Adaptive control apparatus for quantum computing system

Abstract

This invention provides an adaptive control apparatus, which includes a quantum circuit information processing unit, a quantum computing quality evaluation unit, and an adaptive control unit. The quantum circuit information processing unit inputs a quantum circuit information into the quantum computing unit, so that the quantum computing unit performs a calculation according to the quantum circuit information. The quantum computing quality evaluation unit receives the measurement information of at least one quantum bit of the quantum computing unit and performs an error rate calculation according to the measurement information of the quantum bit to generate an error rate. The adaptive control unit receives the error rate outputted by the quantum computing quality evaluation unit. When the error rate is greater than an error rate threshold, the adaptive control unit generates at least one pulse adjustment parameter, and the pulse generation unit generates a pulse signal according to the pulse adjustment parameter and outputs the pulse signal to the quantum computing unit.

Description

[Technical Field]

[0001] The present invention relates to an adaptive control device, and more particularly to an adaptive control device used in a quantum computing system. [Previous Technology]

[0002] The development of quantum computing technology stems from in-depth exploration of the principles of quantum mechanics and is rapidly becoming an important trend in future computing technology. Unlike traditional computers, quantum computers use qubits for computation. These qubits can simultaneously exist in a superposition of 0 and 1, and achieve high-speed computation through quantum entanglement or quantum superposition. Early quantum computing theories were proposed by Richard Feynman and Peter Shor, while current technological development is driven by companies such as IBM, Google, Microsoft, and IonQ.

[0003] Currently, the main quantum computing technologies include superconducting qubits, ion trap qubits, and photonic quantum computing. Although quantum computers still face many challenges at this stage, such as decoherence and error rate control, scientists are gradually improving the usability and stability of quantum computing with the advancement of quantum error correction or quantum superposition technologies.

[0004] Quantum superposition is one of the core concepts of quantum computing, referring to the linear combination of qubits being able to be in both 0 and 1 states simultaneously. This allows quantum computers to perform multiple calculations in parallel when processing information, thus exhibiting stronger computing power than traditional classical computers in certain specific problems. For example, in factorization, quantum simulation, and optimization problems, quantum computing can significantly improve computational efficiency. However, in reality, quantum superposition states are extremely fragile and easily collapse due to environmental noise or measurement, resulting in a high error rate for quantum computers. To overcome this problem, researchers are committed to developing quantum error correction codes and error correction techniques to reduce the impact of external noise on computation results. In addition, the hardware implementation of quantum computing still faces challenges, such as how to stably control a large number of qubits and maintain their coherence. These problems limit the scalability of current quantum computers, making it difficult for them to handle larger-scale computational tasks.

[0005] As mentioned above, in quantum computing systems, they are very susceptible to interference from the external environment (environmental noise), such as temperature changes, electromagnetic field fluctuations, vacuum levels, or ambient air pressure. These interferences may cause qubits to decoherence, causing their original superposition state to disappear rapidly and become a definite classical state (0 or 1). This phenomenon can lead to computational errors. Therefore, how to accurately control quantum systems and reduce environmental noise is a major challenge for quantum computing technology.

[0006] Current quantum computing systems primarily use pulse control techniques to adjust the phase and amplitude of quantum states to generate the desired quantum state. However, due to the influence of environmental noise and quantum decoherence, quantum states are still susceptible to interference, leading to computational errors. Effective methods for reducing environmental noise, mainly applied to dynamical decoupling (DD) and optimal quantum control, both rely on controlling pulse waves to achieve more accurate quantum computing results. Therefore, providing a stable pulse wave control technique to minimize the impact of environmental noise on quantum computing systems remains a significant challenge. [Summary of the Invention]

[0007] In view of the above problems, the object of the present invention is to provide a stable pulse wave control technology, so as to improve the availability and stability of a quantum computing system through an adaptive control device.

