Quantum device

Abstract

To secure a gating speed and a coherence time.SOLUTION: A quantum device includes: a filter having a plurality of notches in a first frequency band lower than a second frequency band; a first qubit resonating in the first frequency band; and a second qubit resonating in the second frequency band. The first qubit is input with a signal having a frequency at which the first qubit resonates via the filter to control a state of the first qubit when executing one-qubit gating, and is input with a signal having a frequency at which the second qubit resonates via the filter to control a state of the second qubit according to a quantum state of the first qubit when executing two-qubit gating.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to quantum devices. [Background technology]

[0002] A method of performing two-qubit gate operations in a quantum computer using superconducting quantum bits (hereinafter also simply referred to as "qubits") is known. In order to control the quantum bits, the quantum bits are coupled to a waveguide and a microwave pulse is irradiated from the waveguide. The stronger the coupling between the quantum bit and the waveguide, the shorter the time required for gate operation of the quantum bit (gate time). On the other hand, the stronger the coupling between the quantum bit and the waveguide, the shorter the lifetime of the quantum bit. In other words, there is a mutually contradictory relationship between extending the lifetime of the quantum bit and shortening the gate time (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2020 / 105732 Summary of the Invention [Problem to be solved by the invention]

[0004] In a two-qubit gate (also known as a cross-resonant gate), a signal having a frequency at which the target qubit resonates is input from a waveguide to the control qubit, causing the state of the target qubit to change depending on the state of the control qubit.

[0005] In the case of a two-qubit gate, it is possible to speed up the gate (shorten the gate time) by increasing the strength of the signal input to the control qubit or by increasing the coupling efficiency between the waveguide and the qubit. However, if the coupling between the control qubit and the input waveguide is too strong, the radiation loss from the control qubit to the input waveguide increases, shortening the coherence time (data retention time) of the control qubit.

[0006] The present disclosure provides quantum devices that can ensure gate speed and coherence time. [Means for solving the problem]

[0007] In one aspect of the present disclosure, a filter having a plurality of notches in a first frequency band that is lower than a second frequency band; a first quantum bit resonating in the first frequency band; a second quantum bit resonating in the second frequency band; A quantum device is provided in which, when a one-qubit gate is executed, a signal having a frequency at which the first quantum bit resonates is input via the filter to control the state of the first quantum bit, and, when a two-qubit gate is executed, a signal having a frequency at which the second quantum bit resonates is input via the filter to control the state of the second quantum bit in accordance with the quantum state of the first quantum bit. Effect of the Invention

[0008] According to the present disclosure, gate speed and coherence time can be ensured. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of quantum bit connections. [Diagram 2] 13 is a diagram for explaining the frequency dependence of the coupling efficiency between a waveguide and a control quantum bit. FIG. [Diagram 3] FIG. 1 is a diagram for explaining a quantum device according to an embodiment of the present invention. [Figure 4] FIG. 13 is a diagram illustrating an example of a frequency characteristic of a coupling efficiency of a filter. [Diagram 5] 1 is a perspective view showing a configuration example of a quantum device according to a first embodiment. [Figure 6] 1 is an equivalent circuit diagram of the quantum device according to the first embodiment. [Figure 7] FIG. 11 is a plan view showing a configuration example of a quantum device according to a second embodiment. [Figure 8] FIG. 11 is an equivalent circuit diagram of the quantum device according to the second embodiment. [Figure 9] 11 is a diagram for explaining the frequency characteristics of the coupling efficiency of a filter and the resonant frequency of each quantum bit. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment will be described below.

[0011] The quantum device of this embodiment includes a filter for correcting the level difference between signals required for a one-qubit gate and a two-qubit gate input to each qubit at each resonant frequency of a control qubit that resonates in a low frequency band and a target qubit that resonates in a high frequency band in order to realize a quantum logic gate of a quantum computer. The quantum computer includes a one-quantum logic gate such as a Pauli gate and a two-quantum logic gate such as a CNOT gate, and performs calculations using these quantum logic gates. The CNOT gate is used to generate a quantum entangled state, etc.

