Coupler and computing device

Abstract

To provide a coupler and a calculator that can improve controllability.SOLUTION: A coupler according to an embodiment includes first through fourth capacitors, first and second inductors, 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 other end of the second inductor is electrically connected to the other end of the first capacitor, the other end of the second inductor, and the other end of the second capacitor. The first Josephson junction is electrically connected to the first and second capacitors. A space is provided which is surrounded by the first inductor, the second inductor and the first Josephson junction. The third capacitor is electrically connectable with a first nonlinear resonator. The fourth capacitor is electrically connectable with a second nonlinear resonator.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION Embodiments of the present invention relate to a coupler and a computing device. [Background technology]

[0002] For example, couplers are used in computing devices that utilize multiple nonlinear resonators, and improved controllability is desired in computing devices. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2019 / 0214971 Summary of the Invention [Problem to be solved by the invention]

[0004] Embodiments of the present invention provide a coupler and a computing device that allow for improved control. [Means for solving the problem]

[0005] According to an embodiment of the present invention, the 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 is provided surrounded by the first inductor, the second inductor, and the first Josephson junction. 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 can be electrically connected 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 can be electrically connected to a second nonlinear resonator. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram illustrating a coupler and a computing device according to the first embodiment. [Figure 2] 2(a) to 2(c) are schematic cross-sectional views illustrating a part of the coupler and the computing device according to the first embodiment. [Figure 3]3A and 3B are schematic plan views illustrating a part of the coupler according to the first embodiment. [Figure 4] 4(a) and 4(b) are graphs illustrating the frequency at the coupler and the computer. [Figure 5] 5(a) and 5(b) are graphs illustrating the coupling strength in the coupler and the computer. [Figure 6] 6(a) and 6(b) are graphs illustrating the characteristics of the coupler and the computer. [Figure 7] 7(a) and 7(b) are graphs illustrating the coupling strength in the coupler and the computer of the second reference example. [Figure 8] 8(a) and 8(b) are graphs illustrating the coupling strength in the coupler and the computer of the third reference example. [Figure 9] FIG. 9 is a graph illustrating probabilities in the coupler and computer according to the first embodiment. [Figure 10] 10(a) and 10(b) are graphs illustrating the resonant frequencies of the coupler and the computer according to the first embodiment. [Figure 11] FIG. 11 is a schematic diagram illustrating the coupler and the calculation device according to the first embodiment. [Figure 12] 12(a) and 12(b) are graphs illustrating the coupling strength in the coupler and the computer according to the first embodiment. [Figure 13] 13(a) and 13(b) are schematic diagrams illustrating the coupler and the calculation device according to the first embodiment. [Figure 14] 14(a) to 14(h) are schematic views illustrating a part of the coupler according to the second embodiment. [Figure 15] 15A and 15B are schematic cross-sectional views illustrating a part of the coupler according to the second embodiment. [Figure 16]Figures 16(a) and 16(b) are schematic plan views illustrating a portion of an example coupler according to the second embodiment, and Figures 16(c) to 16(f) are schematic cross-sectional views illustrating a portion of an example coupler according to the second embodiment. [Figure 17] 17(a) and 17(b) are schematic plan views illustrating a part of another example coupler according to the second embodiment. [Figure 18] 18(a) and 18(b) are schematic plan views illustrating a part of yet another example of a coupler according to the second embodiment. [Figure 19] FIG. 19 is a schematic plan view illustrating yet another example of a coupler and a computer according to the second embodiment. [Figure 20] FIG. 20 is a schematic plan view illustrating yet another example of a coupler and a computer according to the second embodiment. [Figure 21] FIG. 21 is a schematic plan view illustrating yet another example of a coupler and a computer according to the second embodiment. [Figure 22] FIG. 22 is a schematic plan view illustrating yet another example of a coupler and a computer according to the second embodiment. [Figure 23] FIG. 23(a) is a schematic plan view illustrating a coupler and a computer according to the second embodiment, and FIG. 23(b) is a schematic perspective view illustrating a part of the coupler and a computer according to the second embodiment. [Figure 24] FIG. 24 is a schematic plan view illustrating the coupler and the computer according to the second embodiment. [Figure 25] 25(a) and 25(b) are schematic plan views illustrating the coupler and the computer according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as those in reality. Even when the same part is shown, the dimensions and ratios may be different depending on the drawing. In this specification and in each drawing, elements similar to those previously described with reference to the previous drawings are designated by the same reference numerals, and detailed descriptions thereof will be omitted where appropriate.

[0008] (First embodiment) FIG. 1 is a schematic diagram illustrating a coupler and a computing device according to the first embodiment. As shown in FIG. 1, a computer 110 according to the embodiment (computing device) The optical fiber 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.

[0009] 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 .

[0010] 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.

[0011] The second capacitor 12 includes a second capacitor end portion 12e and a second capacitor other end portion 12f. The second inductor 22 includes a second inductor end portion 22e and a second inductor other end portion 22f. The second inductor end portion 22e is electrically connected to the second capacitor end portion 12e. The second inductor other end portion 22f is electrically connected to the first capacitor other end portion 11f, the first inductor other end portion 21f, and the second capacitor other end portion 12f. The potentials of the first capacitor other end portion 11f, the first inductor other end portion 21f, the second capacitor other end portion 12f, and the second inductor other end portion 22f are set to, for example, a fixed potential (for example, ground GND).

[0012] 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.

[0013] A space SP is provided that is surrounded by the first inductor 21, the second inductor 22, and the first Josephson junction 31. The space SP may be surrounded by the first capacitor 11, the second capacitor 12, and the first Josephson junction 31. For example, a loop 10r is formed by the first inductor 21, the second inductor 22, and the first Josephson junction 31. The loop 10r surrounds the space SP. As will be described later, the magnetic flux Φ within the space SP (in the loop 10r) is controllable.

[0014] 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.

[0015] 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.

[0016] In the coupler 10, the first portion 10a including the first capacitor 11 and the first inductor 21 corresponds to the first LC circuit. The second portion 10b including the second capacitor 12 and the second inductor 22 corresponds to the second LC circuit. These LC circuits are connected by a first Josephson junction 31. The magnetic flux Φ in the space SP surrounded by these can be modulated.

[0017] The coupler 10 has multiple modes (for example, two modes). In the embodiment, the LC circuit is provided in the coupler 10, so that the resonant frequencies of the multiple modes can be lowered compared to when only an inductor is provided. For example, it is easy to make the resonant frequencies of the multiple modes in the coupler 10 close to the resonant frequencies of the first nonlinear resonator 50A and the second nonlinear resonator 50B. This allows for strong coupling strength. According to the embodiment, controllability can be improved.

[0018] As will be described later, the coupling strength can be changed by controlling the magnetic flux Φ. For example, the coupling strength can be set to substantially zero to eliminate (turn off) the coupling. As will be described later, by controlling the coupler 10, two-qubit gate operations can be performed at high speed. A coupler and a computing device that can improve controllability can be provided.

