Coupler and computing device

Abstract

Couplers and computing devices capable of improving controllability are provided. According to embodiments, a coupler includes a first capacitor to a fourth capacitor, a first inductor, a second inductor, and a first Josephson junction. The first inductor is electrically connected to the first capacitor. The second inductor is electrically connected to the second capacitor. The second inductor is electrically connected at another end portion to another end portion of the first capacitor, another end portion of the first inductor, and another end portion of the second capacitor. The first Josephson junction is electrically connected to the first capacitor and the second capacitor. A space surrounded by the first inductor, the second inductor, and the first Josephson junction is provided. A third capacitor is capable of being electrically connected to a first nonlinear resonator. A fourth capacitor is capable of being electrically connected to a second nonlinear resonator.

Description

[0001] This application is based on Japanese Patent Application No. 2021-125184 (Filing Date: July 30, 2021) and claims priority thereto. This application incorporates the entire contents of the aforementioned application by reference. TECHNICAL FIELD

[0002] Embodiments of the present application relate to a coupler and a computing device. BACKGROUND

[0003] For example, a coupler is used in a computing device that utilizes a plurality of nonlinear resonators. It is desirable to improve controllability in the computing device. SUMMARY

[0004] Embodiments of the present application provide a coupler and a computing device that can improve controllability.

[0005] Technical Solution to Problem

[0006] According to an embodiment of the present application, a coupler includes a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a first inductor, a second inductor, and a first Josephson junction. The first capacitor includes a first capacitor end and a first capacitor other end. The first inductor includes a first inductor end and a first inductor other end. The first inductor end is electrically connected to the first capacitor end. The second capacitor includes a second capacitor end and a second capacitor other end. The second inductor includes a second inductor end and a second inductor other end. The second inductor end is electrically connected to the second capacitor end. The second inductor other end is electrically connected to the first capacitor other end, the first inductor other end, and the second capacitor other end. The first Josephson junction includes a first Josephson junction end and a first Josephson junction other end. The first Josephson junction end is electrically connected to the first capacitor end. The first Josephson junction other end is electrically connected to the second capacitor end. A space surrounded by the first inductor, the second inductor, and the first Josephson junction is provided. The third capacitor includes a third capacitor end and a third capacitor other end. The third capacitor other end is electrically connected to the first capacitor end. The third capacitor end is electrically connectable to a first nonlinear resonator. The fourth capacitor includes a fourth capacitor end and a fourth capacitor other end. The fourth capacitor other end is electrically connected to the second capacitor end. The fourth capacitor end is electrically connectable to a second nonlinear resonator.

[0007] According to the coupler configured as described above, a coupler and a computing device that can improve controllability can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a schematic view illustrating a coupler and a computing device according to the first embodiment.

[0009] Figure 2 (a) to (c) of FIG. 1 are schematic views illustrating a coupler and a computing device according to the first embodiment. Figure 2 (c) of FIG. 1 is a schematic sectional view illustrating a part of the coupler and the computing device according to the first embodiment.

[0010] Figure 3 (a) and (b) of FIG. 2 are schematic plan views illustrating a part of the coupler according to the first embodiment. Figure 3 (b) of FIG. 2 is a schematic plan view illustrating a part of the coupler according to the first embodiment.

[0011] Figure 4 (a) and (b) of FIG. 3 are schematic views illustrating frequencies in the coupler and the computer. Figure 4 (b) of FIG. 3 is a graph illustrating frequencies in the coupler and the computer.

[0012] Figure 5 (a) and (b) of FIG. 4 are schematic views illustrating coupling strengths in the coupler and the computer. Figure 5 (b) of FIG. 4 is a graph illustrating coupling strengths in the coupler and the computer.

[0013] Figure 6 (a) and (b) of FIG. 5 are schematic views illustrating characteristics of the coupler and the computer. Figure 6 (b) of FIG. 5 is a graph illustrating characteristics of the coupler and the computer.

[0014] Figure 7 (a) and (b) of FIG. 6 are graphs illustrating coupling strengths in a coupler and a computer according to the second reference example. Figure 7 (b) of FIG. 6 is a graph illustrating coupling strengths in the coupler and the computer according to the second reference example.

[0015] Figure 8 (a) and (b) of FIG. 7 are graphs illustrating coupling strengths in a coupler and a computer according to the third reference example. Figure 8 (b) of FIG. 7 is a graph illustrating coupling strengths in the coupler and the computer according to the third reference example.

[0016] Figure 9 is a graph illustrating probabilities in the coupler and the computer according to the first embodiment.

[0017] Figure 10 (a) and (b) of FIG. 8 are graphs illustrating resonance frequencies of the coupler and the computer according to the first embodiment. Figure 10 (b) of FIG. 8 is a graph illustrating resonance frequencies of the coupler and the computer according to the first embodiment.

[0018] Figure 11 is a schematic view illustrating a coupler and a computing device according to the first embodiment.

[0019] Figure 12 (a) and (b) of FIG. 9 are graphs illustrating coupling strengths in the coupler and the computer according to the first embodiment. Figure 12 (b) of FIG. 9 is a graph illustrating coupling strengths in the coupler and the computer according to the first embodiment.

[0020] Figure 13(a) and (b) of FIG. 1 are schematic diagrams illustrating a coupler and a computer involved in the first embodiment. Figure 13

[0021] Figure 14 (a) to (c) of FIG. 2 are schematic diagrams illustrating a coupler involved in the second embodiment. Figure 14

[0022] Figure 15 (a) and (b) of FIG. 3 are schematic diagrams illustrating a part of a coupler involved in the second embodiment. Figure 15

[0023] Figure 16 (a) and (b) of FIG. 4 are schematic diagrams illustrating a part of a coupler involved in the second embodiment. Figure 16 Figure 16 Figure 16

[0024] Figure 17 Figure 17

[0025] Figure 18 Figure 18

[0026] Figure 19

[0027] Figure 20

[0028] Figure 21

[0029] Figure 22

[0030] Figure 23 Figure 23 ​​​​​​​​​​​​​​​​

[0031] Figure 24 Fig. 2 is a schematic plan view illustrating a coupler and a computer according to the second embodiment.

[0032] Figure 25 (a) of Fig. 1 and Figure 25 (b) of Fig. 1 is a schematic plan view illustrating a coupler and a computer according to the second embodiment.

[0033] Reference Signs List

[0034] 10, 10A to 10F coupler; 10a, 10b first part, second part; 10f, 10g first face, second face; 10r ring; 10s base; 11 to 15 first to fifth capacitors; 11L, 12L conductive layer; 11e to 15e first to fifth capacitor end; 11f to 15f first to fifth capacitor other end; 21, 22 first inductor, second inductor; 21L, 22L first conductive layer, second conductive layer; 21e, 22e first inductor end, second inductor end; 21f, 22f first inductor other end, second inductor other end; 31 first Josephson junction; 31e first Josephson junction end; 31f first Josephson junction other end; 35a to 39a, 35b to 39b conductive film; 35i to 39i insulating film; 41, 42 first resonator capacitor, second resonator capacitor; 41e, 42e end; 41f, 42f other end; 50A, 50B first non-linear resonator, second non-linear resonator; 51, 52 first non-linear resonator Josephson junction, second non-linear resonator Josephson junction; 51e, 52e end; 51f, 52f other end; 60 first magnetic field application section; 61 first conductive section; 61i magnetic flux control current; 65a, 65b first excitation conductive section, second excitation conductive section; 66a, 66b first readout resonator, second readout resonator; 70 control section; 81, 82 conductive pattern; 83 conductive section; Φ magnetic flux; 110, 110a, 111, 112, 113, 119a to 119c, 120 to 123, 130 to 132 computer; CS1 coupling strength; CS2 coupling strength; GND ground; J1 to J3, Jn Josephson junction; K1 to K3, Kn Josephson junction; MF1 magnetic flux; Mvl first magnetic flux value; PI probability; SP space m; ST1 to ST4 first to fourth states; fbl, fb2 resonant frequency; fcl, fc2 frequency; fol frequency; tG gate time; tm time DETAILED DESCRIPTION

[0035] Embodiments of the present application will be described below with reference to the drawings.

[0036] The drawings are schematic or conceptual, and the relationships between the thicknesses and widths of the portions, the ratios of the sizes of the portions, and the like are not limited to be the same as those of reality. Even when the same portions are represented, the sizes and ratios thereof are sometimes differently represented from one drawing to another drawing according to the drawings.

[0037] In the present application specification and the drawings, the same elements as those described previously with respect to the drawings already appearing are given the same reference numerals, and detailed description is appropriately omitted.

[0038] (First Embodiment)

[0039] Figure 1 is a schematic view illustrating a coupler and a computing device according to the first embodiment.

