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: applying a working signal to the sensing quantum dot to obtain a target working signal when the sensing quantum dot reads a state; wherein the working signal comprises a first type of synthetic signal composed of a fixed amplitude direct current signal and a variable amplitude direct current signal applied to a gate of the sensing quantum dot; the first type of synthetic signal is applied to the gate of the bit quantum dot, and the target working signal is applied to the gate of the sensing quantum dot to read information of the sensing quantum dot; wherein the first type of synthetic signal is used to form the sensing quantum dot and the bit quantum dot below the gate. 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. Summary of the Invention

[0003] 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.

[0004] 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 method includes:

[0005] A target working signal is obtained when the quantum dot is in its readout state by applying a working signal to the quantum dot; wherein, the working signal includes a first type of composite signal composed of a fixed amplitude DC signal and a variable amplitude DC signal applied to a gate of the quantum dot;

[0006] The first type of synthesized 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 to read the information of the sensing quantum dot;

[0007] The first type of synthesized signal is used to form the inductive quantum dot and the bit quantum dot below the gate.

[0008] Preferably, in the method described above, the working signal further includes a first microwave signal for measuring the information of the sensing quantum dot, wherein the voltage of the first type of synthesized signal varies within a first preset range, and the target working signal for obtaining the reading state of the sensing quantum dot by applying the working signal to the sensing quantum dot includes:

[0009] The first type of synthesized signal and the first microwave signal are applied to the gate of the sensing quantum dot;

[0010] Obtain a first curve showing the voltage of the second microwave signal output by the gate reflection changing with the voltage within the first preset range;

[0011] The target operating signal is determined based on the first curve.

[0012] Preferably, in the method described above, determining the target operating signal based on the first curve includes:

[0013] Determine the target voltage value of the first type of synthesized signal when the voltage change value in the first curve is the largest;

[0014] The first type of synthesized signal with a voltage value of the target voltage value is determined as the target working signal.

[0015] Preferably, in the method described above, the operating signal further includes a first DC voltage signal applied to the gate of the sensing quantum dot, and the target operating signal for obtaining the reading state of the sensing quantum dot by applying the operating signal to the sensing quantum dot further includes:

[0016] Within a second preset range, the voltage of the first DC voltage signal is traversed, and the first type of synthesized signal and the first microwave signal are applied to the gate of the inductive quantum dot;

[0017] Obtain the Coulomb peak phase diagram of the voltage of the second microwave signal output by the gate reflection as a function of the voltage within the first preset range and the voltage within the second preset range;

[0018] The target operating signal is determined based on the Coulomb peak phase diagram.

[0019] Preferably, in the method described above, determining the target operating signal based on the Coulomb peak phase diagram includes:

[0020] Determine the target voltage value of the first type of synthesized signal and the target voltage value of the first DC voltage signal when the voltage change value in the Coulomb peak phase diagram is the largest.

[0021] The first type of synthesized signal with a voltage value of the target voltage value and the first DC voltage signal are determined to be the target working signal.

[0022] The method described above, preferably, involves 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 to read the information of the sensing quantum dot, comprising:

[0023] The first type of synthetic signal is applied to the gate of the bit quantum dot;

[0024] The target operating signal and the first microwave signal are applied to the gate of the sensing quantum dot;

[0025] Information about the sensing quantum dot is obtained based on the change in voltage amplitude of the second microwave signal output from the gate reflection of the sensing quantum dot as a function of the first type of synthesized signal; or,

[0026] The step of 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 to read the information of the sensing quantum dot includes:

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

[0028] The target operating signal is applied to the gate of the sensing quantum dot;

[0029] A second DC voltage signal is applied to the drain of the semiconductor quantum chip;

[0030] Information about the sensing quantum dot is obtained based on the change in voltage amplitude of the signal output from the source of the semiconductor quantum chip as a function of the first type of synthesized signal.

[0031] The method described above, preferably, further includes, before applying an operating signal to the sensing quantum dot to obtain the target operating signal when the sensing quantum dot reads out:

[0032] The voltage amplitude of the fixed amplitude DC signal is preset to be greater than the maximum voltage amplitude of the variable amplitude DC signal.