[0012] One example of a configuration that induces quantum entanglement is the cross resonant gate, which has a control qubit adjacent to an input end and a target qubit coupled to the control qubit, with the control qubit and the target qubit having different resonant frequencies.

[0013] 1 is a diagram showing an example of quantum bit connections. A control signal S for driving a two-qubit gate (cross resonant gate) that couples a control quantum bit 10 and a target quantum bit 20 is input to the control quantum bit 10.

[0014] In a cross resonant gate, to induce quantum entanglement between a control qubit 10 and a target qubit 20 that are adjacent to each other, a control signal S having the same frequency as the resonant frequency of the target qubit 20 is input to the control qubit 10. This causes the state of the target qubit to change according to the quantum state of the control qubit. The control signal S is, for example, a microwave.

[0015] In the case of a cross resonant gate in which a control quantum bit 10 that resonates in a low frequency band is coupled to a target quantum bit 20 that resonates in a high frequency band, it is possible to increase the speed of the gate (shorten the gate time) by increasing the strength of the control signal S input from the waveguide 31 to the control quantum bit 10, or by increasing the coupling efficiency of the control signal S from the waveguide 31 to the control quantum bit 10. However, if the coupling strength between the waveguide 31 and the control quantum bit 10 is too large, the coherence time (data retention time) of the control quantum bit 10 will be shortened.

[0016] Therefore, the quantum device of this embodiment has a filter structure in which the coupling efficiency γ between the waveguide 31 and the control quantum bit 10 has frequency dependence as shown in Fig. 2. The coupling efficiency γ represents the ratio of the intensity of the control signal S input from the waveguide 31 to the control quantum bit 10 to the intensity of the control signal S input to the waveguide 31. The intensity of the control signal S is represented, for example, by the magnitude of the power of the control signal S. The filter structure of this embodiment has coupling characteristics in which the coupling efficiency γ in a second frequency band including the frequency at which the target quantum bit 20 resonates (resonant frequency ω2) is higher than the coupling efficiency γ in a first frequency band including the frequency at which the control quantum bit 10 resonates (resonant frequency ω1).

[0017] Because the coupling efficiency γ is high at the resonance frequency ω2, a control signal S with a relatively high intensity at the resonance frequency ω2 is input to the control qubit 10, thereby speeding up the two-qubit gate between the control qubit 10 and the target qubit 20. On the other hand, because the coupling efficiency γ is low at the resonance frequency ω1, radiation loss from the control qubit 10 to the waveguide at the resonance frequency ω1 is suppressed, and shortening of the coherence time of the control qubit 10 is inhibited. Thus, a two-qubit gate that can ensure gate speed and coherence time can be provided.

[0018] For example, by adopting a filter structure with high coupling efficiency γ at the resonance frequency ω2, the gate speed can be ensured even if the power at the resonance frequency ω2 of the control signal S input to the waveguide 31 is suppressed, compared to a configuration without such a filter structure. By suppressing the power at the resonance frequency ω2 of the control signal S input to the waveguide 31, power saving can be realized.

[0019] For example, the power at the resonant frequency ω2 of the control signal S can be reduced to the power at the resonant frequency ω1 of the control signal S. By making the power at the resonant frequency ω2 of the control signal S and the power at the resonant frequency ω1 of the control signal S equal, it is advantageous for the digital generation of the control signal S. For example, if a signal with a large level difference is generated using a single DA (Digital to Analog) converter, the dynamic range of the signal may be narrowed, and the quality of the signal may be degraded. On the other hand, if multiple DA converters are used, the number of parts increases, which may lead to an increase in the size and cost of the device for generating the control signal S. In contrast, by making the power at the resonant frequency ω2 of the control signal S and the power at the resonant frequency ω1 of the control signal S equal, it is possible to suppress the degradation of signal quality due to insufficient dynamic range, even if the control signal S is generated using a single DA converter.

