Superconducting Circuits

Abstract

To provide a superconducting circuit capable of reducing crosstalk.SOLUTION: A superconducting circuit (1) includes: a ground plane (30) that has a superconducting member; multiple superconducting parts (10) surrounded at intervals from the ground plane by non-conducting parts (40), the multiple superconducting parts each having four coupling ports that interact with the other superconducting parts; a superconducting quantum interference device (12) that sets the resonance frequency of the first superconducting part included in the multiple superconducting parts; and a three-dimensional wiring that forms a superconducting loop surrounding the superconducting quantum interference device with the ground plane. The superconducting quantum interference device is placed in a position where a magnetic field is applied by a current from the bias line (13G) to the first superconducting part in the region within the superconducting loop.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to superconducting circuits. [Background technology]

[0002] By applying a magnetic field to a superconducting quantum interference device (SQUID), the inductance of the SQUID can be changed, and therefore SQUIDs can also be used to change the resonant frequency of superconducting quantum bits (resonators).

[0003] When multiple SQUIDs exist in a circuit, applying a magnetic field to one SQUID can also generate a magnetic field in the other SQUIDs, which can change the resonant frequency of the quantum bit controlled by that SQUID. This phenomenon is called crosstalk. Crosstalk is a problem when controlling multiple SQUIDs independently.

[0004] Patent Document 1 describes reducing crosstalk by providing a ground pad that directs the return current away from the qubit coupler SQUID. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-041088 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technique described in Patent Document 1 may not be able to reduce crosstalk, for example.

[0007] In view of the above-mentioned problems, an object of the present disclosure is to provide a superconducting circuit capable of reducing crosstalk. [Means for solving the problem]

[0008] In a first aspect of the present disclosure, there is provided a superconducting circuit comprising: a ground surface having a superconducting member; a plurality of superconducting sections surrounded by non-conductive sections at intervals from the ground surface, each of the plurality of superconducting sections having four coupling ports for allowing interaction with other superconducting sections; a superconducting quantum interference element that sets the resonant frequency of a first superconducting section included in the plurality of superconducting sections; and three-dimensional wiring that forms a superconducting loop surrounding the superconducting quantum interference element with the ground surface, wherein the superconducting quantum interference element is positioned in a region within the superconducting loop at a position where a magnetic field is applied to the first superconducting section due to a current from a bias line. [Effects of the Invention]

[0009] According to one aspect, crosstalk can be reduced. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing an example of the configuration of each quantum bit etc. in a superconducting circuit 1 according to a first embodiment. [Figure 2] 2 is a diagram showing an example of the configuration around a quantum bit 10G in a superconducting circuit 1 according to the first embodiment. FIG. [Figure 3] 1A and 1B are diagrams illustrating the configuration of the first embodiment and the magnetic field around a SQUID 12G when a bias current flows. [Figure 4] 3A and 3B are diagrams illustrating the magnetic field around the SQUID 12G when a return current flows in the first embodiment. [Figure 5] 10A and 10B are diagrams illustrating the configuration of Modification 1 of the first embodiment and the magnetic field around the SQUID 12G when a bias current flows. [Figure 6] 10A and 10B are diagrams illustrating the magnetic field around the SQUID 12G when a return current flows in the first modification of the first embodiment. [Figure 7]10A and 10B are diagrams illustrating the configuration of Modification 2 of the first embodiment and the magnetic field around the SQUID 12G when a bias current flows. [Figure 8] 10A and 10B are diagrams illustrating the magnetic field around the SQUID 12G when a return current flows in the second modification of the first embodiment. [Figure 9] 10A and 10B are diagrams illustrating the configuration of a third modified example of the first embodiment and the magnetic field around a SQUID 12G when a bias current flows. [Figure 10] 10A and 10B are diagrams illustrating the magnetic field around the SQUID 12G when a return current flows in the third modification of the first embodiment. [Figure 11] 10A and 10B are diagrams illustrating the configuration of a fourth modified example of the first embodiment and the magnetic field around a SQUID 12G when a bias current flows. [Figure 12] 10A and 10B are diagrams illustrating the magnetic field around the SQUID 12G when a return current flows in the fourth modification of the first embodiment. [Figure 13] 10A and 10B are diagrams illustrating the configuration of a fifth modified example of the first embodiment and the magnetic field around a SQUID 12G when a bias current flows. [Figure 14] 13 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in the fifth modification of the first embodiment. FIG. [Figure 15] FIG. 10 is a diagram showing an example of the configuration around a quantum bit 10G in a superconducting circuit 1 according to a sixth modification of the first embodiment. [Figure 16] FIG. 11 is a diagram showing an example of the configuration around a quantum bit 10G in a superconducting circuit 1 according to a seventh modification of the first embodiment. [Figure 17] FIG. 13 is a diagram showing an example of the configuration around a quantum bit 10G in a superconducting circuit 1 according to an eighth modification of the first embodiment. [Figure 18] FIG. 10 is a diagram showing an example of the configuration around a quantum bit 10G in a superconducting circuit 1 according to a second embodiment. [Figure 19] 10A and 10B are diagrams illustrating the configuration of the second embodiment and the magnetic field around the SQUID 12G when a bias current flows. [Figure 20] 10A and 10B are diagrams illustrating the magnetic field around the SQUID 12G when a return current flows in the second embodiment. [Figure 21] 10A and 10B are diagrams illustrating the configuration of Modification 1 of the second embodiment and the magnetic field around the SQUID 12G when a bias current flows. [Figure 22] 10A and 10B are diagrams illustrating the magnetic field around the SQUID 12G when a return current flows in the first modification of the second embodiment. [Figure 23] 10A and 10B are diagrams illustrating the configuration of Modification 2 of the second embodiment and the magnetic field around the SQUID 12G when a bias current flows. [Figure 24] 10A and 10B are diagrams illustrating the magnetic field around the SQUID 12G when a return current flows in the second modification of the second embodiment. [Figure 25] FIG. 10 is a diagram showing an example of the configuration around a quantum bit 10G in a superconducting circuit 1 according to a third modification of the second embodiment. [Figure 26] FIG. 10 is a diagram showing an example of the configuration around a quantum bit 10G in a superconducting circuit 1 according to a third embodiment. [Figure 27] 10A and 10B are diagrams illustrating the configuration of the third embodiment and the magnetic field around the SQUID 12G when a bias current flows. [Figure 28] 11A and 11B are diagrams illustrating the magnetic field around the SQUID 12G when a return current flows in the third embodiment. [Figure 29] 10A and 10B are diagrams illustrating the configuration of Modification 1 of the third embodiment and the magnetic field around the SQUID 12G when a bias current flows. [Figure 30] 13A and 13B are diagrams illustrating the magnetic field around the SQUID 12G when a return current flows in the first modification of the third embodiment. [Figure 31] 10A and 10B are diagrams illustrating the configuration of Modification 2 of the third embodiment and the magnetic field around the SQUID 12G when a bias current flows. [Figure 32]13A and 13B are diagrams illustrating the magnetic field around the SQUID 12G when a return current flows in the second modification of the third embodiment. [Figure 33] 10A and 10B are diagrams illustrating the configuration of a third modified example of the third embodiment and the magnetic field around a SQUID 12G when a bias current flows. [Figure 34] 13A and 13B are diagrams illustrating the magnetic field around the SQUID 12G when a return current flows in the third modification of the third embodiment. [Figure 35] 10A and 10B are diagrams illustrating the configuration of a fourth modified example of the third embodiment and the magnetic field around a SQUID 12G when a bias current flows. [Figure 36] 13A and 13B are diagrams illustrating the magnetic field around the SQUID 12G when a return current flows in the fourth modification of the third embodiment. [Figure 37] 10A and 10B are diagrams illustrating the configuration of a fifth modified example of the third embodiment and the magnetic field around a SQUID 12G when a bias current flows. [Figure 38] 13A and 13B are diagrams illustrating the magnetic field around the SQUID 12G when a return current flows in the fifth modification of the third embodiment. [Figure 39] FIG. 10 is a diagram showing an example of the configuration around a quantum bit 10G in a superconducting circuit 1 according to a sixth modification of the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] The principles of the present disclosure will be described with reference to some exemplary embodiments. It should be understood that these embodiments are set forth for illustrative purposes only, to aid those skilled in the art in understanding and practicing the present disclosure, without implying any limitation on the scope of the disclosure. The disclosure described herein may be implemented in various ways other than those described below. In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0012] (First embodiment) <Configuration> An example of the configuration of a superconducting circuit 1 according to the first embodiment will be described with reference to Fig. 1 to Fig. 4. Fig. 1 is a diagram showing an example of the configuration of each quantum bit, etc. in the superconducting circuit 1 according to the first embodiment. Note that the superconducting circuit 1 of the present disclosure may be used, for example, in a quantum annealing machine, which is a computer that solves combinatorial optimization problems.