[0033] Another aspect of this application provides a measurement and control system for semiconductor quantum dots, which measures qubit quantum dots and sensed quantum dots formed on a semiconductor quantum chip with mutual coupling. The system includes:

[0034] The first measurement module is used to apply a working signal to the sensing quantum dot to obtain the target working signal when the sensing quantum dot is in the readout state; wherein, applying a working signal to the sensing quantum dot includes a first type of composite signal applied to a gate of the sensing quantum dot, which is composed of a fixed amplitude DC signal and a variable amplitude DC signal;

[0035] 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 to read the information of the sensing quantum dot;

[0036] The first type of synthesized signal is used to form the inductive quantum dot and the bit quantum dot below the gate.

[0037] In the system described above, preferably, the first measurement module includes:

[0038] A DC voltage source is used to output the fixed amplitude DC signal;

[0039] An arbitrary waveform generator is used to output the DC signal with varying amplitude;

[0040] Radio frequency source, used to output the first microwave signal.

[0041] In the system described above, preferably, the second measurement module includes a signal acquisition card for acquiring the second microwave signal output from the gate of the sensing quantum dot or the signal output from the source of the semiconductor quantum chip.

[0042] 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 second microwave signal or the current signal 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.

[0043] In another aspect, this application provides 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.

[0044] 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.

[0045] Furthermore, both the inductive quantum dot and the qubit quantum dot employ the first type of synthesized signal, ensuring the synchronization of their voltage responses. This lays the foundation for measuring the qubit quantum dot through the measurement of the inductive quantum dot and guarantees the measurement effect of the qubit quantum dot, thus contributing to the scalable and large-scale practical application of quantum computers based on silicon-based spin qubits. Moreover, by synthesizing fixed and variable amplitudes, the voltage amplitude of the first type of synthesized signal is high, meeting the requirements for testing the inductive quantum dot.

[0046] 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

[0047] Figure 1 A schematic cross-sectional view of the gate structure of a semiconductor quantum chip provided in an embodiment of this application;

[0048] Figure 2 A top view of the gate structure of a semiconductor quantum chip provided in an embodiment of this application;

[0049] Figure 3 A schematic flowchart illustrating a method for measuring semiconductor quantum dots provided in an embodiment of this application;

[0050] Figure 4 A schematic diagram illustrating a fixed-amplitude DC signal and a variable-amplitude DC signal provided in an embodiment of this application;

[0051] 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.

[0052] Figure 6 A flowchart illustrating the determination of a target working signal is provided for an embodiment of this application.

[0053] Figure 7 A flowchart illustrating the determination of a target working signal based on a first curve, provided as an embodiment of this application;

[0054] Figure 8 A flowchart illustrating another process for determining a target working signal, provided in an embodiment of this application;

[0055] Figure 9 A flowchart illustrating the process of determining a target operating signal based on a Coulomb peak phase diagram, provided as an embodiment of this application;

[0056] Figure 10 A specific schematic diagram of a Coulomb peak phase diagram provided in this application embodiment;

[0057] Figure 11 A schematic diagram of a process for measuring inductive quantum dots is provided in an embodiment of this application;

[0058] Figure 12 This is a schematic diagram of another process for measuring inductive quantum dots provided in an embodiment of this application;

[0059] Figure 13 A schematic diagram of a signal transmission link including an impedance matching unit provided in an embodiment of this application;

[0060] Figure 14 A schematic flowchart of an adjustable impedance matching circuit provided in an embodiment of this application;

[0061] Figure 15This is a schematic diagram of the composition of a semiconductor quantum dot measurement and control system provided in an embodiment of this application.

[0062] In the attached diagram:

[0063] 1-Substrate, 3-Impedance matching circuit;

[0064] 11-Drain, 12-Source, 21-Barrier gate, 22-Pump gate, 23-Accumulation gate, 10-First measurement module, 20-Second measurement module;

[0065] First barrier gate -211, second barrier gate -212. Detailed Implementation

[0066] 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.

[0067] 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.

[0068] 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.

