Method for measuring semiconductor quantum dots, measurement and control system and quantum computer

Abstract

The application discloses a kind of semiconductor quantum dot measurement method, measurement and control system and quantum computer, method includes: adjusting impedance matching circuit in measurement link to make the impedance of inductive quantum dot and the characteristic impedance of measurement link match;First direct current voltage signal, first radio frequency reading signal and second direct current voltage signal are applied to the gate of inductive quantum dot to obtain the coulomb peak phase diagram of inductive quantum dot;According to the change value of reflected voltage in coulomb peak phase diagram, determine the first target voltage of first direct current voltage signal and the second target voltage of second direct current voltage signal;Second direct current voltage signal is applied to the gate of bit quantum dot, and first direct current voltage signal with voltage value being first target voltage, second direct current voltage signal with voltage value being second target voltage and first radio frequency reading signal are respectively applied to the gate of inductive quantum dot to read the information of inductive quantum dot.The application improves the measurement efficiency of semiconductor quantum chip.

Description

Technical Field

[0001] This application relates to the field of quantum computer technology, and in particular to a method for measuring semiconductor quantum dots, a measurement and control system, and a quantum computer. Background Technology

[0002] Among numerous quantum computing physics systems, silicon-based spin qubits (also known as semiconductor quantum dots) are internationally recognized as one of the physics systems that hold the promise for scalable, large-scale, practical general-purpose quantum computing in the future, due to their unique advantages such as compatibility with traditional CMOS industrial manufacturing processes, ultra-long quantum coherence characteristics, and potential applications in temperature ranges exceeding 1.5K.

[0003] The spin state of silicon-based spin qubits is difficult to obtain through direct measurement. Currently, the most common measurement method internationally is to use the coupling between the charge detector and the qubit, and adopt the charge-spin conversion mechanism to convert the change information of the electron spin state in the quantum dot into the change of the transport resistance in the nearest charge detector, thereby realizing the detection of the spin state information of silicon-based spin qubits.

[0004] However, this approach also has significant drawbacks. For example, at room temperature, using amplifiers and high-precision signal acquisition equipment, measuring the charge detector typically requires an integration time of 30 μs to 1 ms. The RC filter circuit, composed of the parasitic capacitance of the DC measurement link itself and the large transport resistance of the charge detector, limits the system's measurement bandwidth to the 0-10 kHz range. This low system measurement bandwidth also fails to effectively reduce the 1 / f noise effect on the measurement and control system and the quantum chip. Furthermore, the initialization and manipulation of spin qubits are on the nanosecond or microsecond scale, and the aforementioned relatively slow readout method greatly limits the readout speed of silicon-based spin qubits. Summary of the Invention

[0005] This application provides a method for measuring semiconductor quantum dots, a measurement and control system, and a quantum computer, which solves the problem of slow measurement efficiency of spin quantum dots in the prior art and improves the measurement efficiency.

[0006] This application provides a method for measuring semiconductor quantum dots, wherein qubit quantum dots and sensing quantum dots with mutual coupling are formed on a semiconductor quantum chip, and the state of the sensing quantum dots is read through a measurement link to obtain information about the qubit quantum dots; the method includes:

[0007] Adjust the impedance matching circuit in the measurement link to match the impedance of the sensing quantum dot with the characteristic impedance of the measurement link;

[0008] A first DC voltage signal, a first radio frequency readout signal, and a second DC voltage signal are applied to the gate of the sensing quantum dot to obtain the Coulomb peak phase diagram of the sensing quantum dot;

[0009] The first target voltage of the first DC voltage signal and the second target voltage of the second DC voltage signal are determined based on the change value of the reflected voltage in the Coulomb peak phase diagram.

[0010] The second DC voltage signal is applied to the gate of the bit quantum dot, and a first DC voltage signal with a voltage value of the first target voltage, a second DC voltage signal with a voltage value of the second target voltage, and the first radio frequency readout signal are respectively applied to the gate of the sensing quantum dot to read the information of the sensing quantum dot.

[0011] Preferably, in the method described above, the impedance matching circuit includes an inductor, and a first adjustable capacitor and a second adjustable capacitor electrically connected across the inductor. Adjusting the impedance matching circuit in the measurement link to match the impedance of the sensed quantum dot with the characteristic impedance of the measurement link includes:

[0012] The voltage values ​​of the third DC voltage signal applied to the first adjustable capacitor and the second adjustable capacitor are adjusted respectively to adjust the characteristic impedance of the measurement link;

[0013] A fourth DC voltage signal and a second radio frequency readout signal are applied to the gate of the sensing quantum dot, and the S21 curve showing the change of the attenuation value of the reflected signal as a function of the voltage value of the third DC voltage signal is obtained.

[0014] The voltage value corresponding to the trough position of the S21 curve is determined to be the third target voltage;

[0015] A third DC voltage signal of the third target voltage is applied to the first adjustable capacitor and the second adjustable capacitor to match the characteristic impedance of the measurement link with the impedance of the sensing quantum dot.

[0016] The method described above, preferably, after the step of adjusting the impedance matching circuit in the measurement link to match the impedance of the sensed quantum dot with the characteristic impedance of the measurement link, further includes:

[0017] A fourth DC voltage signal with a voltage value within a first preset range is applied to the gate of the sensing quantum dot;

[0018] The second radio frequency readout signal is applied to the gate of the sensing quantum dot, and the S21 curve of the reflected signal is obtained;

[0019] Determine the target voltage range within the first preset range in which the attenuation change value in the S21 curve is greater than the preset value;

[0020] The fourth DC voltage signal applied to the gate of the sensing quantum dot is updated according to the target voltage range.

[0021] Preferably, in the method described above, the gate includes a barrier gate, a pump gate, and an accumulation gate. Applying a first DC voltage signal, a first RF readout signal, and a second DC voltage signal to the gate of the sensing quantum dot to obtain the Coulomb peak phase diagram of the sensing quantum dot includes:

[0022] The first DC voltage signal is applied to the barrier gate of the inductive quantum dot;

[0023] The second DC voltage signal is applied to the pump gate of the sensing quantum dot;

[0024] The first radio frequency readout signal is applied to the accumulation gate of the sensing quantum dot;

[0025] The relationship between the voltage of the cumulative gate reflection output signal and the voltage changes of the first DC voltage signal and the second DC voltage signal is defined as the Coulomb peak phase diagram.

[0026] The method described above, preferably, involves determining the correspondence between the voltage of the signal reflected and output by the inductive quantum dot and the voltage changes of the first DC voltage signal and the second DC voltage signal, which is the Coulomb peak phase diagram, comprising:

[0027] A first DC voltage signal with a first preset voltage value is applied to the barrier gate, and a second DC voltage signal with a second preset voltage value is applied to the pump gate in sequence. The first radio frequency readout signal is applied to the accumulation gate of the sensing quantum dot to obtain a first correspondence between the voltage of the signal reflected and output by the accumulation gate and the voltage value of the second preset range.

[0028] The voltage values ​​of the first DC voltage signal are traversed within a third preset range, and a second DC voltage signal with voltage values ​​within a second preset range is applied to the pump gate. The first radio frequency readout signal is applied to the accumulation gate of the sensing quantum dot to obtain a second correspondence between the voltage of the signal reflected and output by the accumulation gate and the voltage value within the third preset range.

[0029] The Coulomb peak phase diagram is determined based on the first correspondence and the second correspondence.

