Quantum devices and quantum computers

Abstract

To provide a quantum device capable of suppressing degradation of quantum bit performance even when a quantum chip is flip-chip mounted on an interposer.SOLUTION: A quantum chip (10) is flip-chip mounted to an interposer (20) by bumps (30). A coplanar line 12 that couples adjacent quantum bits is formed in the quantum chip (10). A gap (22) is provided in the interposer (20) at a location facing a central conductor (12a) of the coplanar line (12). A second ground electrode (24) is formed around the gap (22). The interposer (20) includes a connection electrode (40) that connects the second ground electrode (24) around the gap (22). A bump (30A) formed near the connection electrode (40) is connected to a first ground electrode (12b) and the second ground electrode (24).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to quantum devices and quantum computers. [Background technology]

[0002] Patent Document 1 discloses an electronic circuit, an oscillator including the electronic circuit and a magnetic field application unit, and a computing device (quantum computer) including the oscillator and a coupler. Patent Document 2 discloses a quantum bit device including an elongated thin film, a superconducting quantum interference device (SQUID), and a ground plane. The SQUID is in electrical contact with the proximal end of the elongated thin film and has fewer than three Josephson junctions. The ground plane is in the same plane as the elongated thin film and is in electrical contact with the distal end of the elongated thin film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-047999 A [Patent Document 2] Special Publication No. 2018-524795 Summary of the Invention [Problem to be solved by the invention]

[0004] It is known to form an air bridge on a device to suppress slot-line modes, which are undesirable transmission behaviors from coplanar lines, by keeping the ground plane at the same voltage. In Patent Document 2, a crossover air bridge is fabricated on a device to help suppress undesirable slot-line modes and the like from a waveguide. On the other hand, in order to reduce the complexity of wiring for transmitting and receiving a large number of microwave signals and to save layout space, a quantum chip constituting a quantum bit (resonator) may be flip-chip mounted on an interposer using bumps. Here, when a quantum chip provided with an air bridge as described in Patent Document 2 is flip-chip mounted (flip-chip connected) on an interposer, the air bridge may be deformed or destroyed due to the process associated with flip-chip mounting. Therefore, it is difficult to keep the ground plane at the same voltage using an air bridge, and energy leakage modes such as slot-line modes may not be sufficiently suppressed, which may result in a decrease in the performance of the quantum bit.

[0005] The object of the present disclosure has been made to solve such problems, and is to provide a quantum device and a quantum computer that can suppress degradation in quantum bit performance even when a quantum chip is flip-chip mounted on an interposer. [Means for solving the problem]

[0006] A quantum device according to the present disclosure includes a quantum chip constituting a quantum bit, and an interposer facing the quantum chip and having a conductor formed on at least a surface facing the quantum chip, the quantum chip is flip-chip mounted on the interposer by bumps, the quantum chip is formed with a coplanar line for coupling adjacent quantum bits, the coplanar line is composed of a central conductor and a first ground electrode around the central conductor, on the surface of the interposer facing the quantum chip, at a portion of the coplanar line facing the central conductor, the conductor is not formed in part along a path of the coplanar line, and a second ground electrode is formed around the gap where the conductor is not formed, the interposer has a connection electrode connecting the second ground electrode around the gap, and the bump formed in the vicinity of the connection electrode is connected to the first ground electrode and the second ground electrode. Another quantum device according to the present disclosure includes a quantum chip constituting a quantum bit, and an interposer disposed opposite the quantum chip, the quantum chip being flip-chip mounted to the interposer by bumps, the quantum chip having a coplanar line for coupling adjacent quantum bits, the coplanar line including a central conductor and a first ground electrode disposed around the central conductor, the interposer having a second ground electrode formed in a region opposite the first ground electrode, the interposer having a connection electrode connected to the second ground electrode, the bump formed in the vicinity of the connection electrode being connected to the first ground electrode and the second ground electrode, and at least a portion of the connection electrode facing the central conductor across a space.

[0007] The quantum computer according to the present disclosure also includes a plurality of the quantum devices and at least one coupling circuit that couples between a plurality of the quantum bits formed by the plurality of the quantum devices and includes a coupler formed by the central conductor. Effect of the Invention

[0008] According to the present disclosure, it is possible to provide a quantum device and a quantum computer that are capable of suppressing degradation in quantum bit performance even when a quantum chip is flip-chip mounted on an interposer. [Brief description of the drawings]

[0009] [Figure 1] 1 is a diagram showing an overview of a quantum device according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a diagram illustrating a configuration of a quantum device according to a first embodiment. [Diagram 3] FIG. 1 is a diagram illustrating a configuration of a quantum device according to a first embodiment. [Figure 4] FIG. 1 is a diagram illustrating a configuration of a quantum device according to a first embodiment. [Diagram 5] FIG. 1 is a plan view showing a configuration of a quantum chip according to a first embodiment. [Figure 6] FIG. 1 is a plan view showing a configuration of an interposer according to a first embodiment. [Figure 7] FIG. 1 is a circuit diagram showing an oscillator according to a first embodiment. [Figure 8] FIG. 2 is a diagram illustrating an equivalent circuit of the oscillator according to the first embodiment. [Figure 9] FIG. 4 is a side view showing the structure around the gap in the first embodiment. [Figure 10] FIG. 11 is a diagram illustrating a configuration of a quantum device according to a second embodiment. [Figure 11] FIG. 11 is a diagram illustrating a configuration of a quantum device according to a third embodiment. [Figure 12] FIG. 11 is a side view showing the structure around the gap in the third embodiment. [Figure 13] FIG. 2 is a diagram showing a configuration of a quantum computer configured with a plurality of quantum devices according to the above-described embodiment. [Figure 14] FIG. 2 is a plan view showing the configuration of a quantum chip according to a first modified example. [Figure 15] FIG. 11 is a plan view showing a configuration of an interposer according to a first modified example. [Figure 16] FIG. 11 is a plan view showing the configuration of a quantum chip according to a second modified example. [Figure 17] FIG. 11 is a plan view showing the configuration of an interposer according to a second modified example. [Figure 18] FIG. 13 is a plan view showing the configuration of a quantum chip according to a third modified example. [Figure 19] FIG. 13 is a plan view showing the configuration of an interposer according to a third modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Summary of the embodiment of the present disclosure) Prior to describing the embodiments of the present disclosure, an overview of the embodiments of the present disclosure will be described. Fig. 1 is a diagram showing an overview of a quantum device 1 according to the present embodiment.

[0011] The quantum device 1 has a quantum chip 10 constituting a quantum bit (quantum bit circuit, oscillator) and an interposer 20 facing the quantum chip 10. A conductor is formed on at least a surface 20a of the interposer 20 facing the quantum chip 10. The conductor may be a superconducting material or a normal conducting material. The conductor may include a ground electrode, a wiring, a pad, or the like. The quantum chip 10 is flip-chip mounted on the interposer 20 by a bump 30. For example, the quantum device 1 is a device corresponding to one bit of a quantum bit. A quantum computer is configured by arranging a plurality of quantum devices 1 or quantum chips 10.

[0012] Moreover, the quantum chip 10 is formed with a coplanar line 12 that couples adjacent quantum bits. Here, the coplanar line 12 is composed of a central conductor 12a and a first ground electrode 12b around (on both sides of) the central conductor 12a. Furthermore, in the interposer 20, a gap 22 is provided at a portion facing the central conductor 12a of the coplanar line 12. That is, on the surface of the interposer 20 facing the quantum chip 10, at a portion facing the central conductor 12a of the coplanar line 12, a conductor is not formed partially along the path of the coplanar line 12. In this gap 22 where no conductor is formed, a dielectric may be exposed. Then, a second ground electrode 24 is formed around (on both sides of) the gap 22 of the interposer 20. That is, the second ground electrode 24 is formed around the portion where no conductor is formed. That is, the conductor formed on the surface 20a of the interposer 20 has a second ground electrode 24 in a region facing the first ground electrode 12b.

