Information Processing Apparatus, Frequency Adjustment Method, and Frequency Adjustment Program

Abstract

An information processing device equipped with: a quantum bit; a digital circuit for generating a digital signal; a conversion circuit for converting the digital signal into a microwave to be transmitted to the quantum bit; and an adjustment circuit for setting the first frequency of a clock which is used by the digital circuit in a manner such that the harmonic frequency of the first frequency differs from a second frequency of the microwave.

Description

Technical Field

[0001] The present disclosure relates to an information processing apparatus, a frequency adjustment method, and a frequency adjustment program.

Background Art

[0002] Conventionally, a quantum bit device used in a quantum computer using a superconducting circuit including a Josephson junction has been known. The quantum bit device includes a quantum bit placed in a dilution refrigerator, a control line for controlling the state of the quantum bit, and a quantum bit control unit for generating a microwave to be sent to the control line (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when a digital signal is generated in a quantum computer, harmonic noise generated by the digital signal may be superimposed on the microwave.

[0005] The present disclosure provides an information processing apparatus, a frequency adjustment method, and a frequency adjustment program capable of reducing harmonic noise superimposed on a microwave.

Means for Solving the Problems

[0006] In one aspect of the present disclosure, a quantum bit, a digital circuit that generates a digital signal, a conversion circuit that converts the digital signal into a microwave to be transmitted to the quantum bit, An information processing apparatus is provided, which includes an adjustment circuit that sets the first frequency such that a harmonic frequency of the first frequency of a clock used in the digital circuit is different from the second frequency of the microwave.

Advantages of the Invention

[0007] According to the present disclosure, harmonic noise superimposed on the microwave can be reduced.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments will be described.

[0010] FIG. 1 is a diagram showing a configuration example of an information processing system including an information processing apparatus according to an embodiment. The information processing system 200 shown in FIG. 1 is a system that processes information using a computer 500. The information processing system 200 includes an information processing apparatus 100 and a computer 500. The information processing apparatus 100 is connected to the computer 500 by wire or wirelessly.

[0011] The information processing apparatus 100 processes information using the quantum bit 11 in accordance with the command cmd input from the computer 500. The information processing apparatus 100 is also referred to as a quantum computer. The information processing apparatus 100 illustrated in FIG. 1 includes a cooler 10, a digital circuit 20, a conversion circuit 30, an adjustment circuit 40, a conversion circuit 50, and a digital circuit 60.

[0012] The cooler 10 cools the quantum bit 11. The cooler 10 is, for example, a dilution refrigerator that utilizes the dilution heat generated when liquid helium 3 is diluted into liquid helium 4. The cooler 10 may be a device that cools the quantum bit 11 by other cooling methods.

[0013] The quantum bit 11 stores information in a quantum mechanical two-state system. The quantum bit is also referred to as a Qubit. The quantum bit 11 is, for example, a superconducting quantum bit formed by a superconducting circuit including a superconducting Josephson junction. The type of the quantum bit 11 may not be limited to this. The number of the quantum bits 11 is at least one or more.

[0014] The digital circuit 20 generates a digital signal S. The digital circuit 20 generates a digital signal S corresponding to the content of the command cmd in accordance with the command cmd supplied from the computer 500, for example.

[0015] The conversion circuit 30 converts the digital signal S generated by the digital circuit 20 into a microwave M to be transmitted to the cooler 10. The frequency of the microwave M is higher than the frequency (operating frequency f0) used in the digital circuit 20. The operating frequency f0 is an example of the first frequency of the clock used in the digital circuit. The frequency of the microwave M is an example of the second frequency of the microwave transmitted to the quantum bit or the cooler.

[0016] The adjustment circuit 40 has a function of adjusting the frequency of the microwave M to a predetermined frequency F (for example, the resonance frequency of the quantum bit 11), and a function of multiplying the clock of the frequency f0 used in the digital circuit 20. Here, the adjustment circuit 40 has a function of adjusting so that an integral multiple of the frequency f0 (the frequency of the harmonic wave) is different from the predetermined frequency F. Thereby, since the harmonic wave having the frequency multiplied by the use frequency f0 does not appear at the frequency of the microwave M (predetermined frequency F), malfunction of the cooling machine 10 (particularly, the quantum bit 11) due to the noise of the harmonic wave can be reduced.