[0008] To achieve the above objectives, the adaptive control device of the present invention is applied to a quantum computing system, which includes a quantum computing unit and a pulse generation unit. The adaptive control device of the present invention includes a quantum circuit information processing unit, a quantum operation quality evaluation unit, and an adaptive control unit. The quantum circuit information processing unit inputs quantum circuit information into the quantum computing unit and performs quantum operations based on the quantum circuit information; the quantum operation quality evaluation unit receives measurement information of at least one qubit of the quantum computing unit and performs error rate calculation based on the measurement information of the qubit to generate an error rate; and the adaptive control unit receives the error rate output by the quantum operation quality evaluation unit, and when the error rate is greater than an error rate threshold, generates at least one pulse adjustment parameter. The pulse generation unit generates a pulse signal based on the pulse adjustment parameter and outputs the pulse signal to the quantum computing unit.

[0009] In one embodiment, the error rate threshold in the adaptive control unit of the adaptive control device of the present invention is less than 0.2.

[0010] In one embodiment, the adaptive control device of the present invention further includes a pulse adjustment parameter input unit, which includes a pulse adjustment parameter input interface for manually inputting at least one disturbance parameter, and the adaptive control unit regenerates another pulse adjustment parameter based on the disturbance parameter.

[0011] In one embodiment, the pulse adjustment parameter includes an amplitude parameter, a phase parameter, a frequency parameter, or a period parameter.

[0012] In one embodiment, the disturbance parameter may include an amplitude disturbance parameter, a phase disturbance parameter, a frequency disturbance parameter, or a period disturbance parameter.

[0013] In one embodiment, the pulse signal output by the pulse generation unit is a microwave pulse signal or a laser pulse signal.

[0014] In one embodiment, in the adaptive control unit, if the error rate is less than the error rate threshold, the pulse adjustment parameter is maintained.

[0015] In one embodiment, when the pulse adjustment parameter includes an amplitude parameter, the adaptive control unit increases or decreases the amplitude parameter by an amplitude change to generate another pulse adjustment parameter.

[0016] In one embodiment, when the pulse adjustment parameter includes a phase parameter, the adaptive control unit increases or decreases the phase parameter by a phase change to generate another pulse adjustment parameter.

[0017] In one embodiment, when the pulse adjustment parameter includes a frequency parameter, the adaptive control unit increases or decreases the frequency parameter by a frequency change to generate another pulse adjustment parameter.

[0018] In one embodiment, when the pulse adjustment parameter includes a period parameter, the adaptive control unit increases or decreases the period parameter by one period change to generate another pulse adjustment parameter.

[0019] In summary, since the quantum computing quality evaluation unit of the present invention can generate an error rate, and based on the error rate, the adaptive control device of the present invention generates at least one pulse adjustment parameter to respectively control the quantum state and evolution speed, and whether it resonates with the energy level of the qubit, and then generates a precise pulse signal based on the pulse adjustment parameter, the adaptive control device of the present invention can improve the availability and stability of the quantum computing system.

Implementation Method

[0020] Hereinafter, embodiments of the present invention will be specifically described with reference to the figures. Before the specific description, it should be noted that the quantum computing system in this embodiment may include a quantum computing unit (or quantum chip) and a pulse generation unit.

[0021] Please refer to Figure 1. The adaptive control device 1 of the present invention is used in a quantum computing system 2. The quantum computing system 2 includes a quantum computing unit 21 and a pulse generation unit 22. The adaptive control device 1 includes a quantum circuit information processing unit 11, a quantum computing quality evaluation unit 12 and an adaptive control unit 13.

[0022] The quantum circuit information processing unit 11 inputs quantum circuit information into the quantum computing system 2. The quantum computing unit 21 performs quantum computation based on the quantum circuit information and pulse signals generated by the pulse generation unit 22. The quantum computation quality evaluation unit 12 receives measurement information from at least one qubit of the quantum computing unit 21 and performs error rate calculation based on the qubit measurement information to generate an error rate. The error rate is calculated using the following formula: It should be noted that the above error rate calculation method is disclosed in Taiwan Patent Application No. 113113443, and its details are omitted here.