[0013] The interposer 20 also has a connection electrode 40 that connects the second ground electrodes 24 around the gap 22. That is, both ends of the connection electrode 40 are connected to the second ground electrodes 24. For example, a bridge-shaped connection electrode 40 (bridge electrode) that partially connects the second ground electrodes 24 around the gap 22 is formed in a part of the gap 22. For example, the connection electrode 40 may be provided in a part of the gap 22 that is an area where the dielectric is exposed. That is, in a place where no conductor is formed, the connection electrode 40 that connects the second ground electrodes 24 around the place is formed. In other words, at least a part of the connection electrode 40 is provided at a position that overlaps a part of the area facing the central conductor 12a. Note that in FIG. 1, the connection electrode 40 is formed in a straight line, but the connection electrode 40 is not limited to this shape. The bump 30A formed in the vicinity of the connection electrode 40 is connected to the first ground electrode 12b and the second ground electrode 24. At least a portion of the connection electrode 40 faces the central conductor 12a with a space therebetween.

[0014] This allows the two ground electrodes (first ground electrodes 12b) constituting the coplanar line 12 in the quantum chip 10 to have the same potential. Therefore, energy leakage modes such as slot-line modes are suppressed in the coplanar line 12 of the quantum chip 10. This reduces unnecessary interference between quantum bits, improving the coherence of the quantum bits. This makes it possible to suppress deterioration in the performance of the quantum bits.

[0015] Specifically, in the process of flip-chip mounting, film formation and cleaning may be performed on the surfaces of the quantum chip and the interposer on which the bumps are formed or on which the bumps are bonded. Therefore, when mounting a quantum chip with an air bridge already provided on an interposer, film formation and cleaning that do not affect the air bridge are required, which is technically difficult. In other words, the electrode structure of the air bridge formed on the quantum chip may be deformed or destroyed by these film formation and cleaning processes. Therefore, even if the quantum chip is flip-chip mounted on the interposer, it is not possible to keep the ground surface at the same voltage using the air bridge. This may result in insufficient suppression of energy leakage modes such as slot line modes, which may degrade the performance of the quantum bit.

[0016] In contrast, in the quantum device 1 according to the present disclosure, the above-described connection electrodes 40 can provide a function similar to that of an air bridge, making it possible to achieve both a function similar to that of an air bridge and processes such as film formation and cleaning for the surface on which the bumps are formed or bonded. Therefore, in the quantum device 1 according to the present disclosure, it is possible to suppress deterioration in the performance of the quantum bit even when flip-chip mounting is performed.

[0017] (Embodiment 1) Hereinafter, the embodiments will be described with reference to the drawings. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In addition, in each drawing, the same elements are given the same reference numerals, and duplicate explanations are omitted as necessary.

[0018] 2 to 4 are diagrams showing a configuration of a quantum device 50 according to the first embodiment. FIG. 2 is a perspective view showing a structure of the quantum device 50 according to the first embodiment. FIG. 3 is an exploded view showing a stacked structure of the quantum device 50 according to the first embodiment. FIG. 4 is a schematic diagram showing the quantum device 50 according to the first embodiment from the side. The quantum device 50 has a quantum chip 100 and an interposer 200. The quantum device 50 corresponds to the quantum device 1 shown in FIG. 1. The quantum chip 100 corresponds to the quantum chip 10 shown in FIG. 1. The interposer 200 corresponds to the interposer 20 shown in FIG. 1. The quantum device 50 shown in FIG. 2 to FIG. 4 corresponds to, for example, one quantum bit (1 bit).

[0019] Moreover, Fig. 5 is a plan view showing the configuration of the quantum chip 100 (superconducting wiring layer 104) according to the first embodiment. Moreover, Fig. 6 is a plan view showing the configuration of the interposer 200 (superconducting wiring layer 202) according to the first embodiment. Note that Figs. 5 and 6 are views seen from above Fig. 2. Therefore, the configuration of Fig. 5 is superimposed on the configuration of Fig. 6.

[0020] In Fig. 2, the quantum chip 100 and the interposer 200 are shown separated from each other to facilitate understanding of the structure, but in reality, the two are connected as shown in Fig. 4. Specifically, the quantum chip 100 and the interposer 200 are connected by flip-chip connection via the bumps 300. As a result, the quantum chip 100 is flip-chip mounted on the interposer 200. In other words, the quantum chip 100 faces the interposer 200 via the bumps 300.

[0021] 2 to 4, the quantum chip 100 has a substrate 102 and a superconducting wiring layer 104. The superconducting wiring layer 104 is provided on a surface of the substrate 102 facing the interposer 200. As will be described later, the superconducting wiring layer 104 is provided with a circuit of the resonator 110 and the coupler 122. In addition, the superconducting wiring layer 104 is provided with a ground electrode 124 (first ground electrode) around the circuit of the resonator 110 and the coupler 122.

[0022] The interposer 200 also includes a superconducting wiring layer 202, a substrate 204, and a superconducting wiring layer 206. The superconducting wiring layer 202 is provided on the surface of the substrate 204 facing the quantum chip 100. The superconducting wiring layer 206 is provided on the surface of the substrate 204 opposite the quantum chip 100. The interposer 200 is configured to connect the quantum chip 100 to an external circuit (not shown). As will be described later, the superconducting wiring layer 202 is provided with a magnetic field application circuit 212 and a readout unit 214. Therefore, the interposer 200 can function as a quantum interposer. The superconducting wiring layer 202 is provided with a ground electrode 224 (second ground electrode).

[0023] Moreover, the superconducting wiring layer 206 is provided with wiring connected to the superconducting wiring layer 202 via a through electrode 240 provided in the substrate 204. For example, the superconducting wiring layer 206 is provided with wiring 212a and wiring 214a for connecting the magnetic field application circuit 212 and the readout unit 214 to an external circuit. The superconducting wiring layer 206 is provided with a ground electrode 250 (fourth ground electrode) around the wiring 212a and wiring 214a. The through electrode 240 may be formed of a superconducting material. The through electrode 240 penetrates the substrate 204 and connects the ground electrode 224 and the ground electrode 250.

[0024] Here, for example, silicon substrates are used for the substrate 102 and the substrate 204, but the material of the substrate is not limited thereto. For example, sapphire substrates or glass substrates may be used for the substrate 102 and the substrate 204. In addition, in this embodiment, the superconducting wiring layers 104, 202, 206, the bump 300, and the through electrode 240 are realized by a superconductor. Examples of the superconductor material include niobium, niobium nitride, aluminum, indium, lead, tin, rhenium, palladium, titanium, titanium nitride, tantalum, or an alloy containing any of these. Note that it is not necessary that all of the superconducting wiring layers 104, 202, 206, the bump 300, and the through electrode 240 are realized by a superconductor, and a normal conductor may be used for at least a part of them except for the superconducting wiring layer 104. Examples of the normal conductor material include copper, silver, gold, platinum, or an alloy containing any of these. In order to realize a superconducting state, quantum device 50 is used in a temperature environment of, for example, about 10 mK (millikelvin) realized by a refrigerator.

[0025] As shown in FIG. 2, FIG. 3, and FIG. 5, the superconducting wiring layer 104 is formed with a circuit of a resonator 110 and a coupler 122. Specifically, the superconducting wiring layer 104 includes a conductive member 112 having a predetermined shape, a SQUID (superconducting quantum interference device) 116, a ground electrode 124, and a coupler 122. In the first embodiment, the conductive member 112 is formed in a cross shape. In addition, the ground electrode 124 is formed around the conductive member 112 and the coupler 122. In addition, a space G is provided between the conductive member 112 and the ground electrode 124. The conductive member 112 is capacitively coupled to the ground electrode 124 via the space G. That is, the space G constitutes a capacitor 118 described later.