[0017] For example, the adjustment circuit 40 adjusts the use frequency f0 so that the multiplication of the use frequency f0 is different from the predetermined frequency F. When the predetermined frequency F is, for example, 10.00 GHz, when the digital circuit 20 operates at 500 MHz (when the use frequency f0 is 500 MHz), the 20-fold harmonic wave appears as harmonic noise at 10.00 GHz. The adjustment circuit 40 adjusts the operating frequency of the digital circuit 20 to 490 MHz (by adjusting the use frequency f0 to 490 MHz), so that the frequency of the harmonic wave shifts to 9.80 GHz (= 490 MHz × 20). Therefore, the 20-fold harmonic noise of the use frequency f0 does not appear at 10.00 GHz.

[0018] The quantum computer performs control using weak power of -100 dBm or less. However, in a digital circuit that generates a digital signal, there is a large noise such as digital noise. Therefore, a method of increasing the S component so as to increase the signal-to-noise ratio (SN ratio) and then attenuating the entire signal using an attenuator (ATT) can be considered. However, in this method, since the power of the S component is increased, the power consumption may increase. Also, the resolution of the lower bits of a digital-to-analog (DA) converter that converts a digital signal into an analog signal is wasted, and accordingly, the dynamic range may become narrow.

[0019] Also, one of the factors of the noise generated by the digital circuit is the clock signal. In a quantum computer, there may be multiple "bands where it is not desired to carry harmonics (for example, the resonance frequency of qubits, etc.)" and they may deviate from the design values. Therefore, it is difficult to pre-calculate the frequency of the clock signal during design so that the frequency of the harmonics of the clock signal is outside the "band where it is not desired to carry harmonics". Also, using a filter to remove the harmonics of the clock signal and the digital signal, or reducing the accuracy of the clock signal may reduce the quality of the microwave transmitted to the cooler.

[0020] To address these problems, in this embodiment, the adjustment circuit 40 adjusts so that the multiplication of the operating frequency f0 is different from the frequency of the microwave M. As a result, the factors causing harmonic noise to be superimposed on the microwave M are reduced or eliminated, so that the harmonic noise superimposed on the microwave M can be reduced.

[0021] The conversion circuit 50 converts the analog output signal A output from the cooler 10 into a digital output signal B. The output signal B is a digital signal representing the readout result of the state of the qubit 11.

[0022] The digital circuit 60 performs a predetermined process on the digital output signal B from the conversion circuit 50 and outputs it to the computer 500 as readout data d.

[0023] When the microwave M is a signal used for controlling the state of the quantum bit 11 or a signal used for reading out the state of the quantum bit 11, the state of the quantum bit 11 can be read out from the quantum bit 11 by the frequency of the microwave M matching the resonance frequency of the quantum bit 11. The adjustment circuit 40 adjusts the frequency of the microwave M to the resonance frequency of the quantum bit 11 so that the state of the quantum bit 11 can be read out from the output signal A transmitted from the quantum bit 11 or the cooler 10 (for example, read out from the output signal B or the digital data d). Thereby, the readout data d representing the readout result of the state of the quantum bit 11 can be supplied to the computer 500, and the computer 500 can acquire the readout data d from the digital circuit 60.

[0024] The resonance frequency of the quantum bit 11 may drift due to manufacturing variations of the quantum bit 11 or each time the quantum bit 11 is activated. The adjustment circuit 40 may observe the output signal A each time the quantum bit 11 is activated and adjust the frequency of the microwave M to the resonance frequency of the quantum bit 11 each time the quantum bit 11 is activated so that the state of the quantum bit 11 can be read out from the output signal A. Thereby, even if the resonance frequency of the quantum bit 11 deviates from the designed value, the readout data d representing the readout result of the state of the quantum bit 11 can be supplied to the computer 500, and the computer 500 can acquire the readout data d from the digital circuit 60.