[0013] In the example of FIG. 1 , superconducting circuit 1 includes quantum bits 10A, 10B, 10C, 10D, 10E, 10F, 10G, 10H, 10I, 10J, 10K, 10L, 10M, 10N, 10O, 10P, 10Q, 10R, and 10S (hereinafter, simply referred to as "quantum bits 10" when there is no need to distinguish between them) realized by resonators or the like. Note that quantum bits 10 are an example of a "superconducting portion." Superconducting circuit 1 also includes couplers 20A, 20B, 20C, 20D, 20E, 20F, 20G, 20H, 20I, and 20J (hereinafter, simply referred to as "couplers 20" when there is no need to distinguish between them). Superconducting circuit 1 also includes ground plane 30 and non-conductive portion 40. The ground plane 30 may be formed, for example, by laminating a superconducting material on the substrate of the superconducting circuit 1. The non-conductive portion 40 is a region that does not conduct electricity. The non-conductive portion 40 may be formed, for example, by peeling (removing) the conductive material of the ground plane 30 from the substrate of the superconducting circuit 1.

[0014] Each quantum bit 10 has four coupling ports for interacting with four other adjacent quantum bits 10, and is capacitively coupled to coupler 20 via each coupling port. Each quantum bit 10 may be, for example, a superconducting member that is spaced from ground plane 30 by non-conductive portion 40 and surrounded by non-conductive portion 40. Of the superconducting members stacked on the substrate of superconducting circuit 1, the portion surrounded by non-conductive portion 40 may be formed as quantum bit 10, and the portion other than non-conductive portion 40 and quantum bit 10 may be formed as ground plane 30.

[0015] Fig. 2 is a diagram showing an example of the configuration around quantum bit 10G in superconducting circuit 1 according to the first embodiment. Fig. 2 shows an example of a region 201 around quantum bit 10G in Fig. 1. As shown in Fig. 2, for example, quantum bit 10G is connected to coupler 20A via coupled port 11G1, connected to coupler 20B via coupled port 11G2, connected to coupler 20E via coupled port 11G3, and connected to coupler 20F via coupled port 11G4.

[0016] In adiabatic quantum computing such as quantum annealing, when two-body interactions are realized among all qubits in a circuit, the adiabatic evolution of the system over time and the arrival at the lowest energy state corresponds to solving the Ising model. However, in practice, it is difficult to induce two-body interactions between qubits that are far apart. In an embodiment of the present disclosure, adjacent qubits 10 are coupled through interactions (e.g., four-body interactions) to realize an indirect fully coupled qubit representation. Therefore, each qubit 10 has four coupling ports. This method is also known as the LHZ (Lechner, Hauke, Zoller) method, etc.

[0017] Each of the quantum bits 10A-S is electrically connected to a SQUID 12A-S (hereinafter, simply referred to as "SQUID 12" when there is no need to distinguish between them). The SQUID (Superconducting Quantum Interference Device) may be, for example, a device in which two Josephson junctions are connected in a loop by a superconducting line. The quantum bit 10 may have, for example, a lumped-element resonator such as a Josephson Parametric Oscillator (JPO). In this case, the quantum bit 10 oscillates when microwaves having a frequency approximately twice the resonant frequency of the quantum bit 10 are applied to the SQUID 12 above a threshold. The JPO has two oscillation states with different phases, and these two states can be used as the 0 and 1 of the quantum bit. The SQUIDs 12A-S set the resonant frequency of the quantum bits 10A-S when a magnetic field is applied by a bias current supplied from a bias line.

[0018] The superconducting circuit 1 of the present disclosure has three-dimensional wiring including at least one of an air bridge and an interposer, which is provided at a position where a superconducting loop surrounding each SQUID 12 is formed with the ground plane 30. Note that an air bridge is, for example, a structure in which an electrical connection is made by forming an air bridge using a superconductor. Furthermore, in the superconducting circuit 1 of the present disclosure, each SQUID 12 is disposed in a position within the superconducting loop surrounding each SQUID 12 where a magnetic field due to a current from a bias line is applied.

[0019] 2, SQUID 12G is connected at a first end to quantum bit 10G and at a second end to ground plane 30. Furthermore, three-dimensional wiring 14G, which is an air bridge spanning quantum bit 10G, and ground plane 30 form superconducting loop 15G surrounding SQUID 12G. Furthermore, bias current from bias line 13G is conducted in two mutually opposite directions along one side of the superconducting loop.

[0020] (Example of arranging the bias line so that it extends perpendicular to the three-dimensional wiring) An example of a configuration in which a bias line is arranged to extend in a direction perpendicular to the three-dimensional wiring will be described with reference to Figures 3 and 4. Figure 3 is a diagram illustrating the configuration of the first embodiment and the magnetic field around the SQUID 12G when a bias current flows. Figure 4 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in the first embodiment. Figures 3 and 4 illustrate an example of a region 301 around the SQUID 12G in Figure 2.