[0026] Furthermore, a pair of Josephson junctions 114A, 114B are provided between one end 112d of the conductive member 112 and the ground electrode 124a. The pair of Josephson junctions 114A, 114B form a loop circuit to configure the SQUID 116. That is, one end of the SQUID 116 is connected to the conductive member 112, and the other end is connected to the ground electrode 124a. Furthermore, the conductive member 112 and the SQUID 116 configure the resonator 110.

[0027] Couplers 122A to 122D are provided near the four ends 112a to 112d of the conductive member 112, respectively. The couplers 122 are configured to couple adjacent quantum bits. In other words, the couplers 122 are circuits for coupling with other resonators having a similar configuration to the resonator 110. The couplers 122 can be capacitively coupled with the resonator 110 (conductive member 112). Each coupler 122 is formed near the ends 112a to 112d of the conductive member 112 so as to surround each of the ends 112a to 112d. Each coupler 122 has a discontinuous shape, such as a branch portion 122a and a bent portion 122b. With this shape, the couplers 122 surround each of the ends 112a to 112d of the conductive member 112.

[0028] Coplanar line 120 is formed by coupler 122 and ground electrode 124 around coupler 122. For example, coplanar line 120 is configured by providing a gap in ground electrode 124 and forming coupler 122 as a central conductor in the center of the gap. Therefore, coplanar line 120 corresponds to coplanar line 12 shown in FIG. 1, coupler 122 corresponds to central conductor 12a shown in FIG. 1, and ground electrode 124 corresponds to first ground electrode 12b shown in FIG. 1. Coplanar line 120 itself may function as a coupler. In other words, coplanar line 120 may correspond to a "coupler."

[0029] Specifically, as shown in FIG. 5, a coupler 122A is provided near an end 112a of the conductive member 112, which is located 90 degrees counterclockwise from an end 112d where the Josephson junction 114 (SQUID 116) is provided. The coupler 122A and a surrounding ground electrode 124A form a coplanar line 120A. Similarly, a coupler 122B is provided near an end 112b, which is located 90 degrees counterclockwise from the end 112a. The coupler 122B and a surrounding ground electrode 124B form a coplanar line 120B. A coupler 122C is provided near an end 112c, which is located 90 degrees counterclockwise from the end 112b. The coupler 122C and a surrounding ground electrode 124C form a coplanar line 120C. Moreover, a coupler 122D is provided near the end 112d. The coupler 122D and a ground electrode 124D surrounding the coupler 122D form a coplanar line 120D. That is, in the first embodiment, the coupler 122D (coplanar line 120D) is provided near the SQUID 116.

[0030] As shown in FIG. 2, FIG. 3, and FIG. 6, the superconducting wiring layer 202 is formed with a ground electrode 224. Here, a space A is provided in the portion of the superconducting wiring layer 202 facing the resonator 110 and the coupler 122 of the superconducting wiring layer 104. That is, the ground electrode 224 is not formed in the region of the superconducting wiring layer 202 facing the resonator 110 and the coupler 122 of the superconducting wiring layer 104. This is because the characteristics of the quantum bit deteriorate when the resonator 110 and the coupler 122 are close to the ground electrode 224. Specifically, when the resonator 110 and the coupler 122 are close to the ground electrode 224, the resonant frequency and Q value (Quality factor) of the resonator 110, the degree of coupling of the coupler 122, the characteristic impedance of the coplanar line 120, and the like are affected. The ground electrode 224 is connected to the ground electrode 124 via a large number of bumps 300. That is, the plurality of bumps 300 are arranged between the ground electrode 124 and the ground electrode 224. Furthermore, the plurality of bumps 300 are arranged in a lattice pattern or randomly.

[0031] Further, a magnetic field application circuit 212 and a readout unit 214 are provided in the space A. The magnetic field application circuit 212 is provided at a position facing the SQUID 116, and is magnetically coupled to the SQUID 116. The magnetic field application circuit 212 applies a magnetic field to the SQUID 116. The magnetic field is a DC magnetic field or an AC magnetic field. The resonator 110 and the magnetic field application circuit 212 constitute an oscillator 60, which will be described later. Therefore, it can be said that the quantum device 50 constitutes the oscillator 60 (quantum bit, quantum bit circuit).

[0032] The magnetic field application circuit 212 is formed of electrodes and wiring of a predetermined shape. Specifically, as shown in FIG. 2 and FIG. 6, the magnetic field application circuit 212 is configured with electrodes and wiring of a shape with a part of a ring missing, that is, a C-shape. That is, the magnetic field application circuit 212 is configured with electrodes and wiring of a substantially ring shape. When a current flows through the magnetic field application circuit 212, a magnetic field is generated that penetrates the inside of the current path along the substantially ring-shaped electrodes and wiring. In addition, the magnetic field application circuit 212 only needs to be magnetically coupled with the SQUID 116, and the shape does not need to be substantially ring-shaped. In addition, the ground electrode 212b (third ground electrode) of the magnetic field application circuit 212 is connected to the ground electrode 124a via the bumps 300E and 300F. In addition, the ground electrode 212b only needs to be connected to a ground electrode, and may be connected to the ground electrode 224 or the ground electrode 250, not limited to the ground electrode 124a.

[0033] The readout unit 214 is provided at a position facing the conductive member 112 and is capacitively coupled to the conductive member 112. The readout unit 214 is an electrode for reading out the internal state of the resonator 110 (oscillator 60), that is, the oscillation state. The readout unit 214 is connected to an external circuit (control unit) that acquires the internal state of the resonator 110 (oscillator 60) via the superconducting wiring layer 206 (wiring 214a). The shape of the readout unit 214 is, for example, a shape corresponding to the shape of the conductive member 112. In this embodiment, the shape of the readout unit 214 is a cross shape. Also, the readout unit 214 only needs to be capacitively coupled to the conductive member 112, and the shape does not have to be a cross shape. By providing the magnetic field application circuit 212 and the readout unit 214 below the quantum chip 100, the size of the quantum device 50 can be reduced.

[0034] Fig. 7 is a circuit diagram showing an oscillator 60 according to the first embodiment. Fig. 8 is a diagram showing an equivalent circuit of the oscillator 60 according to the first embodiment. The oscillator 60 has a resonator 110 and a magnetic field application circuit 212. The resonator 110 has a SQUID 116 and a capacitor 118. The SQUID 116 is shunted by the capacitor 118 via the conductive member 112.

[0035] The SQUID 116 is a circuit in which two Josephson junctions 114 (114A, 114B) are connected in a circular manner by a superconducting line. That is, the SQUID 116 is a circular loop circuit having two Josephson junctions 114 (114A, 114B). Here, the Josephson junction refers to an element having a structure in which a thin insulating film is sandwiched between two superconductors. More specifically, as shown in FIG. 8, the SQUID 116 includes a first superconducting line 116a that connects the Josephson junction 114A and the Josephson junction 114B, and a second superconducting line 116b that connects the Josephson junction 114A and the Josephson junction 114B. In other words, the resonator 110 includes a SQUID 116 which is a loop circuit in which a first superconducting line 116a and a second superconducting line 116b are joined by a Josephson junction 114A and a Josephson junction 114B. As shown in Fig. 8, the first superconducting line 116a, the Josephson junction 114A, the second superconducting line 116b, and the Josephson junction 114B are connected in a circular manner to form a loop circuit (i.e., the SQUID 116). In other words, in the SQUID 116, the first superconducting line 116a and the second superconducting line 116b are joined by a Josephson junction 114A and a Josephson junction 114B to form a loop.