[0040] As Figure 1 shown, a computer 110 according to the embodiment includes a coupler 10, a first nonlinear resonator 50A, and a second nonlinear resonator 50B. The coupler 10 couples the first nonlinear resonator 50A and the second nonlinear resonator 50B.

[0041] The coupler 10 includes a first capacitor 11, a second capacitor 12, a third capacitor 13, a fourth capacitor 14, a first inductor 21, a second inductor 22, and a first Josephson junction 31.

[0042] The first capacitor 11 includes a first capacitor end 11e and a first capacitor other end 11f. The first inductor 21 includes a first inductor end 21e and a first inductor other end 21f. The first inductor end 21e is electrically connected to the first capacitor end 11e.

[0043] The second capacitor 12 includes a second capacitor end 12e and a second capacitor other end 12f. The second inductor 22 includes a second inductor end 22e and a second inductor other end 22f. The second inductor end 22e is electrically connected to the second capacitor end 12e. The second inductor other end 22f is electrically connected to the first capacitor other end 11f, the first inductor other end 21f, and the second capacitor other end 12f. The electric potentials of the first capacitor other end 11f, the first inductor other end 21f, the second capacitor other end 12f, and the second inductor other end 22f are, for example, set to a fixed potential (for example, ground GND).

[0044] The first Josephson junction 31 includes a first Josephson junction end 31e and a first Josephson junction other end 31f. The first Josephson junction end 31e is electrically connected to the first capacitor end 11e. The first Josephson junction end 31e is also electrically connected to the first inductor end 21e. The first Josephson junction other end 31f is electrically connected to the second capacitor end 12e. The first Josephson junction other end 31f is also electrically connected to the second inductor end 22e.

[0045] A space SP is surrounded by the first inductor 21, the second inductor 22, and the first Josephson junction 31. The space SP can also be surrounded by the first capacitor 11, the second capacitor 12, and the first Josephson junction 31. For example, a ring 10r is formed by the first inductor 21, the second inductor 22, and the first Josephson junction 31. The ring 10r surrounds the space SP. As described later, the magnetic flux Φ in the space SP (in the ring 10r) can be controlled.

[0046] The third capacitor 13 includes a third capacitor end 13e and a third capacitor other end 13f. The third capacitor other end 13f is electrically connected to the first capacitor end 11e. The third capacitor other end 13f is also electrically connected to the first inductor end 21e and the first Josephson junction end 31e. The third capacitor end 13e can be connected to the first nonlinear resonator 50A.

[0047] The fourth capacitor 14 includes a fourth capacitor end 14e and a fourth capacitor other end 14f. The fourth capacitor other end 14f is electrically connected to the second capacitor end 12e. The fourth capacitor other end 14f is also electrically connected to the second inductor end 22e and the first Josephson junction other end 31f. The fourth capacitor end 14e can be connected to the second nonlinear resonator 50B.

[0048] In the coupler 10, the first part 10a including the first capacitor 11 and the first inductor 21 corresponds to the first LC circuit. The second part 10b including the second capacitor 12 and the second inductor 22 corresponds to the second LC circuit. These LC circuits are connected by the first Josephson junction 31. The magnetic flux Φ of the space SP surrounded by these can be modulated.

[0049] The coupler 10 has a plurality of modes (for example, two modes). In the embodiment, by providing the LC circuits described above in the coupler 10, the resonance frequencies of the plurality of modes described above can be lowered compared to the case where only inductors are provided. For example, it is easy to make the resonance frequencies of the plurality of modes in the coupler 10 close to the resonance frequency of the first nonlinear resonator 50A and the resonance frequency of the second nonlinear resonator 50B. Thereby, a strong coupling strength can be obtained. According to the embodiment, controllability can be improved.

[0050] As described later, by controlling the magnetic flux Φ, the coupling strength can be changed. For example, the coupling strength can be made substantially zero, eliminating the coupling (set to off). As described later, by controlling the coupler 10, a two-qubit gate operation can be performed at high speed. A coupler and a computing device that can improve controllability can be provided.

[0051] As Figure 1 As shown, the first nonlinear resonator 50A includes, for example, a first nonlinear resonator Josephson junction 51 and a first resonator capacitor 41. An end 51e of the first nonlinear resonator Josephson junction 51 and an end 41e of the first resonator capacitor 41 are electrically connected to the third capacitor end 13e. The other end 51f of the first nonlinear resonator Josephson junction 51 and the other end 41f of the first resonator capacitor 41 are electrically connected to each other. The potential of the other end 51f and the other end 41f is set to a fixed potential (for example, ground GND), for example. Therefore, for example, the other end 51f of the first nonlinear resonator Josephson junction 51 and the other end 41f of the first resonator capacitor 41 can be electrically connected to the first capacitor other end 11f.

[0052] The end 51e of the first nonlinear resonator Josephson junction 51 and the end 41e of the first resonator capacitor 41 are capacitively coupled to the first portion 10a via the third capacitor 13.

[0053] The second nonlinear resonator 50B includes, for example, a second nonlinear resonator Josephson junction 52 and a second resonator capacitor 42. An end 52e of the second nonlinear resonator Josephson junction 52 and an end 42e of the second resonator capacitor 42 are electrically connected to the fourth capacitor end 14e. The other end 52f of the second nonlinear resonator Josephson junction 52 and the other end 42f of the second resonator capacitor 42 are electrically connected to each other. The potential of the other end 52f and the other end 42f is set to a fixed potential (for example, ground GND), for example. Therefore, for example, the other end 52f of the second nonlinear resonator Josephson junction 52 and the other end 42f of the second resonator capacitor 42 can be electrically connected to the second capacitor other end 12f.

[0054] The end 52e of the second nonlinear resonator Josephson junction 52 and the end 42e of the second resonator capacitor 42 are capacitively coupled to the second portion 10b via the fourth capacitor 14.

[0055] The first nonlinear resonator 50A and the second nonlinear resonator 50B function as two qubits. Among a plurality of energy levels that the first nonlinear resonator 50A and the second nonlinear resonator 50B have, two from the bottom can be used as two states of a qubit. Among the plurality of energy levels, the two from the bottom correspond to a ground state and a first excited state. The above two states of the qubit correspond to computational basis states. For example, the resonant frequency of the first nonlinear resonator 50A corresponds to a value obtained by transforming an energy difference between the two states from the bottom of the first nonlinear resonator 50A into a frequency. For example, the resonant frequency of the second nonlinear resonator 50B corresponds to a value obtained by transforming an energy difference between the two states from the bottom of the second nonlinear resonator 50B into a frequency. By dividing the energy by Planck's constant h, it is possible to transform the frequency corresponding to the energy.

[0056] As shown in Figure 1 , the coupler 10 can also include a first conductive member 61. The first conductive member 61 can apply a magnetic field to the space SP (the loop 10r). For example, a magnetic field is generated by a current supplied to the first conductive member 61. The generated magnetic field is applied to the space SP (the loop 10r). As described later, in accordance with the magnetic flux Φ (magnetic flux based on the magnetic field) in the space SP (the loop 10r), the coupling strength between the first nonlinear resonator 50A and the second nonlinear resonator 50B changes.

[0057] The first conductive member 61 is one example of the first magnetic field application portion 60. As shown in Figure 1 , the computer 110 can also include a control portion 70. The coupler 10 (or the computer 110) can include the first magnetic field application portion 60. The first magnetic field application portion 60 can apply a magnetic field to the space SP (the loop 10r). The control portion 70 can control the first magnetic field application portion 60 to change the magnetic flux Φ in the space SP (the loop 10r). In the case where the first magnetic field application portion 60 includes the first conductive member 61, the control portion 70 can change the magnetic flux Φ by modulating the current supplied to the first conductive member 61.

[0058] Figure 2 (a) to Figure 2 (c) of FIG. 1 are schematic cross-sectional views illustrating a part of the coupler and the computing device according to the first embodiment.

[0059] As shown in Figure 2 (a), for example, the first Josephson junction 31 is provided on the first face 10f of the base 10s. A direction perpendicular to the Z-axis direction is taken as the X-axis direction. A direction perpendicular to the Z-axis direction and the X-axis direction is taken as the Y-axis direction.

[0060] like Figure 2 As shown in (a), the first Josephson junction 31 includes, for example, a conductive film 35a, a conductive film 35b, and an insulating film 35i. The insulating film 35i is disposed between a portion of the conductive film 35a and a portion of the conductive film 35b.

[0061] like Figure 2 As shown in (b), the first nonlinear resonator Josephson junction 51 includes, for example, a conductive film 36a, a conductive film 36b, and an insulating film 36i. The insulating film 36i is disposed between a portion of the conductive film 36a and a portion of the conductive film 36b.