[0069] The spin state information of silicon-based spin qubits is indirectly read out by utilizing the charge-spin conversion mechanism and the change in charge state in adjacent single-electron transistors. Currently, there are two mainstream measurement schemes that are more commonly used internationally: (1) conventional transport measurement, which uses the transport current to detect the weak resistance signal change in the single-electron transistor; (2) radio frequency reflection readout technology, which introduces an "impedance transformer" circuit between the single-electron transistor and the measurement and readout link, thereby constructing an impedance matching network that can provide real-time feedback on the conductance state change in the single-electron transistor.

[0070] Single-electron transistors and spin qubits are typically controlled by a voltage signal applied to the gate, which governs the potential of a two-dimensional electron gas beneath the gate. A measurement signal is then applied to test the charge state of the single-electron transistor. When testing spin qubits 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 period of voltage build-up, voltage stabilization, and voltage holding time to ensure the stability of the DC voltage signal output to the gate.

[0071] 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.

[0072] As attached Figure 1 The 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 electrodes formed on opposite sides of the substrate, respectively, 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 potential of the two-dimensional electron gas to form a qubit quantum dot within the channel, or to form an inductive quantum dot for reading the qubit quantum dot. Furthermore, electrode 23 corresponding to the inductive quantum dot is also used to apply a radio frequency signal to read the inductive quantum dot to obtain information about the qubit quantum dot.

[0073] Appendix Figure 2 This is a cross-sectional schematic diagram of electrodes formed on a substrate with two quantum dots. The electrode structures of the two quantum dots are exactly the same, each including a source, a drain, and several gates. One of the two quantum dots is used as a bit quantum dot to perform quantum computing, and the other is used as a sensing quantum dot to measure the bit quantum dot.

[0074] When applying a measurement signal to read the charge change of the sensed quantum dot, a DC voltage signal needs to be applied to the gate of both the sensed quantum dot and the qubit quantum dot to form the sensed quantum dot and the qubit quantum dot. In addition, when using radio frequency reflection readout technology, a radio frequency readout signal needs to be applied to the gate of the sensed quantum dot, and when using conventional transport measurement, an excitation signal needs to be applied to the drain.

[0075] As attached Figure 3 As shown in the embodiments of this application, a measurement 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. The method includes:

[0076] Step S10: Apply a working signal to the sensing quantum dot to obtain a target working signal when the sensing quantum dot is in a readout state; wherein, the working signal includes a first type of synthesized signal applied to a gate of the sensing quantum dot, which is composed of a fixed amplitude DC signal and a variable amplitude DC signal.

[0077] 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.

[0078] 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. Applying the variable-amplitude first-type synthesized signal to the gate of the sensing quantum dot and reading it allows us to obtain information about the change in the read signal's voltage amplitude with the first-type synthesized signal. Based on this information, we determine the target voltage value of the first-type synthesized signal when the change in the read signal is maximum. The working signal is then updated to the target working signal based on this target voltage value. When the target working signal is applied to the gate of the sensing quantum dot, the quantum dot is most sensitive to changes, making the measurement of the qubit quantum dot more sensitive.

[0079] 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.

[0080] In addition, Figure 4 and attached Figure 5 The 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.

[0081] 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.

[0082] 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 to read the information of the sensing quantum dot.

[0083] 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.

[0084] Combined with appendix Figure 1 and attached Figure 2As shown, when measuring the sensing quantum dot using radio frequency reflection readout technology, a microwave signal for reading needs to be applied to the gate of the sensing quantum dot. The microwave signal for reading is applied to gate 23, and the first type of synthesized signal is applied to gate 22.

[0085] In this embodiment, the working signal also includes a first microwave signal for measuring the information of the sensed quantum dot. The voltage of the first type of synthesized signal varies within a first preset range. For example, the voltage of the variable amplitude DC signal varies in the range of {-1.5V, 1.5V} according to a preset step value. When the voltage value of the fixed amplitude DC signal is 3V, the voltage amplitude of the corresponding synthesized first type of synthesized signal varies in the range of {1.5V, 4.5V}.