[0036] Returning to the explanation using Figs. 2 to 6, as described above, the ground electrode 224 is not formed in the region of the superconducting wiring layer 202 facing the coupler 122. Therefore, as shown in Figs. 2, 3 and 6, the gap 222 is provided in the position of the superconducting wiring layer 202 facing the coupler 122. Specifically, the gap 222A is provided in the position facing the coupler 122A. Similarly, the gap 222B is provided in the position facing the coupler 122B. Furthermore, the gap 222C is provided in the position facing the coupler 122C. Furthermore, the gap 222D is provided in the position facing the coupler 122D. Furthermore, the gap 222E is provided in a location between the magnetic field application circuit 212 (ground electrode 212b) and the ground electrode 224, facing the coupler 122D. 2, a space is formed in the region of the superconducting wiring layer 202 facing the coupler 122, but the present invention is not limited to this configuration. In the region facing the coupler 122 (the region where the ground electrode 224 is not formed), the dielectric (substrate 204) may be exposed. In this case, the gap 222 is formed so that the dielectric is exposed.

[0037] In the first embodiment, a bridge-shaped bridge electrode 400 is provided in each gap 222. That is, the interposer 200 has the bridge electrode 400 formed to span the gap 222. The bridge electrode 400 is formed of a conductor (superconductor). The bridge electrode 400 corresponds to the connection electrode 40 shown in FIG. 1. That is, the connection electrode 40 includes the bridge electrode 400 (first bridge electrode, second bridge electrode).

[0038] Specifically, a bridge electrode 400A (first bridge electrode) is provided in the gap 222A. Similarly, a bridge electrode 400B (first bridge electrode) is provided in the gap 222B. Furthermore, a bridge electrode 400C (first bridge electrode) is provided in the gap 222C. Furthermore, a bridge electrode 400D (first bridge electrode) is provided in the gap 222D. Furthermore, a bridge electrode 400E and a bridge electrode 400F (second bridge electrode) are provided in the gap 222E.

[0039] FIG. 9 is a side view showing a structure around the gap 222 according to the first embodiment. The bridge electrode 400 is formed in a part of the gap 222. The bridge electrode 400 is formed in a bridge shape so as to partially connect the ground electrodes 224 around (both sides of) the gap 222. In other words, the bridge electrode 400 partially connects the ground electrodes 224 around the gap 222. In further other words, the bridge electrode 400 is formed so as to straddle the gap 222. This can reduce the potential difference of the electric potential (ground potential) of the ground electrodes 224 around the gap 222. Ideally, the bridge electrode 400 can make the electric potential (ground potential) of the ground electrodes 224 around the gap 222 equipotential.

[0040] In addition, although the bridge electrode 400 is shown in FIG. 2 in an arc shape, FIG. 2 merely shows the bridge electrode 400 in a schematic manner, and in reality, the bridge electrode 400 does not need to be formed in an arc shape. Rather, as shown in FIG. 9, the bridge electrode 400 is formed so as not to come into contact with the superconducting wiring layer 104 (coupler 122). That is, in order to suppress deterioration of the characteristics of the above-mentioned quantum bit, it is desirable that the bridge electrode 400 is formed as far away as possible from the superconducting wiring layer 104 of the quantum chip 100. Therefore, a part of the bridge electrode 400 (connection electrode) faces the coupler 122 (center conductor) with a space therebetween. Also, as shown in FIG. 6, in the first embodiment, the bridge electrode 400 is formed in a straight line. Also, as shown in FIG. 9, the bridge electrode 400 may be provided on the same plane as the ground electrode 224 (superconducting wiring layer 202). Moreover, the bridge electrode 400 may be formed integrally with the ground electrodes 224 (superconducting wiring layers 202) on both sides of the gap 222. By forming the bridge electrode 400 in this manner, the bridge electrode 400 can be easily formed.

[0041] As described above, the ground electrode 224 is connected to the ground electrode 124 via the bumps 300, and therefore a large number of bumps 300 are connected to the ground electrode 224. Therefore, the bumps 300 may be provided near the bridge electrode 400. Specifically, the bumps 300A are provided on both sides near the bridge electrode 400A. Similarly, the bumps 300B are provided on both sides near the bridge electrode 400B. Moreover, the bumps 300C are provided on both sides near the bridge electrode 400C. Moreover, the bumps 300D are provided on both sides near the bridge electrode 400D. Moreover, the bumps 300D are provided on one end near the bridge electrode 400E, and the bumps 300E are provided at the other end at a location corresponding to the magnetic field application circuit 212. Further, in the vicinity of the bridge electrode 400F, a bump 300D is provided at one end thereof, and a bump 300F is provided at a position corresponding to the magnetic field application circuit 212 at the other end.

[0042] 9, the ground electrodes 124 on both sides of the coupler 122 corresponding to the central conductor in the coplanar line 120 are connected via the bump 300, the ground electrode 224, the bridge electrode 400, the ground electrode 224, and the bump 300. A U-shaped transmission path is therefore formed by the bump 300, the ground electrode 224, the bridge electrode 400, the ground electrode 224, and the bump 300. This U-shaped transmission path functions as an air bridge connecting the ground electrodes 124 on both sides of the coupler 122.

[0043] Specifically, as shown in Fig. 5 and Fig. 6, the ground electrode 124A around the coupler 122A is connected by the bump 300A, the ground electrode 224, the bridge electrode 400A, the ground electrode 224, and the bump 300A. Similarly, the ground electrode 124B around the coupler 122B is connected by the bump 300B, the ground electrode 224, the bridge electrode 400B, the ground electrode 224, and the bump 300B. Also, the ground electrode 124C around the coupler 122C is connected by the bump 300C, the ground electrode 224, the bridge electrode 400C, the ground electrode 224, and the bump 300C. The ground electrode 124D around the coupler 122D is connected by the bump 300D, the ground electrode 224, the bridge electrode 400D, the ground electrode 224, and the bump 300D.

[0044] Furthermore, the ground electrode 124a around the coupler 122D is connected to the ground electrode 124D by the bump 300E, the ground electrode 212b of the magnetic field application circuit 212, the bridge electrode 400E, the ground electrode 224, and the bump 300D. The ground electrode 124a around the coupler 122D is connected to the ground electrode 124D by the bump 300F, the ground electrode 212b of the magnetic field application circuit 212, the bridge electrode 400F, the ground electrode 224, and the bump 300D. Although six bridge electrodes 400 are shown in FIG. 6, the number of bridge electrodes 400 is not limited to six. The bridge electrode 400 may be formed so as to face the coupler 122, which is the central conductor of the coplanar line 120, and to straddle any gap 222 around which the bump 300 is provided.

[0045] In this manner, in the first embodiment, the bump 300, the ground electrode 224, the bridge electrode 400, the ground electrode 224, and the bump 300 function as an air bridge connecting the ground electrodes 124 on both sides of the coupler 122. This can reduce the potential difference between the ground electrodes 124 on both sides of the coupler 122. Preferably, the potential difference between the ground electrodes 124 on both sides of the coupler 122 can be set to zero. This can suppress the occurrence of an energy leakage mode such as an undesirable slotline mode or a coupled slotline mode. That is, it can suppress the electromagnetic field distribution in the width direction (horizontal direction in FIG. 9) from becoming asymmetric between the central conductor (coupler 122) and the ground electrodes 124 around it. This can suppress the energy leakage between the ground electrodes 124 across the central conductor. Therefore, it can suppress the deterioration of the performance of the quantum bit. Specifically, since unnecessary interference between the quantum bits is reduced, the coherence of the quantum bit can be improved.

[0046] Here, as described in Patent Document 2, an air bridge may be formed across the waveguide in order to suppress the occurrence of energy leakage modes such as slot line modes. However, as described above, when flip-chip mounting the quantum chip 100 and the interposer 200, providing an air bridge is not preferable from the viewpoints of technology and space. In contrast, in the first embodiment, a function similar to that of an air bridge can be realized without providing an air bridge, so that the occurrence of the energy leakage mode can be suppressed. Therefore, in the quantum device 50 according to the first embodiment, even when flip-chip mounting is performed, it is possible to suppress the deterioration of the performance of the quantum bit.

