A quantum measurement and control signal feedback device and method based on weak magnetic field detection

Abstract

The present invention discloses a quantum measurement and control signal feedback device and method based on weak magnetic field detection, including a quantum chip, a superconducting quantum interference device detector, a control signal generation module, and a main control module. A first control signal is generated by the control signal generation module to manipulate quantum bits. The change in the state of the quantum bits generates a stray magnetic field, which is captured by the superconducting quantum interference device detector and converted into a weak magnetic signal. The main control module receives the weak magnetic signal, compares it with the first control signal, generates a feedback control signal to adjust the state of the quantum bits, and measures the signal crosstalk between the quantum bits by setting the size and position of the probe, thereby improving the control accuracy. The present invention realizes real-time feedback by monitoring the stray magnetic field generated by the quantum bits through the superconducting quantum interference device detector, does not need to directly read the state of the quantum bits, causes the least interference to the operation of the quantum chip, significantly improves the control accuracy of the quantum chip, and can simultaneously detect the signal crosstalk between the quantum bits.

Description

Technical Field

[0001] The present invention relates to the field of quantum information technology, and particularly to a quantum measurement and control signal feedback device and method based on weak magnetic field detection. Background Art

[0002] With the rapid development of quantum information technology, quantum chips and quantum bit control technology have become hot topics in the research field. As the core component of quantum information processing, quantum chips usually need to work in an extremely low temperature environment to ensure high-precision control signals and feedback control. Traditional quantum chip control methods mainly rely on reading the logical states of quantum bits to achieve feedback control, but this method has deficiencies in real-time performance and anti-interference ability, which may cause delays and instabilities in feedback control, thus affecting the overall performance of quantum chips.

[0003] To overcome these challenges, researchers have begun to use superconducting quantum interference devices for feedback control of weak magnetic field detection. As a highly sensitive magnetic field detector, a superconducting quantum interference device can operate reliably in an extremely low temperature environment and sense the weak stray magnetic field generated by quantum bit control signals. However, although the weak magnetic field detection method based on superconducting quantum interference devices has many theoretical advantages, a series of technical problems still need to be solved in practical applications. For example, in patent CN114037085A, a quantum manipulation feedback system and method, this feedback system needs to characterize the quantum state, and there are problems such as insufficient real-time performance, susceptibility to interference, and inability to detect signal crosstalk.

[0004] Therefore, how to solve the deficiencies and shortages of the prior art through an effective quantum measurement and control signal feedback method has become an important problem that needs to be solved urgently by researchers in this field. Summary of the Invention

[0005] The object of the present invention is to provide a quantum measurement and control signal feedback device and method based on weak magnetic field detection for the above problems.

[0006] The technical solution of the present invention is as follows: a quantum chip, the quantum chip includes an input end and an output end, and a plurality of signal transmission lines connected between the input end and the output end. A first signal node is included on the signal transmission line, and a quantum bit is connected between the first signal node and the output end. The input end is used to receive a control signal; a control signal generation module is used to generate a first control signal for controlling the quantum bit in the quantum chip. The first control signal is transmitted in the plurality of signal transmission lines and generates a stray magnetic field; a superconducting quantum interference device detector is used to detect the weak magnetic signal generated by the stray magnetic field at the first signal node; a main control module is used to compare the first control signal with the weak magnetic signal and generate a feedback control signal, and the feedback control signal is used to adjust the weak magnetic signal to be consistent with the first control signal.

[0007] As an improvement of an embodiment of the present invention, a probe is provided in the superconducting quantum interference device detector, and the projected area of the probe is less than 0.1 mm 2 , and the distance between the probe and the quantum chip is N, where 0.1 mm < N < 5 mm.

[0008] As an improvement of an embodiment of the present invention, the distance N between the probe and the quantum chip is 1 mm.

[0009] As an improvement of an embodiment of the present invention, the feedback control signal inverts the difference between the first control signal and the weak magnetic signal, and is conducted through the feedback loop to the first signal node to compensate for the fluctuation of the first control signal, so that the weak magnetic signal is consistent with the first control signal.

[0010] As an improvement of an embodiment of the present invention, the quantum chip includes a plurality of quantum gates for performing logical operations or quantum operations on qubits, and the quantum gates operate based on the logical states of the qubits to realize the processing and transformation of quantum information.

