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

Abstract

The application discloses a semiconductor quantum dot measurement method, a measurement and control system and a quantum computer. The method comprises the following steps: determining a target working signal applied to a gate of an inductive quantum dot according to a first Coulomb peak phase diagram of a source output signal of the inductive quantum dot; wherein the first Coulomb peak phase diagram is used to represent the relationship between the voltage value of the source output signal and the voltage change sensitivity of the working signal applied to the gate; the working signal comprises a first synthetic signal synthesized by a fixed-amplitude direct current signal and a variable-amplitude direct current signal; the first synthetic signal is applied to the gate of the bit quantum dot, and the target working signal is applied to the gate of the inductive quantum dot; and the information of the bit quantum dot is read according to the source output signal of the inductive quantum dot. The application improves the measurement efficiency of the 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, and 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 exceeding 1.5K in temperature ranges. Achieving efficient measurement of semiconductor quantum dots is a key technology for the practical application of silicon-based spin qubits.

[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 utilize the coupling between the induced quantum dot and the qubit, and to use a charge-spin conversion mechanism to convert the change in the electron spin state of the quantum dot into the change in the transport resistance of the nearest induced quantum dot, thereby realizing the detection of the spin state information of silicon-based spin qubits.

[0004] Transport measurements in induced quantum dots typically employ DC signal transport testing. This involves using a DC voltage source to output a test voltage to the induced quantum dot, and then using a digital multimeter to read the signal output from the quantum dot. However, each change in the high DC voltage source requires a build-up, stabilization, and hold period within the device. Furthermore, the long integration time of the digital multimeter during signal reading significantly limits the measurement speed. In summary, DC signal transport measurements in induced quantum dots are often very time-consuming, severely restricting the testing and characterization speed of silicon-based quantum chips. 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 using current transport measurement methods 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 information about the qubit quantum dots is obtained by measuring the state of the sensing quantum dots. The method includes:

[0007] A target operating signal applied to the gate of the sensing quantum dot is determined based on a first Coulomb peak phase diagram of the source output signal of the sensing quantum dot; wherein, the first Coulomb peak phase diagram is used to characterize the relationship between the voltage value of the source output signal and the voltage change of the operating signal applied to the gate; the operating signal includes a first type of synthesized signal composed of a fixed amplitude DC signal and a variable amplitude DC signal;

[0008] The first type of synthetic signal is applied to the gate of the bit quantum dot, and the target operating signal is applied to the gate of the sensing quantum dot. The information of the bit quantum dot is measured based on the source output signal of the sensing quantum dot.

[0009] The method described above, preferably, includes a barrier gate and a pump gate, and the operating signal further includes a first DC voltage signal applied to the barrier gate of the sensing quantum dot; determining the target operating signal applied to the gate of the sensing quantum dot based on a first Coulomb peak phase diagram of the source output signal of the sensing quantum dot includes:

[0010] The first Coulomb peak phase diagram is determined based on the relationship between the voltage of the source output signal of the sensing quantum dot and the voltage of the first type of synthesized signal applied to the pump gate of the sensing quantum dot.

[0011] The target operating signal is determined based on the first Coulomb peak phase diagram.

[0012] The method described above, preferably, involves determining the first Coulomb peak phase diagram based on the relationship between the voltage of the source output signal of the sensed quantum dot and the voltage of the first type of synthesized signal applied to the barrier gate of the sensed quantum dot and the voltage of the first type of synthesized signal applied to the pump gate of the sensed quantum dot, including:

[0013] A first DC voltage signal with a first preset voltage value is applied to the barrier gate of the sensing quantum dot, a first type of synthesized signal with a first preset range of voltage values ​​is sequentially applied to the pump gate of the sensing quantum dot, and a second DC voltage signal is applied to the drain of the sensing quantum dot to obtain a first correspondence between the voltage of the source output signal of the sensing quantum dot and the voltage value of the first preset range.

[0014] The voltage values ​​of a first DC voltage signal with a voltage value within a second preset range are sequentially applied to the barrier gate of the sensing quantum dot, a first type of synthesized signal with a voltage value within a first preset range is applied to the pump gate of the sensing quantum dot, and a second DC voltage signal is applied to the drain of the sensing quantum dot to obtain a second correspondence between the voltage of the source output signal of the sensing quantum dot and the voltage value within the second preset range.

[0015] The first Coulomb peak phase diagram is determined based on the first correspondence and the second correspondence.

[0016] The method described above, preferably, involves applying a first DC voltage signal with a first preset voltage value to the barrier gate of the sensing quantum dot, sequentially applying a first type of synthesized signal with voltage values ​​within a first preset range to the pump gate of the sensing quantum dot, and applying a second DC voltage signal to the drain of the sensing quantum dot to obtain a first correspondence between the voltage of the source output signal of the sensing quantum dot and the voltage value within the first preset range, including:

[0017] A first DC voltage signal with a first preset voltage value is applied to the barrier gate of the inductive quantum dot;

[0018] The first type of synthesized signal, which applies a voltage value within a first preset range, is sequentially applied to the pump gate of the inductive quantum dot;

[0019] A second DC voltage signal is applied to the drain of the inductive quantum dot;

[0020] The voltage value of the source output signal is acquired when the amplitude of the rising or falling segment of the triangular wave signal changes linearly;

[0021] The voltage value of the source output signal is determined to vary with the amplitude of the rising or falling segment of the triangular wave signal as the first correspondence.