[0019] As shown in FIG. 1 , 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 potentials of the other end 51f and the other end 41f are set to, for example, a fixed potential (e.g., ground GND). 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 may be electrically connected to the first capacitor other end 11f.

[0020] An end 51 e of the first nonlinear resonator Josephson junction 51 and an end 41 e of the first resonator capacitor 41 are capacitively coupled to the first portion 10 a via the third capacitor 13 .

[0021] 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 potentials of the other end 52f and the other end 42f are set to, for example, a fixed potential (e.g., ground GND). 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 may be electrically connected to the second capacitor other end 12f.

[0022] An end 52 e of the second nonlinear resonator Josephson junction 52 and an end 42 e of the second resonator capacitor 42 are capacitively coupled to the second portion 10 b via the fourth capacitor 14 .

[0023] The first nonlinear resonator 50A and the second nonlinear resonator 50B function as two quantum bits. The first nonlinear resonator 50A and the second nonlinear resonator 50B have a plurality of energy levels, of which the two lowest ones can be used as two states of the quantum bit. The two lowest energy levels correspond to the ground state and the first excited state. The two states of the quantum bit correspond to computational basis states. For example, the resonant frequency of the first nonlinear resonator 50A corresponds to the value obtained by converting the energy difference between the two lowest states of the first nonlinear resonator 50A into a frequency. For example, the resonant frequency of the second nonlinear resonator 50B corresponds to the value obtained by converting the energy difference between the two lowest states of the second nonlinear resonator 50B into a frequency. Energy can be converted into a frequency by dividing it by Planck's constant h.

[0024] As shown in FIG. 1, the coupler 10 may include a first conductive member 61. The first conductive member 61 is capable of applying a magnetic field to the space SP (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 (loop 10r). As will be described later, the coupling strength between the first nonlinear resonator 50A and the second nonlinear resonator 50B changes depending on the magnetic flux Φ (magnetic flux based on the magnetic field) in the space SP (loop 10r).

[0025] The first conductive member 61 is one example of the first magnetic field application unit 60. As shown in FIG. 1, the computer 110 may include a control unit 70. The coupler 10 (or the computer 110) may include the first magnetic field application unit 60. The first magnetic field application unit 60 is capable of applying a magnetic field to the space SP (loop 10r). The control unit 70 is capable of controlling the first magnetic field application unit 60 to change the magnetic flux Φ in the space SP (loop 10r). When the first magnetic field application unit 60 includes the first conductive member 61, the control unit 70 is capable of changing the magnetic flux Φ by modulating the current supplied to the first conductive member 61.

[0026] 2(a) to 2(c) are schematic cross-sectional views illustrating a part of the coupler and the computing device according to the first embodiment. 2(a), for example, the first Josephson junction 31 is provided on a first surface 10f of a base body 10s. A direction perpendicular to the first surface 10f is defined as the Z-axis direction. A direction perpendicular to the Z-axis direction is defined as the X-axis direction. A direction perpendicular to the Z-axis direction and the X-axis direction is defined as the Y-axis direction.

[0027] 2(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 provided between a part of the conductive film 35a and a part of the conductive film 35b.

[0028] 2(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 provided between a part of the conductive film 36a and a part of the conductive film 36b.

[0029] 2(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 provided between a part of the conductive film 37a and a part of the conductive film 37b. These conductive films are substantially aligned along the XY plane.

[0030] These conductive films include, for example, at least one selected from the group consisting of Al, Nb, NbN, TiN, NbTiN, and Ta. These materials are superconducting materials. The membrane For example, the substrate 10s includes at least one selected from the group consisting of Al2O3, Nb2O5, NbO2, NbO, and AlN. The substrate 10s includes at least one selected from the group consisting of Si and sapphire. The substrate 10s is, for example, insulating.

[0031] 3A and 3B are schematic plan views illustrating a part of the coupler according to the first embodiment. 3(a), in one example, the first capacitor 11 and the first inductor 21 are provided on the first surface 10f of the base body 10s. The first capacitor 11 is formed by two conductive layers 11L facing each other. The first inductor 21 includes a first conductive layer 21L having a meander structure.

[0032] 3(b), in one example, the second capacitor 12 and the second inductor 22 are provided on the first surface 10f of the base body 10s. The second capacitor 12 is formed by two conductive layers 12L facing each other. The second inductor 22 includes a second conductive layer 22L having a meander structure.

[0033] The conductive layer includes, for example, Al, Nb, NbN, TiN, NbTiN, and Ta.

[0034] In these examples, the first inductor 21 and the second inductor 22 are based on, for example, kinetic inductors. As will be described below, the first inductor 21 and the second inductor 22 may include Josephson junctions.

[0035] Below, an example of simulation results of the characteristics of the coupler 10 (and the computer 110) will be described. In the following simulation model, 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 member 61, the magnetic flux Φ in the space SP (loop 10r) can be changed.

[0036] The following describes the characteristics of the computer 110 according to the embodiment and the characteristics of the computer 119a of the first reference example. In the computer 110, the coupler 10 includes an LC circuit as described above. In the computer 119a of the first reference example, the coupler 10 does not include the first capacitor 11 or the second capacitor 12. That is, in the computer 119a, the first portion 10a includes the first inductor 21 but does not include the first capacitor 11. In the computer 119a, the second portion 10b includes the second inductor 22 but does not include the second capacitor 12. The remaining configuration of the computer 119a is the same as that of the computer 110.

[0037] 4(a) and 4(b) are graphs illustrating the frequency at the coupler and the computer. FIG. 4(a) corresponds to the computer 110 according to the embodiment. FIG. 4(b) corresponds to the computer 119a of the first reference example. The horizontal axis of these figures represents the magnetic flux MF1 in the space SP (loop 10r). The magnetic flux MF1 is normalized by the reduced magnetic flux quantum φ0 to make it dimensionless. The reduced magnetic flux quantum φ0 corresponds to 1 / (2π) times the magnetic flux quantum Φ0. "π" represents the circular constant. The vertical axis of these figures represents the frequency fo1. These figures 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 to, for example, the first quantum bit. The second nonlinear resonator 50B corresponds to, for example, the second quantum bit. As described above, the resonant frequency of a nonlinear resonator corresponds to a value obtained by converting the energy difference between the two lowest states of the nonlinear resonator into a frequency.

[0038] 4(a) and 4(b) illustrate frequencies fc1 and fc2. Frequency fc1 corresponds to one frequency of multiple modes (e.g., two modes) in coupler 10. Frequency fc2 corresponds to another frequency of multiple modes (e.g., two modes) in coupler 10.

[0039] As shown in FIG. 4(a), in the computer 110 according to the embodiment, when the magnetic flux MF1 changes, the frequencies fc1 and fc2 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 approach each other. In this example, at the 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 the frequencies fc1 and fc2 is 11 GHz or more and 19 GHz or less.