[0021] In the example of FIG. 3 , bias current 13G1 from bias line 13G branches into branch current I1, which is conducted along one side 302 of superconducting loop 15G in a direction toward SQUID 12G, and branch current I2, which is conducted away from SQUID 12G. Furthermore, due to the shape of non-conductive portion 40, the portion of ground plane 30 in superconducting loop 15G through which branch current I1 flows is closer to SQUID 12G than the portion of ground plane 30 through which branch current I2 flows. Therefore, magnetic flux M1 caused by branch current I1 is generated relatively strongly in an upward direction at the point where it passes through SQUID 12G. Meanwhile, magnetic flux M2 caused by branch current I2 is generated relatively weakly in a downward direction at the point where it passes through SQUID 12G. Because the value of each branch current is determined by the value of the bias current, the magnetic flux inside SQUID 12G can be changed by changing the value of the bias current. Therefore, bias current 13G1 sets the resonant frequency of quantum bit 10G.

[0022] It should be noted that when using JPOs for multi-bit integration as the quantum bit 10, it is advantageous to use lumped-element JPOs with a small footprint. However, when lumped-element JPOs are arranged in a configuration similar to the LHZ method, the path of the return current of the bias current, which is a cause of crosstalk, becomes more complicated.

[0023] As shown in FIG. 4, when a return current Ir caused by a bias current to a SQUID 12 other than SQUID 12G (e.g., SQUID 12A) flows through the ground plane 30, a magnetic flux Mr caused by the return current Ir is generated within the superconducting loop 15G. Because the magnetic flux within the area surrounded by the superconducting loop is conserved, a shielding current Is is generated in a direction that causes a magnetic flux Ms in the opposite direction to the magnetic flux Mr. Furthermore, SQUID 12G is disposed at a position in the superconducting loop 15G where the value (strength) of the magnetic flux Mr and the value of the magnetic flux Ms are approximately equal. Therefore, the magnetic flux Mr is canceled out by the magnetic flux Ms, thereby reducing the change (fluctuation) of the magnetic flux within SQUID 12G caused by the return current Ir. As a result, crosstalk caused by the bias current for applying a magnetic field to SQUIDs 12 other than SQUID 12G can be appropriately reduced.

[0024] To suppress crosstalk, it is conceivable to form multiple low-impedance return lines for the magnetic field bias current by providing multiple air bridges or the like between the ground planes 30 separated by the coplanar waveguides and the quantum bits 10 (resonators). However, if the number of air bridges or the like is large, it is conceivable that a problem of a decrease in the Q value of the quantum bits 10 may occur due to dielectric loss in the dielectric, such as the resist, remaining after the air bridges are formed. Furthermore, if the fabrication yield of the air bridges or the like is low, it is conceivable that a problem of an increased possibility of shorting out the quantum bits 10 may occur. In the examples of Figures 3 and 4, crosstalk can be adequately reduced by a single air bridge.

[0025] Below, each modification of the first embodiment will be described. Note that the embodiments and modifications described below can be used in appropriate combination. In this case, for example, quantum bit 10A may have the configuration of the first embodiment, and quantum bits 10B-I may have the configuration of modifications 1-8 of the first embodiment, respectively. Furthermore, quantum bit 10J may have the configuration of the second embodiment, and quantum bits 10K-M may have the configuration of modifications 1-3 of the second embodiment, respectively. Furthermore, quantum bit 10N may have the configuration of the third embodiment, and quantum bits 10O-T (quantum bit 10T is not shown) may have the configuration of modifications 1-6 of the third embodiment, respectively.

[0026] (Modification 1 of the First Embodiment: Example of Arranging Bias Lines to Extend in a Direction Parallel to the Three-Dimensional Wiring) An example of a configuration in which the bias lines are arranged to extend in a direction perpendicular to the three-dimensional wiring has been described in Figures 3 and 4. Below, with reference to Figures 5 and 6, an example in which the bias lines are arranged to extend in a direction parallel to the three-dimensional wiring will be described.

[0027] Fig. 5 is a diagram illustrating the configuration of Modification 1 of the first embodiment and the magnetic field around the SQUID 12G when a bias current flows. Fig. 6 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in Modification 1 of the first embodiment.

[0028] In the example of Fig. 5, similarly to the example of Fig. 3, bias current 13G1 from bias line 13G is branched into branch current I1 that is conducted in a direction along one side of superconducting loop 15G toward SQUID 12G, and branch current I2 that is conducted in a direction away from SQUID 12G. Also, based on the same principle (explanation) as in the examples of Fig. 3 and Fig. 4, even if the bias line is arranged to extend in a direction parallel to three-dimensional wiring 14G as shown in Fig. 5 and Fig. 6, the same effect as in the examples of Fig. 3 and Fig. 4 can be obtained.

[0029] (Modification 2 of the First Embodiment: Example of Using Multiple Three-Dimensional Wirings Without Branching the Bias Current) 2 to 6, an example of a configuration has been described in which a superconducting loop 15G surrounding a SQUID 12G is formed by three-dimensional wiring 14G, which is one air bridge, and a ground plane 30, and the bias current is branched. Below, with reference to Figs. 7 and 8, an example of a configuration will be described in which a superconducting loop 15G surrounding a SQUID 12G is formed by three-dimensional wiring 14G1 and three-dimensional wiring 14G2, which are two air bridges, and a ground plane 30, and the bias current is not branched.

[0030] Fig. 7 is a diagram illustrating the configuration of Modification 2 of the first embodiment and the magnetic field around the SQUID 12G when a bias current flows. Fig. 8 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in Modification 2 of the first embodiment.

[0031] 7 and 8 show examples in which the bias line is arranged to extend perpendicular to the three-dimensional wiring. In the examples of Figures 7 and 8, it is necessary to provide three-dimensional wiring 14G2, which is an air bridge, compared to the examples of Figures 2 to 6. However, because the bias current is not branched, the magnetic flux in SQUID 12G can be changed with a smaller bias current value. Furthermore, because three-dimensional wiring 14G2 is provided on bias line 13G rather than on quantum bit 10G, the effect on the Q value of quantum bit 10G is relatively small.

[0032] In the example of Figure 7, bias current 13G1 from L-shaped bias line 13G is conducted in only one direction within superconducting loop 15G, along one side of superconducting loop 15G. Therefore, bias current 13G1 generates two opposing magnetic fluxes M1 and M2 within superconducting loop 15G. Only one of these magnetic fluxes, M1, is applied to SQUID 12G. Therefore, the magnetic flux within SQUID 12G can be changed by changing the value of bias current 13G1. Therefore, the resonant frequency of quantum bit 10G is set by bias current 13G1.