[0022] The method described above, preferably, involves determining the target operating signal based on the first Coulomb peak phase diagram, specifically including:

[0023] Determine the first target voltage of the first DC voltage signal and the second target voltage of the first type of synthesized signal when the voltage change of the output signal in the first Coulomb peak phase diagram is most sensitive.

[0024] The method described above, preferably, involves applying the first type of synthetic signal to the gate of the bit quantum dot, applying the target operating signal to the gate of the sensing quantum dot, and reading the information of the bit quantum dot based on the source output signal of the sensing quantum dot, including:

[0025] A first DC voltage signal corresponding to the first target voltage is applied to the barrier gate of the sensing quantum dot;

[0026] A first-type synthetic signal corresponding to the second target voltage is applied to the pump gate of the sensing quantum dot;

[0027] The first type of synthetic signal is applied to the pump gate of the bit quantum dot;

[0028] A second DC voltage signal is applied to the drain of the inductive quantum dot;

[0029] A second Coulomb peak phase diagram of the source output signal of the sensing quantum dot is obtained; wherein, the second Coulomb peak phase diagram is used to characterize the relationship between the voltage value of the source output signal of the sensing quantum dot and the voltage change of the first type of synthesized signal applied to the pump gate of the qubit quantum dot;

[0030] The information of the bit quantum dot is determined based on the second Coulomb peak phase diagram.

[0031] This application also provides a measurement and control system for semiconductor quantum dots, wherein mutually coupled qubit quantum dots and sensing quantum dots are formed on a semiconductor quantum chip, and information about the qubit quantum dots is obtained by measuring the state of the sensing quantum dots; the system includes:

[0032] The first measurement module is used to determine the target operating signal applied to the gate of the sensing quantum dot based on the first Coulomb peak phase diagram of the source output signal of the sensing quantum dot; wherein, the first Coulomb peak phase diagram is used to characterize the relationship between the voltage value of the source output signal and the voltage change sensitivity of the operating signal applied to the gate; the operating signal is a first type of composite signal synthesized from a fixed amplitude DC signal and a variable amplitude DC signal;

[0033] The second measurement module is used to apply the first type of synthetic signal to the gate of the bit quantum dot, and to apply the target working signal to the gate of the sensing quantum dot, and to read the information of the bit quantum dot according to the source output signal of the sensing quantum dot.

[0034] In the system described above, preferably, both the first measurement module and the second measurement module include:

[0035] A DC voltage source is used to output the fixed amplitude DC signal;

[0036] An arbitrary waveform generator is used to output the DC signal with varying amplitude;

[0037] A signal acquisition card is used to acquire the source output signal of the inductive quantum dot.

[0038] The fixed-amplitude DC signal and the variable-amplitude DC signal are processed into the first type of composite signal by a signal superimposition device.

[0039] In the system described above, preferably, the variable amplitude DC signal includes a triangular wave signal or a sawtooth wave signal, and the signal acquisition card is used to acquire the output signal of the source of the sensing quantum dot when the voltage value of the variable amplitude DC signal changes with the amplitude of the rising or falling segment of the triangular wave signal or the sawtooth wave signal.

[0040] 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 any of the measurement and control systems described above to test quantum dots on a semiconductor quantum chip.

[0041] Compared with existing technologies, this application proposes a method for measuring semiconductor quantum dots. By applying a first type of synthesized signal to the gate of a semiconductor quantum chip, induced quantum dots and qubit quantum dots are formed below the gate. The first type of synthesized signal is synthesized from a fixed amplitude DC signal and a variable amplitude DC signal. The fixed amplitude DC signal is provided by a DC voltage source, and the variable amplitude DC signal is provided by an arbitrary waveform generator. The voltage amplitude change can be preset, and the voltage change response is fast, which makes the response of the first type of synthesized signal applied to the gate fast. This makes the induced quantum dots and qubit quantum dots respond to the first type of synthesized signal faster, thereby improving the measurement efficiency of induced quantum dots.

[0042] Both the inductive quantum dot and the qubit quantum dot are formed using the first type of synthesized signal, which ensures the synchronization of the voltage response of the inductive quantum dot and the qubit quantum dot. This lays the foundation for measuring the qubit quantum dot through the measurement of the inductive quantum dot and ensures the measurement effect of the qubit quantum dot. Furthermore, by synthesizing the fixed amplitude and the variable amplitude, the voltage amplitude of the first type of synthesized signal is high, which meets the requirements for testing the inductive quantum dot.

[0043] Furthermore, by determining the target operating signal applied to the gate of the sensing quantum dot through the measured first Coulomb peak phase diagram, the measurement sensitivity of the sensing quantum dot can be ensured, thereby improving the measurement accuracy of the qubit quantum dot.

[0044] 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

[0045] Figure 1 A schematic cross-sectional view of the gate structure of a semiconductor quantum chip provided in an embodiment of this application;

[0046] Figure 2 A top view of the gate structure of a semiconductor quantum chip provided in an embodiment of this application;

[0047] Figure 3A schematic flowchart illustrating a method for measuring semiconductor quantum dots provided in an embodiment of this application;

[0048] Figure 4 A schematic diagram illustrating a fixed-amplitude DC signal and a variable-amplitude DC signal provided in an embodiment of this application;

[0049] Figure 5 This is a schematic diagram of a DC signal with fixed amplitude and a DC signal with varying amplitude combined, provided in an embodiment of this application.