[0030] Preferably, in the method described above, the second DC voltage signal includes a fixed amplitude DC signal and a triangular wave signal. The process of applying a first DC voltage signal with a first preset voltage value to the barrier gate, sequentially applying second DC voltage signals with voltage values ​​within a second preset range to the pump gate, and applying the first radio frequency readout signal to the accumulation gate of the sensing quantum dot to obtain a first correspondence between the voltage of the signal reflected from the accumulation gate and the voltage value within the second preset range, includes:

[0031] A first DC voltage signal with a first preset voltage value is applied to the barrier gate;

[0032] The second DC voltage signal with a voltage value within a second preset range is sequentially applied to the pump gate;

[0033] The first radio frequency readout signal is applied to the accumulation gate;

[0034] The voltage value of the signal reflected and output by the accumulator gate is obtained when the voltage value of the second DC voltage signal changes linearly with the amplitude of the rising or falling segment of the triangular wave signal.

[0035] The voltage value of the reflected output signal changes with the amplitude of the rising or falling segment of the triangular wave signal, which is the first correspondence.

[0036] Preferably, the method described above involves applying the second DC voltage signal to the gate of the bit quantum dot, and respectively applying a first DC voltage signal and a second DC voltage signal corresponding to the first target voltage and the second target voltage, as well as the first radio frequency readout signal, to the gate of the sensing quantum dot to read the information of the sensing quantum dot, comprising:

[0037] A first DC voltage signal corresponding to the first target voltage is applied to the barrier gate of the sensing quantum dot;

[0038] The second DC voltage signal is applied to the pump gate of the bit quantum dot;

[0039] A second DC voltage signal corresponding to the second target voltage is applied to the pump gate of the sensing quantum dot;

[0040] The first radio frequency readout signal is applied to the cumulative gate of the sensing quantum dot to read the information of the sensing quantum dot.

[0041] Another aspect of this application provides a measurement and control system for semiconductor quantum dots. A semiconductor quantum chip has mutually coupled qubit quantum dots and sensing quantum dots formed on it. The system reads the state of the sensing quantum dots through a measurement link to obtain information about the qubit quantum dots. The system includes:

[0042] The first adjustment module adjusts the impedance matching circuit in the measurement link to match the impedance of the sensing quantum dot with the characteristic impedance of the measurement link.

[0043] The first measurement module is used to apply a first DC voltage signal, a first radio frequency readout signal and a second DC voltage signal to the gate of the sensing quantum dot to obtain the Coulomb peak phase diagram of the sensing quantum dot;

[0044] The first determining module is used to determine the first target voltage of the first DC voltage signal and the second target voltage of the second DC voltage signal based on the change value of the reflected voltage in the Coulomb peak phase diagram.

[0045] The second measurement module is used to apply the second DC voltage signal to the gate of the bit quantum dot, and to apply a first DC voltage signal and a second DC voltage signal corresponding to the first target voltage and the second target voltage, as well as the first radio frequency readout signal, to the gate of the sensing quantum dot to read the information of the sensing quantum dot.

[0046] In the system described above, preferably, the first measurement module includes:

[0047] A DC voltage source is used to output the first DC voltage signal and a fixed amplitude DC signal;

[0048] An arbitrary waveform generator is used to output the triangular wave signal;

[0049] Radio frequency source, used to output the first radio frequency read signal;

[0050] A signal acquisition card is used to acquire the reflected signal output from the gate of the sensing quantum dot;

[0051] The triangular wave signal and the fixed amplitude DC signal are processed into the second DC voltage signal by a signal superimposition device.

[0052] In another aspect, this application provides a quantum computer that uses any of the methods described above to test quantum dots on a semiconductor quantum chip, or uses the system described above to test quantum dots on a semiconductor quantum chip.

[0053] Compared with existing technologies, this application proposes a measurement method for semiconductor quantum dots, which can be applied to radio frequency reflection fast readout technology for the testing and characterization of silicon-based quantum chips. By introducing an impedance matching network between the quantum chip and the measurement link, the impedance matching network is used to provide real-time feedback on the impedance changes of the proximity charge detector caused by the spin state changes of the spin qubits in the quantum chip. Since this new technology does not use traditional low-frequency DC transport, but instead uses an radio frequency signal source as the input signal, it modulates and demodulates the quantum dot signal separately, and reads the signal through a high-frequency signal link. At the same time, it optimizes the gate input signal of the semiconductor quantum chip, which can achieve higher measurement bandwidth and measurement efficiency.

[0054] This application provides a measurement and control system and a quantum computer for semiconductor quantum dots, which include the above-mentioned measurement method for semiconductor quantum dots and therefore have the same beneficial effects, which will not be repeated here. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the gate structure of a semiconductor quantum chip provided in an embodiment of this application;

[0056] Figure 2 A schematic flowchart illustrating a method for measuring semiconductor quantum dots provided in an embodiment of this application;

[0057] Figure 3 A schematic diagram of a DC voltage signal and a triangular wave signal provided in an embodiment of this application;

[0058] Figure 4 This is a schematic diagram of a DC voltage signal and a triangular wave signal synthesized according to an embodiment of this application;

[0059] Figure 5 A specific schematic diagram of a Coulomb peak phase diagram provided in this application embodiment;

[0060] Figure 6 This application provides a schematic diagram of the connection between an impedance matching circuit and a gate in an embodiment of the present application.

[0061] Figure 7 A schematic flowchart illustrating the impedance adjustment of an impedance matching circuit provided in an embodiment of this application;

[0062] Figure 8 A schematic flowchart illustrating an update of the voltage signal applied to the gate of an inductive quantum dot, provided as an embodiment of this application;

[0063] Figure 9 A flowchart illustrating the process of obtaining a Coulomb peak phase diagram provided in this application embodiment. Figure 1 ;

[0064] Figure 10A flowchart illustrating the process of obtaining a Coulomb peak phase diagram provided in this application embodiment. Figure 2 ;

[0065] Figure 11 A schematic diagram of the process for obtaining the first correspondence relationship provided in an embodiment of this application;

[0066] Figure 12 This is a schematic diagram of a process for reading inductive quantum dots, provided as an embodiment of this application.

[0067] Figure 13 This is a schematic diagram of the composition of a semiconductor quantum dot measurement and control system provided in an embodiment of this application.

[0068] In the attached diagram:

[0069] 1-Substrate, 3-Impedance matching circuit;

[0070] 11-Drain, 12-Source, 22-Pump gate, 23-Accumulation gate, 10-First adjustment module, 20-First measurement module, 30-First determination module, 40-Second measurement module;

[0071] 211 - First barrier gate, 212 - Second barrier gate. Detailed Implementation

[0072] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of this application. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0073] In the description of this application, it should be understood that the terms "center", "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0074] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0075] As attached Figure 1 The diagram shows a gate schematic of a semiconductor quantum chip. The applicant has designed a gate schematic of a semiconductor chip for radio frequency reflection readout technology. 1 is the substrate of the semiconductor quantum chip. Electrodes 11 and 12 are the drain and source electrodes formed on opposite sides of the substrate, respectively, and are used to apply DC voltage signals for excitation. Electrodes 211, 212, 22, and 23 are all gate electrodes, but the applied signals and their effects are different. Specifically, electrode 211 is a first barrier gate, electrode 212 is a second barrier gate, and electrode 22 is a pump gate. The pump gate 22 is used to apply a DC voltage signal to adjust the potential of the two-dimensional electron gas below the electrode to form quantum dots in the channel. The quantum dots can be qubit quantum dots or inductive quantum dots for reading qubit quantum dots. The first barrier gate 211 and the second barrier gate 212 are also used to apply DC voltage signals to adjust the potential of the two-dimensional electron gas. The DC voltage signals applied to the first barrier gate 211 and the second barrier gate 212 also have a regulating effect on the potential of the quantum dots. They work together with the DC voltage signal applied to the pump gate 22 to adjust the quantum dots. Electrode 23 is an accumulation gate used to apply a radio frequency signal to read the inductive quantum dots to obtain information about the qubit quantum dots.