[0020] The quantum device 100 of this embodiment shown in FIG. 3 includes a high-pass filter 40 in front of the control quantum bit 10, the high-pass filter having coupling characteristics in which the coupling efficiency γ in a second frequency band including the resonant frequency ω2 is higher than the coupling efficiency γ in a first frequency band including the resonant frequency ω1.

[0021] Fig. 3 is a diagram showing an example of the configuration of a quantum device according to the present embodiment. Quantum device 100 shown in Fig. 3 includes a high-pass filter 40 that transmits a control signal S in a first frequency band with a coupling efficiency γ lower than that in a second frequency band, a control quantum bit 10 that resonates in the first frequency band, and a target quantum bit 20 that resonates in the second frequency band. Quantum device 100 is, for example, a cross resonant gate in which control quantum bit 10 and target quantum bit 20 are coupled via a transmission line 30.

[0022] Highpass filter 40 is an example of a filter that transmits signals in a first frequency band with a lower coupling efficiency γ than a second frequency band. Control qubit 10 is an example of a first qubit that resonates in the first frequency band. Target qubit 20 is an example of a second qubit that resonates in the second frequency band.

[0023] When a one-qubit gate is executed, a signal having a frequency at which control qubit 10 resonates is input to control qubit 10 via high-pass filter 40, thereby controlling the quantum state of control qubit 10. When a two-qubit gate is executed, a control signal S having a frequency at which target qubit 20 resonates is input to control qubit 10 via high-pass filter 40. This causes the state of target qubit 20 to change in response to the quantum state of control qubit 10.

[0024] The high-pass filter 40 provided in the quantum device 100 of this embodiment has multiple notches in a low-frequency band (a first frequency band in which the coupling efficiency γ is suppressed more than in the second frequency band) that includes the resonant frequency of the control quantum bit 10. This makes it possible to ensure a relatively wide width for the first frequency band in which the coupling efficiency γ is suppressed more than in the second frequency band. By ensuring a wide width for the first frequency band, the coupling efficiency characteristic of the high-pass filter 40 in the first frequency band can be made closer to a flat characteristic. As a result, even if the frequency at which the control quantum bit 10 resonates shifts due to manufacturing variations or the like, the operation of the quantum device 100 (cross resonant gate) can be stabilized.

[0025] 4 is a diagram showing an example of the frequency characteristic of the coupling efficiency of a filter. The high-pass filter 40 has a coupling efficiency characteristic that transmits the control signal S in the first frequency band W1 with a coupling efficiency γ lower than that in the second frequency band W2. The high-pass filter 40 has a number of notches (in this example, a first notch 51 and a second notch 52) in the first frequency band W1 that includes the resonant frequency fq1 of the control quantum bit 10.

[0026] The first notch 51 is a frequency characteristic point at which the control signal S1 is minimized at a first notch frequency fn1 included in the first frequency band W1. The second notch 52 is a frequency characteristic point at which the control signal S1 is minimized at a second notch frequency fn2 included in the first frequency band W1. The second notch frequency fn2 is higher than the first notch frequency fn1.

[0027] The high-pass filter 40 has a frequency characteristic A1 having a first notch 51 and a second notch 52 in a first frequency band W1. This allows the width of the first frequency band W1, in which the control signal S input to the control quantum bit 10 is transmitted with a lower coupling efficiency γ than the second frequency band W2, to be expanded compared to the frequency characteristic A2 having one notch 53 having a notch frequency fn3 in a low frequency band. By expanding the width of the first frequency band W1, in which the control signal S is transmitted with a lower coupling efficiency γ than the second frequency band W2, the coupling efficiency characteristic of the high-pass filter 40 in the first frequency band W1 can be made closer to a flat characteristic. As a result, even if the frequency at which the control quantum bit 10 resonates deviates due to manufacturing variations or the like, the operation of the quantum device 100 (cross resonant gate) can be stabilized.