[0011] As an improvement of an embodiment of the present invention, the main control module further includes a signal amplification unit for amplifying the weak magnetic signal detected by the superconducting quantum interference device detector.

[0012] As an improvement of an embodiment of the present invention, the main control module further includes a signal filtering unit for filtering the weak magnetic signal detected by the superconducting quantum interference device detector.

[0013] As an improvement of an embodiment of the present invention, the main control module further includes a comparator for comparing the difference between the weak magnetic signal and the first control signal.

[0014] To achieve one of the above-mentioned invention purposes, an embodiment of the present invention provides a quantum measurement and control signal feedback method based on weak magnetic detection. The quantum measurement and control signal feedback method is applied to the quantum measurement and control signal feedback device described in any one of the above, and includes the following steps: generating a first control signal for controlling qubits in the quantum chip through the control signal generation module and transmitting it to the input end of the quantum chip; the first control signal is transmitted in the plurality of signal transmission lines and generates a stray magnetic field; detecting the weak magnetic signal generated by the stray magnetic field at the first signal node through the superconducting quantum interference device detector; the main control module compares the weak magnetic signal with the first control signal and generates a feedback control signal, and the feedback control signal is used to adjust the weak magnetic signal to be consistent with the first control signal.

[0015] As an improvement of the embodiment of the present invention, the following steps are further included: measuring the signal crosstalk between the qubits by a probe disposed in the superconducting quantum interference device detector and feeding it back to the main control module.

[0016] The quantum measurement and control signal feedback method and device based on weak magnetic detection provided by the embodiment of the present invention have the following advantages: The present invention realizes real-time feedback control by using a superconducting quantum interference device to monitor the stray magnetic field generated by the qubit control signal in real time, without directly reading the qubit state, causing the least interference to the operation of the quantum chip, significantly improving the control accuracy and stability of the quantum chip, and being able to detect the signal crosstalk between the qubits at the same time. Description of the Drawings

[0017] Figure 1 is a schematic diagram of the positions of the quantum chip and the superconducting quantum interference device detector of the present invention;

[0018] Figure 2 is a schematic flow chart of the quantum measurement and control signal feedback method based on weak magnetic detection of the present invention. Detailed Embodiments

[0019] The present invention will be described in detail below in conjunction with the specific embodiments shown in the drawings. However, these embodiments do not limit the present invention, and any structural, method, or functional transformation made by those of ordinary skill in the art based on these embodiments is included in the protection scope of the present invention.

[0020] If the present invention involves directions (such as up, down, left, right, front, back, outside, inside, etc.) when expressing, the involved directions need to be defined.

[0021] The scope of the embodiments herein includes the entire scope of the claims and all available equivalents of the claims. Herein, the terms "first", "second", etc. are only used to distinguish one element from another, and do not require or imply any actual relationship or order between these elements. In fact, the first element can also be called the second element, and vice versa. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, so that a structure, device or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such structure, device or equipment. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the structure, device or equipment including the said element. The various embodiments herein are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0022] The terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. in this article indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing this article and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In the description of this article, unless otherwise specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the communication inside two elements. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0023] Embodiment 1 of the present invention provides a quantum measurement and control signal feedback device based on weak magnetic detection, including:

[0024] A quantum chip 1, as Figure 1 shown, the quantum chip 1 includes an input end 11 and an output end 12, and a plurality of signal transmission lines 13 connected between the input end 11 and the output end 12. A first signal node 14 is included on the signal transmission line 13. A quantum bit 15 is connected between the first signal node 14 and the output end 12. The input end 11 is used to receive a control signal. In practice, a quantum chip is a core component in the field of quantum information technology. Its basic unit is a quantum bit. The logical state of a quantum bit can be 0, 1, and the superposition state of 0 and 1. The state of a quantum bit can be manipulated by an external control signal.

[0025] A control signal generation module, configured to generate a first control signal for controlling the quantum bit 15 in the quantum chip 1. The first control signal is transmitted in the plurality of signal transmission lines 13 and generates a stray magnetic field. In practice, the first control signal can be an electrical signal or a microwave signal, etc. When the quantum bit 15 receives the first control signal, its logical state will change.