[0033] 8, similar to the examples of FIGS. 4 and 6, when a return current Ir caused by a bias current to a SQUID 12 other than SQUID 12G (e.g., SQUID 12A) flows through the ground plane 30, a magnetic flux Mr caused by the return current Ir is generated within the superconducting loop 15G. Because the magnetic flux within the area surrounded by the superconducting loop is conserved, a shielding current Is is generated in a direction that causes a magnetic flux Ms in the opposite direction to the magnetic flux Mr. Furthermore, the SQUID 12G is disposed at a position in the superconducting loop 15G where the value (strength) of the magnetic flux Mr and the value of the magnetic flux Ms are approximately equal. Therefore, the magnetic flux Mr is canceled out by the magnetic flux Ms, thereby reducing the change in the magnetic flux within the SQUID 12G caused by the return current Ir. Therefore, crosstalk caused by the bias current for applying a magnetic field to SQUIDs 12 other than SQUID 12G can be appropriately reduced.

[0034] (Modification 3 of the First Embodiment: Example of Using Multiple Three-Dimensional Wirings Without Branching the Bias Current) 9 and 10, an example of a configuration will be described below in which a superconducting loop 15G surrounding a SQUID 12G is formed by three-dimensional wiring 14G1 and three-dimensional wiring 14G2, which are two air bridges, and a ground plane 30, as in the case of Figures 7 and 8. While Figures 7 and 8 describe an example in which a bias line is arranged to extend in a direction perpendicular to the three-dimensional wiring, Figures 9 and 10 describe an example in which a bias line is arranged to extend in a direction parallel to three-dimensional wiring 14G1 that straddles a quantum bit 10G.

[0035] 9 is a diagram illustrating the configuration of Modification 3 of the first embodiment and the magnetic field around the SQUID 12G when a bias current flows. FIG. 10 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in Modification 3 of the first embodiment. In the example of FIG. 9, as in the example of FIG. 7, bias current 13G1 from L-shaped bias line 13G is conducted in only one direction along one side of superconducting loop 15G within superconducting loop 15G. Furthermore, based on the same principle (explanation) as in the examples of FIGS. 7 and 8, even if the bias current 13G1 is installed in a direction parallel to three-dimensional wiring 14G1, which is an air bridge spanning quantum bit 10G as shown in FIGS. 9 and 10, the same effect as in the examples of FIGS. 7 and 8 can be obtained.

[0036] (Fourth Modification of the First Embodiment: Example of Using an Interposer as Three-Dimensional Wiring) 2 to 10 have been described as examples of using an air bridge as three-dimensional wiring. Below, an example of using an interposer as three-dimensional wiring will be described with reference to FIGS. 11 and 12. FIGS. 11 and 12 show an example in which bias lines are arranged to extend in a direction perpendicular to the three-dimensional wiring. Note that the interposer may be, for example, a substrate that provides electrical continuity between the front and back of a circuit using through electrodes.

[0037] FIG. 11 is a diagram illustrating the configuration of Modification 4 of the first embodiment and the magnetic field around the SQUID 12G when a bias current flows. FIG. 12 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in Modification 4 of the first embodiment. In the example of FIG. 11, similar to the examples of FIGS. 7 and 9, the bias current 13G1 from the L-shaped bias line 13G is conducted in only one direction along one side of the superconducting loop 15G within the superconducting loop 15G. In addition, in the example of FIG. 11, the bias current 13G1 is supplied to the L-shaped bias line 13G from a bonding surface (through electrode) 17A of the interposer. In addition, bonding surfaces 17B and 17C with the interposer are provided near the SQUID 12G. Therefore, a superconducting loop 15G surrounding the SQUID 12G is formed by the ground plane 30 and three-dimensional wiring 14G1 in the interposer that electrically connects between the bonding surfaces 17B and 17C. At the bonding surfaces 17B and 17C, for example, the ground plane 30 of the superconducting circuit 1 is connected to the surface of the interposer facing the superconducting circuit 1 by a bump or the like. Therefore, the ground planes 30 on both sides of the quantum bit 10G are electrically connected via a connection portion (superconducting member) in the surface of the interposer facing the superconducting circuit 1. The same principle (explanation) as in the examples of FIGS. 7 and 8 can be used with the configurations shown in FIGS. 11 and 12 to achieve the same effects as in the examples of FIGS. 7 and 8.

[0038] (Fifth Modification of the First Embodiment: Example of Using an Interposer as Three-Dimensional Wiring) 11 and 12 illustrate an example in which the bias line is arranged to extend in a direction perpendicular to the three-dimensional wiring. In FIGS. 13 and 14, an example in which the bias line is arranged to extend in a direction parallel to the three-dimensional wiring 14G1 that spans the quantum bit 10G is illustrated.

[0039] FIG. 13 is a diagram illustrating the configuration of Modification 5 of the first embodiment and the magnetic field around the SQUID 12G when a bias current flows. FIG. 14 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in Modification 5 of the first embodiment. In the example of FIG. 13, similar to the example of FIG. 11, a bias current 13G1 is supplied to the L-shaped bias line 13G from the bonding surface 17A of the interposer. In addition, bonding surfaces 17B and 17C with the interposer are provided near the SQUID 12G. Therefore, a superconducting loop 15G surrounding the SQUID 12G is formed by the three-dimensional wiring 14G1 in the interposer that electrically connects bonding surfaces 17B and 17C and the ground surface 30.

[0040] 13, similarly to the examples of Fig. 7, Fig. 9, and Fig. 11, bias current 13G1 from L-shaped bias line 13G is conducted in only one direction along one side of superconducting loop 15G within superconducting loop 15G. Further, based on the same principle (explanation) as in the examples of Fig. 7 and Fig. 8, the configurations shown in Fig. 13 and Fig. 14 can also obtain the same effect as in the examples of Fig. 7 and Fig. 8.

[0041] (Sixth Modification of the First Embodiment: Example Using O-Shaped Quantum Bit 10) 1 and 2, an example using a cross-shaped quantum bit 10 has been described. Below, with reference to FIG. 15, an example using an O-shaped quantum bit 10 will be described. FIG. 15 is a diagram showing an example of the configuration around quantum bit 10G in a superconducting circuit 1 according to Modification 6 of the first embodiment. The quantum bit 10 is not limited to the cross shape shown in FIGS. 1 and 2, and an O-shaped quantum bit may also be used. In this case, the inside of region 201 in FIG. 1 may be configured as region 201A in FIG. 15. In the example of FIG. 15, four coupling ports 11G1, 11G2, 11G3, and 11G4 are provided around the outer periphery of the O-shaped structure. In the example of FIG. 15, the inside of region 301 may also have any of the configurations shown in FIGS. 3 and 4, 5 and 6, 7 and 8, 9 and 10, 11 and 12, and 13 and 14.