[0062] like Figure 2 As shown in (c), the second nonlinear resonator Josephson junction 52 includes, for example, a conductive film 37a, a conductive film 37b, and an insulating film 37i. The insulating film 37i is disposed between a portion of the conductive film 37a and a portion of the conductive film 37b. These conductive films are substantially along the X-Y plane.

[0063] These conductive films, for example, contain at least one selected from Al, Nb, NbN, TiN, NbTiN, and Ta. These materials are superconducting materials. The insulating film 38i, for example, contains at least one selected from Al2O3, Nb2O5, NbO2, NbO, and AlN. The substrate 10s, for example, contains at least one selected from Si and sapphire. The substrate 10s, for example, is insulating.

[0064] Figure 3 (a) and Figure 3 (b) is a schematic top view illustrating a portion of the coupler according to the first embodiment.

[0065] like Figure 3 As shown in (a), in one example, a first capacitor 11 and a first inductor 21 are disposed on a first surface 10f of a substrate 10s. The first capacitor 11 is formed by two opposing conductive layers 11L. The first inductor 21 includes a first conductive layer 21L having a tortuous structure.

[0066] like Figure 3 As shown in (b), in one example, a second capacitor 12 and a second inductor 22 are disposed on the first surface 10f of the substrate 10s. The second capacitor 12 is formed by two opposing conductive layers 12L. The second inductor 22 includes a second conductive layer 22L having a tortuous structure.

[0067] The aforementioned conductive layers include, for example, Al, Nb, NbN, TiN, NbTiN, and Ta.

[0068] In these examples, the first inductor 21 and the second inductor 22 are, for example, based on kinetic inductors. As will be described later, the first inductor 21 and the second inductor 22 may also include Josephson junctions.

[0069] The following describes an example of simulation results for the characteristics of coupler 10 (and computer 110). In the simulation model below, the inductance of the first inductor 21 and the second inductor 22 is 2.34 nH. The critical current of the first Josephson junction 31 is 40 nA. The capacitance of the first capacitor 11 and the second capacitor 12 is 39 fF. The capacitance of the third capacitor 13 and the fourth capacitor 14 is 9.74 fF. The critical current of the first nonlinear resonator Josephson junction 51 is 70 nA. The critical current of the second nonlinear resonator Josephson junction 52 is 50 nA. The capacitance of the first resonator capacitor 41 and the second resonator capacitor 42 is 39 fF. For example, by controlling the current supplied to the first conductive component 61, the magnetic flux Φ of the space SP (ring 10r) can be varied.

[0070] Hereinafter, features relating to the computer 110 according to the embodiments and features relating to the computer 119a of the first reference example will be described. In the computer 110, as described above, the coupler 10 includes an LC circuit. In the computer 119a of the first reference example, the coupler 10 does not include the first capacitor 11 and the second capacitor 12. That is, in the computer 119a, the first part 10a includes the first inductor 21 but does not include the first capacitor 11. In the computer 119a, the second part 10b includes the second inductor 22 but does not include the second capacitor 12. The other than that, the configuration of the computer 119a is the same as that of the computer 110.

[0071] Figure 4 (a) and Figure 4 (b) is a graph illustrating the frequency in a coupler and a computer.

[0072] Figure 4 (a) corresponds to the computer 110 involved in the implementation method. Figure 4(b) corresponds to computer 119a of the first reference example. The horizontal axis of these graphs represents the magnetic flux MF1 of the space SP (ring 10r). The magnetic flux MF1 (=2Φ / Φ0) is normalized to be dimensionless by the magnetic flux quantum Φ0. The vertical axis of these graphs corresponds to the frequency fo1. These graphs illustrate the resonant frequency fb1 of the first nonlinear resonator 50A and the resonant frequency fb2 of the second nonlinear resonator 50B. The first nonlinear resonator 50A corresponds, for example, to the first qubit. The second nonlinear resonator 50B corresponds, for example, to the second qubit. As described above, the resonant frequency of the nonlinear resonator corresponds to the value obtained by converting the energy difference between the two states in the nonlinear resonator from bottom to top into frequency.

[0073] Figure 4 (a) and Figure 4 Example (b) illustrates frequencies fc1 and fc2. Frequency fc1 corresponds to the frequency of one of the multiple modes (e.g., two modes) in coupler 10. Frequency fc2 corresponds to the other frequency of the multiple modes (e.g., two modes) in coupler 10.

[0074] like Figure 4 As shown in (a), in the computer 110 according to the embodiment, when the magnetic flux MF1 changes, the frequencies fc1 and fc2 also change. In particular, the frequency fc2 changes significantly. In this example, when the magnetic flux MF1 is approximately 0.66, the frequencies fc1 and fc2 are close to each other. In this example, at a first magnetic flux value Mv1, the frequency fc2 becomes the same as the frequency fc1. The first magnetic flux value Mv1 is approximately 0.66. In this example, the range of frequencies fc1 and fc2 is above 11 GHz and below 19 GHz.

[0075] like Figure 4 As shown in (a), the resonant frequency fb1 of the first nonlinear resonator 50A and the resonant frequency fb2 of the second nonlinear resonator 50B are substantially constant when the magnetic flux MF1 changes. In this example, the resonant frequency fb1 of the first nonlinear resonator 50A is approximately 10.0 GHz. The resonant frequency fb2 of the second nonlinear resonator 50B is approximately 8.4 GHz. Examples of the degree of change of the resonant frequencies fb1 and fb2 when the magnetic flux MF1 changes will be described later.

[0076] Thus, in this embodiment, frequencies fc1 and fc2 are relatively close to resonant frequencies fb1 and fb2. Coupler 10 has multiple modes (at least two modes). That is, coupler 10 can resonate in multiple modes. At least two of the resonant frequencies (frequency fc1 and frequency fc2) in each of these multiple modes are near the aforementioned first magnetic flux value Mv1 (magnetic flux values ​​where frequencies fc1 and fc2 are close to each other), and are respectively higher than resonant frequencies fb1 and fb2, and lower than the sum of resonant frequencies fb1 and fb2. In this embodiment, there exists a state where the resonant frequencies (frequency fc1 and frequency fc2) in each of the multiple modes are lower than the sum of resonant frequencies fb1 and fb2.

[0077] In this embodiment, each of the first part 10a and the second part 10b includes an inductor and a capacitor. This allows the resonant frequencies of multiple modes of the coupler 10 to approach the resonant frequency of a nonlinear resonator. Consequently, for example, a strong coupling strength can be obtained. This provides a coupler and computing device that improves controllability.

[0078] like Figure 4 As shown in (b), in the computer 119a of the first reference example, the resonant frequencies (frequency fc1 and frequency fc2) of the coupler 10 in multiple modes are significantly higher than the resonant frequencies (resonant frequencies fb1 and fb2) of the two nonlinear resonators. Figure 4 As shown in (b), in computer 119a, frequencies fc1 and fc2 are higher than the sum of resonant frequencies fb1 and fb2. Therefore, it is difficult to obtain high coupling strength. In the first reference example, for example, the resonant frequencies of multiple modes of coupler 10 are more than three times the resonant frequencies of the nonlinear resonator.

[0079] In this embodiment, the capacitances of the first capacitor 11 and the second capacitor 12 are large enough to be non-negligible; for example, it is preferable that the capacitances of the first capacitor 11 and the second capacitor 12 are each 0.1 times larger than the capacitances of the third capacitor 13 and the fourth capacitor 14. This, for example, can effectively reduce the resonant frequencies (frequency fc1 and frequency fc2) in multiple modes.

[0080] Furthermore, such as Figure 4 As shown in (a), in this embodiment, the resonant frequency fb1 of the first nonlinear resonator 50A and the resonant frequency fb2 of the second nonlinear resonator 50B are substantially constant relative to the change in magnetic flux MF1. For example, the frequencies of the two qubits do not change substantially. The frequencies of the two qubits are substantially fixed and stable. Couplers and computing devices that improve controllability can be provided.

[0081] Figure 5 (a) andFigure 5 Fig. 2 is a graph illustrating the coupling strength of the coupler and the computer.

[0082] Figure 5 (a) corresponds to the computer 110 according to the embodiment. Figure 5 (b) corresponds to the computer 119a of the first reference example described above. The horizontal axis of these graphs is the magnetic flux MF1 of the space SP (the ring 10r). The vertical axis is the coupling strength CS1.

[0083] As shown in (a) of Fig. 2, the coupling strength CS1 changes when the magnetic flux MF1 changes. By controlling the magnetic flux MF1, the coupling strength CS1 can be controlled. For example, the amplitude of the change of the coupling strength CS1 is about 20 MHz or so. That is, the coupling strength CS1 can be adjusted in the range of -20 MHz to 20 MHz. Figure 5

[0084] Thus, the control section 70 can control the magnetic flux Φ (the magnetic flux MF1) in the space SP, and change the coupling strength CS1 between the first nonlinear resonator 50A and the second nonlinear resonator 50B.