[0047] As described above, since the characteristics of the quantum bit deteriorate when the coupler 122 is close to the ground electrode 224, it is not preferable to form many bridge electrodes 400 in one gap 222. On the other hand, in order to suppress the occurrence of energy leakage modes such as slot line modes in the coplanar line 120, it is preferable to provide many bridge electrodes 400. Therefore, the number of bridge electrodes 400 can be set appropriately depending on, for example, design conditions.

[0048] It is preferable that the bridge electrode 400 is not provided at a position facing the resonator 110 (the conductive member 112 and the SQUID 116). This makes it possible to suppress deterioration of the performance of the quantum bit (the resonator 110). For example, by providing the bridge electrode 400 at a position that does not face the resonator 110 (the conductive member 112 and the SQUID 116), it is possible to suppress deterioration of coherence. Note that the coherence is, for example, a coherence time, which is the time during which the oscillator 60 functions as a quantum bit.

[0049] Moreover, the occurrence of the above-mentioned energy leakage mode is highly likely to occur in a discontinuous shape of the coupler 122, such as a branch or bend of the coplanar line 120. Therefore, it is desirable to provide the bridge electrode 400 at a location corresponding to the discontinuous shape of the coupler 122. For example, as shown in FIG. 5 and FIG. 6, the bridge electrode 400A is formed near the branch portion 122a of the coupler 122A. Similarly, the bridge electrode 400B is formed near the branch portion 122a of the coupler 122B. The bridge electrode 400C is formed near the branch portion 122a of the coupler 122C. Moreover, the bridge electrode 400D is formed near the branch portion 122a of the coupler 122D. Moreover, the bridge electrodes 400E and 400F are formed near the branch portion 122a and the bent portion 122b of the coupler 122D.

[0050] In addition, a gap 222E is provided between the ground electrode 212b of the magnetic field application circuit 212 and the ground electrode 224 at a position facing the coupler 122D (center conductor) near the SQUID 116. A bridge electrode 400E and a bridge electrode 400F are formed so as to straddle the gap 222E. The bridge electrodes 400E and 400F partially connect the ground electrode 212b and the ground electrode 224. One end of the bridge electrodes 400E and 400F is located near the bumps 300E and 300F connected to the ground electrode 124 and the ground electrode 212b, and the other end is located near the bump 300 connected to the ground electrode 124 and the ground electrode 224. As a result, the ground electrodes around the coupler 122D are connected by the three bridge electrodes 400D, 400E, and 400F. Furthermore, the three bridge electrodes 400D, 400E, and 400F are formed near the branch portion 122a of the coupler 122D. Therefore, it is possible to more effectively suppress the occurrence of the energy leakage mode. This configuration can also be applied to other embodiments described later.

[0051] In the present embodiment, the bumps 300 are arranged in a lattice pattern or randomly between the ground electrode 124 and the ground electrode 224. This increases the possibility that the bumps 300 will be arranged near the bridge electrode 400. Furthermore, by arranging the bumps 300 in this manner, the ground electrode 124 and the ground electrode 224 are more reliably connected to each other.

[0052] (Embodiment 2) Next, a second embodiment will be described. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In each drawing, the same elements are given the same reference numerals, and repeated explanations are omitted as necessary. In the second embodiment, the components corresponding to the connection electrode 40 shown in FIG. 1 are different from those in the first embodiment.

[0053] Fig. 10 is a diagram illustrating a configuration of a quantum device 50 according to the second embodiment. Fig. 10 is a perspective view illustrating a quantum device 50 according to the second embodiment. Fig. 10 corresponds to Fig. 2 according to the first embodiment.

[0054] As in the first embodiment, the quantum device 50 according to the second embodiment includes a quantum chip 100 and an interposer 200. The configuration of the quantum chip 100 is substantially similar to that of the first embodiment, and therefore a description thereof will be omitted. The configuration of the interposer 200 is substantially similar to that of the first embodiment, except for the bridge electrode 400, and therefore a description thereof will be omitted. For the positions of the gaps 222 (222A to 222D), please refer to FIG. 2.

[0055] The interposer 200 according to the second embodiment has an outer frame structure 420 of a conductor (superconductor) formed so as to surround the superconducting wiring layer 202 of the interposer 200. The outer frame structure 420 is formed integrally with the ground electrode 224. The outer frame structure 420 has an outer frame portion 422A corresponding to the gap 222A, an outer frame portion 422B corresponding to the gap 222B, an outer frame portion 422C corresponding to the gap 222C, and an outer frame portion 422D corresponding to the gap 222D. In other words, the outer frame portions 422 are provided at positions corresponding to the respective gaps 222 of the outer frame structure 420.

[0056] The outer frame portion 422 connects the ground electrodes 224 around (both ends of) the gap 222. That is, the outer frame portion 422 corresponds to the connection electrode 40 shown in FIG. 1. In other words, the connection electrode 40 includes the outer frame portion 422. In further other words, the outer frame portion 422 functions as the connection electrode 40 shown in FIG. 1. Therefore, the bump 300 formed in the vicinity of the outer frame portion 422 is connected to the ground electrode 124 and the ground electrode 224.

[0057] Specifically, bumps 300A are provided on both sides near outer frame portion 422A. Similarly, bumps 300B are provided on both sides near outer frame portion 422B. Furthermore, bumps 300C are provided on both sides near outer frame portion 422C. Furthermore, bumps 300D are provided on both sides near outer frame portion 422D.

[0058] 9 in the first embodiment, the ground electrodes 124 on both sides of the coupler 122 corresponding to the central conductor in the coplanar line 120 are connected via the bump 300, the ground electrode 224, the outer frame portion 422, the ground electrode 224, and the bump 300. As a result, a U-shaped transmission path is formed by the bump 300, the ground electrode 224, the outer frame portion 422, the ground electrode 224, and the bump 300. This U-shaped transmission path functions as an air bridge connecting the ground electrodes 124 on both sides of the coupler 122.

[0059] Specifically, the ground electrode 124A around the coupler 122A is connected by the bump 300A, the ground electrode 224, the outer frame portion 422A, the ground electrode 224, and the bump 300A. Similarly, the ground electrode 124B around the coupler 122B is connected by the bump 300B, the ground electrode 224, the outer frame portion 422B, the ground electrode 224, and the bump 300B. Also, the ground electrode 124C around the coupler 122C is connected by the bump 300C, the ground electrode 224, the outer frame portion 422C, the ground electrode 224, and the bump 300C. The ground electrode 124D around the coupler 122D is connected by the bump 300D, the ground electrode 224, the outer frame portion 422D, the ground electrode 224, and the bump 300D.

[0060] In this way, in the second embodiment, the bump 300, the ground electrode 224, the outer frame portion 422, the ground electrode 224, and the bump 300 function as an air bridge connecting the ground electrodes 124 on both sides of the coupler 122. Therefore, as in the second embodiment, by providing a conductor outer frame structure 420 formed so as to surround the superconducting wiring layer 202 of the interposer 200 and integral with the ground electrode 224, it is possible to achieve the same effect as in the first embodiment. That is, also in the second embodiment, the potential difference between the ground electrodes 124 on both sides of the coupler 122 can be reduced. Preferably, the potential difference between the ground electrodes 124 on both sides of the coupler 122 can be made zero. Therefore, the configuration according to the second embodiment can also suppress the occurrence of the energy leakage mode in the coupler 122.

[0061] In addition, since there is a low possibility that wiring necessary for realizing quantum bits will be arranged on the outer peripheral portion of the interposer 200, there is a high degree of freedom in wiring. Therefore, even if a ground electrode is arranged on the outer peripheral portion of the interposer 200, there is an extremely low possibility that it will affect the overall arrangement. Therefore, by providing the outer frame structure 420, it is possible to easily form the outer frame portion 422 having substantially the same function as the bridge electrode 400 according to the first embodiment. In other words, it is possible to easily arrange the connection electrode 40 compared to the configuration according to the first embodiment.