[0050] Figure 6 A flowchart illustrating the determination of a target working signal is provided for an embodiment of this application.

[0051] Figure 7 A specific schematic diagram of a Coulomb peak phase diagram provided in this application embodiment;

[0052] Figure 8 A schematic flowchart for determining a first Coulomb peak phase diagram provided in an embodiment of this application;

[0053] Figure 9 A flowchart illustrating the process of determining a first correspondence relationship, provided for an embodiment of this application;

[0054] Figure 10 A schematic diagram of a process for determining quantum dot information based on a Coulomb peak phase diagram is provided in this application embodiment;

[0055] Figure 11 This is a schematic diagram of the composition of a semiconductor quantum dot measurement and control system provided in an embodiment of this application.

[0056] In the attached diagram:

[0057] 1-Substrate;

[0058] 11-Drain, 12-Source, 21-Barrier gate, 22-Pump gate, Accumulation gate, 23-10-First measurement module, 20-Second measurement module;

[0059] 211 - First barrier gate, 212 - Second barrier gate. Detailed Implementation

[0060] 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.

[0061] 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.

[0062] 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.

[0063] The spin state information of silicon-based spin qubits is indirectly read out using a charge-spin conversion mechanism, leveraging the charge state changes in adjacent single-electron transistors. The single-electron transistor and the spin qubit are typically controlled by a voltage signal applied to the gate, which regulates the charge density of the two-dimensional electron gas below the gate; a measurement signal is then applied to test the charge state of the single-electron transistor. When testing the spin qubit using a single-electron transistor, the voltage signal applied to the gate varies linearly within a preset range. The applicant's research found that if a voltage source is used to provide a linearly varying DC voltage signal, each adjustment of the output voltage requires a voltage build-up, voltage stabilization, and voltage holding time to ensure the stability of the DC voltage signal output to the gate.

[0064] The applicant's research found that when the required accuracy is high for a linearly varying voltage signal, the time required for the voltage source to provide a linearly varying voltage signal within a preset range is relatively long, directly affecting the testing efficiency of single-electron transistors, i.e., the measurement efficiency of spin qubits is very low. This application proposes a method for rapid measurement of spin qubits.

[0065] As attached Figure 1The diagram shown illustrates the readout of a prior art gated silicon-based spin qubit. 1 is the substrate of a semiconductor quantum chip. Electrodes 11 and 12 are the drain and source, respectively, formed on opposite sides of the substrate, and are used to apply a DC voltage excitation signal to form a transport channel for a two-dimensional electron gas. Electrodes 21 and 22 are both gate electrodes, used to apply a DC voltage signal to adjust the charge density of the two-dimensional electron gas to form a qubit quantum dot within the channel, or to form a sensing quantum dot for reading the qubit quantum dot. In addition, electrode 23, corresponding to the sensing quantum dot, is also used to apply a radio frequency signal to read the sensing quantum dot to obtain information about the qubit quantum dot.

[0066] Appendix Figure 2 This is a cross-sectional schematic diagram of the electrodes forming two quantum dots on a substrate. The electrode structures of the two quantum dots are identical, each including a source, a drain, and several gates. One quantum dot serves as a qubit quantum dot for quantum computing, while the other acts as a sensing quantum dot for measuring the qubit quantum dot. When applying a measurement signal to read the charge change of the sensing quantum dot, a DC voltage signal needs to be applied to both the gate of the sensing quantum dot and the gate of the corresponding qubit quantum dot to form the sensing quantum dot and the qubit quantum dot, respectively. Furthermore, when using conventional transport measurements, an excitation signal needs to be applied to the drain.

[0067] As attached Figure 3 As shown in the embodiments of this application, a method for measuring semiconductor quantum dots is provided. Bit quantum dots and sensing quantum dots with mutual coupling are formed on a semiconductor quantum chip. Information about the bit quantum dots is obtained by measuring the state of the sensing quantum dots. The method includes:

[0068] Step S10: Determine the target operating signal applied to the gate of the sensing quantum dot based on the first Coulomb peak phase diagram of the source output signal of the sensing quantum dot; wherein, the first Coulomb peak phase diagram is used to characterize the relationship between the voltage value of the source output signal and the voltage change sensitivity of the operating signal applied to the gate; the operating signal includes a first type of synthesized signal composed of a fixed amplitude DC signal and a variable amplitude DC signal.

[0069] Combined with appendix Figure 2 As shown, the sensing quantum dot serves as a readout detector for qubit quantum dots, obtaining information about the qubit quantum dots by reading their data. As mentioned above, a DC voltage signal needs to be applied to the gate of the semiconductor quantum chip to form the sensing quantum dot, and the applied DC voltage signal directly affects the readout sensitivity of the sensing quantum dot.

[0070] In this embodiment, a working signal is first applied to the gate of the sensing quantum dot to form the quantum dot. The working signal is a synthesized signal, including a fixed-amplitude DC signal and a variable-amplitude DC signal. The voltage amplitude of the synthesized first-type signal varies within a preset voltage range. The variable-amplitude first-type synthesized signal is applied to the gate of the sensing quantum dot to form the quantum dot, and a DC voltage signal is applied to the drain of the quantum dot for reading. The source output signal of the sensing quantum dot is also read. Since the voltage amplitude of the first-type synthesized signal varies within the preset range, the relationship between the voltage value of the source output signal of the sensing quantum dot and the change of the first-type synthesized signal applied to the gate can be obtained. That is, the correspondence between the charge change of the sensing quantum dot and the excitation signal applied to the gate can be represented. This correspondence is typically represented by a Coulomb peak phase diagram in semiconductor quantum systems, which allows for a direct reading of the charge change of the sensing quantum dot.