[0028] 4, high-pass filter 40 has first notch 51 and second notch 52 such that resonant frequency fq1 of control quantum bit 10 is between first notch frequency fn1 and second notch frequency fn2. In this case, control quantum bit 10 resonates in a band between first notch frequency fn1 and second notch frequency fn2. In this way, by providing notches above and below resonant frequency fq1 of control quantum bit 10, it is possible to prevent the coupling efficiency γ at resonant frequency fq1 from being excessively suppressed.

[0029] 4 illustrates a frequency characteristic A1 in which the high-pass filter 40 has two notches, a first notch 51 and a second notch 52, in the first frequency band W1. However, the high-pass filter 40 may have three or more notches in the first frequency band W1. This makes it possible to further expand the width of the first frequency band W1 in which the coupling efficiency γ is suppressed more than that of the second frequency band W2.

[0030] The high-pass filter 40 may have a frequency characteristic having at least one resonance point that resonates between the resonance frequency fq1 of the control quantum bit 10 and the resonance frequency fq2 of the target quantum bit 20. The frequency characteristic A1 illustrated in FIG. 4 has a first resonance point 54 having a filter resonance frequency fr1 and a second resonance point 55 having a filter resonance frequency fr2 between the resonance frequencies fq1 and fq2. The filter resonance frequency fr1 is higher than the second notch frequency fn2. The filter resonance frequency fr2 is higher than the filter resonance frequency fr1. The frequency characteristic A2 has one resonance point 56 having a filter resonance frequency fr3 between the resonance frequencies fq1 and fq2.

[0031] The high-pass filter 40 has a frequency characteristic A1 that resonates between the resonant frequencies fq1 and fq2, and thus the coupling efficiency difference D can be increased compared to a case where the high-pass filter 40 has a frequency characteristic that does not resonate between the resonant frequencies fq1 and fq2. The coupling efficiency difference D represents the difference between the coupling efficiency γ in the first frequency band W1 of the high-pass filter 40 and the coupling efficiency γ in the second frequency band W2 of the high-pass filter 40. By increasing the coupling efficiency difference D, the intensity of the control signal S in the first frequency band W1 can be suppressed even if the intensity of the control signal S in the second frequency band W2 is increased. In other words, it is possible to achieve both an increase in gate speed and suppression of shortening of the coherence time.

[0032] The high-pass filter 40 may have a coupling efficiency characteristic that uses Fano resonance to transmit the control signal S in the first frequency band W1 with a coupling efficiency γ lower than that in the second frequency band W2. By using Fano resonance, it becomes easy to achieve a frequency characteristic A1 that can ensure a wide coupling efficiency difference D.

[0033] As shown in FIG. 3, the high-pass filter 40 may include a first filter 41 that forms a first notch 51 and a second filter 42 that forms a second notch 52. Since each notch is formed by a separate filter, the accuracy of the first notch frequency fn1 and the second notch frequency fn2 is improved. For example, the first filter 41 realizes a frequency characteristic having the first notch 51 and a first resonance point 54 by using Fano resonance. The second filter 42 realizes a frequency characteristic having the second notch 52 and a second resonance point 55 by using Fano resonance. The frequency characteristic A1 shown in FIG. 4 can be realized by combining the frequency characteristic of the first filter 41 and the frequency characteristic of the second filter 42.

[0034] Fig. 5 is a diagram showing a configuration example of the quantum device of the first embodiment. The quantum device 101 shown in Fig. 5 is an example of the quantum device 100 described above. The quantum device 101 shown in Fig. 5 includes a substrate 70 having a first layer 71 facing a first direction and a second layer 72 facing a second direction opposite to the first direction. One of the first layer 71 and the second layer 72 is a front layer of the substrate 70, and the other layer is a back layer of the substrate 70. The substrate 70 is a dielectric substrate on which a predetermined conductor pattern is formed.

[0035] A terminal 43 to which a control signal S is input is provided on the first layer 71. A coaxial line 60 that transmits the control signal S is electrically connected to the terminal 43. The terminal 43 is, for example, an electrode such as a planar terminal pad. The coaxial line 60 is an example of a transmission line such as a coaxial cable. The coaxial line 60 is an example of the above-mentioned waveguide 31. The control signal S input to the terminal 43 via the coaxial line 60 passes through an inner layer of the substrate 70 and reaches the control quantum bit 10 provided on the second layer 72. The target quantum bit 20 that couples with the control quantum bit 10 is not shown in FIG. 5, but is provided, for example, on the second layer 72.