[0076] In addition, Figure 1 Only one quantum dot was illustrated in the example; in this embodiment, an inductive quantum dot is used, comprising at least four gate structures. The gate structures of the qubit quantum dot and the inductive quantum dot are similar, both including a first barrier gate 211, a second barrier gate 212, and a pump gate 22, used to apply a DC voltage signal to form a qubit quantum dot. The difference is that the qubit quantum dot's gate does not include an accumulation gate 23 for readout; the measurement of the qubit quantum dot is performed by applying a measurement signal to the accumulation gate 23 of the inductive quantum dot. In a semiconductor quantum chip, the inductive quantum dot and the qubit quantum dot are adjacent. The inductive quantum dot serves as a measurement device for the qubit quantum dot, obtaining information about the qubit quantum dot by measuring the charge changes of the inductive quantum dot.

[0077] Furthermore, when an RF signal is applied to the accumulation gate 23 of the sensing quantum dot to read the charge change of the sensing quantum dot, a DC voltage signal needs to be applied to the gate of the corresponding sensing quantum dot and the gate of the corresponding bit quantum dot to form the sensing quantum dot and the bit quantum dot.

[0078] As attached Figure 2 As shown in this embodiment, a measurement method for measuring semiconductor quantum dots using radio frequency signals is provided. Bit quantum dots and sensing quantum dots with mutual coupling are formed on a semiconductor quantum chip. The state of the sensing quantum dots is read through a measurement link to obtain information about the bit quantum dots. The method includes:

[0079] Step S10: Adjust the impedance matching circuit in the measurement link to match the impedance of the sensing quantum dot with the characteristic impedance of the measurement link.

[0080] In this embodiment, a DC voltage source outputs a DC voltage signal to the gate of a semiconductor quantum chip to form an induced quantum dot or a qubit quantum dot; and an RF source outputs an RF readout signal to the gate of the induced quantum dot for readout. A measurement link is provided between the RF source and the semiconductor quantum chip. The measurement link integrates an impedance matching circuit. By adjusting the impedance matching circuit, the impedance of the induced quantum dot is matched with the characteristic impedance of the measurement link, thereby sensitively measuring the charge change of the induced quantum dot. A high impedance matching degree is achieved when the impedance of the induced quantum dot is equal to the characteristic impedance of the measurement link. The characteristic impedance of the measurement link is typically 50 ohms. By adjusting the impedance matching circuit, the impedance of the induced quantum dot can be adjusted to 50 ohms to match the characteristic impedance of the measurement link.

[0081] The impedance of the quantum dot can be adjusted by the impedance matching circuit. When the impedance of the quantum dot is equal to the characteristic impedance of the measurement link, the reading of the quantum dot is optimal. At this time, the impedance matching circuit is in the most sensitive state for reading the quantum dot. When the charge of the quantum dot changes slightly, it can also be measured by the impedance matching circuit, thereby improving the measurement sensitivity of the quantum dot.

[0082] Step S20: Apply a first DC voltage signal, a first radio frequency readout signal, and a second DC voltage signal to the gate of the sensing quantum dot to obtain the Coulomb peak phase diagram of the sensing quantum dot.

[0083] Combined with appendix Figure 1As shown, applying a voltage signal to the gate corresponding to the sensing quantum dot on a semiconductor quantum chip can form the sensing quantum dot. In this embodiment, the voltage signal applied to the gate of the sensing quantum dot includes a first DC voltage signal and a second DC voltage signal, wherein the voltage values ​​of the first DC voltage signal and the second DC voltage signal are variable. During the testing of the semiconductor chip, a first radio frequency readout signal is applied to the gate of the sensing quantum dot. The reflected voltage of the signal reflected by the sensing quantum dot is measured by a measuring device. The correspondence between this reflected voltage and the voltage values ​​of the first and second DC voltage signals applied to the gate of the sensing quantum dot is represented by a three-dimensional graph, namely, a Coulomb peak phase diagram. The Coulomb peak phase diagram is used to characterize the change in the reflected voltage of the signal reflected from the gate of the sensing quantum dot as a function of the voltage values ​​of the first and second DC voltage signals. Information about the state changes of the sensing quantum dot can be obtained through the reflected voltage in the Coulomb peak phase diagram.

[0084] As described above, when applying a first radio frequency signal to test the sensed quantum dot and obtain the Coulomb peak phase diagram, the voltage value of the second DC voltage signal applied to the intermediate gate of the sensed quantum dot and the qubit quantum dot varies linearly within a preset amplitude range, such as 1V-5V. In existing technologies, the voltage signal is generally provided by a DC voltage source, and the voltage value of the DC voltage signal output by the DC voltage source is generally a fixed value. When manipulating the DC voltage source to output a DC voltage signal with varying voltage values, the response is very slow, directly affecting the measurement efficiency of the sensed quantum dot. Alternatively, an arbitrary waveform generator can be used to output a voltage signal with varying voltage values, but the voltage value of the output voltage signal is generally relatively low, which cannot meet the requirements for testing sensed quantum dots.

[0085] Combined with appendix Figure 3 and attached Figure 4 As shown, in this embodiment, a second DC voltage signal with a voltage value that changes linearly within a preset amplitude range is obtained by synthesizing a fixed-amplitude DC signal and a triangular wave signal; Appendix Figure 3 Examples of a fixed-amplitude DC signal and a triangular wave signal are given respectively. The voltage value of the fixed-amplitude DC signal is constant, while the voltage amplitude of the triangular wave signal varies. The voltage variation curve of the synthesized second DC voltage signal is shown in the attached figure. Figure 4 As shown, it can be observed that the change in the voltage value of the second DC voltage signal corresponds to the change in the voltage amplitude of the triangular wave signal. For example, the voltage value of the fixed amplitude DC signal is 3V, and the voltage amplitude of the triangular wave signal is {-1.5V, 1.5V}. The waveform of the synthesized second DC voltage signal is also a triangular wave signal with a voltage amplitude of {1.5V, 4.5V}. The voltage amplitude changes linearly in both the rising and falling segments, which is used to meet the voltage signal requirements for manipulating inductive quantum dots or bit quantum dots.

[0086] In addition, Figure 3 and attached Figure 4 The curves of the fixed amplitude DC signal, triangular wave signal, and second DC voltage signal shown in the example are for illustrative purposes only. In actual measurement, the output time, voltage value, waveform parameters of the triangular wave, etc., need to be determined according to the requirements, which will not be elaborated in this embodiment.

