration of the first qubit substrate and the second qubit substrate. Figure 17 is a cross-sectional view showing the quantum device according to the sixth embodiment. Figure 18 is a top view showing the first qubit substrate and the second qubit substrate in the quantum device according to the sixth embodiment.

[0061] As shown in Figures 17 and 18, in the quantum device 6 according to the sixth embodiment, the first qubit substrate 100 does not have a first readout through hole 113 and a first ground through hole 114, and the first qubit substrate 100 does not have a conductor layer 172. The first input section 150 is provided on the upper surface 111 of the first substrate 110. A capacitor 190 is connected between the first qubit 120 and the first input section 150. Similarly, the second qubit substrate 200 does not have a second readout through hole 213 and a second ground through hole 214, and the first qubit substrate 100 does not have a conductor layer 172. The second input section 250 is provided on the upper surface 211 of the second substrate 210. A capacitor 290 is connected between the second qubit 220 and the second input section 250.

[0062] In a plan view, the first input section 150 and the second input section 250 are exposed from the capacitive coupling substrate 301. Bonding wires are connected to the first input section 150 and the second input section 250, respectively. In the sixth embodiment, signals to change the state of the first qubit 120 and the second qubit 220 are input from the bonding wires, rather than from the first input probe 421 and the second input probe 422.

[0063] The other configurations of the sixth embodiment are the same as those of the first embodiment.

[0064] The same effects as those of the first embodiment can be obtained with the sixth embodiment as well.

[0065] (Seventh Embodiment) Next, a seventh embodiment will be described. The seventh embodiment differs from the first embodiment mainly in the configuration of the capacitively coupled substrate. Figure 19 is a cross-sectional view showing a quantum device according to the seventh embodiment.

[0066] As shown in Figure 19, the quantum device 7 according to the seventh embodiment has a capacitive coupling substrate 307 instead of the capacitive coupling substrate 301. The capacitive coupling substrate 307 has a shield layer 351 instead of the shield layer 350. The shield layer 351 is thicker than the third electrode 340. The shield layer 351 is made of the same material as, for example, the third electrode 340.

[0067] Furthermore, the quantum device 7 does not have conductive bonding materials 361 and 362, and the shield layer 351 is directly bonded to the conductor layers 171 and 271. The shield layer 351 is bonded to the conductor layers 171 and 271, for example, by diffusion bonding.

[0068] Other configurations of the seventh embodiment are the same as those of the first embodiment.

[0069] The same effects as those of the first embodiment can be obtained with the seventh embodiment as well.

[0070] In addition, in any embodiment, the laminated structure of the shield layer 320 and the insulating film 330 may be repeatedly provided. Furthermore, the quantum device may contain three or more qubit substrates.

[0071] The quantum device relating to this disclosure can be used, for example, in quantum computing.

[0072] 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. [Explanation of Symbols]

[0073] 1, 3, 4, 5, 6, 7: Quantum devices 100: First qubit substrate 110: First board 120: First qubit 130: 1st electrode 200: Second qubit substrate 210: Second board 220: Second qubit 230:Second electrode 301, 302, 304, 305, 307: Capacitive coupling board 310: Third board 320: Shield layer 330: Insulating film 340: 3rd electrode 341:First area 342:Second area 343: Third area 350, 351, 370: Shield layer 390: Conductive layer

Claims

1. The first qubit substrate and The second qubit substrate and Capacitive coupling substrate and It has, The first qubit substrate is The first qubit and A first electrode connected to the first qubit, It has, The second qubit substrate is The second qubit and The second electrode connected to the second qubit, It has, The aforementioned capacitive coupling substrate is A third electrode capacitively coupled to the first electrode and the second electrode, A shielding layer covering the first qubit and the second qubit, An insulating film is provided between the third electrode and the shield layer, A quantum device characterized by having the following features.

2. The first qubit substrate has N sets of the first qubit and the first electrode (where N is an integer of 2 or more), The second qubit substrate has N sets of the second qubit and the second electrode, The capacitive coupling substrate has N of the third electrodes, The quantum device according to claim 1, characterized in that the N third electrodes are electrically insulated from each other.

3. The third electrode is, A first region facing the first electrode, A second region facing the second electrode, A third region is connected to the first region and the second region, and is located between the first region and the second region. It has, The quantum device according to claim 1 or 2, characterized in that the dimension of the third electrode in a second direction perpendicular to the first direction in a plan view in which the first and second electrodes are aligned is smaller in the third region than in the first and second regions.

4. The quantum device according to claim 1 or 2, characterized in that the potential of the third electrode is a floating potential.

5. The first qubit substrate comprises a first substrate and a first conductor layer, The second qubit substrate comprises a second substrate and a second conductor layer. The aforementioned capacitive coupling substrate has a third substrate and a third conductive layer, The first qubit, the first electrode, and the first conductor layer are provided on the capacitive coupling substrate side of the first substrate. The second qubit, the second electrode, and the second conductor layer are provided on the capacitive coupling substrate side of the second substrate. The third conductive layer is provided on the first qubit substrate and the second qubit substrate side of the insulating film. The first conductor layer and the third conductor layer are directly joined together. The quantum device according to claim 1 or 2, characterized in that the second conductor layer and the third conductor layer are directly joined together.

6. The quantum device according to claim 1 or 2, characterized in that the third electrode becomes a superconductor at the temperature in which the first qubit and the second qubit operate.

7. The quantum device according to claim 1 or 2, characterized in that the shielding layer becomes a superconductor at the temperature in which the first qubit and the second qubit operate.

8. The first qubit substrate has a dielectric loss of 1 × 10⁻⁶ －３ The following first substrate is included: The second qubit substrate has a dielectric loss of 1 × 10⁻⁶ －３ The following second substrate is included: The first qubit and the first electrode are provided on the capacitive coupling substrate side of the first substrate. The quantum device according to claim 1 or 2, characterized in that the second qubit and the second electrode are provided on the capacitive coupling substrate side of the second substrate.

9. The aforementioned capacitive coupling substrate has a dielectric loss of 1 × 10 －３ The following third substrate is included: The quantum device according to claim 1 or 2, characterized in that the shield layer is provided on the side of the third substrate that is the first qubit substrate and the second qubit substrate.

10. A step of preparing a first qubit substrate having a first qubit and a first electrode connected to the first qubit, A step of preparing a second qubit substrate having a second qubit and a second electrode connected to the second qubit, A step of preparing a capacitively coupled substrate having a third electrode, a shielding layer, and an insulating film provided between the third electrode and the shielding layer, A step of bonding a first qubit substrate and a second qubit substrate to the capacitive coupling substrate such that the third electrode faces the first electrode and the second electrode, and the shield layer covers the first qubit and the second qubit, A method for manufacturing a quantum device, characterized by having the following features.

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