[0062] (Embodiment 3) Next, a third embodiment will be described. For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. In addition, in each drawing, the same elements are given the same reference numerals, and repeated explanations are omitted as necessary. In the third embodiment, the components corresponding to the connection electrode 40 shown in FIG. 1 are different from the other embodiments.

[0063] Fig. 11 is a diagram illustrating a configuration of a quantum device 50 according to the third embodiment. Fig. 11 is a perspective view illustrating a quantum device 50 according to the third embodiment. Fig. 11 corresponds to Fig. 2 according to the first embodiment.

[0064] As in the first embodiment, the quantum device 50 according to the third embodiment includes a quantum chip 100 and an interposer 200. The configuration of the quantum chip 100 is substantially similar to that of the first embodiment, and therefore a description thereof will be omitted. The configuration of the interposer 200 is substantially similar to that of the first embodiment, except for the bridge electrode 400, and therefore a description thereof will be omitted. For the positions of the gaps 222 (222A to 222D), please refer to FIG. 2.

[0065] FIG. 12 is a side view showing a structure around the gap 222 according to the third embodiment. In the third embodiment, a through electrode 240 is provided near the gap 222. The through electrode 240 and the ground electrode 250 (fourth ground electrode) connect the ground electrodes 224 around (on both sides of) the gap 222. Therefore, the through electrode 240 and the ground electrode 250 correspond to the connection electrode 40 shown in FIG. 1. In other words, the through electrode 240 and the ground electrode 250 form the connection electrode 440. In yet another way, the through electrode 240 and the ground electrode 250 function as the connection electrode 440. In yet another way, the connection electrode 440 includes a configuration formed by the through electrode 240 and the ground electrode 250. With this configuration, a part of the connection electrode 440 (a part of the ground electrode 250) faces the coupler 122 (center conductor) via a space.

[0066] Specifically, the through electrodes 240A are formed near both sides of the gap 222A. The ground electrodes 224 around the gap 222A are connected by a connection electrode 440A composed of the through electrodes 240A and the ground electrode 250A. Similarly, the through electrodes 240B are formed near both sides of the gap 222B. The ground electrodes 224 around the gap 222B are connected by a connection electrode 440B composed of the through electrodes 240B and the ground electrode 250B. Furthermore, the through electrodes 240C are formed near both sides of the gap 222C. The ground electrodes 224 around the gap 222C are connected by a connection electrode 440C composed of the through electrodes 240C and the ground electrode 250C. Furthermore, the through electrodes 240D are formed near both sides of the gap 222D. The ground electrodes 224 around the gaps 222D are connected by a connection electrode 440D that is formed of the through electrode 240D and the ground electrode 250D.

[0067] As described above, the bump 300 is connected to the ground electrode 224 and also to the ground electrode 124. Therefore, as shown in Fig. 12, the ground electrodes 124 on both sides of the coupler 122 are connected via the bump 300, the ground electrode 224, the through electrode 240, the ground electrode 250, the through electrode 240, the ground electrode 224, and the bump 300. Therefore, a U-shaped transmission path is formed by the bump 300, the ground electrode 224, the through electrode 240, the ground electrode 250, the through electrode 240, the ground electrode 224, and the bump 300. This U-shaped transmission path functions as an air bridge that connects the ground electrodes 124 on both sides of the coupler 122.

[0068] Specifically, the ground electrode 124A around the coupler 122A is connected by the bump 300A, the ground electrode 224, the through electrode 240A, the ground electrode 250A, the through electrode 240A, the ground electrode 224, and the bump 300A. Similarly, the ground electrode 124B around the coupler 122B is connected by the bump 300B, the ground electrode 224, the through electrode 240B, the ground electrode 250B, the through electrode 240B, the ground electrode 224, and the bump 300B. Also, the ground electrode 124C around the coupler 122C is connected by the bump 300C, the ground electrode 224, the through electrode 240C, the ground electrode 250C, the through electrode 240C, the ground electrode 224, and the bump 300C. Furthermore, the ground electrode 124D around the coupler 122D is connected by the bump 300D, the ground electrode 224, the through electrode 240D, the ground electrode 250D, the through electrode 240D, the ground electrode 224, and the bump 300D.

[0069] In this manner, in the third embodiment, the bump 300, the ground electrode 224, the through electrode 240, the ground electrode 250, the through electrode 240, the ground electrode 224, and the bump 300 function as an air bridge connecting the ground electrodes 124 on both sides of the coupler 122. Therefore, the third embodiment can also achieve the same effects as the first embodiment. That is, the third embodiment can also reduce the potential difference between the ground electrodes 124 on both sides of the coupler 122. Preferably, the potential difference between the ground electrodes 124 on both sides of the coupler 122 can be set to zero. Therefore, the configuration according to the third embodiment can also suppress the occurrence of the energy leakage mode in the coupler 122.

[0070] Furthermore, in the third embodiment, it is possible to reduce the potential difference between the ground electrodes 124 on both sides of the coupler 122 without forming a structure such as a bridge electrode that spans the gap 222. Therefore, the configuration according to the third embodiment can be simplified in structure compared to the configurations according to the first and second embodiments.

[0071] If the through electrode 240 is too long, that is, if the substrate 204 is too thick, the above effect may be reduced. Therefore, in order to shorten the length of the through electrode 240, it is desirable that the thickness of the substrate 204 is sufficiently thin. For example, it is desirable that the length of the through electrode 240 is sufficiently short with respect to the wavelength (operating wavelength) of a signal used to realize the operation of the quantum bit (a signal (high frequency signal; electromagnetic wave) used to realize the operation of the oscillator 60). For example, it is desirable that the length of the through electrode 240 is 1 / 20 or less of the operating wavelength. In this case, considering the wavelength shortening depending on the effective dielectric constant in the signal path including the through electrode 240, if the length is 1 / 20 or less of the operating wavelength, the phase difference of the instantaneous value becomes sufficiently small, about 18 degrees or less, so that the effect of reducing the potential difference between the ground electrode 124 and the ground electrode 250 can be expected. Therefore, the length of the through electrode 240 is sufficiently short that there is no problem in replacing the path formed by the bump 300, the bridge electrode 400, and the ground electrode 224 with the path formed by the bump 300, the through electrode 240, and the ground electrode 250.

[0072] (Quantum computer) 13 is a diagram showing the configuration of a quantum computer 70 configured with a plurality of quantum devices 50 according to the embodiment described above. The quantum computer 70 is, for example, a quantum annealing type computer that calculates a solution to an arbitrary problem that can be mapped to an Ising model. When a magnetic field is applied by the SQUID 116, an oscillator 60 configured with the quantum devices 50 performs parametric oscillation to realize a quantum bit (quantum bit circuit).

[0073] The quantum computer 70 has a plurality of quantum devices 50 and at least one coupling circuit 80. The coupling circuit 80 is a circuit that couples a plurality of oscillators 60 (qubits, quantum bit circuits) configured by a plurality of quantum devices 50. In other words, the coupling circuit 80 is a circuit that couples a plurality of quantum devices 50. The quantum computer 70 is a computer in which a plurality of oscillators 60 configured by a plurality of quantum devices 50 form a network via the coupling circuit 80. In other words, the quantum computer 70 is configured by arranging a plurality of quantum devices 50 in an array via the coupling circuit 80.

[0074] In the example of FIG. 13, the coupling circuit 80 couples four quantum devices 50 (oscillators 60). The coupling circuit 80 is coupled to the four oscillators 60. The coupling circuit 80 also includes the above-mentioned coupler 122. The above-mentioned coupler 122 is a terminal of the coupling circuit 80 for coupling to the resonator 110 (oscillator 60). Thus, the coupling circuit 80 couples between a plurality of quantum bits formed by a plurality of quantum devices 50, and includes the coupler 122. Note that in the example of FIG. 13, the coupling circuit 80 is connected to four quantum devices 50 (oscillators 60), but the number of quantum devices 50 (oscillators 60) to which one coupling circuit 80 can be coupled can be set as appropriate depending on design conditions.