[0087] In this embodiment, a fixed-amplitude DC signal is provided by a DC voltage source, and a triangular wave signal is provided by an arbitrary waveform generator. The fixed-amplitude DC signal output from the DC voltage source and the triangular wave signal output from the arbitrary waveform generator are combined to form a second DC voltage signal, which is then output. This ensures that the voltage value of the second DC voltage signal applied to the gate of the sensing quantum dot changes linearly within a preset amplitude range, and that the voltage amplitude is relatively high, meeting the requirements for testing the sensing quantum dot. Furthermore, the DC voltage source outputs a fixed-amplitude DC signal, and the arbitrary waveform generator can directly output a triangular wave signal, resulting in a fast response. Consequently, the generation of the second DC voltage signal is also fast, improving the measurement efficiency of the sensing quantum dot.

[0088] Step S30: Determine the first target voltage of the first DC voltage signal and the second target voltage of the second DC voltage signal based on the change value of the reflected voltage in the Coulomb peak phase diagram.

[0089] As described in step S20, the Coulomb peak phase diagram is used to characterize the change in the reflected voltage of the signal output from the gate of the sensing quantum dot as a function of the voltage values ​​of the first DC voltage signal and the second DC voltage signal. Information about the state changes of the sensing quantum dot can be obtained through the reflected voltage in the Coulomb peak phase diagram. The state in which the sensing quantum dot is most sensitive to state changes corresponds to the largest change in the reflected voltage in the Coulomb peak phase diagram. The voltage values ​​of the first and second DC voltage signals at which the largest change in reflected voltage in the Coulomb peak phase diagram is determined as the first target voltage and the second target voltage, and the voltages of the first and second DC voltage signals applied to the gate of the sensing quantum dot are updated.

[0090] As attached Figure 5 The schematic Coulomb peak phase diagram shows the following: the horizontal axis U3 represents the voltage value of the second DC voltage signal, ranging from 2.5V to 4.5V; the left vertical axis U4 represents the voltage value of the first DC voltage signal, ranging from 0V to 3V; and the right vertical axis represents the voltage value of the reflected signal. In the 3D diagram, the brighter the white area, the larger the corresponding voltage value of the reflected signal. The Coulomb peak phase diagram allows us to obtain the voltage values ​​of the first and second DC voltage signals when the voltage change of the reflected signal is significant.

[0091] The measurement of qubit quantum dots is achieved by measuring the charge changes of sensing quantum dots on a quantum chip. Therefore, the sensitivity of the state changes of the sensing quantum dots directly affects the measurement accuracy. A first target voltage and a second target voltage of the first DC voltage signal and the second DC voltage signal, respectively, are determined using a Coulomb peak phase diagram to obtain the state change sensitivity of the sensing quantum dots. During subsequent measurements of the qubit quantum dots, the first DC voltage signal of the first target voltage and the second DC voltage signal of the second target voltage are applied to the gate of the sensing quantum dots to ensure that the sensing quantum dots are in the most sensitive state, thereby improving the measurement accuracy of the qubit quantum dots.

[0092] Step S40: Apply the second DC voltage signal to the gate of the bit quantum dot, and apply a first DC voltage signal with a voltage value of the first target voltage, a second DC voltage signal with a voltage value of the second target voltage, and the first radio frequency readout signal to the gate of the sensing quantum dot to read the information of the sensing quantum dot.

[0093] A second DC voltage signal is applied to the gate of the corresponding qubit quantum dot to form a qubit quantum dot under the gate. The second DC voltage signal applied to the gate of the qubit quantum dot is the same as the second DC voltage signal applied to the gate of the sensing quantum dot, and the parameters of the voltage signal are the same.

[0094] As described above, applying a second DC voltage signal with a voltage value that varies linearly within a preset range to the gate of the sensing quantum dot can improve the response speed of the voltage signal, thereby improving the measurement efficiency of the sensing quantum dot. Similarly, if the voltage signal applied to the gate of the qubit quantum dot is also a second DC voltage signal with a voltage value that varies linearly, the response speed of the voltage signal applied to the qubit quantum dot can be improved, and the measurement efficiency can also be improved when measuring the qubit quantum dot through the sensing quantum dot.

[0095] First, in step S30, the target voltage values ​​of the first DC voltage signal and the second DC voltage signal applied to the gate of the sensing quantum dot are determined. The first DC voltage signal with the first target voltage and the second DC voltage signal with the second target voltage are applied to the gate of the sensing quantum dot to ensure that the sensing quantum dot is in the most sensitive state. Then, the second DC voltage signal is applied to the gate of the bit quantum dot on the semiconductor quantum chip to form the bit quantum dot. Finally, the first radio frequency readout signal is applied to the gate of the sensing quantum dot to read the information of the sensing quantum dot and obtain the information of the bit quantum dot.

[0096] In this embodiment, the induced quantum dot is measured by transmitting an RF readout signal through an impedance matching circuit. The RF readout signal is used as an input signal to modulate and demodulate the induced quantum dot on the quantum chip. The signal is read out through a high-frequency signal link. Compared with the traditional low-frequency DC transmission measurement method, this greatly improves the measurement bandwidth and measurement efficiency.

[0097] Furthermore, when reading the sensed quantum dot, the DC voltage applied to the gates of both the sensed quantum dot and the bit quantum dot for forming the quantum dot is a second DC voltage signal, which improves the response speed of the output voltage signal and thus improves the measurement efficiency of the sensed quantum dot.

[0098] Furthermore, the measurement of qubit quantum dots is achieved by measuring induced quantum dots. When testing induced quantum dots, changes in the induced quantum dots are obtained through an impedance matching circuit. Therefore, the impedance matching circuit and the measurement sensitivity of the induced quantum dots directly affect the measurement of qubit quantum dots. In this embodiment, the impedance of the impedance matching circuit in the measurement link is first adjusted to match the impedance of the induced quantum dots with the characteristic impedance of the measurement link, ensuring the measurement sensitivity of the induced quantum dots. Then, the voltage values ​​of the first and second DC voltage signals applied when the induced quantum dots are most sensitive are obtained through a Coulomb peak phase diagram. Updating the applied first and second DC voltage signals ensures that changes in the induced quantum dots are most sensitive, greatly improving the measurement accuracy of qubit quantum dots.

[0099] As attached Figure 6 As shown, in this embodiment, the impedance matching circuit 3 includes an inductor and a first adjustable capacitor and a second adjustable capacitor electrically connected to the two ends of the inductor. Specifically, the impedance matching circuit 3 adopts an LC impedance matching network of inductor and capacitor, and selects a first adjustable capacitor and a second adjustable capacitor with adjustable capacitance values.

[0100] As attached Figure 7 As shown, in this embodiment, adjusting the impedance matching circuit in the measurement link to match the impedance of the sensing quantum dot with the characteristic impedance of the measurement link includes:

[0101] Step S101: Adjust the voltage values ​​of the third DC voltage signals applied to the first adjustable capacitor and the second adjustable capacitor respectively to adjust the characteristic impedance of the measurement link.

[0102] Combined with appendix Figure 6 As shown, the capacitance values ​​of the first and second adjustable capacitors are adjusted by a third DC voltage signal to adjust the impedance of the impedance matching circuit, ensuring that the impedance of the inductive quantum dot is the same as the impedance of the transmission link, thereby ensuring the measurement accuracy of the inductive quantum dot.

[0103] Step S102: Apply a fourth DC voltage signal and a second radio frequency readout signal to the gate of the sensing quantum dot and obtain the S21 curve showing the change of the attenuation value of the reflected signal with the voltage value of the third DC voltage signal.