[0040] 4(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 is changed. In this example, the resonant frequency fb1 of the first nonlinear resonator 50A is approximately 10.0 G. Hz. The resonant frequency fb2 of the second nonlinear resonator 50B is approximately 8.4 GHz. An example of the degree of change in the resonant frequencies fb1 and fb2 when the magnetic flux MF1 changes will be described later.

[0041] Thus, in the embodiment, the frequencies fc1 and fc2 are relatively close to the resonant frequencies fb1 and fb2. The coupler 10 has a plurality of modes (at least two modes). That is, the coupler 10 can resonate in a plurality of modes. The resonant frequencies (frequencies fc1 and fc2) in each of the plurality of modes are higher than the resonant frequencies fb1 and fb2, respectively, and lower than the sum of the resonant frequencies fb1 and fb2, in the vicinity of the first magnetic flux value Mv1 (magnetic flux values ​​at which the frequencies fc1 and fc2 are close to each other). In the embodiment, there exists a state in which the resonant frequencies (frequencies fc1 and fc2) in each of the plurality of modes are lower than the sum of the resonant frequencies fb1 and fb2.

[0042] In the embodiment, the first portion 10a and the second portion 10b each include an inductor and a capacitor. This allows the resonant frequencies of the multiple modes of the coupler 10 to approach the resonant frequencies of the nonlinear resonator. This, for example, allows for a strong coupling strength to be obtained. A coupler and a computing device with improved controllability can be provided.

[0043] As shown in FIG. 4(b), in the computer 119a of the first reference example, the resonant frequencies (frequency fc1 and frequency fc2) in the multiple modes of the coupler 10 are significantly higher than the resonant frequencies (resonant frequencies fb1 and resonant frequencies fb2) of the two nonlinear resonators. As shown in FIG. 4(b), in the computer 119a, the frequencies fc1 and fc2 are higher than the sum of the resonant frequencies fb1 and fb2. This makes it difficult to obtain high coupling strength. In the first reference example, for example, the resonant frequencies in the multiple modes of the coupler 10 are three or more times the resonant frequencies of the nonlinear resonators.

[0044] In the embodiment, the capacitance of each of the first capacitor 11 and the second capacitor 12 is large enough to be non-negligible, for example, the capacitance of each of the first capacitor 11 and the second capacitor 12 is preferably larger than 0.1 times the capacitance of each of the third capacitor 13 and the fourth capacitor 14. This makes it possible to effectively lower the resonant frequencies (frequency fc1 and frequency fc2) in multiple modes, for example.

[0045] Furthermore, as shown in FIG. 4(a), in the 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 with respect to changes in the magnetic flux MF1. For example, the frequencies of the two quantum bits do not substantially change. The frequencies of the two quantum bits are substantially fixed and stable. A coupler and a computing device capable of improving controllability can be provided.

[0046] 5(a) and 5(b) are graphs illustrating the coupling strength in the coupler and the computer. Fig. 5(a) corresponds to the computer 110 according to the embodiment. Fig. 5(b) corresponds to the computer 119a of the first reference example. The horizontal axis in these figures represents the magnetic flux MF1 in the space SP (loop 10r). The vertical axis represents the coupling strength CS1.

[0047] As shown in Figure 5(a), when the magnetic flux MF1 changes, the coupling strength CS1 changes. By controlling the magnetic flux MF1, the coupling strength CS1 can be controlled. For example, the range of change in the coupling strength CS1 is about 20 MHz. In other words, the coupling strength CS1 can be adjusted in the range of -20 MHz to 20 MHz.

[0048] In this way, the control unit 70 can control the magnetic flux Φ (magnetic flux MF1) in the space SP to change the coupling strength CS1 between the first nonlinear resonator 50A and the second nonlinear resonator.

[0049] 5(a), in this example, when the magnetic flux MF1 is approximately 0.68, the coupling strength CS1 becomes substantially 0. In this way, the control unit 70 can control the magnetic flux Φ (magnetic flux MF1) in the space SP to substantially eliminate the coupling between the first nonlinear resonator 50A and the second nonlinear resonator 50B. In other words, the coupling can be turned off. A coupler and a computing device that can improve controllability can be provided.

[0050] As shown in FIG. 5(b), the computer 119a of the first reference example also has a condition under which the coupling strength CS1 is substantially zero. However, in the computer 119a, when the coupling strength CS1 is not zero, the magnetic flux MF1 is lower than that in the computer 110. Thus, in the first reference example in which no capacitors are 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.

[0051] 6(a) and 6(b) are graphs illustrating the characteristics of the coupler and the computer. FIG. 6(a) corresponds to the computer 110 according to the embodiment. FIG. 6(b) corresponds to the computer 110a of the first reference example. The horizontal axis of these figures is magnetic flux MF1. The vertical axis of these figures is coupling strength CS2 related to residual coupling (so-called ZZ coupling). ZZ coupling corresponds to a state in which fb1 + fb2 - fb3 does not become zero due to residual coupling for a frequency fb3 corresponding to when both of the two quantum bits are in the "1 state." This "deviation" in the ZZ coupling corresponds to coupling strength CS2.

[0052] As described with reference to Figure 4(a), when the magnetic flux Mf1 is about 0.68 (first magnetic flux value Mv1), the coupling strength Cs1 becomes substantially zero. As shown in Figure 6(a), when the magnetic flux Mf1 is about 0.68, the coupling strength Cs2 for the residual coupling can be substantially zero. For example, a robust zero ZZ coupling is obtained.

[0053] On the other hand, as shown in FIG. 6(b), in the computer 119a of the first reference example, the coupling strength CS2 related to the residual coupling cannot be reduced and does not become zero.

[0054] In the first reference example in which no capacitors are provided in the first portion 10a and the second portion 10b, if an attempt is made to reduce the coupling strength CS2 related to the residual coupling, it is necessary to make the frequencies fc1 and fc2 excessively high, which results in a significant reduction in the coupling strength CS1. In the first reference example, it is difficult to obtain a high coupling strength CS1 while reducing the coupling strength CS2 to zero.

[0055] The second and third reference examples will be described below. In the second and third reference examples, no capacitors are provided in the first portion 10a and the second portion 10b. In the second reference example, the value of the inductor is adjusted to obtain a high coupling strength CS1. In the third reference example, the value of the inductor is adjusted to reduce the coupling strength CS2 related to the residual coupling.

[0056] 7(a) and 7(b) are graphs illustrating the coupling strength in the coupler and the computer of the second reference example. These figures correspond to the computer 119b according to the second reference example. In this example, the inductance of the first inductor 21 and the second inductor 22 is 4.1 nH. The horizontal axis of FIGS. 7(a) and 7(b) represents the magnetic flux MF1 in the space SP (loop 10r). The vertical axis of FIG. 7(a) represents the coupling strength CS1. The vertical axis of FIG. 7(b) represents the coupling strength CS2 related to the residual coupling.