[0075] As described above, since the quantum device 50 according to the present embodiment is configured as described above, it is possible to suppress the occurrence of an energy leakage mode in the coupler 122. Therefore, it is possible to suppress the deterioration of the performance of the quantum bit. And, since the quantum computer 70 according to the present embodiment is configured with such a quantum device 50, it is possible to improve the performance of the entire quantum bit.

[0076] (Modification) The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit of the present invention. For example, in the above-described embodiment, the couplers 122 are provided in the vicinity of all of the four ends 112a to 112d of the conductive member 112. However, the couplers 122 do not need to be provided in the vicinity of all of the four ends 112a to 112d of the conductive member 112. The couplers 122 can be appropriately arranged according to the arrangement of the quantum device 50 (oscillator 60) in the quantum computer.

[0077] Moreover, the resonator 110 according to the above-described embodiment is configured such that the conductive member 112 is cross-shaped and the SQUID 116 is provided at an end of the cross shape. However, the configuration of the resonator 110 is not limited to this configuration. And, regardless of the position of the SQUID 116 and the shape of the conductive member 112, the connection electrode 40 (bridge electrode 400, etc.) according to this embodiment is applicable. Note that the following modified examples show modifications to the first embodiment, but the same applies to the other embodiments.

[0078] Fig. 14 is a plan view showing the configuration of a quantum chip 100 (superconducting wiring layer 104) according to the first modified example. Fig. 15 is a plan view showing the configuration of an interposer 200 (superconducting wiring layer 202) according to the first modified example. In the first modified example, the position of the SQUID 116 is different from that of the above-mentioned embodiment.

[0079] 14, one end of the SQUID 116 is connected to a narrowed portion of a cross-shaped conductive member 112, and the other end is connected to a ground electrode 124. The conductive member 112 and the SQUID 116 form a resonator 110.

[0080] Similarly to the above-described embodiment, four couplers 122 are arranged on all four sides of conductive member 112. Specifically, couplers 122 (122A to 122D) are provided near each of four ends 112a to 112d of conductive member 112. Similarly to the above-described embodiment, couplers 122 and ground electrode 124 around coupler 122 form coplanar line 120.

[0081] In addition, since the position of the SQUID 116 is different from that of the above-mentioned embodiment, the position of the magnetic field application circuit 212 that applies a magnetic field to the SQUID 116 is also different from that of the above-mentioned embodiment. That is, as shown in Fig. 15, the magnetic field application circuit 212 is disposed at a position of the superconducting wiring layer 202 facing the SQUID 116 shown in Fig. 14. Also, similar to the above-mentioned embodiment, the cross-shaped readout unit 214 is disposed at a position of the superconducting wiring layer 202 facing the conductive member 112.

[0082] Also in the first modification, gaps 222 are formed at positions of the superconducting wiring layer 202 facing each coplanar line 120. Bridge electrodes 400 are provided so as to straddle each gap 222. Bumps 300 may be provided near the bridge electrodes 400. Thus, the ground electrodes 124 on both sides of the coupler 122 are connected via the bumps 300, the ground electrodes 224, the bridge electrodes 400, the ground electrodes 224, and the bumps 300. This makes it possible to reduce the potential difference between the ground electrodes 124 on both sides of the coupler 122. Thus, in the first modification, as in the above-described embodiment, it is possible to suppress energy leakage between the ground electrodes 124 straddling the central conductor.

[0083] Fig. 16 is a plan view showing the configuration of a quantum chip 100 (superconducting wiring layer 104) according to the second modified example. Fig. 17 is a plan view showing the configuration of an interposer 200 (superconducting wiring layer 202) according to the second modified example. In the second modified example, the shape of the conductive member constituting the resonator 110 is different from that of the above-described embodiment.

[0084] 16, in the second modification, a quadrangular (e.g., square) conductive member 112A is used instead of the cross-shaped conductive member 112. One end of the SQUID 116 is connected to one corner of the conductive member 112A, and the other end is connected to the ground electrode 124. The conductive member 112A and the SQUID 116 form a resonator 110.

[0085] Four couplers 122 are arranged on all four sides of conductive member 112A. Specifically, couplers 122 (122A to 122D) are provided near each of the four sides of conductive member 112A. Similarly to the above-described embodiment, couplers 122 and ground electrodes 124 around couplers 122 form coplanar line 120.

[0086] In addition, since the position of the SQUID 116 is different from that of the above-mentioned embodiment, the position of the magnetic field application circuit 212 that applies a magnetic field to the SQUID 116 is also different from that of the above-mentioned embodiment. That is, as shown in Fig. 17, the magnetic field application circuit 212 is disposed at a position of the superconducting wiring layer 202 facing the SQUID 116 shown in Fig. 16. In addition, a quadrangular (e.g., square) readout section 214A is disposed at a position of the superconducting wiring layer 202 facing the conductive member 112A.

[0087] Also in the second modification, gaps 222 are formed at positions of the superconducting wiring layer 202 facing the respective coplanar lines 120. Bridge electrodes 400 are provided so as to straddle the respective gaps 222. Bumps 300 may be provided near the bridge electrodes 400. Thus, the ground electrodes 124 on both sides of the coupler 122 are connected via the bumps 300, the ground electrodes 224, the bridge electrodes 400, the ground electrodes 224, and the bumps 300. This makes it possible to reduce the potential difference between the ground electrodes 124 on both sides of the coupler 122. Thus, in the second modification, as in the above-described embodiment, it is possible to suppress energy leakage between the ground electrodes 124 straddling the central conductor.

[0088] Fig. 18 is a plan view showing the configuration of a quantum chip 100 (superconducting wiring layer 104) according to a third modified example. Fig. 19 is a plan view showing the configuration of an interposer 200 (superconducting wiring layer 202) according to a third modified example. In the third modified example, the shape of the conductive member constituting the resonator 110 is different from that of the above-described embodiment.

[0089] 18, in the third modified example, a circular conductive member 112B is used instead of the cross-shaped conductive member 112. One end of the SQUID 116 is connected to the conductive member 112B, and the other end is connected to the ground electrode 124. The conductive member 112B and the SQUID 116 form a resonator 110.

[0090] Moreover, four couplers 122 are arranged on all four sides of conductive member 112B. Specifically, couplers 122 (122A to 122D) are provided near each of the four sides of conductive member 112B. Moreover, similar to the above-described embodiment, couplers 122 and ground electrodes 124 around couplers 122 form coplanar line 120.

[0091] In addition, since the position of the SQUID 116 is different from that of the above-mentioned embodiment, the position of the magnetic field application circuit 212 that applies a magnetic field to the SQUID 116 is also different from that of the above-mentioned embodiment. That is, as shown in Fig. 19, the magnetic field application circuit 212 is disposed at a position of the superconducting wiring layer 202 facing the SQUID 116 shown in Fig. 18. In addition, a circular readout unit 214B is disposed at a position of the superconducting wiring layer 202 facing the conductive member 112B.

[0092] Also in the third modification, gaps 222 are formed at positions of the superconducting wiring layer 202 facing each coplanar line 120. Bridge electrodes 400 are provided so as to straddle each gap 222. Bumps 300 may be provided near the bridge electrodes 400. Thus, the ground electrodes 124 on both sides of the coupler 122 are connected via the bumps 300, the ground electrodes 224, the bridge electrodes 400, the ground electrodes 224, and the bumps 300. This makes it possible to reduce the potential difference between the ground electrodes 124 on both sides of the coupler 122. Thus, in the third modification, as in the above-described embodiment, it is possible to suppress energy leakage between the ground electrodes 124 straddling the central conductor.

[0093] Although the present invention has been described above with reference to the embodiment, the present invention is not limited to the above. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the invention.