[0085] As shown in (a) of Fig. 2, in this example, the coupling strength CS1 becomes substantially 0 when the magnetic flux MF1 is about 0.68. Thus, the control section 70 controls the magnetic flux Φ (the magnetic flux MF1) in the space SP, and can substantially eliminate the coupling between the first nonlinear resonator 50A and the second nonlinear resonator 50B. That is, the coupling can be turned off. A coupler and a computer device that can improve controllability can be provided. Figure 5

[0086] As shown in (b) of Fig. 2, in the computer 119a of the first reference example, there is also a condition in which the coupling strength CS1 becomes substantially 0. However, in the computer 119a, the magnetic flux MF1 at which the coupling strength CS1 is not 0 is lower than that in the computer 110. Thus, in the first reference example in which the capacitors are not provided in the first portion 10a and the second portion 10b, it is difficult to obtain a high coupling strength CS1. In the embodiment, a high coupling strength CS1 can be obtained, and the coupling can be turned off. Figure 5

[0087] (a) and (b) are graphs illustrating the characteristics of the coupler and the computer. Figure 5 Figure 6 (a) corresponds to the computer 110 according to the embodiment.

[0088] Figure 6 Figure 6 ​​​​(b) corresponds to the computer 110a of the 1st reference example. The horizontal axis of these graphs is the magnetic flux MF1. The vertical axis of these graphs is the coupling strength CS2 related to the residual coupling (so-called ZZ coupling). The ZZ coupling corresponds to a state in which, with respect to the frequency fb3 corresponding to the "1 state" of both of the two qubits, fb1 + fb2 - fb3 does not become zero due to the residual coupling. This "offset" in the ZZ coupling corresponds to the coupling strength CS2.

[0089] As explained with respect to Figure 6 (a), the coupling strength CS1 substantially becomes zero at the magnetic flux MF1 of about 0.68 (1st magnetic flux value Mv1). As explained with respect to Figure 4 (a), the coupling strength CS2 related to the residual coupling can substantially be zero at the magnetic flux MF1 of about 0.68. For example, a robust zero ZZ coupling can be obtained.

[0090] On the other hand, as shown in (b) of Figure 6 , in the computer 119a of the 1st reference example, it is not possible to reduce the coupling strength CS2 related to the residual coupling to zero.

[0091] In the 1st reference example in which the capacitors are not provided in the 1st and 2nd sections 10a and 10b, when the coupling strength CS2 related to the residual coupling is to be reduced, it is necessary to excessively increase the frequency fc1 and the frequency fc2, as a result of which the coupling strength CS1 significantly becomes low. In the 1st reference example, it is difficult to obtain a high coupling strength CS1 while making the coupling strength CS2 zero.

[0092] Hereinafter, the 2nd and 3rd reference examples will be explained. In the 2nd and 3rd reference examples, the capacitors are not provided in the 1st and 2nd sections 10a and 10b, either. In the 2nd reference example, the values of the inductors are adjusted so that a high coupling strength CS1 can be obtained. In the 3rd reference example, the values of the inductors are adjusted so that the coupling strength CS2 related to the residual coupling becomes low.

[0093] Figure 6 (a) and Figure 7 (b) are graphs illustrating the coupling strength in the coupler and the computer of the 2nd reference example.

[0094] These graphs correspond to the computer 119b related to the 2nd reference example. In the 2nd reference example, in this example, the inductances of the 1st and 2nd inductors 21 and 22 are 4.1 nH. Figure 7 (a) and Figure 7 (b) of the 2nd reference example. Figure 7 The vertical axis of (a) of the 2nd reference example is the coupling strength CS1. Figure 7The vertical axis of (b) is the coupling strength CS2, which is related to the residual coupling.

[0095] like Figure 7 As shown in (a), in the second reference example, there exists a condition where the coupling strength CS1 is substantially zero (coupled inactive). In the second reference example, a higher coupling strength CS1 can be obtained compared to the first reference example. However, as... Figure 7 As shown in (b), in the second reference example, the coupling strength CS2 is greater than that in the first reference example, and does not become 0. Thus, in the second reference example, a low coupling strength CS2 cannot be obtained.

[0096] Figure 7 (a) and Figure 8 (b) is a graph illustrating the coupling strength between the coupler and the computer in the third reference example.

[0097] These figures correspond to the computer 119c described in the third reference example. In the third reference example, the inductance of the first inductor 21 and the second inductor 22 is 1.63 nH. Figure 8 (a) and Figure 8 The horizontal axis of (b) is the magnetic flux MF1 of the space SP (ring 10r). Figure 8 The vertical axis of (a) is the coupling strength CS1. Figure 8 The vertical axis of (b) is the coupling strength CS2, which is related to the residual coupling.

[0098] like Figure 8 As shown in (a), in the third reference example, there exists a condition where the coupling strength CS1 is substantially zero (coupled inactivation). In the third reference example, the coupling strength CS1 is significantly low. Figure 8 As shown in (b), in the third reference example, the coupling strength CS2 is lower than that in the first reference example, but it is not actually zero.

[0099] As mentioned above, in the first to third reference examples where no capacitors were provided in Part 10a and Part 20b, it was not possible to simultaneously obtain a substantially zero coupling strength CS2, a high coupling strength CS1, and inactive coupling.

[0100] In this embodiment, capacitors are provided in the first part 10a and the second part 10b. As a result, a substantially zero coupling strength CS2, a high coupling strength CS1, and inactive coupling can be obtained.

[0101] When capacitors are provided in Part 10a and Part 20b, the component size increases. Therefore, it is generally advisable to avoid providing capacitors in Part 10a and Part 20b.

[0102] On the other hand, in the embodiment, as described above, the capacitor is provided in the first part 10a and the second part 10b. Thereby, for example, the coupling strength CS2 of substantially zero, the coupling strength CS1 of high, and the non-activation of the coupling can be obtained. This is a particular effect involved in the embodiment. The particular effect has not been known in the past. The particular effect was first clarified by a fully quantum-mechanical analysis by the inventors of the present application.

[0103] The following describes an example of the characteristics related to the operation of the two-qubit gate. For example, when the operation of the two-qubit gate is not performed, the magnetic flux MF1 is set to a value at which the coupling strength CS1 becomes zero (the above-described first magnetic flux value Mvl, about 0.68). When the operation of the two-qubit gate is performed, the magnetic flux MF1 is modulated. The frequency of the modulation is the difference between the resonance frequency fbl and the resonance frequency fb2, which is about 1.55 GHz in this example. In this simulation, the amplitude of the modulation is 0.12. That is, the magnetic flux MF1 is sinusoidally vibrated between 0.56 and 0.80.

[0104] Figure 8 is a graph illustrating the probability in the coupling and the computer involved in the first embodiment. Figure 9 The horizontal axis of is the time tm. The vertical axis is the probability Pl.

[0105] In Figure 9 is illustrated the probabilities Pl of the first state ST1 to the fourth state ST4. In the first state ST1, for example, the first nonlinear resonator 50A is "1" and the second nonlinear resonator 50B is "0". In the second state ST2, for example, the first nonlinear resonator 50A is "0" and the second nonlinear resonator 50B is "1". In the third state ST3, for example, the first nonlinear resonator 50A is "1" and the second nonlinear resonator 50B is "1". In the fourth state ST4, for example, the first nonlinear resonator 50A is "0" and the second nonlinear resonator 50B is "0".

[0106] As Figure 9 shown in, at the time tm of 0, the probability Pl of the first state ST1 is 1 and the probability Pl of the second state ST2 is 0. As the time tm elapses, the probability Pl of the first state ST1 and the probability Pl of the second state ST2 change. In this example, at the time tm of about 12 ns, the probability Pl of the first state ST1 becomes the same as the probability Pl of the second state ST2. The probability Pl of the first state ST1 exceeds the probability Pl of the second state ST2 at the time tm of about 12 ns. In this example, the operation of the two-qubit gate can be completed in the time tm of 12 ns.

[0107] In this implementation, a short gate time (gating time) tG can be obtained. High-speed execution of two-qubit gates is possible. Couplers and computing devices that improve controllability can be provided. The gate time tG is, for example, greater than 10 ns and less than about 20 ns.

[0108] Thus, in this implementation, by modulating the magnetic flux MF1 (magnetic flux Φ) at an appropriate frequency, a two-qubit gate operation is performed with respect to the first nonlinear resonator 50A and the second nonlinear resonator 50B. During the period when the magnetic flux MF1 is not modulated, the coupling is kept inactive (coupling strength CS1 and coupling strength CS2 are essentially zero).