[0086] As attached Figure 6 As shown, the target working signal for obtaining the readout state of the sensing quantum dot by applying a working signal to the sensing quantum dot in step S10 includes:

[0087] Step S101: Apply the first type of synthetic signal and the first microwave signal to the gate of the sensing quantum dot.

[0088] A first type of synthesized signal is applied to the gate corresponding to the sensed quantum dot to form the sensed quantum dot below the gate, and a first microwave signal is applied to another gate to measure the sensed quantum dot. The first microwave signal is typically provided by an radio frequency source.

[0089] Step S102: Obtain a first curve showing the voltage of the second microwave signal output by the gate reflection changing with the voltage within the first preset range.

[0090] The measurement of the sensed quantum dot is a reflective measurement, that is, after applying a first microwave signal to the gate of the sensed quantum dot, the gate will reflect and output a second microwave signal carrying quantum dot information. The voltage of the first type of synthesized signal varies within a first preset range. By measuring, a one-to-one correspondence can be obtained between the voltage of the second microwave signal and the voltage within the first preset range. After traversing the voltage within the first preset range, several sets of one-to-one corresponding data are obtained. These sets of data are then processed to obtain a first curve.

[0091] Step S103: Determine the target working signal based on the first curve.

[0092] The first curve represents the relationship between the voltage of the reflected output second microwave signal and the voltage within a first preset range. It can also represent the sensitivity of the quantum dot. The voltage within the first preset range when the quantum dot is most sensitive can be selected from the first curve and determined as the target voltage of the first type of synthesized signal.

[0093] When determining the target working signal in step S103 above, in conjunction with the attached... Figure 7 As shown, determining the target operating signal based on the first curve includes:

[0094] Step S1031: Determine the target voltage value of the first type of synthesized signal when the voltage change value in the first curve is the largest.

[0095] Step S1032: Determine the first type of synthesized signal with a voltage value of the target voltage value as the target working signal.

[0096] The first curve can be used to determine a data point where the voltage change of the second microwave signal is at its maximum. This data point represents the most sensitive response of the inductive quantum dot to the first type of synthesized signal. By determining the voltage within a first preset range corresponding to this data point, the target voltage value of the first type of synthesized signal can be determined. The first type of synthesized signal with this target voltage value is the target operating signal applied to the gate of the inductive quantum dot, ensuring the measurement sensitivity of the qubit quantum dot through the inductive quantum dot.

[0097] Continue as attached Figure 1 and attached Figure 2 As shown, the gates for forming the induced quantum dots and qubit quantum dots include three gates: the middle one is the pump gate, and the two on either side are barrier gates. Forming induced quantum dots and qubit quantum dots requires applying a first type of synthesized signal not only to the pump gate but also to the barrier gates. The voltage values ​​of both the first DC voltage signal and the first type of synthesized signal affect the sensitivity of the induced quantum dots. Therefore, the voltage values ​​of both the first DC voltage signal and the first type of synthesized signal need to be adjusted to target values.

[0098] Therefore, in conjunction with the appendix Figure 8 As shown, in this embodiment, the step of applying a working signal to the sensing quantum dot to obtain the target working signal when the sensing quantum dot is in its readout state further includes:

[0099] Step S111: Traverse the voltage of the first DC voltage signal within the second preset range, and apply the first type of synthesized signal and the first microwave signal to the gate of the sensing quantum dot.

[0100] In steps S101-S102, the voltage value of the applied first type of synthetic signal varies within a preset range, while the voltage of the first DC voltage signal applied to the gate of the sensing quantum dot varies within a second preset range. When the first microwave signal is applied to the gate of the sensing quantum dot, the second microwave signal reflected from the gate can be measured using a measuring device.

[0101] Step S112: Obtain the Coulomb peak phase diagram of the voltage of the second microwave signal output by the gate reflection as a function of the voltage within the first preset range and the voltage within the second preset range.

[0102] As attached 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 gate in step S111 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.

[0103] 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 third preset range. Steps S111-S112 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 third preset range. Steps S111-S112 are repeated to obtain another Coulomb peak phase diagram.