[0094] A part or all of the above-described embodiments can be described as, but is not limited to, the following supplementary notes. (Appendix 1) A quantum chip that constitutes quantum bits; an interposer facing the quantum chip and having a conductor formed on at least a surface facing the quantum chip; having The quantum chip is flip-chip mounted on the interposer by bumps; a coplanar line for coupling adjacent quantum bits is formed on the quantum chip, the coplanar line being composed of a central conductor and a first ground electrode around the central conductor; on a surface of the interposer facing the quantum chip, at a location facing the central conductor of the coplanar line, the conductor is not formed partially along a path of the coplanar line, and a second ground electrode is formed around the gap where the conductor is not formed, the interposer has a connection electrode that connects the second ground electrode around the gap, the bump formed near the connection electrode is connected to the first ground electrode and the second ground electrode; Quantum devices. (Appendix 2) The quantum chip is provided with a resonator, the connection electrode is formed at a position of the interposer not facing the resonator; 2. The quantum device of claim 1. (Appendix 3) The resonator has a conductive member of a predetermined shape, The central conductor is provided in the vicinity of the conductive member. 3. The quantum device of claim 2. (Appendix 4) the connection electrode includes a first bridge electrode having a bridge shape formed so as to span a part of the gap, the bump formed in the vicinity of the first bridge electrode is connected to the first ground electrode and the second ground electrode; 4. The quantum device of claim 1. (Appendix 5) the central conductor has a discontinuous shape; The first bridge electrode is provided at a location in the gap that corresponds to the discontinuous shape. 5. The quantum device of claim 4. (Appendix 6) The first bridge electrode is formed on the same plane as the second ground electrode around the gap. 6. The quantum device according to claim 4 or 5. (Appendix 7) The quantum chip is provided with a resonator, The resonator has a SQUID (superconducting quantum interference device), The central conductor is provided in the vicinity of the SQUID, the interposer is provided with a magnetic field application circuit that applies a magnetic field to the SQUID; a gap is provided between a third ground electrode and the second ground electrode of the magnetic field application circuit at a position facing the central conductor in the vicinity of the SQUID, the interposer has a bridge-shaped second bridge electrode formed so as to span a part of the gap, the third ground electrode and the second ground electrode are partially connected by the second bridge electrode; 7. The quantum device of claim 1. (Appendix 8) one end of the second bridge electrode is located near the bumps connected to the first ground electrode and the third ground electrode, and the other end of the second bridge electrode is located near the bumps connected to the first ground electrode and the second ground electrode. 8. The quantum device of claim 7. (Appendix 9) the interposer has a conductor outer frame structure formed integrally with the second ground electrode, the outer frame structure being formed so as to surround a superconducting wiring layer facing the quantum chip of the interposer; an outer frame portion of the outer frame structure provided at a position corresponding to the gap functions as the connection electrode; 2. The quantum device of claim 1. (Appendix 10) a fourth ground electrode is formed on a surface of the interposer opposite to a surface facing the quantum bit; a through electrode is provided between the second ground electrode and the fourth ground electrode, the through electrode connecting the second ground electrode and the fourth ground electrode and passing through a substrate of the interposer; The through electrode in the vicinity of the gap and the fourth ground electrode form the connection electrode. 2. The quantum device of claim 1. (Appendix 11) The length of the through electrode is equal to or less than a predetermined value with respect to the wavelength of a signal operating to realize the quantum bit. 11. The quantum device of claim 10. (Appendix 12) The length of the through electrode is 1 / 20 or less of the wavelength. 12. The quantum device of claim 11. (Appendix 13) The bumps are arranged in a lattice pattern or randomly between the first ground electrode and the second ground electrode. 13. A quantum device according to any one of claims 1 to 12. (Appendix 14) A plurality of the quantum devices according to any one of claims 1 to 13; At least one coupling circuit that couples a plurality of the quantum bits that are each formed of a plurality of the quantum devices and includes a coupler that is formed of the central conductor; A quantum computer having the above structure. (Appendix 15) A quantum chip that constitutes quantum bits; An interposer provided opposite the quantum chip; having The quantum chip is flip-chip mounted on the interposer by bumps; a coplanar line for coupling adjacent quantum bits is formed on the quantum chip, the coplanar line being composed of a central conductor and a first ground electrode around the central conductor; a second ground electrode is formed on the interposer in a region facing the first ground electrode; the interposer has a connection electrode connected to the second ground electrode, the bump formed near the connection electrode is connected to the first ground electrode and the second ground electrode, At least a part of the connection electrode faces the central conductor with a space therebetween. Quantum devices. [Explanation of symbols]

[0095] 1 Quantum Devices 10. Quantum Chip 12 Coplanar Line 12a Center conductor 12b First ground electrode 20 Interposer 22 Gap 24 Second ground electrode 30 Bump 40 Connection electrode 50 Quantum Devices 60 Oscillator 70 Quantum computer 80 coupling circuit 100 Quantum Chips 102 Substrate 104 Superconducting Wiring Layer 110 resonator 112 Conductive materials 114 Josephson Junction 118 Capacitor 120 Coplanar Line 122 Coupler 122a Branching part 122b Bent part 124 Ground electrode 200 Interposer 202 Superconducting wiring layer 204 Substrate 206 Superconducting Wiring Layer 212 Magnetic field application circuit 214 Readout section 222 Gap 224 Ground electrode 240 Through electrode 250 Ground electrode 300 Bump 400 Bridge Electrode 420 Outer Frame Structure 422 Outer frame 440 Connection electrode

Claims

1. Quantum chips and An interposer provided opposite the quantum chip; having the quantum chip is mounted on the interposer; The quantum chip is provided with a coplanar line including a central conductor and a first ground electrode surrounding the central conductor; a second ground electrode is formed on the interposer in a region facing the first ground electrode; a connection electrode connected to the second ground electrode, at least a portion of the connection electrode facing a portion of the central conductor across a space; a bump connected to the first ground electrode and the second ground electrode is formed near the connection electrode; Quantum devices.

2. The quantum chip is provided with a resonator, the connection electrode is formed at a position of the interposer not facing the resonator; The quantum device of claim 1 .

3. The resonator has a conductive member of a predetermined shape, The central conductor is provided in the vicinity of the conductive member. The quantum device of claim 2.

4. a transmission path formed by the connection electrode, the second ground electrode, and the bump connects the first ground electrodes provided on both sides of the coplanar line at a distance from each other; The quantum device of claim 1 .

5. a gap in which the second ground electrode is not formed is present along a path of the coplanar line at a portion of the interposer facing the quantum chip and facing the central conductor of the coplanar line, the connection electrode includes a first bridge electrode formed so as to span a part of the gap, the bump formed in the vicinity of the first bridge electrode is connected to the first ground electrode and the second ground electrode; The quantum device of claim 4.

6. the central conductor has a discontinuous shape; The first bridge electrode is provided at a location in the gap that corresponds to the discontinuous shape. The quantum device of claim 5 .

7. The first bridge electrode is formed on the same plane as the second ground electrode around the gap.

7. The quantum device according to claim 5 or 6.

8. The quantum chip is provided with a resonator, The resonator has a SQUID (superconducting quantum interference device), the central conductor is provided in the vicinity of the SQUID, the interposer is provided with a magnetic field application circuit that applies a magnetic field to the SQUID; a gap is provided between a third ground electrode and the second ground electrode of the magnetic field application circuit at a position facing the central conductor in the vicinity of the SQUID, the interposer has a bridge-shaped second bridge electrode formed so as to span a part of the gap, the third ground electrode and the second ground electrode are partially connected by the second bridge electrode; 8. A quantum device according to any one of claims 1 to 7.

9. one end of the second bridge electrode is located near the bumps connected to the first ground electrode and the third ground electrode, and the other end of the second bridge electrode is located near the bumps connected to the first ground electrode and the second ground electrode. The quantum device of claim 8.

10. A plurality of the quantum devices according to any one of claims 1 to 9; At least one coupling circuit that couples a plurality of quantum bits formed by a plurality of the quantum devices and includes a coupler formed by the central conductor; A quantum computer having the above structure.

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