[0071] In this embodiment, the relationship between the voltage value of the source output signal of the sensed quantum dot and the change of the first type of synthesized signal applied to the gate is represented by a first Coulomb peak phase diagram. This diagram can intuitively show the relationship between the charge change sensitivity of the sensed quantum dot and the voltage of the first type of synthesized signal. Furthermore, based on the information from the changes in the first Coulomb peak phase diagram, the target voltage value of the first type of synthesized signal when the drain output signal change is maximized is determined. The working signal is then updated to the target working signal based on this target voltage value. This ensures that the sensed quantum dot is most sensitive to changes when the target working signal is applied to its gate, making the measurement of the qubit quantum dot more sensitive.

[0072] Combined with appendix Figure 4 and attached Figure 5 As shown, in this embodiment, a first-type synthesized signal with linearly changing voltage value is obtained by synthesizing a fixed-amplitude DC signal and a variable-amplitude DC signal; Appendix Figure 4 Examples of fixed-amplitude DC signals and variable-amplitude DC signals are provided. The voltage value of the fixed-amplitude DC signal is constant, while the voltage amplitude of the variable-amplitude DC signal varies. The voltage variation curves of the synthesized first-type signal are shown in the attached figure. Figure 5 As shown, it can be observed that the change in voltage value of the first type of synthesized signal corresponds to the change in voltage amplitude of the DC signal with varying amplitude. For example, the voltage value of the fixed amplitude DC signal is 3V, and the voltage amplitude of the varying amplitude DC signal is {-1.5V, 1.5V}. After synthesis, the voltage amplitude of the first type of synthesized signal is {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.

[0073] In addition, Figure 4 and attached Figure 5The curves of the fixed amplitude DC signal, the variable amplitude DC signal, and the first type of composite signal shown in the example are only for illustrative purposes. In actual measurement, the output time of the signal, the voltage amplitude, the number of repetitions of the variable amplitude DC signal, etc. need to be determined according to the requirements, which will not be elaborated in this embodiment.

[0074] In this embodiment, a fixed-amplitude DC signal is provided by a DC voltage source, and a variable-amplitude DC signal is provided by an arbitrary waveform generator. The fixed-amplitude DC signal output from the DC voltage source and the variable-amplitude DC signal output from the arbitrary waveform generator are combined, so that the first-type composite signal applied to the gate of the sensing quantum dot is also a linearly varying voltage signal with a high voltage amplitude, meeting the requirements for testing the sensing quantum dot. Furthermore, the DC voltage source outputs a fixed-value voltage signal, and the arbitrary waveform generator can directly output a triangular wave signal with a fast response, thus generating the first-type composite signal quickly, which improves the measurement efficiency of the sensing quantum dot.

[0075] Step S20: Apply the first type of synthetic signal to the gate of the bit quantum dot, and apply the target working signal to the gate of the sensing quantum dot, and read the information of the bit quantum dot according to the source output signal of the sensing quantum dot.

[0076] The gate structure and formation principle of qubit quantum dots and inductive quantum dots are the same. A first-type synthetic signal is also applied to the gate of the qubit quantum dot to form the qubit quantum dot. The fast response of the first-type synthetic signal allows the qubit quantum dot to respond quickly, thus improving measurement efficiency when measuring qubit quantum dots using inductive quantum dots. Furthermore, after determining the target working signal applied to the gate of the inductive quantum dot in step S10, the signal applied to the gate of the inductive quantum dot is updated to the target working signal, ensuring the measurement sensitivity of the inductive quantum dot and improving measurement accuracy.

[0077] Combined with appendix Figure 1 and attached Figure 2 As shown, when measuring the induced quantum dot using current transport measurement technology, it is also necessary to apply a DC voltage signal for reading to the drain of the induced quantum dot and measure the source output signal of the induced quantum dot. The charge change of the induced quantum dot can be obtained from the change of the source output signal of the induced quantum dot, and then the quantum state information of the bit quantum dot can be obtained.

[0078] Combined with appendix Figure 1 and attached Figure 2 As shown, the gate includes a barrier gate and a pump gate, both used to apply a DC voltage signal to form a quantum dot. The pump gate is located in the middle, and barrier gates are symmetrically arranged on both sides of the pump gate. The operating signal also includes a first DC voltage signal applied to the barrier gate of the sensed quantum dot. (See attached diagram) Figure 6 As shown, determining the target operating signal applied to the gate of the sensing quantum dot based on the first Coulomb peak phase diagram of the source output signal of the sensing quantum dot includes:

[0079] Step S101: Determine the first Coulomb peak phase diagram based on the relationship between the voltage of the source output signal of the sensing quantum dot and the voltage of the first type of synthesized signal applied to the pump gate of the sensing quantum dot.

[0080] In this embodiment, the operating signal includes not only a first type of synthesized signal applied to the pump gate, but also a first DC voltage signal applied to the barrier gate of the inductive quantum dot. The charge density in the two-dimensional electron gas below the gate is adjusted by the combined action of the first type of synthesized signal and the first DC voltage signal to form the inductive quantum dot. Therefore, when measuring the voltage of the source output signal of the inductive quantum dot, both the voltage of the first DC voltage signal and the voltage of the first type of synthesized signal will affect the measurement result.