[0104] The preset value of the first DC voltage signal applied to the barrier gate 211 in steps S111-S112 is traversed within a second preset range, and then combined with the first DC voltage signal applied to the second 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 first barrier gate 211 and the second barrier gate 212 can be determined, ensuring higher sensitivity of the sensing quantum dot.

[0105] Step S113: Determine the target working signal based on the Coulomb peak phase diagram.

[0106] Specifically, information about the state changes of the induced quantum dot can be obtained from the voltage of the second microwave signal in the Coulomb peak phase diagram. (Combined with the attached...) Figure 9 As shown, in this embodiment, determining the target operating signal based on the Coulomb peak phase diagram includes:

[0107] Step S1131: Determine the target voltage value of the first type of synthesized signal and the target voltage value of the first DC voltage signal when the voltage change value in the Coulomb peak phase diagram is the largest.

[0108] Step S1132: Determine the first type of synthesized signal with a voltage value of the target voltage value and the first DC voltage signal as the target working signal.

[0109] The Coulomb peak phase diagram is used to characterize the change in voltage of the second microwave signal output from the gate reflection of the sensing 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 sensing quantum dot can be obtained from the voltage of the second microwave signal in the Coulomb peak phase diagram. The state in which the sensing quantum dot is most sensitive to state changes corresponds to the maximum change in voltage of the second microwave signal in the Coulomb peak phase diagram. The voltage values ​​of the first DC voltage signal and the first type of synthesized signal at which the voltage change of the second microwave signal in the Coulomb peak phase diagram is maximized are determined as target voltage values, and the voltages of the first DC voltage signal and the first type of synthesized signal applied to the gate of the sensing quantum dot are updated accordingly.

[0110] Combined with appendix Figure 10 The three-dimensional phase diagram of the Coulomb peak shown is attached. Figure 10 In the diagram, the horizontal axis U3 represents the voltage value of the first type of synthesized signal, with 2.5V-4.5V corresponding to the first preset voltage range; the left vertical axis U4 represents the voltage value of the first DC voltage signal, with 0V-3V corresponding to the second preset voltage range; the right vertical axis represents the voltage value of the second microwave signal. The brighter the white area in the 3D diagram, the larger the corresponding voltage value of the second microwave signal. Using the Coulomb peak phase diagram, the target voltage values ​​of the first DC voltage signal and the first type of synthesized signal can be obtained when the voltage change of the second microwave signal is significant.

[0111] As attached Figure 11 As shown, after determining the target operating signal applied to the sensing quantum dot, this embodiment provides a method for reading the sensing quantum dot using radio frequency reflection readout technology. The step of applying the first type of synthesized signal to the gate of the qubit quantum dot and applying the target operating signal to the gate of the sensing quantum dot to read the information of the sensing quantum dot includes:

[0112] Step S201: Apply the first type of synthetic signal to the gate of the bit quantum dot.

[0113] Step S202: Apply the target operating signal and the first microwave signal to the gate of the sensing quantum dot.

[0114] Step S203: Obtain information about the sensing quantum dot based on the change in voltage amplitude of the second microwave signal output by the gate reflection of the sensing quantum dot as a function of the first type of synthesized signal.

[0115] Specifically, a first type of synthetic signal is first applied to the gate of the semiconductor quantum chip to form a qubit quantum dot below the gate; then a target working signal is applied to the gate of the sensing quantum dot to generate the sensing quantum dot below the gate. As described above, the sensing quantum dot generated by the target working signal has higher measurement sensitivity; then a first microwave signal for reading is applied through the gate of the sensing quantum dot, and a measuring device is used to collect information on the voltage change of the second microwave signal reflected from the gate of the sensing quantum dot as a function of the voltage amplitude of the first type of synthetic signal, thereby obtaining information about the sensing quantum dot, and then obtaining information about the qubit quantum dot through the information about the sensing quantum dot.

[0116] Furthermore, in step S201, the voltage amplitude of the first synthesized signal applied to the gate of the qubit quantum dot varies within a preset voltage range. When the voltage amplitude of the first synthesized signal applied to the gate of the qubit quantum dot changes, the state of the qubit quantum dot also changes. Adjacent sensing quantum dots can sensitively sense the change in the qubit quantum dot and obtain information about the qubit quantum dot by measuring the sensing quantum dots.