[0025] The adjustment circuit 40 may adjust the operating frequency f0 so that the signal-to-noise ratio of the microwave M looped back before being input to the cooler 10 satisfies a predetermined reference value. Thereby, it is possible to reduce harmonics of frequencies not intended by the designer (for example, harmonics generated in the microwave M by the operation of software).

[0026] Next, a specific configuration example of the information processing system will be described.

[0027] FIG. 2 is a diagram showing a specific configuration example of an information processing system including an information processing apparatus according to an embodiment shown in FIG. 1. The information processing apparatus 100 includes a cooler 10 and a control device 300. The control device 300 is a device that controls the cooler 10 according to a command cmd input from a computer 500. The control device 300 includes a digital circuit 20, a conversion circuit 30, an adjustment circuit 40, a conversion circuit 50, and a digital circuit 60.

[0028] The control device 300 generates a plurality of microwaves M1, M2, M3 having different frequencies according to a command cmd input from the computer 500 and transmits them to the cooler 10. The microwave M1 is a control signal used for controlling the state of the quantum bit 11. The microwave M2 is a readout signal used for reading out the state of the quantum bit 11. The microwave M3 is a pump signal used for parametrically amplifying a signal representing the readout result of the state of the quantum bit 11 by an amplifier 14.

[0029] The cooler 10 cools the quantum bit 11. The cooler 10 includes, for example, a quantum bit 11, attenuators (ATT) 15, 16, 17, and an amplifier 14. The quantum bit 11 includes a resonator 12 used for controlling the state of the quantum bit 11 and a resonator 13 used for reading out the state of the quantum bit 11. The attenuators 15, 16, 17 attenuate the corresponding microwaves M1, M2, M3, respectively. The amplifier 14 is a parametric amplifier that parametrically amplifies a signal representing the state of the quantum bit 11 read by the resonator 13.

[0030] The digital circuit 20 generates a digital signal S according to a command cmd input from the computer 500. The digital circuit 20 includes, for example, a control signal generation unit 21, a writing unit 22, a RAM (Random Access Memory) 23, a reading unit 24, a read signal generation unit 25, a multiplication unit 26, and a control unit 27. The digital circuit 20 is formed by, for example, an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or a microcomputer, etc.

[0031] The control signal generation unit 21 generates a control signal for controlling the state of the quantum bit 11 according to the command cmd input from the computer 500. The writing unit 22 temporarily stores the control signal generated by the control signal generation unit 21 in the RAM 23. The reading unit 24 reads the control signal from the RAM 23 and outputs the read control signal as a digital signal S1.

[0032] The read signal generation unit 25 generates a read signal for reading the state of the quantum bit 11 according to the command cmd input from the computer 500. The read signal generation unit 25 outputs the generated read signal as a digital signal S2.

[0033] The control unit 27 controls the frequency adjustment of the phase-locked loop (PLL42) according to the command cmd input from the computer 500. The PLL42 outputs an operating frequency f0 according to the command cmd and adjusts the operating frequency f0 to the frequency specified by the command cmd. The multiplication unit 26 generates clock signals CK0, CK1, CK2 having frequencies obtained by multiplying the operating frequency f0. The frequencies of the clock signals CK0, CK1, CK2 are different from each other.

[0034] The control signal generation unit 21 and the writing unit 22 operate according to a clock signal CK0 used for the interface with the computer 500. The reading unit 24 and the DA converter 31 operate according to a clock signal CK1 for DA conversion. The DA converter 33 operates according to a clock signal CK2 for DA conversion.

[0035] The conversion circuit 30 includes a DA converter 31, a mixer 32, a DA converter 33, a mixer 34, and a multiplier 35.

[0036] The DA converter 31 is a circuit that converts the digital signal S1 into an analog signal RF1. The analog signal RF1 is an RF (Radio Frequency) signal. The frequency of the analog signal RF1 changes with the change in the operating frequency f0. The mixer 32 performs up-conversion of the analog signal RF1 to a microwave M1 by multiplying the analog signal RF1 by a local oscillation signal LO1. The local oscillation signal LO1 has a higher frequency than the analog signal RF1.