[0036] Because quantum device 101 has a configuration in which control signal S is transmitted from first layer 71 to second layer 72, the length of the transmission line that transmits control signal S from terminal 43 to control quantum bit 10 is relatively short (substantially equal to the thickness of substrate 70). For this reason, in conventional technology, it is difficult to provide a high-pass filter having coupling efficiency characteristics such as the above-mentioned frequency characteristic A1 on the transmission line from terminal 43 to control quantum bit 10 due to space constraints.

[0037] Therefore, in quantum device 101 of the first embodiment, high-pass filter 40 (more specifically, first filter 41 and second filter 42) that utilizes Fano resonance interference for coupling efficiency characteristics is provided in first layer 71. For this reason, even in quantum device 101 having a configuration in which it is difficult to ensure a sufficient length of the transmission line that transmits control signal S from terminal 43 to control quantum bit 10, it becomes easy to form high-pass filter 40 having the above-mentioned frequency characteristic A1.

[0038] The first filter 41 and the second filter 42 are provided around the terminal 43. This makes it easy to form the high-pass filter 40 having the above-mentioned frequency characteristic A1 that transmits the control signal S input from the terminal 43 to the control quantum bit 10 with a low coupling efficiency γ. In this example, the second filter 42 is formed to face the first filter 41 across the terminal 43.

[0039] The first filter 41 includes a first resonator 44 adjacent to the terminal 43, and the second filter 42 includes a second resonator 45 adjacent to the terminal 43. The first resonator 44 is a high-frequency circuit that forms a first resonance point 54 of the frequency characteristic A1, and the second resonator 45 is a high-frequency circuit that forms a second resonance point 55 of the frequency characteristic A1. The second resonator 45 is formed to face the first resonator 44 across the terminal 43. The first resonator 44 is disposed between the terminal 43 and the ground 73. The second resonator 45 is disposed between the terminal 43 and the ground 73. The ground 73 is formed on the first layer 71.

[0040] The first resonator 44 includes a first conductor pattern 46 formed on the first layer 71. The second resonator 45 includes a second conductor pattern 47 formed on the first layer 71. The first conductor pattern 46 and the second conductor pattern 47 are, for example, linear conductors that are folded back multiple times and formed in a sector-shaped area as shown in FIG.

[0041] The control quantum bit 10 has a Josephson junction 11 that does not overlap with the first resonator 44 and the second resonator 45 in a plan view of the substrate 70. This reduces the effect of crosstalk between the first resonator 44 and the second resonator 45 on the Josephson junction 11, making it possible to maintain the coherence time of the control quantum bit 10 (the average time that the quantum bit maintains the excited state "1").

[0042] 6 is an equivalent circuit diagram of the quantum device of the first embodiment shown in FIG. 5. The substrate 70 has a substrate capacitance C F The substrate capacitance C F is the coupling capacitance between terminal 43 and control qubit 10, and is included in first filter 41 and second filter .

[0043] The first filter 41 has a first capacitance C between the terminal 43 and the first conductor pattern 46 of the first resonator 44. k and a second capacitance C between the first conductor pattern 46 of the first resonator 44 and the control quantum bit 10. q That is, the first conductor pattern 46 includes a first capacitance C k and a second capacitance C q The first notch 51 forms a first capacitance C k and the second capacitance C q to the control qubit 10 via the first resonator 44 and the substrate capacitance C F It is formed by destructive interference of the signal transmitted from the waveguide directly to the control qubit 10 via (Fano resonance).