[0109] like Figure 9 As shown, the probabilities P1 of the third state ST3 and the fourth state ST4 are essentially 0. This enables the realization of a stable two-qubit gate.

[0110] Figure 9 (a) and Figure 10 (b) is a graph illustrating the resonant frequencies of the coupler and computer according to the first embodiment.

[0111] The horizontal axis of these graphs represents the magnetic flux MF1. Figure 10 The vertical axis of (a) is the resonant frequency fb1 of the first nonlinear resonator 50A. Figure 10 The vertical axis of (b) is the resonant frequency fb2 of the second nonlinear resonator 50B.

[0112] like Figure 10 As shown in (a), when the magnetic flux MF1 changes from 0 to 1, the resonant frequency fb1 of the first nonlinear resonator 50A changes around 10 GHz. The magnitude of the change in the resonant frequency fb1 is approximately 300 MHz.

[0113] like Figure 10 As shown in (b), when the magnetic flux MF1 changes from 0 to 1, the resonant frequency fb2 of the second nonlinear resonator 50B changes around 8.4 GHz. The magnitude of the change in the resonant frequency fb2 is approximately 100 MHz.

[0114] Thus, in this implementation, changes in the resonant frequency of the nonlinear resonator can be suppressed when the magnetic flux MF1 changes. The frequency of the qubit is stable. The frequency of the qubit can be substantially fixed. Couplers and computing devices that improve controllability can be provided.

[0115] According to the embodiment, for example, a high coupling strength CS1 can be obtained. For example, a fast two-qubit gate operation can be performed. For example, the coupling of a plurality of nonlinear resonators can be deactivated while obtaining a high coupling strength CS1. The frequency variation of the nonlinear resonator (qubit) caused by the magnetic flux is small, and the stability of the qubit can be maintained. According to the embodiment, for example, a coupler and a computing device that can improve controllability can be provided.

[0116] For example, consider a fourth reference example in which two qubits having different frequencies are directly coupled, and a microwave is irradiated to perform a two-qubit gate. In the fourth reference example, a microwave of the frequency of one of the two qubits is irradiated to the other of the two qubits. In the fourth reference example, the characteristics depend on a high-order perturbation term. In the fourth reference example, it is difficult to realize a high-speed gate.

[0117] For example, consider a fifth reference example in which two qubits having different frequencies are directly coupled, and a microwave is irradiated to perform a two-qubit gate. In the fifth reference example, a microwave corresponding to the difference between the frequencies of the two qubits is irradiated. In the fifth reference example, the characteristics also depend on a high-order perturbation term. In the fifth reference example, it is also difficult to realize a high-speed gate.

[0118] In contrast, in the embodiment, by using the coupler 10 described above, a high-speed gate can be realized.

[0119] The frequency of the "− mode" of the coupler 10 corresponds to the frequency fc2 described above, for example. In the embodiment, the frequency of the "− mode" can be adjusted with the magnetic flux Φ within the ring 10r. Thereby, the activation (on) and deactivation (off) of the coupling can be realized. Even if the difference between the frequencies of the two qubits is large, substantially complete deactivation of the coupling can be realized. Even if the coupling strength is increased, deactivation can be performed. Speedup is also possible. A coupler and a computing device that can improve controllability can be provided.

[0120] In one example to which the embodiment relates, the capacitance of the first capacitor 11 is larger than 0.1 times the capacitance of the first resonator capacitor 41, for example. The capacitance of the second capacitor 12 is larger than 0.1 times the capacitance of the second resonator capacitor 42, for example. Thereby, the frequency of the coupler 10 can be easily lowered.

[0121] In one example to which the embodiment relates, the capacitance of the third capacitor 13 is larger than 0.1 times the capacitance of the first resonator capacitor 41, for example. The capacitance of the fourth capacitor 14 is larger than 0.1 times the capacitance of the second resonator capacitor 42, for example. Thereby, the frequency of the coupler 10 can be easily lowered.

[0122] Figure 10 is a schematic view illustrating a coupler and a computing device to which the first embodiment relates.

[0123] like Figure 11 As shown, in the computer 111 according to the embodiment, the coupler 10 includes a fifth capacitor 15. The other configurations in the computer 111 may be the same as those in the computer 110.

[0124] The fifth capacitor 15 includes a fifth capacitor end 15e and a fifth capacitor other end 15f. The fifth capacitor end 15e is electrically connected to the first capacitor end 11e. The fifth capacitor end 15e is also electrically connected to the first Josephson junction end 31e, the first inductor end 21e, and the third capacitor other end 13f. The fifth capacitor other end 15f is electrically connected to the second capacitor end 12e. The fifth capacitor other end 15f is also electrically connected to the first Josephson junction other end 31f, the second inductor end 22e, and the fourth capacitor other end 14f. The fifth capacitor 15 facilitates adjustments to coupling characteristics, for example. For example, the position of the zero point of ZZ coupling can be adjusted. For example, the fifth capacitor 15 can improve the robustness of couplers and computers against magnetic flux fluctuations.

[0125] For example, the capacitance of the fifth capacitor 15 is smaller than that of the first capacitor 11 and smaller than that of the second capacitor 12. The fifth capacitor 15 is provided as needed and can also be omitted.

[0126] The first nonlinear resonator Josephson junction 51 and the second nonlinear resonator Josephson junction 52 may also include parasitic capacitance. The parasitic capacitance is smaller than the capacitance of the first capacitor 11 to the fifth capacitor 15 (e.g., about 1 fF) and can be ignored.

[0127] Figure 11 (a) and Figure 12 (b) is a graph illustrating the coupling strength between the coupler and the computer according to the first embodiment.

[0128] These figures correspond to the computer 111 involved in the implementation. In this example, the capacitance of the fifth capacitor 15 in the computer 111 is 1.6 fF. Figure 12 (a) and Figure 12 The horizontal axis of (b) is the magnetic flux MF1 of the space SP (ring 10r). Figure 12 The vertical axis of (a) is the coupling strength CS1. Figure 12 The vertical axis of (b) is the coupling strength CS2, which is related to the residual coupling.

[0129] like Figure 12 As shown in (a), a high coupling strength CS1 can be obtained in computer 111. There exists a magnetic flux MF1 where the coupling strength CS1 is essentially zero. The first magnetic flux value Mv1 is, for example, 0.62.Figure 12 The coupling strength CS1 can be substantially zero as shown in (b) of FIG. 9. By providing the fifth capacitor 15, it is possible to robustly make ZZ zero. It becomes easier to substantially maintain ZZ zero.

[0130] Figure 12 (a) of FIG. 10 and Figure 13 (b) of FIG. 10 are schematic diagrams illustrating the coupler and the computing device involved in the first embodiment.

[0131] As shown in Figure 13 (a) of FIG. 11 and Figure 13 (b) of FIG. 11, in the couplers 112 and 113, a plurality of first Josephson junctions 31 is provided. The plurality of first Josephson junctions 31 is connected in series. One end of the plurality of first Josephson junctions 31 corresponds to the first Josephson junction end 31e. The other end of the plurality of first Josephson junctions 31 corresponds to the first Josephson junction other end 31f.

[0132] (Second Embodiment)

[0133] Figure 13 (a) to Figure 14 (h) of FIG. 14 are schematic diagrams illustrating a part of the coupler involved in the second embodiment.

[0134] As shown in Figure 14 (a) of FIG. 15, the first inductor 21 can also include a first inductor Josephson junction (Josephson junction J1 or the like). As shown in Figure 14 (b) and Figure 14 (c) of FIG. 15, the first inductor 21 can also include a plurality of first inductor Josephson junctions (Josephson junctions J1 to J3 or the like). As shown in Figure 14 (d) of FIG. 15, the plurality of first inductor Josephson junctions can include Josephson junctions J1 to Josephson junctions Jn (n is an integer of two or more). The plurality of first inductor Josephson junctions are electrically connected in series to each other.

[0135] As shown in Figure 14 (e) of FIG. 16, the second inductor 22 can also include a second inductor Josephson junction (Josephson junction K1 or the like). As shown in Figure 14 (f) and Figure 14 (g) of FIG. 16, the second inductor 22 can also include a plurality of second inductor Josephson junctions (Josephson junctions K1 to K3 or the like). As shown in Figure 14 (h) of FIG. 16, the plurality of second inductor Josephson junctions can include Josephson junctions K1 to Josephson junctions Kn (n is an integer of two or more). The plurality of second inductor Josephson junctions are electrically connected in series to each other.

[0136] Figure 14 (a) of FIG. 17 and Figure 15(b) is a schematic cross-sectional view illustrating a portion of the coupler according to the second embodiment.