[0117] It should be added that, in the above-mentioned use of radio frequency reflection readout technology to read the sensed quantum dots, the first microwave signal used for reading is all transmitted through an auxiliary... Figure 2 The second microwave signal is also acquired through the accumulator gate 23.

[0118] As attached Figure 12 As shown, after determining the target operating signal applied to the sensing quantum dot, this embodiment provides a method for reading the sensing quantum dot using current transport testing technology. The step of applying the first type of synthesized signal to the gate of the qubit quantum dot and applying the target operating signal to the gate of the sensing quantum dot to read the information of the sensing quantum dot includes:

[0119] Step S211: Apply the first type of synthetic signal to the gate of the bit quantum dot.

[0120] Step S212: Apply the target operating signal to the gate of the sensing quantum dot.

[0121] Step S213: Apply a second DC voltage signal to the drain of the semiconductor quantum chip.

[0122] Step S214: Obtain information about the sensing quantum dot based on the change in voltage amplitude of the signal output from the source of the semiconductor quantum chip as a function of the first type of synthesized signal.

[0123] When testing the induced quantum dot using current transport measurement, steps S211-S212 are the same as steps S201-S202, both used to form a bit quantum dot under the gate where the first type of synthetic signal is applied, and to apply a target working signal on the gate of the induced quantum dot to generate the induced quantum dot under the gate. As described above, the induced quantum dot generated by the target working signal has higher measurement sensitivity.

[0124] When measuring after forming qubit quantum dots and highly sensitive sensing quantum dots, a second DC voltage signal is applied to the drain of the semiconductor quantum chip. The second DC voltage signal is used as an excitation signal for measurement. The voltage of the signal output from the source is collected by the measurement device to obtain information on the voltage amplitude of the first type of synthesized signal, thereby obtaining information on the sensing quantum dots. The information on the qubit quantum dots is obtained through the information on the sensing quantum dots.

[0125] In this embodiment, whether the measurement is performed using the radio frequency reflection readout technology of steps S201-S203 or the current transport method of steps S211-S214, the first type of synthesized signal is used to form qubit quantum dots and sensing quantum dots. As described above, the first type of synthesized signal has a fast response, and the qubit quantum dots and sensing quantum dots have a fast response, which can greatly improve the measurement efficiency of sensing quantum dots.

[0126] In this embodiment, when the fixed-amplitude DC signal and the variable-amplitude DC signal in the first synthesized signal are preset, the amplitude of the fixed-amplitude DC signal is greater than the maximum amplitude of the variable-amplitude DC signal; and the voltage amplitude of the variable-amplitude DC signal varies within a positive and negative range. The fixed-amplitude DC signal is output from a DC voltage source, and the variable-amplitude DC signal is output from an arbitrary waveform generator. For the DC voltage source, a DC signal with a higher voltage amplitude can be output; for the arbitrary waveform generator, a voltage signal with a relatively lower voltage amplitude is output, ensuring that the output voltage signal is within its rated range. Furthermore, the voltage signal with a preset variable amplitude range output by the arbitrary waveform generator generally varies within a positive and negative range, ensuring that the power consumption of the arbitrary waveform generator is low.

[0127] Combined with appendix Figure 4 and attached Figure 5 As shown in the example, the voltage amplitude of the fixed-amplitude DC signal is set to 3V, and the range of the variable-amplitude DC signal is set to {-1.5V, 1.5V}, achieving a voltage amplitude of {1.5V, 4.5V} for the first type of synthesized signal. Alternatively, the voltage amplitude of the fixed-amplitude DC signal can be set to 3.5V, and the range of the variable-amplitude DC signal can be set to {-1V, 1V}, achieving a voltage amplitude of {2.5V, 4.5V} for the first type of synthesized signal.