[0104] A fourth DC voltage signal is used to form the induced quantum dot, and a second radio frequency readout signal is used to read the information of the induced quantum dot. When the voltage value of the third DC voltage signal is adjusted, the impedance of the impedance matching circuit changes, and the reflected signal output from the gate of the induced quantum dot read through the impedance matching circuit also changes. Specifically, the attenuation value of the reflected signal changes with the voltage value of the third DC voltage signal, and the S21 curve of the attenuation value change can be obtained by acquiring the reflected signal with a measuring device. In this embodiment, a vector network analyzer can be used as the measuring device.

[0105] Step S103: Determine the voltage value corresponding to the trough of the S21 curve as the third target voltage. The S21 curve characterizes the attenuation of the reflected signal. At the trough of the S21 curve, the impedance matching circuit has the highest sensitivity to the induced quantum dot pairs. The voltage value corresponding to this trough is determined as the voltage value of the third DC voltage signal, which is the third target voltage.

[0106] Step S104: Apply a third DC voltage signal equal to the third target voltage to the first and second adjustable capacitors to match the impedance of the sensed quantum dot with the characteristic impedance of the measurement link. The third target voltage at which the impedance matching circuit achieves optimal response sensitivity is determined by obtaining the S21 curve of the reflected signal output from the gate of the sensed quantum dot through steps S101-S103. Apply the third DC voltage signal, equal to the third target voltage, to the first and second adjustable capacitors. By adjusting the impedance of the impedance matching circuit, the impedance of the sensed quantum dot is matched with the characteristic impedance of the measurement link, ensuring optimal sensitivity for reading the sensed quantum dot.

[0107] Continue to attach Figure 6 The schematic diagram of the impedance matching circuit shown includes a first adjustable capacitor and a second adjustable capacitor. When adjusting the third DC voltage signal applied to the first and second adjustable capacitors, the same third DC voltage signal can be used for synchronous adjustment, or two third DC voltage signals with different voltage values ​​can be used to adjust the first and second adjustable capacitors respectively.

[0108] The first adjustable capacitor and the second adjustable capacitor are adjusted by using two third DC voltage signals with different voltage values. For the two third DC voltage signals, steps S101-S104 are executed respectively to determine the third target voltage of the third DC voltage signal applied to the first adjustable capacitor and the second adjustable capacitor respectively. This embodiment will not be described in detail.

[0109] In addition, as attached Figure 8 As shown, in one embodiment of this application, after adjusting the impedance matching circuit in the measurement link to match the impedance of the sensing quantum dot with the characteristic impedance of the measurement link, the method further includes:

[0110] Step 111: Apply a fourth DC voltage signal with a voltage value within a first preset range to the gate of the inductive quantum dot.

[0111] Step 112: Apply the second radio frequency readout signal to the gate of the sensing quantum dot and obtain the S21 curve of the reflected signal.

[0112] Combined with appendix Figure 1 As shown, when reading the sensed quantum dot, a DC voltage needs to be applied to the pump gate 22 and an RF readout signal needs to be applied to the accumulation gate 23. In this embodiment, the fourth DC voltage signal applied to the gate of the semiconductor quantum chip includes multiple voltage values ​​within a first preset range, for example, the first preset range is {2.5V, 4.5V}. The first preset range includes several voltage values. While applying the fourth DC voltage signal corresponding to each voltage value to the gate of the sensed quantum dot, a second RF readout signal is applied to the same gate, and the S21 parameter of the reflected signal is obtained through a measuring device. After traversing all the voltage values ​​within the first preset range, an S21 curve including multiple S21 parameters is obtained; the attenuation value of the S21 curve changes with the voltage values ​​within the first preset range.

[0113] Step 113: Determine the target voltage range within the first preset range where the attenuation change value in the S21 curve is greater than a preset value. The change information of the sensing quantum dot can be obtained by measuring the S21 parameters of the reflected signal using a measuring device. The attenuation change value can be determined by the attenuation value of the S21 curve. For example, if the maximum attenuation value in the S21 curve is 30dB and the minimum is 10dB, then the attenuation change value is 20dB. The attenuation change value characterizes the response sensitivity of the sensing quantum dot to changes in the fourth DC voltage signal. It can be understood that the larger the attenuation change value, the more sensitive the measurement of the sensing quantum dot is to the fourth DC voltage signal applied to the gate of the sensing quantum dot. When the attenuation change value is very small, the measurement of the sensing quantum dot is insensitive.

[0114] Specifically, for the attenuation change value, a preset value can be set. Then, based on the measured S21 curve, it is determined whether the voltage value of the fourth DC voltage signal meets the attenuation change value requirement. If the attenuation change value requirement is not met, the voltage value within the first preset range needs to be adjusted, and the process returns to step S11. When the attenuation change value requirement is met, the voltage range within the first preset range corresponding to the attenuation change value in the S21 curve that is greater than the preset value is determined as the target voltage range.

[0115] Step 114: Update the fourth DC voltage signal applied to the gate of the sensing quantum dot according to the target voltage range. After determining the target voltage range in step S113, update the first preset range of the fourth DC voltage signal applied to the gate of the sensing quantum dot to ensure that the sensing quantum dot responds sensitively when an RF readout signal is applied to the gate of the sensing quantum dot.

[0116] As attached Figure 9 As shown, applying a first DC voltage signal, a first radio frequency readout signal, and a second DC voltage signal to the gate of the sensing quantum dot to obtain the Coulomb peak phase diagram of the sensing quantum dot includes:

[0117] Step S201: Apply the first DC voltage signal to the barrier gate of the inductive quantum dot.

[0118] Step S202: Apply the second DC voltage signal to the pump gate of the inductive quantum dot.

[0119] Step S203: Apply the first radio frequency readout signal to the accumulation gate of the sensing quantum dot.

[0120] When reading the sensed quantum dot, a first DC voltage signal and a second DC voltage signal need to be applied to the barrier gate and the pump gate respectively to form the sensed quantum dot, and then a first radio frequency readout signal is applied through the accumulation gate of the sensed quantum dot to perform the readout.

[0121] Step S204: Determine the correspondence between the voltage of the signal reflected by the inductive quantum dot and the voltage changes of the first DC voltage signal and the second DC voltage signal as the Coulomb peak phase diagram.

[0122] After applying a first DC voltage signal, a second DC voltage signal, and a first RF readout signal to the barrier gate, pump gate, and accumulation gate of the sensing quantum dot in steps S201 and S203, the accumulation gate reflects and outputs a reflected signal. The voltage of the reflected signal can be obtained by acquiring and processing the reflected signal using a measurement device. As described above, the voltage values ​​of the applied first and second DC voltage signals affect the reflected output signal; therefore, the voltage of the reflected signal corresponds to the voltage values ​​of the first and second DC voltage signals. When the voltage values ​​of the first and second DC voltage signals change, the voltage of the reflected signal obtained by the measurement device also changes accordingly. The correspondence between the voltage of the reflected signal and the changes in the voltage values ​​of the first and second DC voltage signals is defined as a Coulomb peak phase diagram. It should be noted that the Coulomb peak phase diagram is a three-dimensional data diagram, obtained by repeatedly changing the voltage values ​​of the first and second DC voltage signals and measuring the voltage of the reflected signal.