[0044] The second filter 42 has a third capacitance C between the terminal 43 and the second conductor pattern 47 of the second resonator 45.k2 and a fourth capacitance C between the second conductor pattern 47 of the second resonator 45 and the control quantum bit 10. q2 That is, the second conductor pattern 47 includes a third capacitance C k2 and a fourth capacitance C q2 The second notch 52 forms a third capacitance C k2 and the fourth capacity C q2 to the control qubit 10 via the second resonator 45, and the substrate capacitance C F qubit 10.

[0045] The first resonator 44 has a fifth capacitance C between the first conductor pattern 46 and the ground 73. R and a first inductor L between the first conductor pattern 46 and the ground 73. R The first resonator 44 includes a fifth capacitance C R and the first inductor L R The first resonance point 54 is formed by the first resonator 44.

[0046] The second resonator 45 has a sixth capacitance C R2 and a second inductor L between the second conductor pattern 47 and the ground 73. R2 The second resonator 45 includes a sixth capacitance C R2 and the second inductor L R2 The second resonance point 55 is formed by the second resonator 45.

[0047] Fig. 7 is a plan view showing an example of the configuration of a quantum device according to the second embodiment. A quantum device 102 shown in Fig. 7 is an example of the quantum device 100 described above. The quantum device 102 shown in Fig. 7 includes a substrate 70 having an input line 75 to which a control signal S is input, and an output line 76 to which a control quantum bit 10 is connected. The quantum device 102 includes a high-pass filter 40 including a plurality of filters (in this example, a first filter 41 and a second filter 42) connected in series between the input line 75 and the output line 76.

[0048] The first filter 41 includes a first resonator 44 adjacent to an input line 75, and the second filter 42 includes a second resonator 45 adjacent to an output line 76. The first resonator 44 is a high-frequency circuit that forms a first resonance point 54 of the frequency characteristic A1, and the second resonator 45 is a high-frequency circuit that forms a second resonance point 55 of the frequency characteristic A1. The second resonator 45 is formed to face the first resonator 44 across a capacitive coupling. The first resonator 44 is disposed between the input line 75 and the second resonator 45 so as to be surrounded by the ground 73. The second resonator 45 is disposed between the first resonator 44 and the output line 76 so as to be surrounded by the ground 73. The ground 73 is formed on the first layer 71.

[0049] The first resonator 44 includes a first conductor pattern 46 formed on the first layer 71. The second resonator 45 includes a second conductor pattern 47 formed on the first layer 71. The first conductor pattern 46 and the second conductor pattern 47 are, for example, linear conductors that are folded back multiple times.

[0050] 8 is an equivalent circuit diagram of the quantum device of the second embodiment shown in FIG. 7. The quantum device 102 has a capacitance C RE1 and the capacitance C between the first filter 41 and the second filter 42. RE2 The quantum device 102 also includes a capacitance C between the input line 75 and the output line 76 or the control qubit 10. RE3 and the capacitance C between the second filter 42 and the output line 76 or the control qubit 10. QRThe plurality of notches including the first notch 51 and the second notch 52 are connected to the input line 75 via a capacitance C RE1 , capacity C RE2、 Capacity C QR A signal transmitted to the output line 76 via the first and second resonators by RE3 4. The interference is formed by destructive interference of the signal transmitted directly to output line 76 by

[0051] The first resonator 44 has a capacitance C R1 and a first inductor L between the first conductor pattern 46 and the ground 73. R1 The first resonator 44 includes a capacitance C R and the first inductor L R The first resonance point 54 is formed by the first resonator 44.

[0052] The second resonator 45 has a capacitance C R2 and a second inductor L between the second conductor pattern 47 and the ground 73. R2 The second resonator 45 includes a capacitance C R2 and the second inductor L R2 The second resonance point 55 is formed by the second resonator 45.

[0053] 9 is a diagram illustrating the frequency characteristics of the coupling efficiency of the filter and the resonant frequency of each quantum bit. Target quantum bit 20 may include multiple target quantum bits (in this example, four target quantum bits 20a, 20b, 20c, and 20d) that resonate at different frequencies in second frequency band W2.