[0081] The phase diagram of the first Coulomb peak obtained by measurement is attached. Figure 7 As shown, the horizontal axis U3 represents the voltage value of the first type of synthesized signal, with a voltage value change from 2.5V to 4.5V; the vertical axis U4 on the left represents the voltage value of the first DC voltage signal, with a voltage value change from 0V to 3V; the vertical axis on the right represents the voltage value of the source output signal. The brighter the white area in the 3D graph, the larger the voltage value of the corresponding source output signal.

[0082] Step S102: Determine the target working signal based on the first Coulomb peak phase diagram.

[0083] Combined with appendix Figure 7 As shown, the target voltage values ​​of the first DC voltage signal and the first type of synthesized signal can be obtained by using the first Coulomb peak phase diagram when the voltage change of the source output signal is significant.

[0084] As attached Figure 8 As shown, the first Coulomb peak phase diagram is determined based on the relationship between the voltage of the source output signal of the sensing quantum dot and the voltage of the first type of synthesized signal applied to the barrier gate of the sensing quantum dot and the voltage of the first type of synthesized signal applied to the pump gate of the sensing quantum dot, including:

[0085] Step S1011: Apply a first DC voltage signal with a first preset voltage value to the barrier gate of the sensing quantum dot, sequentially apply a first type of synthesized signal with a voltage value within a first preset range to the pump gate of the sensing quantum dot, and apply a second DC voltage signal to the drain of the sensing quantum dot to obtain a first correspondence between the voltage of the source output signal of the sensing quantum dot and the voltage value within the first preset range.

[0086] Step S1012: Sequentially apply the voltage values ​​of the first DC voltage signal with a voltage value within a second preset range to the barrier gate of the sensing quantum dot, apply the first type of synthesized signal with a voltage value within a first preset range to the pump gate of the sensing quantum dot, and apply the second DC voltage signal to the drain of the sensing quantum dot to obtain a second correspondence between the voltage of the source output signal of the sensing quantum dot and the voltage value within the second preset range.

[0087] As described in step S101 above, the first Coulomb peak phase diagram is data showing the voltage change of the source output signal of the sensed quantum dot with the voltage of the first DC voltage signal and the voltage of the first type of synthesized signal. Specifically, the voltage value of the first DC voltage signal is first set to a first preset voltage value, and the voltage value of the first type of synthesized signal is set to a second preset range. Several voltage values ​​within the second preset range are sequentially traversed. When traversing each voltage value, a second DC voltage signal is applied to the drain of the sensed quantum dot, and the first correspondence between the voltage value of the source output signal of the sensed quantum dot and the voltage value within the first preset range is measured. For example, if the voltage value of the first DC voltage signal is set to 3V, and the first preset range is determined to be {2.5V, 4.5V}, then a first type of synthesized 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 source output signal and the voltage value within the second preset range.

[0088] In addition, the voltage value of the first DC voltage signal is traversed within a second preset range, and a first type of synthesized signal of voltage value within the first preset range is repeatedly applied to the pump gate. Then, a second DC voltage signal is applied to the drain of the sensing quantum dot, and a second correspondence is measured between the voltage value of the source output signal of the sensing quantum dot and the voltage value change within the second preset range.

[0089] For example, the second 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 first type of synthesized signal is traversed within the first preset range to obtain the current voltage value of the source output signal. Then, the voltage value of the first DC voltage signal is set to 1V, and the first type of synthesized signal is traversed within the first preset range to obtain the current voltage value of the source output signal. This process continues until all voltage values ​​within the second preset range have been traversed, thus obtaining the second correspondence between the voltage values ​​of the source output signal and the voltage values ​​within the second preset range.

[0090] It should be added that when obtaining the first and second correspondences, the first type of synthesized signals are traversed within a first preset range. The step values ​​of the first and second preset ranges are adjusted according to the specific test accuracy requirements; this embodiment is merely an example.

[0091] Step S1013: Determine the first Coulomb peak phase diagram based on the first correspondence and the second correspondence.

[0092] In both steps S1011 and S1012, the first and second correspondences obtained are one-to-one corresponding data. These correspondences can be displayed in a three-dimensional coordinate graph, which is the first Coulomb peak phase diagram, as detailed in the attached figure. Figure 7 As shown.

[0093] Combined with appendix Figure 2 As shown, the barrier gate of the quantum dot includes a first barrier gate 211 and a second barrier gate 212. When the first DC voltage signal is applied to the barrier gate in step S1012 for traversal, the first DC voltage signal applied to the first barrier gate 211 and the second barrier gate 212 can be applied and traversed respectively.

[0094] Specifically, firstly, the first DC voltage signal applied to the first barrier gate 211 is set to a preset value. Then, the first DC voltage signal applied to the second barrier gate 212 is traversed within a second preset range. Steps S1012 and S1013 are repeated to obtain a Coulomb peak phase diagram. Next, the preset value of the first DC voltage signal applied to the first barrier gate 211 is adjusted, and the first DC voltage signal applied to the second barrier gate 212 is traversed within the second preset range. Steps S1012 and S1013 are repeated to obtain another Coulomb peak phase diagram.

[0095] The preset value of the first DC voltage signal applied to the first barrier gate 211 is traversed within a second preset range, and then combined with the first DC voltage signal applied to the second barrier gate 212 being 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 gates 211 and 212 respectively can be determined, ensuring higher sensitivity of the sensing quantum dots.