[0026] A superconducting quantum interference device detector 2, configured to detect a weak magnetic signal generated by the stray magnetic field at the first signal node 14. Here, the superconducting quantum interference device detector 2 is a high-sensitivity magnetic field detector that can detect weak magnetic field changes in an extremely low-temperature environment. In the present invention, the superconducting quantum interference device detector 2 described is used to detect the stray magnetic field at the first signal node 14 and convert the detected weak magnetic signal into an electrical signal for output.

[0027] The main control module is used to compare the first control signal with the field-weakening signal and generate a feedback control signal, which is used to adjust the field-weakening signal to be consistent with the first control signal.

[0028] Here, before the device starts, initialization operations need to be performed, including setting the working parameters of the quantum chip 1, calibrating the sensitivity of the superconducting quantum interference device detector 2, and configuring the control logic of the main control module, etc. The control signal generation module generates the first control signal according to a preset algorithm or instruction, and transmits the first control signal to the quantum chip 1 to manipulate the state of the quantum bit 15. The first control signal is transmitted in the several signal transmission lines 13 and generates a stray magnetic field. The superconducting quantum interference device detector 2 senses the magnetic field signal and converts it into an electrical signal and outputs it to the main control module. The main control module receives the first control signal and the field-weakening signal output by the superconducting quantum interference device detector 2, and compares and analyzes the first control signal with the field-weakening signal. If there is a difference between the first control signal and the field-weakening signal, the main control module will generate a corresponding feedback control signal, and based on the feedback control signal, adjust the fluctuation of the first control signal, thereby improving the accuracy of the control of the quantum chip 1. At the same time, the main control module can also detect the signal crosstalk between the quantum bits 15 on the quantum chip 1 in real time, and adjust the position and size of the probe 21 in the superconducting quantum interference device detector 2 according to the detection result to optimize the detection effect.

[0029] In this embodiment, a probe 21 is provided in the superconducting quantum interference device detector 2, and the projected area of the probe 21 is less than 0.1 mm 2 , and the distance between the probe 21 and the quantum chip 1 is N, 0.1 mm < N < 5 mm. Preferably, N = 1 mm. It can be understood that setting N to 1 mm can not only maintain an appropriate interval between the probe 21 and the quantum chip 1, reduce the physical contact between the probe 21 and the quantum chip 1, thereby reducing the noise and interference generated by the contact, but also ensure that the superconducting quantum interference device detector 2 can capture the magnetic field signal, improving the accuracy and reliability of the measurement.

[0030] In this embodiment, the feedback control signal inverts the difference between the first control signal and the field-weakening signal, and conducts it through the feedback loop to the first signal node 14 to compensate for the fluctuation of the first control signal, so that the field-weakening signal is consistent with the first control signal.

[0031] Here, a feedback loop connecting the main control module and the quantum chip 1 is also provided on the main control module. The feedback loop is used to conduct a feedback control signal to the first signal node 14. In practice, the state of the quantum bit 15 in the quantum chip 1 needs to be regulated by a control signal. However, due to factors such as environmental noise and system instability, the directly applied first control signal often fluctuates, which will affect the stability and accuracy of the state of the quantum bit 15. The feedback control signal is generated based on the difference between the first control signal and the weak magnetic signal detected by the superconducting quantum interference device detector 2 at the first signal node 14. This difference reflects the deviation of the first control signal relative to the weak magnetic signal. To eliminate this deviation, a feedback control signal opposite in phase to the difference is generated. The role of the feedback control signal is to finely adjust the weak magnetic signal through the feedback loop to compensate for the fluctuation of the first control signal. It can be understood that in this way, the precise control of the state of the quantum bit 15 and the high-stability operation of the quantum chip 1 are achieved.

[0032] In this embodiment, the quantum chip 1 includes a plurality of quantum gates for performing logical operations or quantum operations on the quantum bit 15. The quantum gates operate based on the logical state of the quantum bit 15 to realize the processing and transformation of quantum information.

[0033] In practice, the quantum gates can be single-quantum-bit 15 gates, such as Hadamard gate, Pauli-X gate (NOT gate), Phase gate, etc.; two-quantum-bit 15 gates: such as Controlled-NOT gate (CNOT gate), Controlled-Z gate, etc.; multi-quantum-bit 15 gates: such as Toffoli gate, Fredkin gate, etc. It can be understood that the quantum gates operate based on the logical state of the quantum bit 15 and play a crucial role in quantum information processing.