[0137] like Figure 15 As shown in (a), the first inductor 21 includes a plurality of first inductor Josephson junctions (Josephson junctions J1 to J3, etc.). The plurality of first inductor Josephson junctions are disposed on the first surface 10f of the substrate 10s. The plurality of first inductor Josephson junctions (Josephson junctions J1 to J3, etc.) include a conductive film 38a, a conductive film 38b, and an insulating film 38i. The insulating film 38i is disposed between the conductive film 38a and the conductive film 38b.

[0138] like Figure 15 As shown in (b), the second inductor 22 includes a plurality of second inductor Josephson junctions (Josephson junctions K1 to K3, etc.). The plurality of second inductor Josephson junctions are disposed on the first surface 10f of the substrate 10s. The plurality of second inductor Josephson junctions (Josephson junctions K1 to K3, etc.) include a conductive film 39a, a conductive film 39b, and an insulating film 39i. The insulating film 39i is disposed between the conductive film 39a and the conductive film 39b.

[0139] Conductive films 38a, 38b, 39a, and 39b may also include the material contained in conductive film 35a. Insulating films 38i and 39i may also include the material contained in insulating film 35i.

[0140] Figure 15 (a)~ Figure 16 (f) is a schematic diagram illustrating a portion of the coupler involved in the second embodiment.

[0141] Figure 16 (a) and Figure 16 (b) is the top view. Figure 16 (c) is Figure 16 (a) A1-A2 profile. Figure 16 (e) is Figure 16 (a) Sectional view along lines A3-A4. Figure 16 (d) is Figure 16 (b) Sectional view of line B1-B2. Figure 16 (f) is Figure 16 (b) Sectional view of line B3-B4.

[0142] like Figure 16 As shown in (c), the first capacitor 11 may also include two conductors extending along the Z-axis in the substrate 10s. Figure 16As shown in (d) of FIG. 1, the second capacitor 12 can also include two conductors extending in the Z-axis direction in the base 10s. These capacitors have, for example, a longitudinal configuration (or a substrate-through configuration). These capacitors can include, for example, TSVs (through-silicon vias). The planar size of the capacitors can be reduced.

[0143] As shown in (a) of FIG. 1, the first inductor 21 includes a Josephson junction J1. In this example, the stacking direction of the conductive film 38a, the insulating film 38i, and the conductive film 38b crosses the first face 10f in the Josephson junction J1. The junction portion can be reduced. Figure 16

[0144] As shown in (b) of FIG. 1, the second inductor 22 includes a Josephson junction K1. In this example, the stacking direction of the conductive film 39a, the insulating film 39i, and the conductive film 39b crosses the first face 10f in the Josephson junction K1. The junction portion can be reduced. Figure 16

[0145] Figure 16 (a) and (b) of FIG. 2 are schematic plan views illustrating a portion of the coupler according to the second embodiment. Figure 17 As shown in (a) of FIG. 2, the first inductor 21 includes a Josephson junction J1 and a Josephson junction J2. As shown in (b) of FIG. 2, the second inductor 22 includes a Josephson junction K1 and a Josephson junction K2. In these Josephson junctions, the stacking direction also crosses the first face 10f.

[0146] Figure 17 Figure 17 (a) and (b) of FIG. 3 are schematic plan views illustrating a portion of the coupler according to the second embodiment.

[0147] Figure 17 As shown in (a) of FIG. 3, the first inductor 21 includes a plurality of Josephson junctions (Josephson junctions J1 to Josephson junctions Jn). As shown in (b) of FIG. 3, the second inductor 22 includes a plurality of Josephson junctions (Josephson junctions K1 to Josephson junctions Kn). In these Josephson junctions, the stacking direction also crosses the first face 10f. Figure 18

[0148] Figure 18 Figure 18

[0149] Figure 18 is a schematic plan view illustrating the coupler and the computer according to the second embodiment.

[0150] As shown in (a) of FIG. 4, the first inductor 21 includes a Josephson junction J1. In this example, the stacking direction of the conductive film 38a, the insulating film 38i, and the conductive film 38b crosses the first face 10f in the Josephson junction J1. The junction portion can be reduced. Figure 19 ​​​​​​​​As shown, in the computer 120 according to the embodiment, a first conductive member 61 is provided as a first magnetic field applying unit 60. At least a portion of the first conductive member 61 is along the X-Y plane. A magnetic flux control current 61i is supplied to the first conductive member 61 from the control unit 70. The first resonator capacitor 41 (and the first nonlinear resonator Josephson junction 51) can be coupled to other couplers 10A. The second resonator capacitor 42 (and the second nonlinear resonator Josephson junction 52) can be coupled to other couplers 10B.

[0151] Figure 19 This is a schematic top view illustrating the coupler and computer involved in the second embodiment.

[0152] like Figure 20 As shown, in the computer 121 according to the embodiment, portions of the third capacitor 13 and the first resonator capacitor 41 are inclined relative to the direction from the other end 11f of the first capacitor toward the end 11e of the first capacitor (in this example, the Y-axis direction). Portions of the fourth capacitor 14 and the second resonator capacitor 42 are inclined relative to the direction from the other end 12f of the second capacitor toward the end 12e of the second capacitor (in this example, the Y-axis direction). The first resonator capacitor 41 (and the first nonlinear resonator Josephson junction 51) can be coupled to other couplers 10A, 10C, and 10F. The second resonator capacitor 42 (and the second nonlinear resonator Josephson junction 52) can be coupled to other couplers 10B, 10E, and 10F.

[0153] Figure 20 This is a schematic top view illustrating the coupler and computer involved in the second embodiment.

[0154] like Figure 21 As shown, in the computer 122 according to the embodiment, the first resonator capacitor 41 (and the first nonlinear resonator Josephson junction 51) can be coupled to other couplers 10A and 10C. The second resonator capacitor 42 (and the second nonlinear resonator Josephson junction 52) can be coupled to other couplers 10B and 10D.

[0155] Figure 21 This is a schematic top view illustrating the coupler and computer involved in the second embodiment.

[0156] like Figure 22As shown, the computer 123 involved in the embodiment may include a first excitation conductor 65a and a second excitation conductor 65b. The control unit 70 can excite the first nonlinear resonator 50A via the first excitation conductor 65a. The control unit 70 can excite the second nonlinear resonator 50B via the second excitation conductor 65b. Signals containing AC components are supplied to the first excitation conductor 65a and the second excitation conductor 65b, for example.

[0157] like Figure 22 As shown, the computer 123 may include a first readout resonator 66a and a second readout resonator 66b. The control unit 70 can detect the state of the first nonlinear resonator 50A via the first readout resonator 66a. The control unit 70 can detect the state of the second nonlinear resonator 50B via the second readout resonator 66b. For example, the resonant frequency fb1 of the first nonlinear resonator 50A can be identified by measuring the reflection spectrum via the first excitation conductor 65a or the first readout resonator 66a. For example, the resonant frequency fb2 of the second nonlinear resonator 50B can be identified by measuring the reflection spectrum via the second excitation conductor 65b or the second readout resonator 66b.

[0158] Figure 22 (a) and Figure 23 (b) is a schematic diagram illustrating the coupler and computer according to the second embodiment.

[0159] Figure 23 (a) is the top view. Figure 23 (b) is a stereoscopic view obtained by magnifying a portion of the coupler and computer.

[0160] like Figure 23 (a) and Figure 23 As shown in (b), in the computer 130, a first conductive member 61 is provided as a first magnetic field application unit 60. For example, the direction from the coupler 10 to at least a portion of the first conductive member 61 is along the Z-axis direction (the direction intersecting the first surface 10f). The first conductive member 61 is, for example, a coaxial line. In the portion of the first conductive member 61 close to the coupler 10, the flux control current 61i includes a component in the direction intersecting the Z-axis direction (along the X-Y plane).

[0161] Figure 23 This is a schematic top view illustrating the coupler and computer involved in the second embodiment.

[0162] like Figure 24 As shown, in computer 131, the first resonator capacitor 41 has a vertical configuration (see reference). Figure 24 (c) and Figure 16of (d)). The vertical type configuration includes two conductors extending in the Z-axis direction in the base 10s.

[0163] Figure 16 of (a) and Figure 25 of (b) is a schematic plan view illustrating the coupler and the computer involved in the second embodiment.