[0057] As shown in FIG. 7(a), in the second reference example, there is a condition where the coupling strength CS1 is substantially zero (coupling is off). In the second reference example, a high coupling strength CS1 is obtained compared to the first reference example. However, as shown in FIG. 7(b), in the second reference example, the coupling strength CS2 is larger 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.

[0058] 8(a) and 8(b) are graphs illustrating the coupling strength in the coupler and the computer of the third reference example. These figures correspond to the computer 119c according to the third reference example. In this example, the inductance of the first inductor 21 and the second inductor 22 is 1.63 nH. The horizontal axis of FIGS. 8(a) and 8(b) represents the magnetic flux MF1 in the space SP (loop 10r). The vertical axis of FIG. 8(a) represents the coupling strength CS1. The vertical axis of FIG. 8(b) represents the coupling strength CS2 related to the residual coupling.

[0059] As shown in Figure 8(a), in the third reference example, there is a condition where the coupling strength CS1 is substantially zero (coupling is off). In the third reference example, the coupling strength CS1 is significantly low. As shown in Figure 8(b), in the third reference example, the coupling strength CS2 is lower than in the first reference example, but is not substantially zero.

[0060] As described above, in the first to third reference examples in which no capacitors are provided in the first portion 10a and the second portion 10b, a substantially zero coupling strength CS2, a high coupling strength CS1, and off coupling cannot be obtained simultaneously.

[0061] In the embodiment, capacitors are provided in the first portion 10a and the second portion 10b, which results in a substantially zero coupling strength CS2, a high coupling strength CS1, and an off coupling.

[0062] If capacitors are provided in the first portion 10a and the second portion 10b, the element size will increase, so providing capacitors in the first portion 10a and the second portion 10b is generally avoided.

[0063] In contrast, in the embodiment, as described above, capacitors are provided in the first portion 10a and the second portion 10b. This results in, for example, a substantially zero coupling strength CS2, a high coupling strength CS1, and an off coupling. This is a special effect of the embodiment. This effect was not previously known. This special effect was first revealed by a fully quantum-mechanical analysis conducted by the inventors of the present application.

[0064] Below, we will explain an example of characteristics related to two-qubit gate operations. For example, when two-qubit gate operations are not performed, the magnetic flux MF1 is set to a value (the above-mentioned first magnetic flux value Mv1, approximately 0.68) at which the coupling strength CS1 becomes zero. When two-qubit gate operations are performed, the magnetic flux MF1 is modulated. The modulation frequency is the difference between the resonant frequency fb1 and the resonant frequency fb2, which is approximately 1.55 GHz in this example. In this simulation, the modulation amplitude is 0.12. That is, the magnetic flux MF1 oscillates in a sinusoidal manner between 0.56 and 0.80.

[0065] 9 is a graph illustrating the probability in the coupler and computer according to the first embodiment. The horizontal axis of FIG. 9 represents time tm, and the vertical axis represents the probability P1.

[0066] 9 illustrates the probability P1 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".

[0067] As shown in FIG. 9, when time tm is 0, the probability P1 of the first state ST1 is 1, and the probability P1 of the second state ST2 is 0. As time tm passes, the probability P1 of the first state ST1 and the probability P1 of the second state ST2 change. In this example, when time tm is approximately 12 ns, the probability P1 of the first state ST1 becomes the same as the probability P1 of the second state ST2. When time tm exceeds approximately 12 ns, the probability P1 of the first state ST1 becomes lower than the probability P1 of the second state ST2. In this example, a two-qubit gate operation can be completed in time tm of 12 ns.

[0068] In the embodiment, a short gate time tG can be obtained. A two-qubit gate can be executed at high speed. A coupler and a computing device that can improve controllability can be provided. The gate time tG is, for example, not less than 10 ns and not more than 20 ns.

[0069] Thus, in the embodiment, by modulating the magnetic flux MF1 (magnetic flux Φ) at an appropriate frequency, two-qubit gate operations are performed for the first nonlinear resonator 50A and the second nonlinear resonator 50B. During periods when the magnetic flux MF1 is not modulated, the coupling is kept off (the coupling strengths CS1 and CS2 are substantially zero).

[0070] As shown in Figure 9, the probability P1 of the third state ST3 and the probability P1 of the fourth state ST4 are substantially 0. A stable two-qubit gate is possible.

[0071] 10(a) and 10(b) are graphs illustrating the resonant frequencies of the coupler and the computer according to the first embodiment. The horizontal axis in these figures represents the magnetic flux MF1, the vertical axis in Figure 10(a) represents the resonant frequency fb1 of the first nonlinear resonator 50A, and the vertical axis in Figure 10(b) represents the resonant frequency fb2 of the second nonlinear resonator 50B.

[0072] 10(a), the resonant frequency fb1 of the first nonlinear resonator 50A changes near approximately 10 GHz when the magnetic flux MF1 changes from 0 to 1. The change width (degree of change) of the resonant frequency fb1 is approximately 300 MHz.

[0073] 10(b), the resonant frequency fb2 of the second nonlinear resonator 50B changes near approximately 8.4 GHz when the magnetic flux MF1 changes from 0 to 1. The change width (degree of change) of the resonant frequency fb2 is approximately 100 MHz.

[0074] In this way, in the embodiment, when the magnetic flux MF1 changes, the change in the resonant frequency of the nonlinear resonator can be suppressed. The frequency of the quantum bit is stable. The frequency of the quantum bit can be substantially fixed. A coupler and a computing device capable of improving controllability can be provided.

[0075] According to the embodiments, for example, a high coupling strength CS1 can be obtained. For example, fast two-qubit gate operation is possible. For example, the coupling of multiple nonlinear resonators can be turned off while obtaining a high coupling strength CS1. The frequency change of the nonlinear resonator (qubit) due to magnetic flux is small, and the stability of the qubit is maintained. According to the embodiments, for example, a coupler and a computing device that can improve controllability can be provided.

[0076] For example, a fourth reference example can be considered in which two quantum bits with different frequencies are directly coupled and irradiated with microwaves to execute a two-qubit gate. In the fourth reference example, microwaves with the frequency of one of the two quantum bits are irradiated to the other of the two quantum bits. In the fourth reference example, the characteristics depend on high-order perturbation terms. In the fourth reference example, high-speed gates are difficult to implement.

[0077] For example, a fifth reference example can be considered in which two quantum bits with different frequencies are directly coupled and a two-qubit gate is executed by irradiating microwaves. In the fifth reference example, microwaves corresponding to the difference in frequency between the two quantum bits are irradiated. 5In the reference example as well, the characteristics depend on high-order perturbation terms. In the fifth reference example as well, it is difficult to implement a high-speed gate.

[0078] In contrast to this, in the embodiment, the use of the above coupler 10 enables high-speed gating.