[0037] The DA converter 33 is a circuit that converts the digital signal S2 into an analog signal RF2. The analog signal RF2 is an RF signal. The frequency of the analog signal RF2 changes with the change in the operating frequency f0. The mixer 34 performs up-conversion of the analog signal RF2 to a microwave M2 by multiplying the analog signal RF2 by a local oscillation signal LO2. The local oscillation signal LO2 has a higher frequency than the analog signal RF2. The multiplier 35 generates a microwave M3 having a frequency twice that of the microwave M2.

[0038] The adjustment circuit 40 adjusts the operating frequency f0 such that the multiplication of the frequency of the analog signal RF1 is different from a predetermined frequency F1 (in this example, the resonance frequency of the resonator 12 used for controlling the state of the quantum bit 11). Thereby, the noise of the harmonic components that affect the resonance of the resonator 12 can be reduced. Also, the adjustment circuit 40 adjusts the operating frequency f0 such that the multiplication of the frequency of the analog signal RF2 is different from a predetermined frequency F2 (in this example, the resonance frequency of the resonator 13 used for reading the state of the quantum bit 11). Thereby, the noise of the harmonic components that affect the resonance of the resonator 13 can be reduced.

[0039] The adjustment circuit 40 may have a local oscillator 41 that adjusts the frequency of the local oscillation signal LO1 input to the mixer 32 such that the frequency of the microwave M1 matches a predetermined frequency F1 (in this example, the resonance frequency of the resonator 12 used for controlling the state of the quantum bit 11). Thereby, it is possible to achieve both the reduction of the noise of the harmonic components that affect the resonance of the resonator 12 and the control of the frequency of the microwave M1 to the frequency that resonates the resonator 12.

[0040] The adjustment circuit 40 may have a local oscillator 41 that adjusts the frequency of the local oscillation signal LO2 input to the mixer 34 such that the frequency of the microwave M2 matches a predetermined frequency F2 (in this example, the resonance frequency of the resonator 13 used for reading the state of the quantum bit 11). Thereby, it is possible to achieve both the reduction of the noise of the harmonic components that affect the resonance of the resonator 13 and the control of the frequency of the microwave M2 to the frequency that resonates the resonator 13.

[0041] The adjustment circuit 40 may have a local oscillator 41 that adjusts the frequency of the local oscillation signal LO2 input to the mixer 34 such that the frequency of the microwave M3 matches a predetermined frequency F3 (in this example, a frequency twice the resonance frequency of the resonator 13). Thereby, it is possible to achieve both the reduction of the noise of the harmonic components that affect the parametric amplification of the amplifier 14 and the control of the frequency of the microwave M3 to the frequency that parametrically oscillates the amplifier 14.

[0042] In this example, the adjustment circuit 40 includes a control unit 27, a local oscillator 41, and a PLL 42. The local oscillator 41 is an example of a first adjustment circuit that adjusts the frequency of microwaves. In this example, according to the first frequency adjustment signal output from the control unit 27, the frequencies of the microwaves M1, M2, and M3 are adjusted. The PLL 42 is an example of a second adjustment circuit that adjusts the operating frequency f0. In this example, according to the second frequency adjustment signal output from the control unit 27, the operating frequency f0 is adjusted. The adjustment circuit 40 uses at least one of the local oscillator 41 and the PLL 42 to adjust the multiplication of the operating frequency f0 so that it is different from the frequencies of the microwaves M1, M2, and M3. Thereby, the noise of the harmonic components that affect the control and reading of the quantum bit 11 can be reduced.

[0043] In this example, the local oscillator 41 adjusts the frequencies of the microwaves M1, M2, and M3 to predetermined frequencies F1, F2, and F3 corresponding thereto according to the first frequency adjustment signal output from the control unit 27. On the other hand, the PLL 42 adjusts the operating frequency f0 according to the second frequency adjustment signal output from the control unit 27 so that the multiplication of the operating frequency f0 is different from the predetermined frequencies F1, F2, and F3. Thereby, it is possible to achieve both the reduction of the noise of the harmonic components that affect the control and reading of the state of the quantum bit 11 and the control of the frequencies of the respective microwaves to the respective predetermined frequencies.