[0164] Figure 25 of (a) illustrates the conductive pattern 81 provided on the first face 10f of the base 10s. Figure 25 of (b) illustrates the conductive pattern 82 provided on the second face 10g of the base 10s. The second face 10g is the face opposite to the first face 10f. As Figure 25 of (a) and Figure 25 Figure 25 In the computer 132, a part of the conductive pattern 81 is electrically connected to the conductive pattern 82 through the conductive member 83 in the Z-axis direction in the base 10s as shown in (b) of FIG. 8. For example, the electrical connection to the outside can be made via the conductive pattern 82. The conductive member 83 is, for example, a substrate-through-type connection member. In the embodiment, a part of the conductive member (a ground GND of a fixed potential or a circuit element) can be placed in one of the first face 10f and the second face 10g of the base 10s, and another part of the conductive member can be provided in the other of the first face 10f and the second face 10g, and the one part and the other part can be connected through the substrate-through-type connection member. In the embodiment, the connection based on capacitive coupling can be made in a flip-chip configuration or the like.

[0165] In addition to the above description regarding the second embodiment, the configuration described regarding the first embodiment can be applied within a technically feasible range.

[0166] Hereinafter, the characteristics of the coupler 10 and the computer 110 involved in the embodiment will be described.

[0167] The Lagrangian operator of the system including the coupler 10, the first nonlinear resonator 50A coupled to the coupler 10, and the second nonlinear resonator 50B coupled to the coupler 10 is represented by the following first equation.

[0168]

[0169] The left side of the first equation is the Lagrangian operator of the system including the coupler 10, the first nonlinear resonator 50A coupled to the coupler 10, and the second nonlinear resonator 50B coupled to the coupler 10.

[0170] The first term on the right side of the first equation is the Lagrangian operator of the first nonlinear resonator 50A. The second term on the right side of the first equation is the Lagrangian operator of the second nonlinear resonator 50B. The third term on the right side of the first equation is the Lagrangian operator of the coupler 10. The fourth term on the right side of the first equation is the Lagrangian operator representing the interaction of the coupler 10, the first nonlinear resonator 50A, and the second nonlinear resonator 50B.

[0171] The Lagrangian operator of the first nonlinear resonator 50A is represented by the following second equation. In the second equation, "C1" is the capacitance of the first resonator capacitor 41.

[0172]

[0173] The Lagrangian operator of the second nonlinear resonator 50B is represented by the following third equation. In the third equation, "C2" is the capacitance of the second resonator capacitor 42.

[0174]

[0175] The Lagrangian operator representing the interaction of the coupler 10, the first nonlinear resonator 50A, and the second nonlinear resonator 50B is represented by the following fourth equation. In the fourth equation, "C c " is the capacitance of each of the third capacitor 13 and the fourth capacitor 14.

[0176]

[0177] The Lagrangian operator of the coupler 10 is represented by the following fifth equation. In the fifth equation, "C" is the capacitance of each of the first capacitor 11 and the second capacitor 12.

[0178]

[0179] Here, φ is a magnetic flux operator. φ has a relationship with the phase difference θ represented by the following sixth equation.

[0180] φ = φ0θ... (6)

[0181] Magnetic flux operator φ with respect to the "+ mode" of the coupler 10 c+ is represented by the following seventh equation.

[0182] φ u+ ≡ φ c1 + φ c2 ... (7)

[0183] Magnetic flux operator φ with respect to the "- mode" of the coupler 10 c－ is represented by the following eighth equation.

[0184] φ c-≡ φ c1 - φ c2 …(8)

[0185] In the 7th equation and the 8th equation, φ c1 is a magnetic flux operator for the 1st part 10a. In the 8th equation and the 9th equation, φ c2 is a magnetic flux operator for the 2nd part 10b.

[0186] In the right side of the above 4th equation, in the 1st term and the 2nd term, the signs are exchanged. The coupling between the qubits via the ± mode is eliminated.

[0187] In the above 5th equation, the 1st term and the 2nd term on the right side correspond to the “+ mode”. In the 5th equation, the 3rd term to the 6th term on the right side correspond to the “- mode”. The “+ mode” corresponds to the LC resonator. The “- mode” corresponds to the fluxonium qubit. By the presence of the fluxonium qubit, the frequency becomes variable.

[0188] Thus, in the embodiment, both the “+ mode” and the “- mode” are present in the coupler 10. By utilizing the “- mode”, a variable frequency can be obtained.

[0189] In the above, for simplicity, the case where the capacitances of the 1st capacitor 11 and the 2nd capacitor 12 are respectively identical (C) to each other is explained. For simplicity, the case where the capacitances of the 3rd capacitor 13 and the 4th capacitor 14 are respectively identical (Cc) to each other is explained. In the embodiment, the capacitance of the 1st capacitor 11 can be different from the capacitance of the 2nd capacitor 12. In the embodiment, the capacitance of the 3rd capacitor 13 can be different from the capacitance of the 4th capacitor 14.

[0190] The embodiment can include the following configurations (for example, technical solutions).

[0191] (Configuration 1)

[0192] A coupler includes:

[0193] a 1st capacitor including a 1st capacitor end and a 1st capacitor other end;

[0194] a 1st inductor including a 1st inductor end and a 1st inductor other end, the 1st inductor end being electrically connected to the 1st capacitor end;

[0195] a 2nd capacitor including a 2nd capacitor end and a 2nd capacitor other end;

[0196] a second inductor including a second inductor end and a second inductor other end, the second inductor end being electrically connected with the second capacitor end, the second inductor other end being electrically connected with the first capacitor other end, the second inductor other end, and the second capacitor other end;

[0197] a first Josephson junction including a first Josephson junction end and a first Josephson junction other end, the first Josephson junction end being electrically connected with the first capacitor end, the first Josephson junction other end being electrically connected with the second capacitor end, a space being provided which is surrounded by the first inductor, the second inductor, and the first Josephson junction;

[0198] a third capacitor including a third capacitor end and a third capacitor other end, the third capacitor other end being electrically connected with the first capacitor end, the third capacitor end being electrically connectable with a first nonlinear resonator; and

[0199] a fourth capacitor including a fourth capacitor end and a fourth capacitor other end, the fourth capacitor other end being electrically connected with the second capacitor end, the fourth capacitor end being electrically connectable with a second nonlinear resonator.

[0200] (Configuration 2)

[0201] the coupler according to Configuration 1,

[0202] the first inductor includes a first conductive layer having a meander configuration,

[0203] the second inductor includes a second conductive layer having a meander configuration.

[0204] (Configuration 3)

[0205] the coupler according to Configuration 1,

[0206] the first inductor includes a first inductor Josephson junction,

[0207] the second inductor includes a second inductor Josephson junction.

[0208] (Configuration 4)

[0209] the coupler according to Configuration 1,

[0210] the first inductor includes a plurality of first inductor Josephson junctions which are electrically connected in series with each other,

[0211] the second inductor includes a plurality of second inductor Josephson junctions which are electrically connected in series with each other.

[0212] (Constitution 5)

[0213] The coupler according to any one of Constitutions 1 to 4,

[0214] Further provided is a fifth capacitor including a fifth capacitor end and a fifth capacitor other end,

[0215] The fifth capacitor end is electrically connected to the first capacitor end,

[0216] The fifth capacitor other end is electrically connected to the second capacitor end.

[0217] (Constitution 6)

[0218] The coupler according to Constitution 5,

[0219] The capacitance of the fifth capacitor is smaller than the capacitance of the first capacitor and smaller than the capacitance of the second capacitor.

[0220] (Constitution 7)

[0221] The coupler according to any one of Constitutions 1 to 5,

[0222] The capacitance of each of the first capacitor and the second capacitor is larger than 0.1 times the capacitance of each of the third capacitor and the fourth capacitor.

[0223] (Constitution 8)

[0224] The coupler according to any one of Constitutions 1 to 7,

[0225] Further provided is a first conductive member capable of applying a magnetic field to the space,

[0226] The strength of coupling between the first nonlinear resonator and the second nonlinear resonator varies according to the magnetic flux in the space.

[0227] (Constitution 9)

[0228] The coupler according to any one of Constitutions 1 to 8,

[0229] The coupler is capable of resonating in a plurality of modes,

[0230] The resonant frequency in each of the plurality of modes is higher than the resonant frequency of the first nonlinear resonator, higher than the resonant frequency of the second nonlinear resonator, and lower than the sum of the resonant frequency of the first nonlinear resonator and the resonant frequency of the second nonlinear resonator.

[0231] (Constitution 10)

[0232] A computer comprising:

[0233] The coupler according to any one of Embodiments 1 to 7;

[0234] The first nonlinear resonator; and

[0235] The second nonlinear resonator.