[0023] The adaptive control unit 13 receives the error rate output by the quantum computing quality evaluation unit 12. When the error rate is greater than an error rate threshold, it generates at least one pulse adjustment parameter. It should be noted that in this embodiment, the error rate threshold represents a user's tolerance for the error rate, for example, a value less than 0.2. The pulse adjustment parameter includes at least one amplitude parameter, one phase parameter, one frequency parameter, or one period parameter. Of course, the adaptive control unit 13 can also generate more than one pulse adjustment parameter. In other words, the pulse adjustment parameter can include any combination of two, three, or four of the aforementioned parameters, thereby changing the pulse signal output by the pulse generation unit 22.

[0024] The following uses a microwave pulse signal to further illustrate the control operation of the adaptive control unit 13 of the present invention.

[0025] A controllable square wave microwave pulse signal can be expressed as: where, : amplitude modulation function, which varies with time. : square wave pulse envelope function. T: pulse period. is a positive integer, representing the time point of the i-th square wave center. τ: pulse width. : carrier frequency. : phase modulation function.

[0026] As mentioned above, according to the square wave microwave pulse signal equation, a specific pulse signal can be generated by appropriately adjusting the pulse parameter (), thereby controlling the quantum state of the qubit to conform to the target state. In other words, as long as the pulse adjustment is precise, quantum gates such as X gate, Y gate, and Hadamard gate can be implemented. That is to say, when the error rate is greater than an error rate threshold, the adaptive control unit 13 can generate a pulse adjustment parameter to adjust any one of the four parameters (). For example, within a time interval, if the generated pulse adjustment parameter is to decrease T, the number of pulses will increase; conversely, if the generated pulse adjustment parameter is to increase T, the number of pulses will decrease. Whether to decrease or increase T depends on the adjustment. After the adjustment, the quantum computing quality evaluation unit 12 receives the measurement information of the qubit from the quantum computing unit 21 again, and performs error rate calculation based on the measurement information of the qubit to obtain another error rate (adjusted error rate), until the error rate is less than the error rate threshold before no further adjustment is made.

[0027] Of course, the adjustment method for other parameters is roughly the same as that for the T parameter. For example, the phase can be adjusted. That is, if the phase is adjusted to and the error rate after the phase adjustment is greater than the error rate threshold (the error rate before adjustment), then the phase system is immediately adjusted to . At this time, if the error rate after adjustment is less than the error rate before adjustment, then the phase system continues to be adjusted to until the error rate is less than the error rate threshold before no further adjustment is made. In short, in this embodiment, the pulse adjustment parameter is the phase adjustment parameter after the phase parameter is increased or decreased by a phase change (;), and when the error rate after adjustment is less than the error rate before adjustment, the phase adjustment parameter continues to be adjusted in the direction of decreasing (). Of course, other parameter adjustment methods are also done in the same way. Here, it should be noted that the aforementioned symbols represent a change in any parameter.

[0028] As can be seen from the above, in the embodiments, when the pulse adjustment parameter includes a phase parameter, the adaptive control unit increases or decreases the phase parameter by a phase change amount to generate another pulse adjustment parameter; similarly, when the pulse adjustment parameter includes an amplitude parameter, the adaptive control unit increases or decreases the amplitude parameter by an amplitude change amount to generate another pulse adjustment parameter. The same applies when the pulse adjustment parameter includes a frequency parameter or a period parameter.

[0029] Furthermore, it should be noted that the adaptive control unit 13 of the present invention can also generate two or more pulse adjustment parameters, such as a pulse adjustment parameter for adjusting the amplitude and a pulse adjustment parameter for adjusting the phase. In this case, the adaptive control unit 13 controls the quantum state and its evolution process. Moreover, the adjustment method for other square wave pulse signals, such as square wave laser pulse signals, is the same.

[0030] Referring to Figure 2, the adaptive control device 1 of the present invention may further include a pulse adjustment parameter input unit 14. The pulse adjustment parameter input unit 14 includes a pulse adjustment parameter input interface (not shown) for manually inputting at least one disturbance parameter. The adaptive control unit 13 then regenerates another pulse adjustment parameter based on the disturbance parameter. For example, if we find that the pulse adjustment parameter generated by the adaptive control unit 13 decreases the period T but increases the error rate, the operator can manually input a larger period T value or value through the pulse adjustment parameter input interface, thereby changing the disturbance direction of the original pulse adjustment parameter to increase the period T, thus reducing the error rate. It is worth mentioning that in this embodiment, the disturbance parameter is not only used to disturb the direction of the pulse adjustment parameter generated by the adaptive control unit 13 to increase or decrease, but can also be used to accelerate the increase or decrease of the original pulse adjustment parameter, thereby accelerating the reduction of the error rate.