[0079] The "-mode" frequency of the coupler 10 corresponds to, for example, the above frequency fc2. In this embodiment, the "-mode" frequency is adjusted by the magnetic flux Φ in the loop 10r. This allows the coupling to be turned on and off. Even if the difference in frequency between the two quantum bits is large, the coupling can be turned off substantially completely. Even if the coupling strength is increased, the coupling can be turned off. Higher speeds are also possible. A coupler and a computing device with improved controllability can be provided.

[0080] In one example of the embodiment, for example, the capacitance of the first capacitor 11 is greater than 0.1 times the capacitance of the first resonator capacitor 41. For example, the capacitance of the second capacitor 12 is greater than 0.1 times the capacitance of the second resonator capacitor 42. This makes it easier to lower the frequency of the coupler 10.

[0081] In one example of the embodiment, for example, the capacitance of the third capacitor 13 is greater than 0.1 times the capacitance of the first resonator capacitor 41. For example, the capacitance of the fourth capacitor 14 is greater than 0.1 times the capacitance of the second resonator capacitor 42. This makes it easier to lower the frequency of the coupler 10.

[0082] FIG. 11 is a schematic diagram illustrating the coupler and the calculation device according to the first embodiment. 11, in a computer 111 according to the embodiment, the coupler 10 includes a fifth capacitor 15. The remaining configuration of the computer 111 may be the same as that of the computer 110.

[0083] 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, for example, facilitates adjustment of coupling characteristics. For example, the position of the zero point of the ZZ coupling can be adjusted. For example, the fifth capacitor 15 can provide a coupler and a computer that are robust against magnetic flux fluctuations.

[0084] For example, the capacitance of the fifth capacitor 15 is smaller than the capacitance of the first capacitor 11 and smaller than the capacitance of the second capacitor 12. The fifth capacitor 15 is provided as needed and may be omitted.

[0085] The first nonlinear resonator Josephson junction 51 and the second nonlinear resonator Josephson junction 52 may include a parasitic capacitance. The parasitic capacitance is small (for example, about 1 fF) compared to the capacitance of the first to fifth capacitors 11 to 15, and can be ignored.

[0086] 12(a) and 12(b) are graphs illustrating the coupling strength in the coupler and the computer according to the first embodiment. These figures correspond to a computer 111 according to an embodiment. In this example, the capacitance of the fifth capacitor 15 in the computer 111 is 1.6 fF. The horizontal axes of FIGS. 12(a) and 12(b) represent the magnetic flux MF1 in the space SP (loop 10r). The vertical axis of FIG. 12(a) represents the coupling strength CS1. The vertical axis of FIG. 12(b) represents the coupling strength CS2 related to the residual coupling.

[0087] As shown in FIG. 12(a), a high coupling strength CS1 is obtained in the computer 111. There is a magnetic flux MF1 at which the coupling strength CS1 is substantially zero. The first magnetic flux value Mv1 is, for example, 0.62. As shown in FIG. 12(b), the coupling strength CS1 can be substantially zero. By providing the fifth capacitor 15, for example, the ZZ coupling can be robustly set to zero. It becomes easier to maintain the ZZ coupling at substantially zero.

[0088] 13(a) and 13(b) are schematic diagrams illustrating the coupler and the calculation device according to the first embodiment. 13(a) and 13(b), a plurality of first Josephson junctions 31 are provided in couplers 112 and 113. The plurality of first Josephson junctions 31 are connected in series. One end of the plurality of first Josephson junctions 31 corresponds to a first Josephson junction end 31e. The other end of the plurality of first Josephson junctions 31 corresponds to a first Josephson junction other end 31f.

[0089] (Second embodiment) 14(a) to 14(h) are schematic views illustrating a part of the coupler according to the second embodiment. As shown in FIG. 14(a), the first inductor 21 may include a first inductor Josephson junction (such as Josephson junction J1). As shown in FIGS. 14(b) and 14(c), the first inductor 21 may include a plurality of first inductor Josephson junctions (such as Josephson junctions J1 to J3). As shown in FIG. 14(d), the plurality of first inductor Josephson junctions may include Josephson junctions J1 to Jn (n is an integer of 2 or more). The plurality of first inductor Josephson junctions are electrically connected in series with each other.

[0090] As shown in FIG. 14(e), the second inductor 22 may include a second inductor Josephson junction (such as Josephson junction K1). As shown in FIGS. 14(f) and 14(g), the second inductor 22 may include a plurality of second inductor Josephson junctions (such as Josephson junctions K1 to K3). As shown in FIG. 14(h), the plurality of second inductor Josephson junctions may include Josephson junction K1 to Josephson junction Kn (n is an integer of 2 or more). The plurality of second inductor Josephson junctions are electrically connected in series with each other.

[0091] 15A and 15B are schematic cross-sectional views illustrating a part of the coupler according to the second embodiment. 15(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 provided on a first surface 10f of a base body 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 provided between the conductive film 38a and the conductive film 38b.

[0092] 15(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 provided on the first surface 10f of the base body 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 provided between the conductive film 39a and the conductive film 39b.

[0093] The conductive films 38a, 38b, 39a, and 39b may contain the material contained in the conductive film 35a. The insulating films 38i and 39i may contain the material contained in the insulating film 35i.

[0094] 16(a) to 16(f) are schematic views illustrating a part of the coupler according to the second embodiment. Figures 16(a) and 16(b) are plan views. Figure 16(c) is a cross-sectional view taken along line A1-A2 in Figure 16(a). Figure 16(e) is a cross-sectional view taken along line A3-A4 in Figure 16(a). Figure 16(d) is a cross-sectional view taken along line B1-B2 in Figure 16(b). Figure 16(f) is a cross-sectional view taken along line B3-B4 in Figure 16(b).

[0095] As shown in FIG. 16(c), the first capacitor 11 may include two conductors extending along the Z-axis direction in the base body 10s. As shown in FIG. 16(d), the second capacitor 12 may include two conductors extending along the Z-axis direction in the base body 10s. These capacitors may have, for example, a vertical structure (or a through-substrate structure). These capacitors may include, for example, a TSV (through-silicon via). This allows the planar size of the capacitor to be reduced.

[0096] 16(e), the first inductor 21 includes a Josephson junction J1. In this example, in the Josephson junction J1, the stacking direction of the conductive film 38a, the insulating film 38i, and the conductive film 38b intersects with the first surface 10f. This makes it possible to reduce the size of the junction.

[0097] 16(f), the second inductor 22 includes a Josephson junction K1. In this example, in the Josephson junction K1, the stacking direction of the conductive film 39a, the insulating film 39i, and the conductive film 39b intersects with the first surface 10f. This makes it possible to reduce the size of the junction.

[0098] 17A and 17B are schematic plan views illustrating a part of the coupler according to the second embodiment. 17(a), the first inductor 21 includes Josephson junctions J1 and J2. As shown in Fig. 17(b), the second inductor 22 includes Josephson junctions K1 and K2. The stacking direction of these Josephson junctions also intersects with the first surface 10f.