[0044] For example, consider a case where the multiplier 26 quadruples the operating frequency f0 of 500 MHz and the DA converter 31 creates an analog signal RF1 of 2 GHz. When the PLL 42 changes the operating frequency f0 to 490 MHz, the frequency of the analog signal RF1 decreases to 1.96 GHz (= 490 MHz × 4). The local oscillator 41 compensates for this frequency difference with a local oscillation signal LO1 in the microwave frequency band. Specifically, assume that the frequency of the microwave M1 is adjusted to 10 GHz by the 2 GHz analog signal RF1 and the 8 GHz local oscillation signal LO1. If the PLL 42 changes the operating frequency f0 to 490 MHz and the local oscillator 41 changes the frequency of the local oscillation signal LO1 to 8.04 GHz, as a result, the frequency of the microwave M1 is maintained at 10 GHz by the 1.96 GHz analog signal RF1 and the 8.04 GHz local oscillation signal LO1. The same applies to the other microwaves M2 and M3.

[0045] The conversion circuit 50 converts the analog output signal A output from the cooler 10 into a digital output signal B. The conversion circuit 50 includes a mixer 51 and an AD (Analog to Digital) converter 52.

[0046] The mixer 51 multiplies the analog output signal A output from the amplifier 14 by the local oscillation signal LO3 to down-convert the analog output signal A into an analog signal RF3. The local oscillation signal LO3 has a lower frequency than the analog output signal A. The analog signal RF3 is an RF signal. The AD converter 52 is a circuit that converts the analog signal RF3 into a digital signal B.

[0047] The digital circuit 60 generates read data d from the digital signal B according to a command cmd input from the computer 500. The digital circuit 60 includes, for example, a writing unit 62, a RAM 63, a reading unit 64, a transmitting unit 65, a multiplier 61, and a determination unit 66. The digital circuit 60 is formed by, for example, an FPGA, an ASIC, or a microcomputer.

[0048] The writing unit 62 temporarily stores the digital signal B in the RAM 63. The reading unit 64 reads the digital signal B from the RAM 63 and converts the read digital signal B into read data d. The transmitting unit 65 transmits the read data d to the computer 500. The determination unit 66 determines whether the SN ratio of the microwave M1 (which may be the microwave M2 or M3) looped back before being input to the cooler 10 satisfies a predetermined reference value, and outputs the read data d including the determination result to the computer 500. The frequency multiplying unit 61 generates clock signals CK0 and CK1 having frequencies obtained by multiplying the operating frequency f0. The frequencies of the clock signals CK0 and CK1 are different from each other.

[0049] The writing unit 62 and the AD converter 52 operate according to the clock signal CK1 for AD conversion. The determination unit 66, the transmitting unit 65, and the reading unit 64 operate according to the clock signal CK0 used in the interface with the computer 500.

[0050] Figure 3 is a hardware configuration diagram of a computer. The computer 500 shown in Figure 3 includes a drive device 501, an auxiliary storage device 502, a memory device 503, a CPU (Central Processing Unit) 504, and an interface device 505, etc., which are interconnected by a bus 506 respectively.

[0051] The program for realizing the processing in the computer 500 is provided by the recording medium 507. When the recording medium 507 recording the program is set in the drive device 501, the program is installed from the recording medium 507 to the auxiliary storage device 502 via the drive device 501. However, the installation of the program does not necessarily have to be performed from the recording medium 507, and it may be downloaded from another computer via a network. The auxiliary storage device 502 stores the installed program and also stores necessary files, data, etc.

[0052] When there is an instruction to start a program, the memory device 503 reads and stores the program from the auxiliary storage device 502. The CPU 504 is a processor that executes the functions related to the computer 500 according to the program stored in the memory device 503. The interface device 505 is used as an interface for connecting to the outside.