[0054] The control quantum bit 10 has a resonant frequency fq1 within the first frequency band W1. By providing multiple notches in the first frequency band W1, the control signal S input to the control quantum bit 10 is transmitted with a lower coupling efficiency γ in the low frequency band that includes the resonant frequency fq1 than in the second frequency band W2.

[0055] On the other hand, the multiple target quantum bits 20a, 20b, 20c, and 20d have resonant frequencies fq2a, fq2b, fq2c, and fq2d within the second frequency band W2. The high-pass filter 40 has a coupling efficiency γ in the first frequency band W1 that is lower than the coupling efficiency γ in the second frequency band W2. The multiple target quantum bits 20a, 20b, 20c, and 20d resonate at frequencies included in the high-frequency band with flat characteristics of the frequency characteristics of the high-pass filter 40.

[0056] As described above, the embodiment has been described, but the above embodiment is presented as an example, and the present invention is not limited to the above embodiment. The above embodiment can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention and its equivalents described in the claims.

[0057] The following supplementary notes are further disclosed regarding the above embodiment. (Appendix 1) a filter having a plurality of notches in a first frequency band that is lower than a second frequency band; a first quantum bit resonating in the first frequency band; a second quantum bit resonating in the second frequency band; a signal having a frequency at which the first quantum bit resonates is input via the filter to the first quantum bit when a one-qubit gate is executed, thereby controlling the state of the first quantum bit, and a signal having a frequency at which the second quantum bit resonates is input via the filter to the first quantum bit when a two-qubit gate is executed, thereby controlling the state of the second quantum bit in accordance with the quantum state of the first quantum bit. (Appendix 2) 2. The quantum device of claim 1, wherein the filter resonates between a resonant frequency of the first quantum bit and a resonant frequency of the second quantum bit. (Appendix 3) 3. The quantum device of claim 1 or 2, wherein the plurality of notches includes a first notch having a first notch frequency and a second notch having a second notch frequency higher than the first notch frequency and lower than a resonant frequency of the filter. (Appendix 4) 4. The quantum device of claim 3, wherein the filter includes a first filter that forms the first notch and a second filter that forms the second notch. (Appendix 5) 5. The quantum device of claim 4, comprising a substrate having a first layer in which the first filter and the second filter are provided, and a second layer in which the first quantum bit is provided. (Appendix 6) a terminal for receiving a signal having a frequency at which the first quantum bit or the second quantum bit resonates is provided in the first layer; 6. The quantum device of claim 5, wherein the first filter and the second filter are provided around the terminal. (Appendix 7) 7. The quantum device of claim 6, wherein the second filter faces the first filter across the terminal. (Appendix 8) the first filter includes a first resonator proximate to the terminal; 8. The quantum device of claim 6 or 7, wherein the second filter includes a second resonator proximate to the terminal. (Appendix 9) 9. The quantum device of claim 8, wherein the first quantum bit has a Josephson junction that does not overlap with the first resonator and the second resonator in a plan view of the substrate. (Appendix 10) the first filter includes a first capacitance between the terminal and the first resonator, and a second capacitance between the first resonator and the first quantum bit; 10. The quantum device of claim 8, wherein the second filter includes a third capacitance between the terminal and the second resonator, and a fourth capacitance between the second resonator and the first quantum bit. (Appendix 11) the first filter and the second filter include a coupling capacitance between the terminal and the first quantum bit; 11. The quantum device of any one of Additions 8 to 10, wherein interference between a signal through the first resonator and a signal through the coupling capacitance forms the first notch, and interference between a signal through the second resonator and a signal through the coupling capacitance forms the second notch. (Appendix 12) the first resonator includes a first conductor pattern forming the first capacitance and the second capacitance, a fifth capacitance between the first conductor pattern and ground, and a first inductor between the first conductor pattern and ground, 11. The quantum device of claim 10, wherein the second resonator includes a second conductor pattern forming the third capacitance and the fourth capacitance, a sixth capacitance between the second conductor pattern and ground, and a second inductor between the second conductor pattern and ground. (Appendix 13) 13. The quantum device of claim 1, wherein the first quantum bit resonates in a band between the plurality of notches. (Appendix 14) 14. The quantum device of claim 1, wherein the second quantum bit includes a plurality of quantum bits that resonate at different frequencies in the second frequency band. (Appendix 15) 15. The quantum device of any one of claims 1 to 14, wherein the filter utilizes Fano resonance. [Explanation of symbols]