[0096] As attached Figure 9 As shown, the varying amplitude DC signal includes a triangular wave signal. A first DC voltage signal with a first preset voltage value is applied to the barrier gate of the sensing quantum dot. A first type of synthesized signal with voltage values ​​within a first preset range is sequentially applied to the pump gate of the sensing quantum dot. A second DC voltage signal is applied to the drain of the sensing quantum dot to obtain a first correspondence between the voltage of the source output signal of the sensing quantum dot and the voltage value within the first preset range. This includes:

[0097] Step S10111: Apply a first DC voltage signal with a first preset voltage value to the barrier gate of the inductive quantum dot;

[0098] Step S10112: Sequentially apply a first type of synthesized signal with a voltage value within a first preset range to the pump gate of the sensing quantum dot;

[0099] Step S10113: Apply a second DC voltage signal to the drain of the inductive quantum dot;

[0100] Step S10114: Collect the voltage value of the source output signal when the amplitude of the rising or falling segment of the triangular wave signal changes linearly;

[0101] Step S10115: Determine the voltage value of the source output signal as a function of the amplitude of the rising or falling segment of the triangular wave signal as the first correspondence.

[0102] In step S1011 above, the voltage value of the first type of synthesized signal varies within a first preset range. As described above, the first type of synthesized signal is synthesized from a fixed-amplitude DC signal and a variable-amplitude DC signal. In this embodiment, the variable-amplitude DC signal is a triangular wave signal, and the voltage value of the first type of synthesized signal varies with the amplitude of the triangular wave signal. For details, please refer to the attached diagram. Figure 5 The schematic curve shows that the voltage value within the first 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 first preset range, the voltage value of the first type of synthesized signal includes several continuous rising and falling segments.

[0103] In this embodiment, when the voltage value of the first type of synthesized 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 first type of synthesized 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 voltage of the source output signal of the induced quantum dot using a measuring device, multiple measurements are performed and the average value is taken; when multiple measurements are performed with the first type of synthesized signal applied to the pump gate as the complete rising segment or the falling segment, the voltage value of the reflected signal during the rising or falling segment can be collected, which can improve the measurement accuracy of the voltage of the reflected signal.

[0104] For example, when measuring 10 times, if the first type of synthesized signal applied to the pump gate is always a complete rising segment, the voltage value of the reflected signal during the rising segment is collected; or if the first type of synthesized signal applied to the pump gate is always a complete falling segment, the voltage value of the reflected signal during the falling segment is collected.

[0105] In this embodiment, determining the target operating signal based on the first Coulomb peak phase diagram specifically includes: determining the first target voltage of the first DC voltage signal when the voltage change of the output signal in the first Coulomb peak phase diagram is most sensitive, and the second target voltage of the first type of synthesized signal.

[0106] The first Coulomb peak phase diagram is used to characterize the change in voltage of the source output signal of the sensed quantum dot as a function of the voltage values ​​of the first DC voltage signal and the first type of synthesized signal. Information about the state changes of the sensed quantum dot can be obtained from the voltage of the source output signal in the first Coulomb peak phase diagram. The state in which the change in voltage of the source output signal in the first Coulomb peak phase diagram is the largest corresponds to the state of the sensed quantum dot that is most sensitive to state changes. The first target voltage of the first DC voltage signal and the second target voltage of the first type of synthesized signal are determined when the change in voltage of the source output signal in the first Coulomb peak phase diagram is the largest, and the voltages of the first DC voltage signal and the first type of synthesized signal applied to the gate of the sensed quantum dot are updated accordingly.

[0107] As attached Figure 10 As shown, the method includes applying the first type of synthesized signal to the gate of the bit quantum dot, applying the target operating signal to the gate of the sensing quantum dot, and reading the information of the bit quantum dot based on the source output signal of the sensing quantum dot, including:

[0108] Step S201: Apply a first DC voltage signal corresponding to the first target voltage to the barrier gate of the sensing quantum dot.

[0109] Step S202: Apply a first type of synthesized signal corresponding to the second target voltage to the pump gate of the sensing quantum dot.

[0110] Step S203: Apply the first type of synthesized signal to the pump gate of the bit quantum dot.

[0111] First, through steps S201-S202, a first DC voltage signal corresponding to a first target voltage is applied to the barrier gate of the sensing quantum dot, and a first type of synthetic signal corresponding to a second target voltage is applied to the pump gate of the sensing quantum dot to form the sensing quantum dot with the highest measurement sensitivity. Then, through step S203, the first type of synthetic signal is applied to the pump gate of the qubit quantum dot to form the qubit quantum dot. As described above, when using the first type of synthetic signal to form both the sensing quantum dot and the qubit quantum dot, the signal generation response speed is fast.

[0112] Step S204: Apply a second DC voltage signal to the drain of the inductive quantum dot.

[0113] Step S205: Obtain the second Coulomb peak phase diagram of the source output signal of the sensing quantum dot; wherein, the second Coulomb peak phase diagram is used to characterize the relationship between the voltage value of the source output signal of the sensing quantum dot and the voltage change of the first type of synthesized signal applied to the pump gate of the bit quantum dot.

[0114] Step S206: Determine the information of the bit quantum dot based on the second Coulomb peak phase diagram.