[0053] As an example of the recording medium 507, a portable recording medium such as a CD-ROM, a DVD disk, or a USB memory can be mentioned. As an example of the auxiliary storage device 502, an HDD (Hard Disk Drive) or a flash memory can be mentioned. Both the recording medium 507 and the auxiliary storage device 502 correspond to computer-readable recording media.

[0054] FIG. 4 is a flowchart showing a first example of a frequency adjustment method. The frequency adjustment method shown in FIG. 4 is realized by the control device 300 operating according to a command cmd from the computer 500. The frequency adjustment program for causing the computer 500 to execute each process shown in FIG. 4 is stored in the above-mentioned auxiliary storage device 502.

[0055] In step S10, the computer 500 outputs a command cmd (search command) for searching the resonance frequency of the quantum bit 11. The adjustment circuit 40 sweeps the use frequency f0 from the design value according to the search command. As a result, the frequency of the microwave M1 transmitted from the conversion circuit 30 sweeps from the design value. The computer 500 refers to the read data d generated by the conversion circuit 50 and the digital circuit 60 based on the output signal A transmitted from the cooler 10, and searches for the frequency that reacts to the read data d. The search result of the frequency that reacts is stored as a predetermined frequency F1 in the storage device of the computer 500. Similarly, the computer 500 sweeps the frequencies of the microwaves M2 and M3, searches for the frequency that reacts to the read data d, and stores the search result of the frequency that reacts as predetermined frequencies F2 and F3 in the storage device.

[0056] In step S20, computer 500 calculates the operating frequency f0 in digital circuit 20. Computer 500 determines whether the multiplication of the operating frequency f0 matches the predetermined frequencies F1, F2, F3. If the multiplication of the operating frequency f0 does not match the predetermined frequencies F1, F2, F3, computer 500 outputs a command cmd (first setting command) for setting the operating frequency f0. On the other hand, if the multiplication of the operating frequency f0 matches the predetermined frequencies F1, F2, F3, computer 500 outputs a command cmd (first setting command) for changing the operating frequency f0, for example, in units of 0.1 MHz.

[0057] In step S30, control unit 27 of adjustment circuit 40 sets the operating frequency f0 generated by PLL 42 to the frequency specified by the first setting command.

[0058] In step S40, computer 500 calculates the frequencies of analog signals RF1, RF2 that change according to the operating frequency f0 set in step S30.

[0059] In step S50, computer 500 sets the frequencies of microwaves M1, M2, M3. Computer 500 outputs a command cmd (second setting command) for setting the frequency of local oscillation signal LO1 so that the frequency of microwave M1 matches the predetermined frequency F1 according to the analog signal RF1 calculated in step S40. Control unit 27 of adjustment circuit 40 sets the frequency of local oscillation signal LO1 to the frequency specified by the second setting command. Similarly, computer 500 outputs a command cmd (second setting command) for setting the frequency of local oscillation signal LO2 so that the frequency of microwave M2 matches the predetermined frequency F2 according to the analog signal RF2 calculated in step S40. Control unit 27 of adjustment circuit 40 sets the frequency of local oscillation signal LO2 to the frequency specified by the second setting command.

[0060] As described above, since the information processing apparatus 100 according to this embodiment includes two frequency variable functions of the PLL 42 and the local oscillator 41, the degree of freedom in setting the microwave frequency range is increased as compared with a form having only one frequency variable function. As a result, it becomes easier to achieve both reduction of noise of harmonic components that affect the control and reading of the state of the quantum bit 11 and control of the frequency of each microwave to each predetermined frequency.

[0061] FIG. 5 is a flowchart showing a second example of the frequency adjustment method. The frequency adjustment method shown in FIG. 5 is realized by the control device 300 operating according to a command cmd from the computer 500. A frequency adjustment program for causing the computer 500 to execute each process shown in FIG. 5 is stored in the auxiliary storage device 502 described above. The descriptions of steps S10, S20, S30, S40, and S50 are omitted because they are the same as those in FIG. 4.