[0034] In this embodiment, the main control module further includes a signal amplification unit for amplifying the weak magnetic signal detected by the superconducting quantum interference device detector 2.

[0035] Here, the main task of the signal amplification unit is to amplify the weak electrical signal output by the superconducting quantum interference device detector 2 so that subsequent signal processing can be carried out accurately and effectively. To reduce noise interference during amplification, the signal amplification unit can use a low-noise amplifier to ensure that while amplifying the signal, the noise generated by itself is minimized. Since the superconducting quantum interference device detector 2 may generate signals of different amplitudes in different application scenarios, the signal amplification unit described in this embodiment has a gain adjustable function, allowing users to adjust the amplification factor according to actual needs, so as to achieve the best signal quality. To maintain the integrity of the signal, the signal amplification unit also has high linearity, that is, a good linear relationship should be maintained between the input signal and the second signal. It can be understood that this helps to reduce distortion and avoid errors caused by non-linear effects. In addition, to reduce the influence of electromagnetic interference and radio frequency interference, the signal amplification unit and its peripheral circuits adopt shielding measures to ensure the purity of the signal. The main control module effectively solves the problem of the weak second signal of the superconducting quantum interference device detector 2 by integrating the signal amplification unit, improving the sensitivity and accuracy of the entire system.

[0036] In this embodiment, the main control module further includes a signal filtering unit, and the signal filtering unit is used to perform filtering processing on the weak magnetic signal detected by the superconducting quantum interference device detector 2.

[0037] In practice, since the signals received by the main control module are usually accompanied by various noises and interferences, direct processing may lead to inaccurate signals. Therefore, the main control module in this embodiment introduces a signal filtering unit to perform filtering processing on the received first control signal and weak magnetic signal, thereby improving the signal-to-noise ratio and overall quality of the signal. According to application requirements and signal characteristics, the signal filtering unit can use different types of filters, such as low-pass filters, high-pass filters, band-pass filters, or band-stop filters. Different filters can respectively remove noises higher or lower than a specific frequency, or only allow signals within a specific frequency range to pass. To improve the adaptability and flexibility of the filter, the signal filtering unit can also adopt adaptive filtering technology. It can be understood that the adaptive filtering technology can automatically adjust the parameters of the filter according to the change of the input signal, so as to effectively suppress different types of noises. To verify the effect of the filtering unit, it is necessary to evaluate the quality of the signal before and after filtering, and the improvement degree of the signal quality by the filtering unit can be objectively reflected by calculating indicators such as signal-to-noise ratio, mean square error, and peak signal-to-noise ratio.

[0038] In this embodiment, the main control module further includes a comparator, and the comparator is used to compare the difference between the weak magnetic signal and the first control signal.

[0039] Here, a high-precision difference calculation circuit is integrated inside the comparator, which can calculate the difference between the weak magnetic signal and the first control signal in real time. The deviation of the weak magnetic signal can be judged through the calculated difference, so as to take corresponding correction measures. It can be understood that in this embodiment, the main control module realizes the function of comparing the difference between the weak magnetic signal and the first control signal by integrating the comparator, effectively improving the accuracy of signal feedback.

[0040] Embodiment 2 of the present invention provides a quantum measurement and control signal feedback method based on weak magnetic detection. The quantum measurement and control signal feedback method is applied to the quantum measurement and control signal feedback device described in any one of the above, as Figure 2 shown, including the following steps:

[0041] Step 101: Generate a first control for controlling qubit 15 in quantum chip 1 through the control signal generation module and transmit it to the input terminal 11 of the quantum chip 1;

[0042] Step 102: The first control signal is transmitted in the plurality of signal transmission lines and generates a stray magnetic field;

[0043] Step 103: Detect the weak magnetic signal generated by the stray magnetic field at the first signal node 14 through the superconducting quantum interference device;

[0044] Step 104: The main control module compares the weak magnetic signal with the first control signal and generates a feedback control signal, which is used to adjust the weak magnetic signal and the first control signal to be consistent.

[0045] In this embodiment, the following steps are further included: measuring the signal crosstalk between the qubits 15 through the probe 21 disposed in the superconducting quantum interference device detector 2 and feeding it back to the main control module.