[0058] 10 Control qubit 11 Josephson junction 20 Targeted Qubits 30 Transmission Lines 31 Waveguide 40 High Pass Filter 41 First Filter 42 Second Filter 43 Terminal 44 1st resonator 45 Second resonator 46 First conductor pattern 47 Second Conductor Pattern 51 1st notch 52 2nd notch 53 Notch 54 1st resonance point 55 2nd resonance point 56 Resonance point 60 coaxial line 70 Substrate 71 1st layer 72 2nd layer 73,74 Grand 75 Input Line 76 Output Line 100,101,102 Quantum Devices S Control Signal

Claims

1. a filter having a plurality of notches in a first frequency band lower than a second frequency band; a first quantum bit resonating in the first frequency band; a second quantum bit resonating in the second frequency band; a signal having a frequency at which the first quantum bit resonates is input via the filter to the first quantum bit when a one-qubit gate is executed, thereby controlling a state of the first quantum bit; and a signal having a frequency at which the second quantum bit resonates is input via the filter to the first quantum bit when a two-qubit gate is executed, thereby controlling the state of the second quantum bit in accordance with the quantum state of the first quantum bit.

2. The quantum device of claim 1 , wherein the filter resonates between a resonant frequency of the first quantum bit and a resonant frequency of the second quantum bit.

3. 3. The quantum device of claim 2, wherein the plurality of notches includes a first notch having a first notch frequency and a second notch having a second notch frequency greater than the first notch frequency and less than a resonant frequency of the filter.

4. The quantum device of claim 3 , wherein the filter includes a first filter that forms the first notch and a second filter that forms the second notch.

5. 5. The quantum device of claim 4, comprising a substrate having a first layer in which the first filter and the second filter are provided, and a second layer in which the first quantum bit is provided.

6. a terminal to which a signal having a frequency at which the first quantum bit or the second quantum bit resonates is input is provided in the first layer; The quantum device according to claim 5 , wherein the first filter and the second filter are provided around the terminal.

7. The quantum device according to claim 6 , wherein the second filter faces the first filter across the terminal.

8. the first filter includes a first resonator proximate to the terminal; The quantum device of claim 6 , wherein the second filter includes a second resonator proximate to the terminal.

9. The quantum device according to claim 8 , wherein the first quantum bit has a Josephson junction that does not overlap with the first resonator and the second resonator in a plan view of the substrate.

10. the first filter includes a first capacitance between the terminal and the first resonator, and a second capacitance between the first resonator and the first quantum bit; 9. The quantum device of claim 8, wherein the second filter includes a third capacitance between the terminal and the second resonator, and a fourth capacitance between the second resonator and the first quantum bit.

11. the first filter and the second filter include a coupling capacitance between the terminal and the first quantum bit; 9. The quantum device of claim 8, wherein interference between a signal through the first resonator and a signal through the coupling capacitance forms the first notch, and interference between a signal through the second resonator and a signal through the coupling capacitance forms the second notch.

12. the first resonator includes a first conductor pattern forming the first capacitance and the second capacitance, a fifth capacitance between the first conductor pattern and ground, and a first inductor between the first conductor pattern and ground, 11. The quantum device of claim 10, wherein the second resonator includes a second conductor pattern forming the third capacitance and the fourth capacitance, a sixth capacitance between the second conductor pattern and ground, and a second inductor between the second conductor pattern and ground.

13. The quantum device of claim 1 , wherein the first quantum bit resonates in a band sandwiched between the plurality of notches.

14. The quantum device of claim 1 , wherein the second quantum bit includes a plurality of quantum bits that resonate at different frequencies in the second frequency band.

15. 13. The quantum device of claim 1, wherein the filter utilizes Fano resonance.

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