[0062] In step S60, the computer 500 acquires, from the read data d, the measurement result of the signal-to-noise ratio of the resonance frequency of the quantum bit 11 by the determination unit 66. Thereby, the computer 500 can grasp harmonic waves of frequencies that are not intended by the designer (for example, harmonic waves generated in the microwave M1 or the like due to the operation of software).

[0063] In step S70, the computer 500 determines whether or not the signal-to-noise ratio satisfies a predetermined reference value. If the signal-to-noise ratio does not satisfy the predetermined reference value, the computer 500 returns to the process of step S20. In step S20, the computer 500 recalculates the use frequency f0 in the digital circuit 20 so that the multiplication of the use frequency f0 does not match the predetermined frequencies F1, F2, and F3. Thereby, harmonic waves of frequencies that are not intended by the designer (for example, harmonic waves generated in the microwave M1 or the like due to the operation of software) can be reduced.

[0064] For example, when the width of the resonance frequency of the quantum bit 11 is a, if there is harmonic noise within the range of ±a / 2 from the center of a, the operating frequency f0 is changed so that the resonance frequency of the quantum bit 11 changes in units of a / 2.

[0065] Although the embodiments have been described above, the technology of the present disclosure is not limited to the above embodiments. Various modifications and improvements such as combinations or replacements with some or all of other embodiments are possible.

Explanation of reference numerals

[0066] 10 Cooler 11 Quantum bit 12, 13 Resonator 14 Amplifier 15, 16, 17 Attenuator 20 Digital circuit 30 Conversion circuit 40 Adjustment circuit 50 Conversion circuit 60 Digital circuit 100 Information processing apparatus 200 Information processing system 300 Control apparatus 500 Computer A Output signal B Digital signal M Microwave S Digital signal

Claims

1. A quantum bit, A digital circuit that generates a digital signal, A conversion circuit that converts the digital signal into a microwave to be transmitted to the quantum bit, An information processing apparatus comprising: an adjustment circuit that sets the first frequency so that a harmonic frequency of the first frequency of a clock used in the digital circuit is different from a second frequency of the microwave.

2. The information processing apparatus according to claim 1, wherein the adjustment circuit sets the second frequency to a predetermined frequency and sets the first frequency so that an integer multiple of the first frequency is different from the predetermined frequency.

3. The conversion circuit includes a converter that converts the digital signal into an analog signal and a mixer that performs up-conversion of the analog signal into the microwave, The second frequency changes with a change in the first frequency, The information processing apparatus according to claim 2, wherein the adjustment circuit adjusts the first frequency so that an integer multiple of the first frequency is different from the predetermined frequency.

4. The information processing apparatus according to claim 1, wherein the adjustment circuit includes a first adjustment circuit that adjusts the second frequency to a predetermined frequency and a second adjustment circuit that adjusts the first frequency so that an integer multiple of the first frequency is different from the second frequency.

5. The information processing apparatus according to any one of claims 2 to 4, wherein the predetermined frequency is a resonance frequency of the quantum bit.

6. The information processing apparatus according to claim 5, wherein the adjustment circuit adjusts the second frequency to the resonance frequency so that the state of the quantum bit is read from an output signal from the quantum bit or an output signal from a cooler that cools the quantum bit.

7. The adjustment circuit according to claim 6, wherein the adjustment circuit observes the output signal every time the device is activated, and adjusts the second frequency to the resonance frequency every time the device is activated so that the state of the quantum bit is read from the output signal.

8. The digital circuit generates a digital signal, The conversion circuit converts the digital signal into a microwave to be transmitted to the quantum bit, A frequency adjustment method, wherein the adjustment circuit adjusts the first frequency so that an integer multiple of the first frequency of the clock used in the digital circuit is different from the second frequency of the microwave.

9. A digital circuit generates a digital signal, A conversion circuit converts the digital signal into a microwave to be transmitted to the quantum bit, An adjustment circuit adjusts the first frequency so that an integer multiple of the first frequency of the clock used in the digital circuit is different from the second frequency of the microwave, A frequency adjustment program for causing a computer to execute the process.

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