[0046] Here, in the quantum chip 1, due to the relatively short spatial distance between the qubits 15, the changes in their states may affect each other, resulting in signal crosstalk, thereby interfering with the control of the qubits 15. Therefore, in this embodiment, on the basis of the original feedback control method, a signal crosstalk measurement step is introduced. The probe 21 is disposed in the superconducting quantum interference device detector 2 and is used to measure the signal crosstalk between the qubits 15. The probe 21 can be a highly sensitive magnetic field sensor. When measuring the signal crosstalk between the qubits 15, the distance between the probe 21 and the quantum chip 1 is 0.1 mm, so that the interference between the qubits 15 can be captured. The main control module not only receives the weak magnetic signal from the superconducting quantum interference device detector 2, but also receives the signal crosstalk information from the probe 21. Based on this information, the main control module can more accurately evaluate the state of the qubits 15. It can be understood that by introducing the signal crosstalk measurement step, the accuracy and reliability of the quantum measurement and control signal feedback method are further improved.

[0047] It should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0048] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A quantum measurement and control signal feedback device based on weak magnetic field detection, characterized in that: include: A quantum chip (1), the quantum chip comprising an input end (11) and an output end (12), and a plurality of signal transmission lines (13) connected between the input end and the output end, the signal transmission line (13) comprising a first signal node (14), a quantum bit (15) being connected between the first signal node (14) and the output end (12), the input end (11) being used to receive a control signal; A control signal generating module, used to generate a first control signal for controlling a quantum bit in the quantum chip, wherein the first control signal is transmitted in the plurality of signal transmission lines and generates a stray magnetic field; A superconducting quantum interference device detector (2) is used to detect a weak magnetic signal generated by a stray magnetic field at the first signal node (14); the superconducting quantum interference device detector (2) is provided with a probe (21), and the projection area of ​​the probe is less than 0.1 mm 2 , the distance between the probe and the quantum chip is N, 0.1 mm <N<5mm; The main control module is used to compare the first control signal with the weak magnetic signal and generate a feedback control signal, wherein the feedback control signal is used to adjust the weak magnetic signal to be consistent with the first control signal.

2. The feedback device according to claim 1, characterized in that: The distance between the probe and the quantum chip is N=1 mm.

3. The feedback device according to claim 1, characterized in that: The feedback control signal inverts the difference between the first control signal and the weak magnetic signal, and is transmitted to the first signal node (14) through a feedback loop to compensate for the fluctuation of the first control signal, so that the weak magnetic signal is consistent with the first control signal.

4. The feedback device according to claim 1, characterized in that: The quantum chip includes a plurality of quantum gates for performing logical operations or quantum operations on quantum bits. The quantum gates operate based on the logical states of the quantum bits to achieve processing and transformation of quantum information.

5. The feedback device according to claim 1, characterized in that: The main control module also includes a signal amplification unit, which is used to amplify the weak magnetic signal detected by the superconducting quantum interference device detector.

6. The feedback device according to claim 1, characterized in that: The main control module also includes a signal filtering unit, which is used to filter the weak magnetic signal detected by the superconducting quantum interference device detector.

7. The feedback device according to claim 1, characterized in that: The main control module further includes a comparator, and the comparator is used to compare the difference between the weak magnetic signal and the first control signal.

8. A quantum measurement and control signal feedback method based on weak magnetic field detection, characterized in that: The quantum measurement and control signal feedback method is applied to the quantum measurement and control signal feedback device according to any one of claims 1 to 7, comprising the following steps: Generating a first control signal for controlling a quantum bit in a quantum chip (1) through the control signal generation module and transmitting the first control signal to an input end (11) of the quantum chip; The first control signal is transmitted in the plurality of signal transmission lines (13) and generates a stray magnetic field; Detecting a weak magnetic signal generated by a stray magnetic field at the first signal node (14) by means of the superconducting quantum interference device detector (2); The main control module compares the weak magnetic signal with the first control signal and generates a feedback control signal, wherein the feedback control signal is used to adjust the weak magnetic signal to be consistent with the first control signal.

9. The quantum measurement and control signal feedback method according to claim 8, characterized in that: The following steps are also included: The signal crosstalk between the quantum bits (15) is measured by a probe (21) arranged in the superconducting quantum interference device detector (2) and fed back to the main control module.

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