[0115] After forming qubit quantum dots and highly sensitive sensing quantum dots, measurements are performed by applying a second DC voltage signal to the drain of the semiconductor quantum chip. This second DC voltage signal serves as the excitation signal for measurement. The measurement device acquires information about the voltage variation of the source output signal with the voltage amplitude of the first type of synthesized signal, i.e., the second Coulomb peak phase diagram. The second Coulomb peak phase diagram characterizes the relationship between the voltage value of the source output signal of the sensing quantum dot and the voltage variation of the first type of synthesized signal applied to the barrier gate of the qubit quantum dot. The voltage variation in the second Coulomb peak phase diagram provides information about the charge variation of the sensing quantum dot, and thus, information about the qubit quantum dot can be obtained from this charge variation information.

[0116] As attached Figure 11As 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. Information about the qubit quantum dots is obtained by measuring the state of the sensing quantum dots. The system includes: a first measurement module 10, used to determine a target operating signal applied to the gate of the sensing quantum dot based on a first Coulomb peak phase diagram of the source output signal of the sensing quantum dot; wherein, the first Coulomb peak phase diagram is used to characterize the relationship between the voltage value of the source output signal and the sensitivity of the voltage change of the operating signal applied to the gate; the operating signal is a first type of synthesized signal composed of a fixed amplitude DC signal and a variable amplitude DC signal; and a second measurement module 20, used to apply the first type of synthesized signal to the gate of the qubit quantum dot, and apply the target operating signal to the gate of the sensing quantum dot, and read the information of the qubit quantum dot based on the source output signal of the sensing quantum dot.

[0117] The first measurement module 10 may include signal source devices such as a DC voltage source and an arbitrary waveform generator, used to output a first type of synthesized signal to the gate of the sensing quantum dot; it may also include signal analysis instruments such as a vector network analyzer and a spectrum analyzer, used to process and analyze the read signal to determine the target working signal.

[0118] The second measurement module 10 may include signal source devices such as a DC voltage source and an arbitrary waveform generator, used to output the first type of synthesized signal to the gate of the bit quantum dot and output the target working signal to the gate of the sensing quantum dot; it may also include signal analysis instruments such as a vector network analyzer and a spectrum analyzer, used to process and analyze the read signal to determine the target working signal.

[0119] Specifically, in this embodiment, both the first measurement module and the second measurement module include: a DC voltage source for outputting the fixed amplitude DC signal; an arbitrary waveform generator for outputting the variable amplitude DC signal; and a signal acquisition card for acquiring the source output signal of the inductive quantum dot; wherein the fixed amplitude DC signal and the variable amplitude DC signal are processed into the first type of synthesized signal by a signal superposition device.

[0120] In a more specific implementation, the variable amplitude DC signal includes a triangular wave signal or a sawtooth wave signal, and the signal acquisition card is used to acquire the output signal of the source of the sensing quantum dot when the voltage value of the variable amplitude DC signal changes with the amplitude of the rising or falling segment of the triangular wave signal or the sawtooth wave signal.

[0121] When the voltage value of the varying amplitude DC signal is the rising segment of a triangular wave or sawtooth wave signal, the voltage signal applied to the pump gate of the qubit quantum dot gradually increases from a small voltage to a large voltage; when the voltage value of the varying amplitude DC signal is the falling segment of a triangular wave or sawtooth wave signal, the voltage signal applied to the pump gate of the qubit quantum dot gradually decreases from a large voltage to a small voltage. When measuring the reflected signal output from the pump gate of the qubit quantum dot using a signal acquisition card, multiple measurements are performed and the average value is taken. Selecting a complete rising or falling segment of the varying amplitude DC signal applied to the qubit gate and acquiring the voltage value of the second microwave signal during the rising or falling segment can improve the measurement accuracy of the voltage of the second microwave signal.

[0122] 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 any of the above-described semiconductor quantum dot systems to test quantum dots on a semiconductor quantum chip.

[0123] 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.

[0124] 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 for measuring semiconductor quantum dots, characterized in that, A semiconductor quantum chip has mutually coupled qubit quantum dots and sensing quantum dots formed on it. Information about the qubit quantum dots is obtained by measuring the state of the sensing quantum dots. The method includes: A target operating signal applied to the gate of the sensing quantum dot is determined based on a first Coulomb peak phase diagram of the source output signal of the sensing quantum dot; wherein, the first Coulomb peak phase diagram is used to characterize the relationship between the voltage value of the source output signal and the voltage change of the operating signal applied to the gate; the operating signal includes a first type of synthesized signal composed of a fixed amplitude DC signal and a variable amplitude DC signal; The first type of synthetic signal is applied to the gate of the bit quantum dot, and the target operating signal is applied to the gate of the sensing quantum dot. The information of the bit quantum dot is measured based on the source output signal of the sensing quantum dot.

2. The method as described in claim 1, characterized in that, The gate includes a barrier gate and a pump gate, and the operating signal also includes a first DC voltage signal applied to the barrier gate of the sensing quantum dot; The target operating signal applied to the gate of the sensing quantum dot is determined based on the first Coulomb peak phase diagram of the source output signal of the sensing quantum dot, including: The first Coulomb peak phase diagram is determined based on the relationship between the voltage of the source output signal of the sensing quantum dot and the voltage of the first type of synthesized signal applied to the pump gate of the sensing quantum dot. The target operating signal is determined based on the first Coulomb peak phase diagram.