[0128] The range of voltage amplitude variation for the first type of synthesized signal can be determined based on the measurement sensitivity of the inductive quantum dot, with reference to... Figure 10 In the example Coulomb peak phase diagram, the voltage amplitude variation range of the first type of synthesized signal on the horizontal axis can be set to {2.5V, 4.5V}, {3V, 4.5V}, or {3.5V, 5V}, as long as it can sensitively reflect the voltage change of the second microwave signal output from the gate of the sensing quantum dot. The voltage amplitude range of the variable amplitude DC signal is set according to the voltage amplitude variation range of the first type of synthesized signal, and is set according to the positive and negative ranges; thus, the voltage amplitude of the fixed amplitude DC signal is set.

[0129] When using radio frequency readout reflection technology for measurement, an impedance matching unit is set on the signal transmission link between the radio frequency source and the semiconductor quantum chip. The state of the sensed quantum dot is read through the impedance matching unit to obtain the information of the bit quantum dot. Before step S201, the method further includes adjusting the resonant frequency of the impedance matching circuit so that the impedance matching circuit resonates with the sensed quantum dot, so that the impedance matching circuit is in a readout-sensitive state.

[0130] Specifically, the frequency of the impedance matching circuit is adjustable. By adjusting the resonant frequency of the impedance matching circuit, the resonance effect between the impedance matching circuit and the induced quantum dot is optimized. At this time, the impedance matching circuit is in the most sensitive state for reading the induced quantum dot. When the charge of the induced quantum dot changes slightly, it can also be measured by the impedance matching circuit. The frequency of the impedance matching circuit at this resonant frequency is determined as the reading frequency, thereby improving the measurement sensitivity of the induced quantum dot.

[0131] Combined with appendix Figure 13 As shown, 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.

[0132] Combined with appendix Figure 14 As shown, in this embodiment, adjusting the resonant frequency of the impedance matching circuit in the measurement link so that the frequency of the impedance matching circuit is at the reading frequency includes:

[0133] Step S21: Adjust the voltage values ​​of the third DC voltage signal applied to the first adjustable capacitor and the second adjustable capacitor respectively to adjust the resonant frequency of the impedance matching circuit.

[0134] Combined with appendix Figure 13As shown, the capacitance values ​​of the first and second adjustable capacitors are adjusted by a third DC voltage signal to adjust the resonant frequency of the impedance matching circuit, ensuring that the resonant frequency of the impedance matching circuit resonates with the frequency of the inductive quantum dot, thereby ensuring the measurement accuracy of the inductive quantum dot.

[0135] Step S22: Apply a fourth DC voltage signal and a first microwave signal to the gate of the inductive 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.

[0136] A fourth DC voltage signal is used to form the induced quantum dot, and a first microwave signal is used to read the information from the induced quantum dot. When the voltage value of the third DC voltage signal is adjusted, the resonant frequency of the impedance matching circuit changes, and the reflected signal output from the gate of the induced quantum dot read by 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.

[0137] Step S23: 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 exhibits 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.

[0138] Step S24: Apply a third DC voltage equal to the third target voltage to the first and second adjustable capacitors to bring the frequency of the impedance matching circuit to the readout frequency. 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 reflection of the sensed quantum dot through steps S21-S23. Apply a third DC voltage signal with the third target voltage value to the first and second adjustable capacitors to adjust the frequency of the impedance matching circuit to the readout frequency, ensuring optimal sensitivity for reading the sensed quantum dot.

[0139] As attached Figure 15As shown, based on the same application concept, this application embodiment also provides a semiconductor quantum dot measurement and control system for measuring qubit quantum dots and sensing quantum dots formed on a semiconductor quantum chip with mutual coupling. The system includes: a first measurement module 10, used to apply a working signal to the sensing quantum dot to obtain a target working signal when the sensing quantum dot is in a readout state; wherein, applying the working signal to the sensing quantum dot includes a first type of synthesized signal composed of a fixed amplitude DC signal and a variable amplitude DC signal applied to a gate of the sensing quantum dot; 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 working signal to the gate of the sensing quantum dot to read the information of the sensing quantum dot; wherein, the first type of synthesized signal is used to form the sensing quantum dot and the qubit quantum dot below the gate.