[0099] 18A and 18B are schematic plan views illustrating a part of the coupler according to the second embodiment. 18(a), the first inductor 21 includes a plurality of Josephson junctions (Josephson junctions J1 to Jn). As shown in Fig. 18(b), the second inductor 22 includes a plurality of Josephson junctions (Josephson junctions K1 to Kn). The stacking direction of these Josephson junctions also intersects with the first surface 10f.

[0100] FIG. 19 is a schematic plan view illustrating the coupler and the computer according to the second embodiment. As shown in FIG. 19, in a computer 120 according to the embodiment, a first conductive member 61 is provided as a first magnetic field application unit 60. At least a portion of the first conductive member 61 is along the XY plane. A magnetic flux control current 61i is supplied to the first conductive member 61 from a control unit 70. The first resonator capacitor 41 (and the first nonlinear resonator Josephson junction 51) can be coupled to another coupler 10A. The second resonator capacitor 42 (and the second nonlinear resonator Josephson junction 52) can be coupled to another coupler 10B.

[0101] FIG. 20 is a schematic plan view illustrating the coupler and the computer according to the second embodiment. 20, in the computer 121 according to the embodiment, the portion included in the third capacitor 13 and the portion included in the first resonator capacitor 41 are inclined with respect to the direction from the other end 11f of the first capacitor to the first capacitor end 11e (in this example, the Y-axis direction). The portion included in the fourth capacitor 14 and the portion included in the second resonator capacitor 42 are inclined with respect to the direction from the other end 12f of the second capacitor to the second capacitor end 12e (in this example, the Y-axis direction). The first resonator capacitor 41 (and the first nonlinear resonator Josephson junction 51) are inclined with respect to the direction from the other end 12f of the second capacitor to the second capacitor end 12e (in this example, the Y-axis direction). D The second resonator capacitor 42 (and the second nonlinear resonator Josephson junction 52) can be coupled to other couplers 10B, 10E, and 10F.

[0102] FIG. 21 is a schematic plan view illustrating the coupler and the computer according to the second embodiment. 21, 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.

[0103] FIG. 22 is a schematic plan view illustrating the coupler and the computer according to the second embodiment. 22, the computer 123 according to the embodiment may include a first excitation conductor 65a and a second excitation conductor 65b. The control unit 70 is capable of exciting the first nonlinear resonator 50A via the first excitation conductor 65a. The control unit 70 is capable of exciting the second nonlinear resonator 50B via the second excitation conductor 65b. For example, a signal including an AC component is supplied to the first excitation conductor 65a and the second excitation conductor 65b.

[0104] As shown in FIG. 22 , 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.

[0105] 23(a) and 23(b) are schematic diagrams illustrating a coupler and a computer according to the second embodiment. Fig. 23(a) is a plan view, and Fig. 23(b) is an enlarged perspective view of a part of the coupler and the computer. As shown in Figures 23(a) and 23(b), a first conductive member 61 is provided as the first magnetic field application unit 60 in the computer 130. For example, the direction from the coupler 10 to at least a part of the first conductive member 61 is along the Z-axis direction (a direction intersecting with the first surface 10f). The first conductive member 61 is, for example, a coaxial line. In the part where the first conductive member 61 approaches the coupler 10, the magnetic flux control current 61i includes a component in a direction intersecting with the Z-axis direction (a direction along the XY plane).

[0106] FIG. 24 is a schematic plan view illustrating the coupler and the computer according to the second embodiment. 24, the first resonator capacitor 41 has a vertical structure (see FIGS. 16(c) and 16(d)) in the computer 131. The vertical structure includes two conductors extending along the Z-axis direction in the base body 10s.

[0107] 25(a) and 25(b) are schematic plan views illustrating the coupler and the computer according to the second embodiment. FIG. 25(a) illustrates a conductive pattern 81 provided on the first surface 10f of the base body 10s. FIG. 25(b) illustrates a conductive pattern 82 provided on the second surface 10g of the base body 10s. The second surface 10g is the surface opposite the first surface 10f. As shown in FIGS. 25(a) and 25(b), in the computer 132, a portion of the conductive pattern 81 is electrically connected to the conductive pattern 82 by a conductive member 83 extending along the Z-axis direction of the base body 10s. For example, electrical connection to the outside may be made via the conductive pattern 82. The conductive member 83 may be, for example, a through-substrate connecting member. In an embodiment, a portion of the conductive member (a ground GND or a circuit element at a fixed potential) may be placed on one of the first surface 10f and the second surface 10g of the base body 10s, and another portion of the conductive member may be provided on the other of the first surface 10f and the second surface 10g, and the two portions may be connected by a through-substrate connecting member. In an embodiment, the connection may be made by capacitive coupling, such as in a flip-chip configuration.

[0108] In addition to the above description of the second embodiment, the configuration described in relation to the first embodiment can be applied to the extent technically possible.

[0109] The characteristics of the coupler 10 and the computer 110 according to the embodiment will be described below. The Lagrangian of a 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 expressed by the following first equation.

number

[0110] The first term on the right side of the first equation is the Lagrangian of the first nonlinear resonator 50A. The second term on the right side of the first equation is the Lagrangian of the second nonlinear resonator 50B. The third term on the right side of the first equation is the Lagrangian of the coupler 10. The fourth term on the right side of the first equation is the Lagrangian that represents the interaction between the coupler 10, the first nonlinear resonator 50A, and the second nonlinear resonator 50B.

[0111] The Lagrangian of the first nonlinear resonator 50A is expressed by the following second equation: In the second equation, “C1” is the capacitance of the first resonator capacitor 41.

number

[0112] The Lagrangian of the second nonlinear resonator 50B is expressed by the following third equation: In the third equation, “C2” is the capacitance of the second resonator capacitor 42.

number

[0113] The Lagrangian representing the interaction between the coupler 10, the first nonlinear resonator 50A, and the second nonlinear resonator 50B is expressed by the following fourth equation. c " is the capacitance of each of the third capacitor 13 and the fourth capacitor 14.

number

[0114] The Lagrangian of the coupler 10 is expressed by the following equation 5: In equation 5, "C" is the capacitance of each of the first capacitor 11 and the second capacitor 12.

number

[0115] Here, φ is a magnetic flux operator. φ has a relationship with the phase difference θ expressed by the following equation (6).

[0116]

number

[0117] Flux operator φ for the "+ mode" of coupler 10 c+ is expressed by the following equation 7.

[0118]

number

[0119] The flux operator φ for the "-mode" of the coupler 10 c- is expressed by the following equation 8.

[0120]

number

[0121] In the seventh and eighth equations, φ c1is the magnetic flux operator for the first part 10a. In the eighth and ninth equations, φ c2 is the flux operator for the second part 10b.

[0122] On the right-hand side of the fourth equation above, the signs of the first and second terms are swapped. This cancels out the coupling between quantum bits via the ± modes.