[0123] Based on the descriptions of steps S111-S114, the target voltage range of the fourth DC voltage signal applied to the gate of the sensing quantum dot can be determined by the range of the decay change value of the S21 curve; wherein, the fourth DC voltage signal applied to the pump gate of the sensing quantum dot is used to form the sensing quantum dot, i.e., attached... Figure 1 Electrode 22. In step S202, the second DC voltage signal applied to the barrier gate of the sensing quantum dot is also used to form the sensing quantum dot. Therefore, the voltage of the second DC voltage signal can be preset according to the target voltage range of the fourth DC voltage signal to ensure that after the second DC voltage signal is applied to the pump gate of the sensing quantum dot, the voltage change of the reflected output signal obtained when the first RF readout signal is applied to the accumulation gate for testing is more obvious, thereby improving the resolution of the Coulomb peak phase diagram.

[0124] Combined with appendix Figure 10 As shown, in one embodiment of this application, determining the correspondence between the voltage of the signal reflected and output by the induced quantum dot and the voltage changes of the first DC voltage signal and the second DC voltage signal, which is the Coulomb peak phase diagram, includes:

[0125] Step S2031: Apply a first DC voltage signal with a first preset voltage value to the barrier gate, sequentially apply a second DC voltage signal with a second preset voltage value to the pump gate, and apply the first radio frequency readout signal to the accumulation gate of the sensing quantum dot to obtain a first correspondence between the voltage of the signal reflected and output by the accumulation gate and the voltage value of the second preset range.

[0126] Step S2032: Traverse the voltage value of the first DC voltage signal within a third preset range, apply a second DC voltage signal with a voltage value within a second preset range to the pump gate, and apply the first radio frequency readout signal to the accumulation gate of the sensing quantum dot to obtain a second correspondence between the voltage of the signal reflected and output by the accumulation gate and the voltage value within the third preset range.

[0127] As described in steps S201-S203 above, the Coulomb peak phase diagram is data showing the voltage of the reflected signal output from the gate of the sensed quantum dot as a function of the voltage of the first DC voltage signal and the voltage of the second DC voltage signal. Specifically, the voltage value of the first DC voltage signal is first set to a first preset voltage value. Then, several voltage values ​​within a second preset range are sequentially iterated. During each iteration, a first radio frequency readout signal is applied to the accumulation gate of the sensed quantum dot, and the first correspondence between the voltage value of the reflected signal output and the voltage values ​​within the second preset range is measured. For example, if the voltage value of the first DC voltage signal is set to 3V, and the second preset range is determined to be {2.5V, 4.5V}, then a second DC voltage signal that linearly varies within {2.5V, 4.5V} is applied to the pump gate of the sensed quantum dot to obtain the correspondence between the voltage value of the reflected signal and the voltage values ​​within the second preset range.

[0128] Furthermore, by iterating through the voltage values ​​of the first DC voltage signal within a third preset range, and repeatedly applying a second DC voltage signal with a voltage value within a second preset range to the pump gate and applying a first radio frequency readout signal to the accumulation gate, a second correspondence is obtained in which the voltage of the signal reflected and output by the sensed quantum dot changes with the voltage value within the third preset range.

[0129] For example, the third preset range is {0V, 5V}, with a voltage step of 0.5V. At the start of the traversal, the voltage value of the first DC voltage signal is set to 0.5V. The second DC voltage signal is traversed within the second preset range to obtain the current voltage value of the reflected signal. Then, the voltage value of the first DC voltage signal is set to 1V, and the second DC voltage signal is traversed within the second preset range to obtain the current voltage value of the reflected signal. This process continues until all voltage values ​​within the third preset range have been traversed, thus obtaining a second correspondence between the voltage values ​​of the reflected signal and the voltage values ​​within the third preset range.

[0130] It should be added that when obtaining the first and second correspondences, the second DC voltage is traversed within the second preset range. The step values ​​of the second and third preset ranges are adjusted according to the specific test accuracy requirements; this embodiment is merely an example.

[0131] Step S2033: Determine the Coulomb peak phase diagram based on the first correspondence and the second correspondence.

[0132] In particular, the first and second correspondences obtained in steps S2031 and S2032 are both one-to-one corresponding data. These correspondences can be displayed in a three-dimensional coordinate graph, i.e., the Coulomb peak phase diagram, as detailed in the attached figure. Figure 5 As shown.

[0133] Combined with appendix Figure 1 As shown, the gate of the sensing quantum dot includes a barrier gate 211 and a barrier gate 212. When the first DC voltage signal is applied to the gate in step S2032 for traversal, the first DC voltage signal applied to the barrier gate 211 and the barrier gate 212 can be applied and traversed separately.

[0134] Specifically, firstly, the first DC voltage signal applied to the barrier gate 211 is set to a preset value. Then, the first DC voltage signal applied to the barrier gate 212 is traversed within a third preset range. Steps S2032 and S2033 are repeated to obtain a Coulomb peak phase diagram. Next, the preset value of the first DC voltage signal applied to the barrier gate 211 is adjusted, and the first DC voltage signal applied to the barrier gate 212 is traversed within the third preset range. Steps S2032 and S2033 are repeated to obtain another Coulomb peak phase diagram.

[0135] The preset value of the first DC voltage signal applied to the barrier gate 211 can be traversed within a fourth preset range, and then combined with the first DC voltage signal applied to the barrier gate 212 traversed within a third preset range to obtain several Coulomb peak phase diagrams. Based on these Coulomb peak phase diagrams, the target voltage values ​​of the first DC voltage signals applied to the barrier gate 211 and barrier gate 212 respectively can be determined, ensuring higher sensitivity of the sensing quantum dot.

[0136] Combined with appendix Figure 11 As shown, in one embodiment of this application, the step of applying a first DC voltage signal with a first preset voltage value to the barrier gate, and sequentially applying second DC voltage signals with voltage values ​​within a second preset range to the pump gate to obtain a first correspondence between the voltage of the signal reflected and output by the induced quantum dot and the voltage values ​​within the second preset range, includes:

[0137] Step S20311: Apply a first DC voltage signal with a first preset voltage value to the barrier gate.

[0138] Step S20312: Sequentially apply a second DC voltage signal with a voltage value within a second preset range to the pump gate.

[0139] Step S20313: Apply the first radio frequency readout signal to the accumulation gate.

[0140] Step S20314: Collect the voltage value of the signal reflected and output by the cumulative gate when the voltage value of the second DC voltage signal changes linearly with the amplitude of the rising or falling segment of the triangular wave signal.

[0141] Step S20315: Obtain the first correspondence relationship by which the voltage value of the reflected output signal changes with the amplitude of the rising or falling segment of the triangular wave signal.

[0142] In step S2031 above, the voltage value of the second DC voltage signal varies within a second preset range. As described above, the second DC voltage signal is synthesized from a second DC voltage signal and a triangular wave signal. The voltage value of the second DC voltage signal varies with the amplitude of the triangular wave signal. For details, please refer to the appendix. Figure 5 The schematic curve shows that the voltage value within the second preset range is not monotonically increasing or decreasing, but changes synchronously with the rising and falling segments of the triangular wave signal. Therefore, within the second preset range, the voltage value of the second DC voltage signal includes several consecutive rising and falling segments.