[0042] (Seventh Modification of the First Embodiment: Example Using Four Three-Dimensional Wirings) FIG. 16 is a diagram showing an example of the configuration around a quantum bit 10G in a superconducting circuit 1 according to Modification 7 of the first embodiment. Instead of the configuration in region 201 of FIG. 2, a superconducting loop 15G surrounding a SQUID 12G may be formed using four three-dimensional wirings 161, 162, 163, and 164 as shown in region 201B of FIG. 16. In the example of FIG. 16, the inside of region 301 may also have any of the configurations shown in FIGS. 3 and 4, 5 and 6, 7 and 8, 9 and 10, 11 and 12, and 13 and 14. This allows for the same effect to be obtained by the same principle (explanation) as in any of FIGS. 3 and 4, 5 and 6, 7 and 8, 9 and 10, 11 and 12, and 13 and 14.

[0043] (Variation 8 of the First Embodiment: Example of Using Three 3D Wirings) FIG. 17 is a diagram showing an example of the configuration around a quantum bit 10G in a superconducting circuit 1 according to Modification 8 of the first embodiment. Instead of the configuration in region 201 of FIG. 2, a superconducting loop 15G surrounding a SQUID 12G may be formed using three three-dimensional wirings 171, 172, and 173 as shown in region 201C of FIG. 17. In the example of FIG. 17, the inside of region 301 may have any of the configurations shown in FIGS. 3 and 4, 5 and 6, 7 and 8, 9 and 10, 11 and 12, and 13 and 14. This allows for the same effect to be obtained by the same principle (explanation) as in any of FIGS. 3 and 4, 5 and 6, 7 and 8, 9 and 10, 11 and 12, and 13 and 14.

[0044] (Second embodiment: an example using a quantum bit 10 in which two L-shaped structures each having two coupling parts are connected by a SQUID 12) In the first embodiment, an example of a configuration was described in which a SQUID 12 is connected to a cross-shaped or O-shaped quantum bit 10 as shown in Figures 2 and 15. In the second embodiment, an example will be described in which a quantum bit 10 is used in which two L-shaped parts (a "first part" and a "second part") each having two coupling parts are connected by a SQUID 12 as shown in Figure 18.

[0045] 18 is a diagram showing an example of the configuration around the quantum bit 10G in the superconducting circuit 1 according to the second embodiment. In the superconducting circuit 1 according to the second embodiment, the region 201 in FIG. 1 is replaced with the region 201D in FIG. 18. In the second embodiment, for example, the SQUID 12 is not grounded (electrically connected to the ground plane 30). This reduces the risk of electrostatic breakdown of the Josephson junction (Josephson element) included in the SQUID 12.

[0046] Fig. 19 is a diagram illustrating the configuration of the second embodiment and the magnetic field around the SQUID 12G when a bias current flows. Fig. 20 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in the second embodiment. Figs. 19 and 20 show an example of a region 401 around the SQUID 12G in Fig. 18.

[0047] In the example of FIG. 19, quantum bit 10G has two parts, each of which has an L-shaped structure. Furthermore, SQUID 12G is electrically connected at one end to the first part of quantum bit 10G and at the other end to the second part of quantum bit 10G. Furthermore, the example of FIG. 19 also includes three-dimensional wiring 14G1 and three-dimensional wiring 14G2 that form superconducting loop 15G with ground plane 30. Furthermore, in the example of FIG. 19, similar to the example of FIG. 3, bias current 13G1 from bias line 13G is branched into branch current I1 that is conducted along one side of the superconducting loop toward SQUID 12G and branch current I2 that is conducted away from SQUID 12G. Branch current I1 and branch current I2 generate magnetic fluxes in opposite directions within superconducting loop 15G, so that the magnetic flux within superconducting loop 15G is maintained. Furthermore, the portion of ground plane 30 in superconducting loop 15G through which branch current I1 flows is closer to SQUID 12G than the portion of ground plane 30 through which branch current I2 flows in superconducting loop 15G. Because the value of each branch current is determined by the value of the bias current, the magnetic flux inside SQUID 12G can be changed by changing the value of the bias current. Therefore, the resonant frequency of quantum bit 10G is set by bias current 13G1.

[0048] 20, similar to the example of FIG. 4, when a return current Ir caused by a bias current to a SQUID 12 other than SQUID 12G (e.g., SQUID 12A) flows through the ground plane 30, a magnetic flux Mr caused by the return current Ir is generated within the superconducting loop 15G. Because the magnetic flux within the area surrounded by the superconducting loop is conserved, a shielding current Is is generated in a direction that causes a magnetic flux Ms in the opposite direction to the magnetic flux Mr. Furthermore, the SQUID 12G is disposed at a position in the superconducting loop 15G where the value (strength) of the magnetic flux Mr and the value of the magnetic flux Ms are approximately equal. Therefore, the magnetic flux Mr is canceled out by the magnetic flux Ms, and the change in the magnetic flux inside the SQUID 12G caused by the return current Ir can be reduced. Therefore, crosstalk caused by the bias current for applying a magnetic field to SQUIDs 12 other than SQUID 12G can be appropriately reduced.

[0049] (Modification 1 of the Second Embodiment: Example of a Configuration in Which Bias Current is Not Branched) 19 and 20 have described an example of a configuration in which the bias current is branched in the second embodiment. Below, with reference to Fig. 21 and Fig. 22, an example of a configuration in which the bias current is not branched in the second embodiment will be described.

[0050] Fig. 21 is a diagram illustrating the configuration of Modification 1 of the second embodiment and the magnetic field around the SQUID 12G when a bias current flows. Fig. 22 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in Modification 1 of the second embodiment. In the example of Fig. 21, three-dimensional wiring 14G3, which is an air bridge, is provided on the bias line 13G, and three-dimensional wirings 14G1, 14G2, and 14G3 and a ground plane 30 form a superconducting loop 15G surrounding the SQUID 12G.

[0051] 21 and 22, it is necessary to provide three-dimensional wiring 14G3, which is an air bridge, compared to the examples of Figures 19 and 20. However, because the bias current is not branched, the magnetic flux in SQUID 12G can be changed with a smaller bias current value. Also, because three-dimensional wiring 14G3 is provided on bias line 13G rather than on quantum bit 10G, the effect on the Q value of quantum bit 10G is relatively small.

[0052] In the example of FIG. 21, SQUID 12G is electrically connected at one end to a first portion of quantum bit 10G and at the other end to a second portion of quantum bit 10G. Also, in the example of FIG. 21, three-dimensional wiring 14G1 and three-dimensional wiring 14G2 are provided, which form superconducting loop 15G with ground plane 30. Also, in the example of FIG. 21, similar to the example of FIG. 7, bias current 13G1 from L-shaped bias line 13G is conducted within superconducting loop 15G in only one direction, along one side of superconducting loop 15G. Therefore, by changing the value of bias current 13G1, magnetic flux M1 inside SQUID 12G can be changed. Therefore, the resonant frequency of quantum bit 10G is set by bias current 13G1.