[0031] In this embodiment, the disturbance parameter is an amplitude disturbance parameter, a phase disturbance parameter, a frequency disturbance parameter, or a period disturbance parameter.

[0032] Please refer to Figure 2. The adaptive control device 1 of the present invention can be combined with the quantum computing system 2 to form a quantum computing system with an adaptive control device. In other words, in practical applications, the adaptive control device 1 and the quantum computing system 2 in this embodiment can be integrated to form a more complete quantum computing system.

[0033] In summary, since the quantum computing quality evaluation unit of the present invention can generate an error rate, and based on the error rate, the adaptive control device of the present invention generates at least one pulse adjustment parameter to respectively control the quantum state and evolution speed, and whether it resonates with the energy level of the qubit, and then generates a precise pulse signal based on the pulse adjustment parameter, the adaptive control device of the present invention can improve the availability and stability of the quantum computing system. [Simplified Explanation of the Diagram]

[0034] Figure 1 is a block diagram illustrating the adaptive control device of the present invention used in a quantum computing system.

[0035] Figure 2 is another block diagram illustrating the adaptive control device of the present invention used in a quantum computing system.

Claims

1. An adaptive control device is used in a quantum computing system, the quantum computing system including a quantum computing unit and a pulse generation unit, the adaptive control device comprising: a quantum circuit information processing unit that inputs quantum circuit information into the quantum computing unit and performs quantum operations based on the quantum circuit information; a quantum operation quality evaluation unit that receives measurement information of at least one qubit of the quantum computing unit and performs error rate calculation based on the measurement information of the qubit to generate an error rate; and an adaptive control unit that receives the error rate output by the quantum operation quality evaluation unit, and when the error rate is greater than an error rate threshold, increases or decreases a change amount to generate at least one pulse adjustment parameter, the pulse generation unit generates a pulse signal based on the pulse adjustment parameter and outputs the pulse signal to the quantum computing unit; and maintains the pulse adjustment parameter until the error rate is less than the error rate threshold.

2. The adaptive control device as claimed in claim 1, wherein the error rate threshold in the adaptive control unit is less than 0.

2.

3. The adaptive control device as claimed in claim 1 further includes a pulse adjustment parameter input unit, which includes a pulse adjustment parameter input interface for manually inputting at least one disturbance parameter, and the adaptive control unit regenerates another pulse adjustment parameter based on the disturbance parameter.

4. The adaptive control device as described in claim 1 or claim 3, wherein the pulse adjustment parameter includes an amplitude parameter, a phase parameter, a frequency parameter, or a period parameter.

5. The adaptive control device as claimed in claim 3, wherein the disturbance parameter includes an amplitude disturbance parameter, a phase disturbance parameter, a frequency disturbance parameter, or a period disturbance parameter.

6. The adaptive control device as claimed in claim 1, wherein the pulse signal output by the pulse generation unit is a microwave pulse signal or a laser pulse signal.

7. The adaptive control device as claimed in claim 4, wherein when the pulse adjustment parameter includes the amplitude parameter, the adaptive control unit increases or decreases the amplitude parameter by an amplitude change to generate another pulse adjustment parameter.

8. The adaptive control device as claimed in claim 4, wherein when the pulse adjustment parameter includes the phase parameter, the adaptive control unit increases or decreases the phase parameter by a phase change to generate another pulse adjustment parameter.

9. The adaptive control device as claimed in claim 4, wherein when the pulse adjustment parameter includes the frequency parameter, the adaptive control unit increases or decreases the frequency parameter by a frequency change to generate another pulse adjustment parameter.

10. The adaptive control device as claimed in claim 4, wherein when the pulse adjustment parameter includes the period parameter, the adaptive control unit increases or decreases the period parameter by a period change to generate another pulse adjustment parameter.

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