[0143] In this embodiment, when the voltage value of the second DC voltage signal is the rising segment of the triangular wave signal, the voltage signal applied to the pump gate gradually increases from a small voltage to a large voltage; when the voltage value of the second DC voltage signal is the falling segment of the triangular wave signal, the voltage signal applied to the pump gate gradually decreases from a large voltage to a small voltage. When measuring the reflected signal output from the pump gate of the sensed quantum dot using a measuring device, multiple measurements are performed and the average value is taken. When multiple measurements are performed with the second DC voltage signal applied to the pump gate selected as the complete rising segment or the falling segment selected, the voltage value of the reflected signal during the rising or falling segment can be collected, which can improve the measurement accuracy of the reflected signal voltage.

[0144] For example, when measuring 10 times, if the second DC voltage signal applied to the pump gate is selected as the complete rising segment, the voltage value of the reflected signal during the rising segment is collected; or if the second DC voltage signal applied to the pump gate is selected as the complete falling segment, the voltage value of the reflected signal during the falling segment is collected.

[0145] As attached Figure 12As shown, in this embodiment, after determining the first target voltage of the first DC voltage signal and the second target voltage of the second DC voltage signal, when testing the sensing quantum dot, the step of applying the second DC voltage signal to the gate of the qubit quantum dot, and applying the first DC voltage signal and the second DC voltage signal corresponding to the first target voltage and the second target voltage, as well as the first radio frequency readout signal, to the gate of the sensing quantum dot to read the information of the sensing quantum dot includes:

[0146] Step S401: Apply a first DC voltage signal corresponding to the first target voltage to the barrier gate of the sensing quantum dot.

[0147] Step S402: Apply the second DC voltage signal to the pump gate of the bit quantum dot.

[0148] Step S403: Apply a second DC voltage signal corresponding to the second target voltage to the pump gate of the sensing quantum dot.

[0149] Step S404: Apply the first radio frequency readout signal to the accumulation gate of the sensing quantum dot to read the information of the sensing quantum dot.

[0150] As attached Figure 13 As shown, based on the same application concept, this application embodiment also provides a semiconductor quantum dot measurement and control system. A semiconductor quantum chip has mutually coupled qubit quantum dots and sensing quantum dots formed on it. The state of the sensing quantum dots is read through a measurement link to obtain information about the qubit quantum dots. The measurement and control system includes: a first adjustment module 10, used to adjust the impedance matching circuit in the measurement link to match the impedance of the sensing quantum dots with the characteristic impedance of the measurement link; and a first measurement module 20, used to apply a first DC voltage signal, a first radio frequency readout signal, and a second DC voltage signal to the gate of the sensing quantum dots to obtain the Coulomb peak phase diagram of the sensing quantum dots; wherein, the second... The DC voltage signal includes a second DC voltage signal and a triangular wave signal; the voltage value of the second DC voltage signal varies with the amplitude of the triangular wave signal; the first determining module 30 is used to determine the first target voltage of the first DC voltage signal and the second target voltage of the second DC voltage signal based on the change value of the reflected voltage in the Coulomb peak phase diagram; the second measuring module 40 is used to apply the second DC voltage signal to the gate of the bit quantum dot, and apply the first DC voltage signal and the second DC voltage signal corresponding to the first target voltage and the second target voltage, as well as the first radio frequency readout signal, to the gate of the sensing quantum dot to read the information of the sensing quantum dot.

[0151] Combined with appendix Figure 1As shown, forming inductive quantum dots and bit quantum dots on a semiconductor quantum chip requires applying multiple DC voltage signals and a second DC voltage signal. It also requires applying a radio frequency readout signal to read the inductive quantum dots to obtain information about the bit quantum dots, and measuring the reflected signal acquired after applying the radio frequency readout signal.

[0152] Specifically, the first adjustment module 10 used to adjust the impedance of the impedance matching circuit can be a DC voltage source, and the impedance of the impedance matching circuit can be adjusted by adjusting the voltage signal output by the DC voltage source. The impedance matching circuit can be found in the attached diagram. Figure 6 The circuit structure shown is a first inductor, a first adjustable capacitor, and a second adjustable capacitor.

[0153] In addition, the first measurement module 20 may include signal analysis instruments such as a DC voltage source, a radio frequency source, a vector network analyzer, and a spectrum analyzer to provide the required first DC voltage signal, first radio frequency readout signal, and second DC voltage signal; the first measurement module may also include data analysis software or data processing software installed in a computer to process the data of the reflected signal output from the gate of the sensed quantum dot to obtain the Coulomb peak phase diagram.

[0154] The first determining module 30 may include image analysis software installed in a computer to determine the first target voltage of the first DC voltage signal and the second target voltage of the second DC voltage signal based on the change value of the reflected voltage in the Coulomb peak phase diagram. The second measuring module 40 may include signal source devices such as a DC voltage source and an RF source to provide the required first DC voltage signal, second RF readout signal, and second DC voltage signal. The second measuring module may also include signal analysis instruments such as a vector network analyzer and a spectrum analyzer to process the data of the reflected signal output from the gate of the sensed quantum dot to obtain information about the sensed quantum dot.

[0155] In this embodiment, the first measurement module 20 includes: a DC voltage source 201 for outputting the first DC voltage signal and the second DC voltage signal; an arbitrary waveform generator 202 for outputting the triangular wave signal; a radio frequency source 203 for outputting the first radio frequency readout signal; and a signal acquisition card 204 for acquiring the reflected signal output from the gate of the sensing quantum dot; wherein the triangular wave signal and the second DC voltage signal are processed into the second DC voltage signal by a signal superimposed device.

[0156] Combined with appendix Figure 1As shown, it should be added that the first and second radio frequency signals are applied to the accumulator gate 23, the reflected signal is also output through the accumulator gate 23, and the signal acquisition card also acquires the signal through the accumulator gate 23. In specific applications, a directional coupler is set outside the accumulator gate 23 of the semiconductor quantum chip. The input end of the directional coupler receives the first and second radio frequency signals and transmits them to the accumulator gate 23 through the output end. The output end of the directional coupler is also used to receive the reflected signal output by the accumulator gate 23 and output it to the signal acquisition card through the coupling end of the directional coupler.

[0157] When acquiring the reflected signal output by the cumulative gate 23 through the signal acquisition card 2, the reflected signal output by the gate of the inductive quantum dot is acquired during the rising or falling segment of the triangular wave signal output by the arbitrary waveform generator.

[0158] Based on the same concept, embodiments of this application also provide a quantum computer that uses any of the above-described semiconductor quantum dot measurement methods to test quantum dots on a semiconductor quantum chip, or uses the above-described semiconductor quantum dot measurement and control system to test quantum dots on a semiconductor quantum chip.

[0159] In the description of this specification, references to terms such as "some embodiments" or "example" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. The illustrative expressions of the above terms in this specification do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0160] The above are merely preferred embodiments of this application and do not constitute any limitation on this application. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in this application without departing from the scope of the technical solutions of this application shall still fall within the protection scope of this application.

Claims

1. A method of measuring a semiconductor quantum dot, characterized by, A semiconductor quantum chip is formed with a bit quantum dot and an induction quantum dot which are coupled with each other, and a state of the induction quantum dot is read by a measurement link to obtain information of the bit quantum dot; the method comprises: adjusting an impedance matching circuit in the measurement link to match an impedance of the induction quantum dot with a characteristic impedance of the measurement link; applying a first direct current voltage signal, a first radio frequency reading signal and a second direct current voltage signal to a gate of the induction quantum dot to obtain a Coulomb peak phase diagram of the induction quantum dot; determining a first target voltage of the first direct current voltage signal and a second target voltage of the second direct current voltage signal according to a change value of a reflected voltage in the Coulomb peak phase diagram; applying the second direct current voltage signal to a gate of the bit quantum dot, and applying the first direct current voltage signal with the first target voltage, the second direct current voltage signal with the second target voltage and the first radio frequency reading signal to the gate of the induction quantum dot to read information of the induction quantum dot.