[0053] 22, similar to the example of FIG. 4, when a return current Ir caused by a bias current to a SQUID 12 other than SQUID 12G (e.g., SQUID 12A) flows through the ground plane 30, a magnetic flux Mr caused by the return current Ir is generated within the superconducting loop 15G. Because the magnetic flux within the area surrounded by the superconducting loop is conserved, a shielding current Is is generated in a direction that causes a magnetic flux Ms in the opposite direction to the magnetic flux Mr. Furthermore, the SQUID 12G is disposed at a position in the superconducting loop 15G where the value (strength) of the magnetic flux Mr and the value of the magnetic flux Ms are approximately equal. Therefore, the magnetic flux Mr is canceled out by the magnetic flux Ms, and the change in the magnetic flux inside the SQUID 12G caused by the return current Ir can be reduced. Therefore, crosstalk caused by the bias current for applying a magnetic field to SQUIDs 12 other than SQUID 12G can be appropriately reduced.

[0054] (Modification 2 of the Second Embodiment: Example of Using an Interposer as Three-Dimensional Wiring) 19 to 22 have described an example in which an air bridge is used as three-dimensional wiring in the second embodiment. Below, with reference to FIGS. 23 and 24, an example in which an interposer is used as three-dimensional wiring in the second embodiment will be described.

[0055] FIG. 23 is a diagram illustrating the configuration of Modification 2 of the second embodiment and the magnetic field around the SQUID 12G when a bias current flows. FIG. 24 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in Modification 2 of the second embodiment. In the example of FIG. 23, as in the example of FIG. 21, the SQUID 12G is electrically connected to the quantum bit 10G at both ends. The example of FIG. 23 also includes three-dimensional wiring 14G1 and three-dimensional wiring 14G2 that form the superconducting loop 15G with the ground plane 30. The bias current 13G1 from the L-shaped bias line 13G is conducted within the superconducting loop 15G in only one direction, along one side of the superconducting loop 15G. In the example of FIG. 23, the bias current 13G1 is supplied to the L-shaped bias line 13G from the bonding surface 17A of the interposer. Furthermore, bonding surfaces 17B, 17C, 17D, and 17E with the interposer are provided near the SQUID 12G. Therefore, a superconducting loop 15G surrounding the SQUID 12G is formed by three-dimensional wiring 14G1, which is an interposer that electrically connects bonding surface 17B and bonding surface 17C, three-dimensional wiring 14G2 within the interposer that electrically connects bonding surface 17D and bonding surface 17E, and ground surface 30.

[0056] At bonding surfaces 17B and 17C, for example, the ground surface 30 of the superconducting circuit 1 and the surface of the interposer facing the superconducting circuit 1 are connected by bumps or the like. Therefore, the ground surfaces 30 on both sides of the quantum bit 10G are electrically connected via a connection portion (superconducting member) in the surface of the interposer facing the superconducting circuit 1. Similarly, at bonding surfaces 17D and 17E, for example, the ground surface 30 of the superconducting circuit 1 and the surface of the interposer facing the superconducting circuit 1 are connected by bumps or the like. Using the same principle (explanation) as in the examples of FIGS. 21 and 22, etc., the configurations shown in FIGS. 23 and 24 can also achieve the same effects as in the examples of FIGS. 21 and 22, etc.

[0057] (Modification 3 of the Second Embodiment: Example using a quantum bit 10 in which two O-shaped portions are connected by a SQUID 12) 19 to 24 have been described with reference to an example using a quantum bit 10 in which two L-shaped portions are connected by a SQUID 12. Hereinafter, with reference to FIG. 25, an example using a quantum bit 10 in which two O-shaped portions are connected by a SQUID 12 will be described. FIG. 25 is a diagram showing an example of the configuration around quantum bit 10G in a superconducting circuit 1 according to Modification 3 of the second embodiment. The inside of region 201 in FIG. 1 may be configured as region 201E in FIG. 25. In the example of FIG. 25, four coupling ports 11G1, 11G2, 11G3, and 11G4 are provided around the periphery of the O-shaped structure. In the example of FIG. 25, the inside of region 401 may also have the configuration shown in any of FIGS. 19 and 20, 21 and 22, and 23 and 24.

[0058] (Third embodiment: an example using a quantum bit 10 in which a SQUID 12 with one end grounded is connected between two L-shaped structures) In the second embodiment, an example was described in which a quantum bit 10 is connected by a SQUID 12 that is not electrically connected to the ground surface 30. In the third embodiment, an example is described in which a quantum bit 10 is connected between two L-shaped structures and a SQUID 12, one end of which is electrically connected to the ground surface 30, is connected as shown in Fig. 26 .

[0059] Fig. 26 is a diagram showing an example of the configuration around the quantum bit 10G in the superconducting circuit 1 according to the second embodiment. In the superconducting circuit 1 according to the third embodiment, the region 201 in Fig. 1 is replaced with the region 201F in Fig. 26. In the third embodiment, one end of the SQUID 12 is electrically connected to the ground plane 30, so the equivalent circuit is the same as in the first embodiment, but the left-right symmetry can be improved compared to the first embodiment.

[0060] FIG. 27 is a diagram illustrating the configuration of the third embodiment and the magnetic field around the SQUID 12G when a bias current flows. FIG. 28 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in the third embodiment. FIGS. 27 and 28 illustrate an example of a region 501 around the SQUID 12G in FIG. 26. In the example of FIG. 27, the SQUID 12G is electrically connected to the quantum bit 10G at one end and electrically connected to the ground plane 30 at the other end. Furthermore, in the example of FIG. 27, three-dimensional wirings 14G1 and 14G2 are provided as air bridges that each span the quantum bit 10G, and the three-dimensional wirings 14G1 and 14G2 and the ground plane 30 form a superconducting loop 15G that surrounds the SQUID 12G.

[0061] In the example of Figure 27, similar to the example of Figure 3, bias current 13G1 from bias line 13G branches into branch current I1, which is conducted along one side of the superconducting loop toward SQUID 12G, and branch current I2, which is conducted away from SQUID 12G. Branch currents I1 and I2 generate magnetic fluxes in opposite directions within superconducting loop 15G, maintaining the magnetic flux within superconducting loop 15G. Furthermore, the portion of ground plane 30 through which branch current I1 flows in superconducting loop 15G is closer to SQUID 12G than the portion of ground plane 30 through which branch current I2 flows in superconducting loop 15G. Because the values ​​of each branch current are determined by the value of the bias current, the magnetic flux within SQUID 12G can be changed by changing the value of the bias current. Therefore, the resonant frequency of quantum bit 10G is set by bias current 13G1.