[0123] In the above equation 5, the first and second terms on the right-hand side correspond to the "+ mode." In equation 5, the third to sixth terms on the right-hand side correspond to the "- mode." The "+ mode" corresponds to the LC resonator. The "- mode" corresponds to the flaxonium qubit. The presence of the flaxonium qubit makes the frequency variable.

[0124] In this manner, in this embodiment, the coupler 10 simultaneously has two modes, the "+ mode" and the "- mode." By using the "- mode," a variable frequency can be obtained.

[0125] For simplicity, the above description is given for the case where the first capacitor 11 and the second capacitor 12 have the same capacitance (C). For simplicity, the above description is given for the case where the third capacitor 13 and the fourth capacitor 14 have the same capacitance (C c ) is described. In the embodiment, the capacitance of the first capacitor 11 may be different from the capacitance of the second capacitor 12. In the embodiment, the capacitance of the third capacitor 13 may be different from the capacitance of the fourth capacitor 14.

[0126] The embodiment may include the following configurations (e.g., technical solutions). (Configuration 1) 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 connected to the first capacitor other end, the 1 the second inductor electrically connected to the other end of the inductor and the other end of the second capacitor; 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 and the first Josephson junction other end being electrically connected to the second capacitor end, and the first Josephson junction having a space 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, and the third capacitor end being electrically connectable to a first nonlinear resonator; 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, and the fourth capacitor end being electrically connectable to a second nonlinear resonator; Coupler with.

[0127] (Configuration 2) the first inductor includes a first conductive layer having a meander structure; 2. The coupler of configuration 1, wherein the second inductor includes a second conductive layer having a meander structure.

[0128] (Configuration 3) the first inductor includes a first inductor Josephson junction; 2. The coupler of configuration 1, wherein the second inductor includes a second inductor Josephson junction.

[0129] (Configuration 4) the first inductor includes a plurality of first inductor Josephson junctions, the plurality of first inductor Josephson junctions being electrically connected in series with one another; 2. The coupler of configuration 1, wherein the second inductor includes a plurality of second inductor Josephson junctions, the plurality of second inductor Josephson junctions being electrically connected in series with one another.

[0130] (Configuration 5) a fifth capacitor including a fifth capacitor end and a fifth capacitor other end; the fifth capacitor end is electrically connected to the first capacitor end; The coupler according to any one of configurations 1 to 4, wherein the other end of the fifth capacitor is electrically connected to the end of the second capacitor.

[0131] (Configuration 6) 6. The coupler of configuration 5, wherein the capacitance of the fifth capacitor is smaller than the capacitance of the first capacitor and smaller than the capacitance of the second capacitor.

[0132] (Configuration 7) 6. The coupler of any one of configurations 1 to 5, wherein the capacitance of each of the first capacitor and the second capacitor is greater than 0.1 times the capacitance of each of the third capacitor and the fourth capacitor.

[0133] (Configuration 8) Further, a first conductive member capable of applying a magnetic field to the space is provided, 8. The coupler of any one of configurations 1 to 7, wherein a coupling strength between the first nonlinear resonator and the second nonlinear resonator varies depending on a magnetic flux in the space.

[0134] (Configuration 9) the coupler is capable of resonating in multiple modes; A coupler described in any one of configurations 1 to 8, wherein the resonant frequency in each of the multiple 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.

[0135] (Configuration 10) a coupler according to any one of configurations 1 to 7; the first nonlinear resonator; the second nonlinear resonator; A calculator equipped with.

[0136] (Configuration 11) The first nonlinear resonator is a first nonlinear resonator Josephson junction; a first resonator capacitor; Including, an end of the first nonlinear resonator Josephson junction and an end of the first resonator capacitor are electrically connected to an end of the third capacitor; the other end of the first nonlinear resonator Josephson junction and the other end of the first resonator capacitor are electrically connected to the other end of the first capacitor; The second nonlinear resonator comprises: a second nonlinear resonator Josephson junction; a second resonator capacitor; Including, an end of the second nonlinear resonator Josephson junction and an end of the second resonator capacitor are electrically connected to an end of the fourth capacitor; 11. The computer of configuration 10, wherein the other end of the second nonlinear resonator Josephson junction and the other end of the second resonator capacitor are electrically connected to the other end of the second capacitor.

[0137] (Configuration 12) the capacitance of the first capacitor is greater than 0.1 times the capacitance of the first resonator capacitor; 12. The computer of claim 11, wherein the capacitance of the second capacitor is greater than 0.1 times the capacitance of the second resonator capacitor.

[0138] (Configuration 13) the capacitance of the third capacitor is greater than 0.1 times the capacitance of the first resonator capacitor; 13. The computer of claim 12, wherein the capacitance of the fourth capacitor is greater than 0.1 times the capacitance of the second resonator capacitor.

[0139] (Configuration 14) Further comprising a control unit, the coupler further includes a first magnetic field application unit capable of applying a magnetic field to the space; 14. The computer according to any one of configurations 10 to 13, wherein the control unit controls the first magnetic field application unit to change the magnetic flux in the space.

[0140] (Configuration 15) the first magnetic field application unit includes a first conductive member, 15. The computer according to configuration 14, wherein the control unit changes the magnetic flux by modulating a current supplied to the first conductive member.

[0141] (Configuration 16) 16. The computer of claim 14 or 15, wherein the change in the magnetic flux performs a two-qubit gate operation on the first nonlinear resonator and the second nonlinear resonator.

[0142] (Configuration 17) 16. The computer according to claim 14, wherein the control unit is capable of controlling the magnetic flux in the space to change the coupling strength between the first nonlinear resonator and the second nonlinear resonator.

[0143] (Configuration 18) 16. The computer of claim 14, wherein the control unit is capable of controlling the magnetic flux in the space to substantially eliminate coupling between the first nonlinear resonator and the second nonlinear resonator.

[0144] (Configuration 19) the coupler is capable of resonating in multiple modes; 19. The computer of any one of configurations 10 to 18, wherein the resonant frequency in each of the plurality of modes is less than or equal to twice the resonant frequency of the first nonlinear resonator and less than or equal to twice the resonant frequency of the second nonlinear resonator.

[0145] (Configuration 20) the coupler is capable of resonating in multiple modes; 19. The computer of any one of configurations 10 to 18, wherein a resonant frequency in each of the plurality of modes is 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.

[0146] According to the embodiment, a coupler and a computing device that can improve controllability can be provided.

[0147] The embodiments of the present invention have been described above with reference to examples. However, the present invention is not limited to these examples. For example, the specific configurations of elements such as nonlinear resonators, inductors, capacitors, and conductive members included in a coupler or computing device are within the scope of the present invention as long as a person skilled in the art can implement the present invention in a similar manner and obtain similar effects by appropriately selecting them from known ranges.

[0148] Any combination of two or more elements of each example within the scope of technical feasibility is also included within the scope of the present invention as long as it encompasses the gist of the present invention.