2. The method of claim 1, wherein, The impedance matching circuit comprises an inductor, and a first adjustable capacitor and a second adjustable capacitor electrically connected to both ends of the inductor, and the adjusting of the impedance matching circuit in the measurement link to match the impedance of the induction quantum dot with the characteristic impedance of the measurement link comprises: adjusting voltage values of third direct current voltage signals applied to the first adjustable capacitor and the second adjustable capacitor respectively to adjust the characteristic impedance of the measurement link; applying a fourth direct current voltage signal and a second radio frequency reading signal to the gate of the induction quantum dot to obtain an S21 curve of an attenuation value of a reflected signal changing with voltage values of the third direct current voltage signals; determining a voltage value corresponding to a wave trough position of the S21 curve as a third target voltage; applying the third direct current voltage signal with the third target voltage to the first adjustable capacitor and the second adjustable capacitor to match the characteristic impedance of the measurement link with the impedance of the induction quantum dot.

3. The method of claim 2, wherein, After the step of adjusting the impedance matching circuit in the measurement link to match the impedance of the induction quantum dot with the characteristic impedance of the measurement link, the method further comprises: applying fourth direct current voltage signals with voltage values in a first preset range to the gate of the induction quantum dot; applying the second radio frequency reading signal to the gate of the induction quantum dot to obtain an S21 curve of a reflected signal; determining a target voltage range in the first preset range in which an attenuation change value is greater than a preset value in the S21 curve; updating the fourth direct current voltage signal applied to the gate of the induction quantum dot according to the target voltage range.

4. The method of claim 1, wherein, The gate comprises a barrier gate, a pumping gate and an accumulation gate, and the applying of the first direct current voltage signal, the first radio frequency reading signal and the second direct current voltage signal to the gate of the induction quantum dot to obtain the Coulomb peak phase diagram of the induction quantum dot comprises: applying the first direct current voltage signal to the barrier gate of the induction quantum dot; applying the second direct current voltage signal to the pumping gate of the induction quantum dot; applying the first radio frequency reading signal to the accumulation gate of the induction quantum dot; The correspondence relationship between the voltage of the signal of the accumulated gate reflection output and the voltage of the first direct current voltage signal and the voltage of the second direct current voltage signal is determined as the Coulomb peak phase diagram.

5. The method of claim 4, wherein, The correspondence relationship between the voltage of the signal of the inductive quantum dot reflection output and the voltage of the first direct current voltage signal and the voltage of the second direct current voltage signal is determined as the Coulomb peak phase diagram, comprising: A first direct current voltage signal of a first preset voltage value is applied to the barrier gate, a second direct current voltage signal of a second preset range of voltage values is sequentially applied to the pump gate, and the first radio frequency reading signal is applied to the accumulated gate of the inductive quantum dot, so as to obtain a first correspondence relationship between the voltage of the signal of the accumulated gate reflection output and the voltage values of the second preset range. The voltage values of the first direct current voltage signal are traversed in a third preset range, a second direct current voltage signal of a second preset range of voltage values is applied to the pump gate, and the first radio frequency reading signal is applied to the accumulated gate of the inductive quantum dot, so as to obtain a second correspondence relationship between the voltage of the signal of the accumulated gate reflection output and the voltage values of the third preset range. The Coulomb peak phase diagram is determined according to the first correspondence relationship and the second correspondence relationship.

6. The method of claim 5, wherein, The second direct current voltage signal comprises a fixed amplitude direct current signal and a triangular wave signal, the first direct current voltage signal of the first preset voltage value is applied to the barrier gate, the second direct current voltage signal of the second preset range of voltage values is sequentially applied to the pump gate, and the first radio frequency reading signal is applied to the accumulated gate of the inductive quantum dot, so as to obtain a first correspondence relationship between the voltage of the signal of the accumulated gate reflection output and the voltage values of the second preset range. A first direct current voltage signal of a first preset voltage value is applied to the barrier gate. A second direct current voltage signal of a second preset range of voltage values is sequentially applied to the pump gate. The first radio frequency reading signal is applied to the accumulated gate. The voltage value of the signal of the accumulated gate reflection output is collected when the voltage value of the second direct current voltage signal linearly changes with the amplitude of the rising section or the falling section of the triangular wave signal. The first correspondence relationship is obtained between the voltage value of the signal of the reflection output and the change of the amplitude of the rising section or the falling section of the triangular wave signal.

7. The method of claim 4, wherein, The second direct current voltage signal is applied to the gate of the inductive quantum dot, and the first direct current voltage signal and the second direct current voltage signal corresponding to the first target voltage and the second target voltage and the first radio frequency reading signal are respectively applied to the gate of the inductive quantum dot to read the information of the inductive quantum dot, comprising: A first direct current voltage signal corresponding to the first target voltage is applied to the barrier gate of the inductive quantum dot. The second direct current voltage signal is applied to the pump gate of the inductive quantum dot. A second direct current voltage signal corresponding to the second target voltage is applied to the pump gate of the inductive quantum dot. applying the first radio frequency reading signal to the gate of the sensing quantum dot to read information of the sensing quantum dot.

8. A measurement and control system of semiconductor quantum dots, characterized in that, A semiconductor quantum chip is provided with a bit quantum dot and a sensing quantum dot which are coupled to each other, and a state of the sensing quantum dot is measured by a measurement link to obtain information of the bit quantum dot; the system comprises: a first adjusting module configured to adjust an impedance matching circuit in the measurement link to match an impedance of the sensing quantum dot with a characteristic impedance of the measurement link; a first measuring module configured to apply a first direct current voltage signal, a first radio frequency reading signal and a second direct current voltage signal to the gate of the sensing quantum dot to obtain a Coulomb peak phase diagram of the sensing quantum dot; a first determining module configured to determine a first target voltage of the first direct current voltage signal and a second target voltage of the second direct current voltage signal according to a change value of a reflected voltage in the Coulomb peak phase diagram; a second measuring module configured to apply the second direct current voltage signal to the gate of the bit quantum dot, and apply a first direct current voltage signal and a second direct current voltage signal corresponding to the first target voltage and the second target voltage, respectively, and the first radio frequency reading signal to the gate of the sensing quantum dot to read information of the sensing quantum dot.

9. The system of claim 8, wherein, The first measuring module comprises: a direct current voltage source configured to output the first direct current voltage signal and a fixed-amplitude direct current signal; an arbitrary waveform generator configured to output a triangular wave signal; a radio frequency source configured to output the first radio frequency reading signal; a signal acquisition card configured to acquire a reflected signal output by the gate of the sensing quantum dot; wherein the triangular wave signal and the fixed-amplitude direct current signal are processed into the second direct current voltage signal by a signal superimposer.

10. A quantum computer, characterized by, The method of any one of claims 1-7 is used to test quantum dots on a semiconductor quantum chip, or the system of claim 8 or 9 is used to test quantum dots on a semiconductor quantum chip.

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