[0062] 28, similar to the example of FIG. 4, when a return current Ir caused by a bias current to a SQUID 12 other than SQUID 12G (e.g., SQUID 12A) flows through the ground plane 30, a magnetic flux Mr caused by the return current Ir is generated within the superconducting loop 15G. Because the magnetic flux within the area surrounded by the superconducting loop is conserved, a shielding current Is is generated in a direction that causes a magnetic flux Ms in the opposite direction to the magnetic flux Mr. Furthermore, the SQUID 12G is disposed at a position in the superconducting loop 15G where the value (strength) of the magnetic flux Mr and the value of the magnetic flux Ms are approximately equal. Therefore, the magnetic flux Mr is canceled out by the magnetic flux Ms, thereby reducing the change in the magnetic flux within the SQUID 12G caused by the return current Ir. Therefore, crosstalk caused by the bias current for applying a magnetic field to SQUIDs 12 other than SQUID 12G can be appropriately reduced.

[0063] (Modification 1 of the Third Embodiment: Example of Arranging Bias Lines to Extend in a Direction Perpendicular to the Three-Dimensional Wiring) 27 and 28 have described an example of a configuration in which bias lines are arranged to extend in a direction parallel to the three-dimensional wiring. Below, with reference to Fig. 29 and Fig. 30, an example in which bias lines are arranged to extend in a direction perpendicular to the three-dimensional wiring will be described.

[0064] FIG. 29 is a diagram illustrating the configuration of Modification 1 of the third embodiment and the magnetic field around the SQUID 12G when a bias current flows. FIG. 30 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in Modification 1 of the third embodiment. In the example of FIG. 29, similar to the example of FIG. 27, the SQUID 12G is electrically connected at one end to the quantum bit 10G and at the other end to the ground plane 30. Also, in the example of FIG. 29, similar to the example of FIG. 27, the bias current 13G1 from the bias line 13G is branched into a branch current I1 that is conducted in a direction along one side of the superconducting loop 15G toward the SQUID 12G and a branch current I2 that is conducted away from the SQUID 12G. Furthermore, based on the same principle (explanation) as the examples of FIGS. 27 and 28, even if the bias line is arranged to extend in a direction perpendicular to the three-dimensional wiring 14G as shown in FIGS. 29 and 30, the same effect as the examples of FIGS. 27 and 28 can be obtained.

[0065] (Modification 2 of the Third Embodiment: Example of Using Three 3D Wirings Without Branching the Bias Current) 27 to 30 have described examples of a configuration in which a superconducting loop 15G surrounding a SQUID 12G is formed by three-dimensional wiring 14G1 and 14G2 and a ground plane 30, and the bias current is branched. Below, with reference to Figs. 31 and 32, an example of a configuration in which a superconducting loop 15G surrounding a SQUID 12G is formed by three-dimensional wiring 14G1, 14G2, and 14G3 and a ground plane 30, and the bias current is not branched will be described.

[0066] FIG. 31 is a diagram illustrating the configuration of Modification 2 of the third embodiment and the magnetic field around the SQUID 12G when a bias current flows. FIG. 32 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in Modification 2 of the third embodiment. FIGS. 31 and 32 show an example in which bias lines are arranged to extend in a direction parallel to three-dimensional wiring 14G1 and 14G2, which are air bridges that each span the quantum bit 10G. In the example of FIG. 31, similar to the example of FIG. 27, the SQUID 12G is electrically connected at one end to the quantum bit 10G and at the other end to the ground plane 30. In addition, in the example of FIG. 31, the bias current 13G1 from the L-shaped bias line 13G is conducted within the superconducting loop 15G in only one direction, along one side of the superconducting loop 15G. Furthermore, the same effect can be obtained in the third embodiment based on the same principle (explanation) as in the examples of FIGS. 7 and 8.

[0067] (Modification 3 of the third embodiment: Example of using multiple three-dimensional wirings without branching the bias current) In Figures 31 and 32, an example is described in which the bias line is arranged to extend in a direction parallel to the three-dimensional wiring 14G1 and 14G2, but in Figures 33 and 34, an example is described in which the bias line is arranged to extend in a direction perpendicular to the three-dimensional wiring 14G1 and 14G2.

[0068] FIG. 33 is a diagram illustrating the configuration of Modification 3 of the third embodiment and the magnetic field around the SQUID 12G when a bias current flows. FIG. 34 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in Modification 3 of the third embodiment. In the example of FIG. 33, similar to the example of FIG. 31, the SQUID 12G is electrically connected to the quantum bit 10G at one end and electrically connected to the ground plane 30 at the other end. Also, in the example of FIG. 33, similar to the example of FIG. 31, the bias current 13G1 from the L-shaped bias line 13G is conducted within the superconducting loop 15G in only one direction along one side of the superconducting loop 15G. The same effect can be obtained by the same principle (explanation) as in the examples of FIGS. 31 and 32.

[0069] (Fourth Modification of the Third Embodiment: Example of Using an Interposer as Three-Dimensional Wiring) 27 to 34 have described examples in which an air bridge is used as three-dimensional wiring. Below, an example in which an interposer is used as three-dimensional wiring will be described with reference to Figures 35 and 36. Figures 35 and 36 show examples in which bias lines are arranged to extend in a direction parallel to the three-dimensional wiring.

[0070] FIG. 35 illustrates the configuration of Modification 4 of the third embodiment and the magnetic field around the SQUID 12G when a bias current flows. FIG. 36 illustrates the magnetic field around the SQUID 12G when a return current flows in Modification 4 of the third embodiment. In the example of FIG. 33, similar to the example of FIG. 31, the SQUID 12G is electrically connected to the quantum bit 10G at one end and to the ground plane 30 at the other end. Also, in the example of FIG. 35, similar to the example of FIG. 31, the bias current 13G1 from the L-shaped bias line 13G is conducted in only one direction along one side of the superconducting loop 15G within the superconducting loop 15G. Also, in the example of FIG. 35, the bias current 13G1 is supplied to the L-shaped bias line 13G from the bonding surface 17A of the interposer. Also, bonding surfaces 17B, 17C, 17D, and 17E with the interposer are provided near the SQUID 12G. Therefore, a superconducting loop 15G surrounding the SQUID 12G is formed by three-dimensional wiring 14G1 in the interposer that electrically connects bonding surface 17B and bonding surface 17C, three-dimensional wiring 14G2 in the interposer that electrically connects bonding surface 17D and bonding surface 17E, and ground surface 30. Then, the same effect can be obtained by the same principle (explanation) as in the examples of Figures 31 and 32.

[0071] (Modification 5 of the Third Embodiment: Example (Part 2) of Using an Interposer as Three-Dimensional Wiring) 35 and 36 show an example in which the bias lines are arranged so as to extend in a direction parallel to the three-dimensional wiring. In Fig. 37 and 38, an example in which the bias lines are arranged so as to extend in a direction perpendicular to the three-dimensional wiring will be described.