[0149] All couplers and computing devices that can be implemented by a person skilled in the art by appropriately modifying the design based on the coupler and computing device described above as embodiments of the present invention also fall within the scope of the present invention as long as they include the gist of the present invention.

[0150] Within the scope of the concept of the present invention, a person skilled in the art may conceive of various modifications and alterations, and it is understood that these modifications and alterations also fall within the scope of the present invention.

[0151] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0152] 10, 10A to 10F... couplers, 10a, 10b... first and second portions, 10f, 10g... first and second surfaces, 10r... loop, 10s... substrate, 11 to 15... first to fifth capacitors, 11L, 12L... conductive layers, 11e to 15e... first to fifth capacitor ends, 11f to 15f... other ends of first to fifth capacitors, 21, 22... first and second inductors, 21L, 22L... first and second conductive layers, 21e, 22e... first and second inductor ends, 21f, 22f... other ends of first and second inductors, 31... first Josephson junction, 31e... first Josephson junction end, 31f... other end of first Josephson junction, 35a to 39a, 35b to 39b... conductive films, 35i to 39i...insulating film, 41, 42...first and second resonator capacitors, 41e, 42e...end portions, 41f, 42f...other end portions, 50A, 50B...first and second nonlinear resonators, 51, 52...first and second nonlinear resonator Josephson junctions, 51e, 52e...end portions, 51f, 52f...other end portions, 60...first magnetic field application unit, 61...first conductive member, 61i...magnetic flux control current, 65a, 65b...first and second excitation conductive units, 66a, 66b...first and second readout resonators, 70...control unit, 81, 82...conductive patterns, 83...conductive member, 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, Mv1...first magnetic flux value, P1...probability, SP...space m, ST1 to ST4...first to fourth states, fb1, fb2...resonant frequency, fc1, fc2...frequency, fo1...frequency, tG...gate time, tm...time

Claims

1. 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 portion and a second inductor other end portion, the second inductor end portion being electrically connected to the second capacitor end portion, and the second inductor other end portion being electrically connected to the first capacitor other end portion, the first inductor other end portion, and the second capacitor other end portion; 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 and the first Josephson junction other end being electrically connected to the second capacitor end; Equipped with the first capacitor end is electrically connectable to a first nonlinear resonator; the second capacitor end is electrically connectable to a second nonlinear resonator; It can resonate in multiple modes, A coupler, wherein 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.

2. the first inductor includes a first conductive layer having a meander structure; The coupler of claim 1 , wherein the second inductor includes a second conductive layer having a meander structure.

3. the first inductor includes a first inductor Josephson junction; 10. The coupler of claim 1, wherein the second inductor comprises a second inductor Josephson junction.

4. the first inductor includes a plurality of first inductor Josephson junctions, the plurality of first inductor Josephson junctions being electrically connected in series with one another; 2. The coupler of claim 1, wherein the second inductor includes a plurality of second inductor Josephson junctions, the plurality of second inductor Josephson junctions being electrically connected in series with one another.

5. a fifth capacitor including a fifth capacitor end and a fifth capacitor other end; the fifth capacitor end is electrically connected to the first capacitor end; 4. The coupler according to claim 1, wherein the other end of the fifth capacitor is electrically connected to the end of the second capacitor.

6. 6. The coupler of claim 5, wherein the capacitance of the fifth capacitor is less than the capacitance of the first capacitor and less than the capacitance of the second capacitor.

7. a first conductive member capable of applying a magnetic field to a space surrounded by the first inductor, the second inductor, and the first Josephson junction; 7. The coupler according to claim 1, wherein a coupling strength between the first nonlinear resonator and the second nonlinear resonator changes depending on a magnetic flux in the space.

8. the coupler is capable of resonating in multiple modes; by controlling a magnetic flux in a space surrounded by the first inductor, the second inductor, and the first Josephson junction, it is possible to substantially cancel the coupling between the first nonlinear resonator and the second nonlinear resonator; A coupler according to any one of claims 1 to 6, wherein when coupling between the first nonlinear resonator and the second nonlinear resonator is substantially eliminated, the resonant frequencies in the multiple modes are higher than the resonant frequencies of the first nonlinear resonator and higher than the resonant frequencies of the second nonlinear resonator.

9. the first nonlinear resonator comprises a first nonlinear resonator Josephson junction and a first resonator capacitor; 9. The coupler according to claim 1, wherein the second nonlinear resonator comprises a second nonlinear resonator Josephson junction and a second resonator capacitor.

10. The coupler of claim 1; the first nonlinear resonator; the second nonlinear resonator; A calculator equipped with.

11. The first nonlinear resonator comprises: a first nonlinear resonator Josephson junction; a first resonator capacitor; Including, an end of the first nonlinear resonator Josephson junction and an end of the first resonator capacitor are electrically connected to an end of the first capacitor; the other end of the first nonlinear resonator Josephson junction and the other end of the first resonator capacitor are electrically connected to the other end of the first capacitor; The second nonlinear resonator comprises: a second nonlinear resonator Josephson junction; a second resonator capacitor; Including, an end of the second nonlinear resonator Josephson junction and an end of the second resonator capacitor are electrically connected to an end of the second capacitor; 11. The computer of claim 10, wherein the other end of the second nonlinear resonator Josephson junction and the other end of the second resonator capacitor are electrically connected to the other end of the second capacitor.

12. the capacitance of the first capacitor is greater than 0.1 times the capacitance of the first resonator capacitor; 12. The computer of claim 11, wherein the capacitance of the second capacitor is greater than 0.1 times the capacitance of the second resonator capacitor.

13. Further comprising a control unit, the coupler further includes a first magnetic field applying unit capable of applying a magnetic field to a space surrounded by the first inductor, the second inductor, and the first Josephson junction; The computer according to claim 11 or 12, wherein the control unit is capable of controlling the first magnetic field application unit to change the magnetic flux in the space.

14. the first magnetic field applying unit includes a first conductive member, The computer according to claim 13 , wherein the control unit is configured to change the magnetic flux by modulating a current supplied to the first conductive member.

15. The computer of claim 13 , wherein the change in magnetic flux performs a two-qubit gate operation on the first nonlinear resonator and the second nonlinear resonator.

16. 14. The computer according to claim 13, wherein the control unit is capable of changing a coupling strength between the first nonlinear resonator and the second nonlinear resonator by controlling the magnetic flux in the space.

17. 14. The computer according to claim 13, wherein the control unit is capable of controlling the magnetic flux in the space to substantially cancel coupling between the first nonlinear resonator and the second nonlinear resonator.

18. the coupler is capable of resonating in multiple modes; 11. The computer according to claim 10, wherein a resonant frequency in each of the plurality of modes is equal to or less than twice the resonant frequency of the first nonlinear resonator and equal to or less than twice the resonant frequency of the second nonlinear resonator.

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