3. The method as described in claim 2, characterized in that, The first Coulomb peak phase diagram is determined based on the relationship between the voltage of the source output signal of the sensed quantum dot and the voltage of the first DC voltage signal applied to the barrier gate of the sensed quantum dot and the voltage of the first type of synthesized signal applied to the pump gate of the sensed quantum dot, including: A first DC voltage signal with a first preset voltage value is applied to the barrier gate of the sensing quantum dot, a first type of synthesized signal with a first preset range of voltage values ​​is sequentially applied to the pump gate of the sensing quantum dot, and a second DC voltage signal is applied to the drain of the sensing quantum dot to obtain a first correspondence between the voltage of the source output signal of the sensing quantum dot and the voltage value of the first preset range. The voltage values ​​of a first DC voltage signal with a voltage value within a second preset range are sequentially applied to the barrier gate of the sensing quantum dot, a first type of synthesized signal with a voltage value within a first preset range is applied to the pump gate of the sensing quantum dot, and a second DC voltage signal is applied to the drain of the sensing quantum dot to obtain a second correspondence between the voltage of the source output signal of the sensing quantum dot and the voltage value within the second preset range. The first Coulomb peak phase diagram is determined based on the first correspondence and the second correspondence.

4. The method as described in claim 3, characterized in that, The varying amplitude DC signal includes a triangular wave signal. A first DC voltage signal with a first preset voltage value is applied to the barrier gate of the sensing quantum dot. A first type of synthesized signal with voltage values ​​within a first preset range is sequentially applied to the pump gate of the sensing quantum dot. A second DC voltage signal is applied to the drain of the sensing quantum dot. A first correspondence between the voltage of the source output signal of the sensing quantum dot and the voltage value within the first preset range is obtained, including: A first DC voltage signal with a first preset voltage value is applied to the barrier gate of the inductive quantum dot; The first type of synthesized signal, which applies a voltage value within a first preset range, is sequentially applied to the pump gate of the inductive quantum dot; A second DC voltage signal is applied to the drain of the inductive quantum dot; The voltage value of the source output signal is acquired when the amplitude of the rising or falling segment of the triangular wave signal changes linearly; The voltage value of the source output signal is determined to vary with the amplitude of the rising or falling segment of the triangular wave signal as the first correspondence.

5. The method as described in claim 3, characterized in that, Determining the target operating signal based on the first Coulomb peak phase diagram specifically includes: Determine the first target voltage of the first DC voltage signal and the second target voltage of the first type of synthesized signal when the voltage change of the output signal in the first Coulomb peak phase diagram is most sensitive.

6. The method as described in claim 5, characterized in that, Applying the first type of synthesized signal to the gate of the bit quantum dot, and applying the target operating signal to the gate of the sensing quantum dot, and reading the information of the bit quantum dot based on the source output signal of the sensing quantum dot, including: A first DC voltage signal corresponding to the first target voltage is applied to the barrier gate of the sensing quantum dot; A first-type synthetic signal corresponding to the second target voltage is applied to the pump gate of the sensing quantum dot; The first type of synthetic signal is applied to the pump gate of the bit quantum dot; A second DC voltage signal is applied to the drain of the inductive quantum dot; A second Coulomb peak phase diagram of the source output signal of the sensing quantum dot is obtained; wherein, the second Coulomb peak phase diagram is used to characterize the relationship between the voltage value of the source output signal of the sensing quantum dot and the voltage change of the first type of synthesized signal applied to the pump gate of the qubit quantum dot; The information of the bit quantum dot is determined based on the second Coulomb peak phase diagram.

7. A measurement and control system for semiconductor quantum dots, characterized in that, A semiconductor quantum chip has mutually coupled qubit quantum dots and sensing quantum dots formed on it. Information about the qubit quantum dots is obtained by measuring the state of the sensing quantum dots. The system includes: The first measurement module is used to determine the target operating signal applied to the gate of the sensing quantum dot based on the first Coulomb peak phase diagram of the source output signal of the sensing quantum dot; wherein, the first Coulomb peak phase diagram is used to characterize the relationship between the voltage value of the source output signal and the voltage change sensitivity of the operating signal applied to the gate; the operating signal is a first type of composite signal synthesized from a fixed amplitude DC signal and a variable amplitude DC signal; The second measurement module is used to apply the first type of synthetic signal to the gate of the bit quantum dot, and to apply the target working signal to the gate of the sensing quantum dot, and to read the information of the bit quantum dot according to the source output signal of the sensing quantum dot.

8. The system as described in claim 7, characterized in that, Both the first measurement module and the second measurement module include: A DC voltage source is used to output the fixed amplitude DC signal; An arbitrary waveform generator is used to output the DC signal with varying amplitude; A signal acquisition card is used to acquire the source output signal of the inductive quantum dot. The fixed-amplitude DC signal and the variable-amplitude DC signal are processed into the first type of composite signal by a signal superimposition device.

9. The system as described in claim 8, characterized in that, The varying amplitude DC signal includes a triangular wave signal or a sawtooth wave signal. The signal acquisition card is used to acquire the output signal of the source of the sensing quantum dot when the voltage value of the varying amplitude DC signal changes with the amplitude of the rising or falling segment of the triangular wave signal or the sawtooth wave signal.

10. A quantum computer, characterized in that, The quantum dots on the semiconductor quantum chip are tested using the method described in any one of claims 1-6, or using the measurement and control system described in any one of claims 7-9.

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