[0072] FIG. 37 is a diagram illustrating the configuration of Modification 5 of the third embodiment and the magnetic field around the SQUID 12G when a bias current flows. FIG. 38 is a diagram illustrating the magnetic field around the SQUID 12G when a return current flows in Modification 5 of the third embodiment. In the example of FIG. 37, similar to the example of FIG. 35, the SQUID 12G is electrically connected to the quantum bit 10G at one end and electrically connected to the ground plane 30 at the other end. Also, in the example of FIG. 37, similar to the example of FIG. 35, a bias current 13G1 is supplied to the L-shaped bias line 13G from the bonding surface 17A of the interposer. Also, bonding surfaces 17B, 17C, 17D, and 17E with the interposer are provided near the SQUID 12G. Therefore, a superconducting loop 15G surrounding the SQUID 12G is formed by three-dimensional wiring 14G1 in the interposer that electrically connects bonding surface 17B and bonding surface 17C, three-dimensional wiring 14G2 in the interposer that electrically connects bonding surface 17D and bonding surface 17E, and ground surface 30. Then, the same effect can be obtained by the same principle (explanation) as in the examples of Figures 31 and 32.

[0073] (Variation 6 of the Third Embodiment: Example of Using a SQUID 12 with One End Grounded and a Quantum Bit 10 with Two O-Shaped Portions Connected) 26 to 38 have been described as examples in which a quantum bit 10 having two L-shaped portions connected to a SQUID 12 with one end grounded is used. Below, with reference to Fig. 39, an example in which a quantum bit 10 having two O-shaped portions connected to a SQUID 12 with one end grounded is used will be described.

[0074] FIG. 39 is a diagram showing an example of the configuration around quantum bit 10G in superconducting circuit 1 according to Modification 6 of the third embodiment. The inside of region 201 in FIG. 1 may be configured as region 201F in FIG. 39. In the example of FIG. 39, four coupling ports 11G1, 11G2, 11G3, and 11G4 are provided on the outer periphery of the O-shaped structure. In the example of FIG. 39, the inside of region 401 may also have any of the configurations shown in FIGS. 27 and 28, 29 and 30, 31 and 32, 33 and 34, 35 and 36, and 37 and 38.

[0075] <Effects of this disclosure> According to the present disclosure, there is provided a superconducting circuit 1 having a quantum bit 10 having four coupling ports that allow interaction with four other adjacent quantum bits, a SQUID 12 connected to quantum bit 10 and that sets the resonant frequency of quantum bit 10 using a current from a bias line, and three-dimensional wiring such as an air bridge provided at a position that forms a superconducting loop surrounding SQUID 12 with ground plane 30. As a result, crosstalk can be appropriately reduced.

[0076] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the invention. [Explanation of symbols]

[0077] 1 Superconducting circuits 10 qubits 10A~S qubits 11G1 Bonded Port 11G2 Bonded Port 11G3 Bonded Port 11G4 Bonded Port 12G SQUID 13G bias line 13G1 bias current 14G three-dimensional wiring 14G1 3D wiring 14G2 3D wiring 14G3 3D wiring 15G superconducting loop 17A Joint surface 17A joint surface 17B joint surface 17C joint surface 17D joint surface 17E joint surface 20 Coupler 20A~J Couplers 30 Ground surface 40 Non-conductive part 161 Three-dimensional wiring 162 Three-dimensional wiring 163 Three-dimensional wiring 164 Three-dimensional wiring 171 Three-dimensional wiring 172 Three-dimensional wiring 173 Three-dimensional wiring M1, M2, Mr, Ms Magnetic fluxes [[ID=三十五]]Ir Return current Is Shielding current I1, I2 Branch currents

Claims

1. a ground plane having a superconducting material; a plurality of superconducting sections surrounded by a non-conductive section at intervals from the ground plane, each of the plurality of superconducting sections having four coupling ports for allowing interaction with other superconducting sections; and a superconducting quantum interference device that sets a resonance frequency of a first superconducting section included in the plurality of superconducting sections; and three-dimensional wiring that forms, together with the ground plane, a superconducting loop surrounding the superconducting quantum interference device, the superconducting quantum interference device is disposed in a region within the superconducting loop at a position where a magnetic field caused by a current from a bias line to the first superconducting portion is applied; Superconducting circuits.

2. the three-dimensional wiring includes at least one of an air bridge and an interposer; 10. The superconducting circuit of claim 1.

3. the superconducting quantum interference device is connected at a first end to the first superconducting portion and at a second end to the ground plane; the three-dimensional wiring is disposed at a position spanning the first superconducting portion, a current from the bias line to the superconducting quantum interference device is conducted in two directions opposite to each other along one side of a superconducting loop surrounding the superconducting quantum interference device; 3. The superconducting circuit according to claim 1 or 2.

4. the superconducting quantum interference device is connected at a first end to the first superconducting portion and at a second end to the ground plane; the three-dimensional wiring includes a first three-dimensional wiring that crosses the first superconducting portion and a second three-dimensional wiring that crosses the bias line, a current from the bias line to the superconducting quantum interference device is conducted in only one direction along one side of the superconducting loop; 4. The superconducting circuit according to claim 1.

5. the first and second portions of the first superconducting portion are separated by the superconducting quantum interference device; the superconducting quantum interference device is connected at a first end to the first portion and at a second end to the second portion; a plurality of three-dimensional wirings that form a superconducting loop surrounding the superconducting quantum interference device together with the ground plane; a current is conducted from the bias line to the superconducting quantum interference device in two directions opposite to each other along one side of the superconducting loop; 5. A superconducting circuit according to any one of claims 1 to 4.

6. the first and second portions of the first superconducting portion are separated by the superconducting quantum interference device; the superconducting quantum interference device is connected at a first end to the first portion and at a second end to the second portion; a plurality of three-dimensional wirings that form a superconducting loop surrounding the superconducting quantum interference device together with the ground plane; a current from the bias line to the superconducting quantum interference device is conducted in only one direction along one side of the superconducting loop; 6. A superconducting circuit according to any one of claims 1 to 5.

7. the superconducting quantum interference device is connected at a first end to the first superconducting portion and at a second end to the ground plane; the three-dimensional wiring includes a first three-dimensional wiring and a second three-dimensional wiring each spanning the first superconducting portion, a current is conducted from the bias line to the superconducting quantum interference device in two directions opposite to each other along one side of the superconducting loop; 7. A superconducting circuit according to any one of claims 1 to 6.

8. the superconducting quantum interference device is connected at a first end to the first superconducting portion and at a second end to the ground plane; the three-dimensional wiring includes a first three-dimensional wiring and a second three-dimensional wiring each spanning the first superconducting portion, a current from the bias line to the superconducting quantum interference device is conducted in only one direction along one side of the superconducting loop; 8. A superconducting circuit according to any one of claims 1 to 7.

Images