[0236] (Embodiment 11)

[0237] The computer according to Embodiment 10,

[0238] The first nonlinear resonator includes:

[0239] a first nonlinear resonator Josephson junction; and

[0240] a first resonator capacitor,

[0241] an end portion of the first nonlinear resonator Josephson junction and an end portion of the first resonator capacitor are electrically connected to an end portion of the third capacitor,

[0242] the other end portion of the first nonlinear resonator Josephson junction and the other end portion of the first resonator capacitor are electrically connected to the other end portion of the first capacitor,

[0243] The second nonlinear resonator includes:

[0244] a second nonlinear resonator Josephson junction; and

[0245] a second resonator capacitor,

[0246] an end portion of the second nonlinear resonator Josephson junction and an end portion of the second resonator capacitor are electrically connected to an end portion of the fourth capacitor,

[0247] the other end portion of the second nonlinear resonator Josephson junction and the other end portion of the second resonator capacitor are electrically connected to the other end portion of the second capacitor.

[0248] (Embodiment 12)

[0249] The computer according to Embodiment 11,

[0250] a capacitance of the first capacitor is larger than 0.1 times a capacitance of the first resonator capacitor,

[0251] a capacitance of the second capacitor is larger than 0.1 times a capacitance of the second resonator capacitor.

[0252] (Embodiment 13)

[0253] The computer according to Embodiment 12,

[0254] the capacitance of the third capacitor is larger than 0.1 times the capacitance of the first resonator capacitor,

[0255] the capacitance of the fourth capacitor is larger than 0.1 times the capacitance of the second resonator capacitor.

[0256] (Configuration 14)

[0257] The computer according to any one of Configurations 10 to 13,

[0258] Further provided is a control section,

[0259] The coupler further includes a first magnetic field application section capable of applying a magnetic field to the space,

[0260] The control section controls the first magnetic field application section, and is capable of changing the magnetic flux in the space.

[0261] (Configuration 15)

[0262] The computer according to Configuration 14,

[0263] The first magnetic field application section includes a first conductive member,

[0264] The control section changes the magnetic flux by modulating a current supplied to the first conductive member.

[0265] (Configuration 16)

[0266] The computer according to Configuration 14 or 15,

[0267] A two-qubit gate operation on the first nonlinear resonator and the second nonlinear resonator is performed by the change in the magnetic flux.

[0268] (Configuration 17)

[0269] The computer according to Configuration 14 or 15,

[0270] The control section controls the magnetic flux in the space, and is capable of changing the coupling strength between the first nonlinear resonator and the second nonlinear resonator.

[0271] (Configuration 18)

[0272] The computer according to Configuration 14 or 15,

[0273] The control section controls the magnetic flux in the space, and is capable of substantially eliminating the coupling between the first nonlinear resonator and the second nonlinear resonator.

[0274] (Configuration 19)

[0275] The computer according to any one of the configurations 10 to 18,

[0276] The coupler is capable of resonating in a plurality of modes,

[0277] The resonant frequency in each of the plurality of modes is twice or less the resonant frequency of the first nonlinear resonator and twice or less the resonant frequency of the second nonlinear resonator.

[0278] (Configuration 20)

[0279] The computer according to any one of the configurations 10 to 18,

[0280] The coupler is capable of resonating in a plurality of modes,

[0281] The resonant frequency in each of the plurality of modes is higher than the resonant frequency of the first nonlinear resonator, higher than the resonant frequency of the second nonlinear resonator, and lower than the sum of the resonant frequency of the first nonlinear resonator and the resonant frequency of the second nonlinear resonator.

[0282] According to the embodiments, it is possible to provide a coupler and a computing device that can improve controllability.

[0283] The above describes embodiments of the present application with reference to examples. However, the present application is not limited to these examples. For example, as to the specific configurations of each element of the nonlinear resonator, the inductor, the capacitor, and the conductive member, etc. included in the coupler or the computing device, as long as the present application can be implemented and the same effects can be obtained by appropriately selecting from the known range by those skilled in the art, it is included in the scope of the present application.

[0284] As long as the gist of the present application is included, a technical solution obtained by combining two or more elements of each example within the technically feasible range also belongs to the scope of the present application.

[0285] As long as the gist of the present application is included, all couplers and computing devices that can be appropriately designed and implemented by those skilled in the art according to the coupler and the computing device described above as embodiments of the present application also belong to the scope of the present application.

[0286] In the scope of the idea of the present application, various modification examples and correction examples that can be thought of by those skilled in the art are also considered to belong to the scope of the present application.

[0287] The above describes several embodiments of the present application, but these embodiments are presented as examples and are not intended to limit the scope of the application. These new embodiments can be implemented in other various ways and various omissions, substitutions, and changes can be made without departing from the scope of the application. These embodiments and variations thereof are included in the scope, spirit of the application, and are included in the scope of the application as recited in the claims and equivalents thereof.

Claims

1. A coupler comprising: a first capacitor including a first capacitor end and a first capacitor other end; a first inductor including a first inductor end and a first inductor other end, the first inductor end being electrically connected to the first capacitor end; a second capacitor including a second capacitor end and a second capacitor other end; a second inductor including a second inductor end and a second inductor other end, the second inductor end being electrically connected to the second capacitor end, the second inductor other end being electrically connected to the first capacitor other end, the first inductor other end, and the second capacitor other end; a first Josephson junction including a first Josephson junction end and a first Josephson junction other end, the first Josephson junction end being electrically connected to the first capacitor end, the first Josephson junction other end being electrically connected to the second capacitor end, a space being provided surrounded by the first inductor, the second inductor, and the first Josephson junction; a third capacitor including a third capacitor end and a third capacitor other end, the third capacitor other end being electrically connected to the first capacitor end, the third capacitor end being capable of being electrically connected to a first nonlinear resonator; and a fourth capacitor including a fourth capacitor end and a fourth capacitor other end, the fourth capacitor other end being electrically connected to the second capacitor end, the fourth capacitor end being capable of being electrically connected to a second nonlinear resonator, the coupler being capable of resonating in a plurality of modes, a resonant frequency in each of the plurality of modes being higher than a resonant frequency of the first nonlinear resonator, higher than a resonant frequency of the second nonlinear resonator, and lower than a sum of the resonant frequency of the first nonlinear resonator and the resonant frequency of the second nonlinear resonator.

2. The coupler according to claim 1, the first inductor including a first conductive layer having a meander configuration, the second inductor including a second conductive layer having a meander configuration.

3. The coupler according to claim 1, the first inductor including a first inductor Josephson junction, the second inductor including a second inductor Josephson junction.

4. The coupler according to claim 1, the first inductor including a plurality of first inductor Josephson junctions, the plurality of first inductor Josephson junctions being electrically connected in series to each other, the second inductor including a plurality of second inductor Josephson junctions, the plurality of second inductor Josephson junctions being electrically connected in series to each other.

5. The coupler according to claim 1, further comprising a first conductive member capable of applying a magnetic field to the space, a strength of coupling between the first nonlinear resonator and the second nonlinear resonator varying in accordance with a magnetic flux in the space.

6. The coupler according to claim 1, a magnetic flux in the space being controlled, a coupling between the first nonlinear resonator and the second nonlinear resonator being capable of being substantially eliminated. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ In a state where the coupling is substantially eliminated, the resonance frequency in each of the plurality of modes is higher than the resonance frequency of the first nonlinear resonator, higher than the resonance frequency of the second nonlinear resonator, and lower than the sum of the resonance frequency of the first nonlinear resonator and the resonance frequency of the second nonlinear resonator.

7. A computer comprising: the coupler according to claim 1; the first nonlinear resonator; and the second nonlinear resonator.

8. The computer according to claim 7, the first nonlinear resonator includes: a first nonlinear resonator Josephson junction; and a first resonator capacitor, an end portion of the first nonlinear resonator Josephson junction and an end portion of the first resonator capacitor are electrically connected to the third capacitor end portion, the other end portion of the first nonlinear resonator Josephson junction and the other end portion of the first resonator capacitor are electrically connected to the first capacitor other end portion, the second nonlinear resonator includes: a second nonlinear resonator Josephson junction; and a second resonator capacitor, an end portion of the second nonlinear resonator Josephson junction and an end portion of the second resonator capacitor are electrically connected to the fourth capacitor end portion, the other end portion of the second nonlinear resonator Josephson junction and the other end portion of the second resonator capacitor are electrically connected to the second capacitor other end portion.

9. The computer according to claim 7, further comprising a control section, the coupler includes a first conductive member capable of applying a magnetic field to the space, the strength of coupling between the first nonlinear resonator and the second nonlinear resonator varies in accordance with the magnetic flux in the space.

10. The computer according to claim 9, the control section controls the magnetic flux in the space, capable of substantially eliminating the coupling between the first nonlinear resonator and the second nonlinear resonator, in a state where the coupling is substantially eliminated, the resonance frequency in each of the plurality of modes is higher than the resonance frequency of the first nonlinear resonator, higher than the resonance frequency of the second nonlinear resonator, and lower than the sum of the resonance frequency of the first nonlinear resonator and the resonance frequency of the second nonlinear resonator.

Images