[0140] Specifically, the first measurement module 10 may include signal source devices such as a DC voltage source, a radio frequency source, and an arbitrary waveform generator, for outputting 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, for processing and analyzing the read signal to determine the target working signal.

[0141] The second measurement module 10 may include signal source devices such as a DC voltage source, a radio frequency source, and an arbitrary waveform generator, for outputting a first type of synthesized signal to the gate of the bit quantum dot and outputting a 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, for processing and analyzing the read signals to determine the target working signal.

[0142] Specifically, the first measurement module 10 in this embodiment includes: a DC voltage source for outputting the fixed amplitude DC signal; an arbitrary waveform generator for outputting the variable amplitude DC signal; and a radio frequency source for outputting a first microwave signal.

[0143] In addition, in this embodiment, the second measurement module 20 includes a signal acquisition card or a high-precision digital multimeter, as well as various signal amplifiers, etc., for acquiring the second microwave signal output from the gate of the sensing quantum dot or the signal output from the source of the semiconductor quantum chip.

[0144] In a 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 second microwave signal or the current signal 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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, Methods for forming mutually coupled qubit quantum dots and sensing quantum dots on a semiconductor quantum chip include: A target working signal is obtained when the quantum dot is in its readout state by applying a working signal to the quantum dot; wherein, the working signal includes a first type of composite signal composed of a fixed amplitude DC signal and a variable amplitude DC signal applied to a gate of the quantum dot; The first type of synthesized 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 to read the information of the sensing quantum dot; The first type of synthesized signal is used to form the inductive quantum dot and the bit quantum dot below the gate.

2. The method as described in claim 1, characterized in that, The working signal further includes a first microwave signal for measuring the information of the sensing quantum dot, wherein the voltage of the first type of synthesized signal varies within a first preset range, and the target working signal for obtaining the reading state of the sensing quantum dot by applying the working signal to the sensing quantum dot includes: The first type of synthesized signal and the first microwave signal are applied to the gate of the sensing quantum dot; Obtain a first curve showing the voltage of the second microwave signal output by the gate reflection changing with the voltage within the first preset range; The target operating signal is determined based on the first curve.

3. The method as described in claim 2, characterized in that, Determining the target operating signal based on the first curve includes: Determine the target voltage value of the first type of synthesized signal when the voltage change value in the first curve is the largest; The first type of synthesized signal with a voltage value of the target voltage value is determined as the target working signal.

4. The method as described in claim 2, characterized in that, The operating signal further includes a first DC voltage signal applied to the gate of the sensing quantum dot, and the target operating signal for obtaining the reading state of the sensing quantum dot by applying the operating signal to the sensing quantum dot further includes: Within a second preset range, the voltage of the first DC voltage signal is traversed, and the first type of synthesized signal and the first microwave signal are applied to the gate of the inductive quantum dot; Obtain the Coulomb peak phase diagram of the voltage of the second microwave signal output by the gate reflection as a function of the voltage within the first preset range and the voltage within the second preset range; The target operating signal is determined based on the Coulomb peak phase diagram.

5. The method as described in claim 4, characterized in that, Determining the target operating signal based on the Coulomb peak phase diagram includes: Determine the target voltage value of the first type of synthesized signal and the target voltage value of the first DC voltage signal when the voltage change value in the Coulomb peak phase diagram is the largest. The first type of synthesized signal with a voltage value of the target voltage value and the first DC voltage signal are determined to be the target working signal.

6. The method as described in claim 1, characterized in that, The step of 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 to read the information of the sensing quantum dot includes: The first type of synthetic signal is applied to the gate of the bit quantum dot; The target operating signal and the first microwave signal are applied to the gate of the sensing quantum dot; Information about the sensing quantum dot is obtained based on the change in voltage amplitude of the second microwave signal output from the gate reflection of the sensing quantum dot as a function of the first type of synthesized signal; or, The step of 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 to read the information of the sensing quantum dot includes: The first type of synthetic signal is applied to the gate of the bit quantum dot; The target operating signal is applied to the gate of the sensing quantum dot; A second DC voltage signal is applied to the drain of the semiconductor quantum chip; Information about the sensing quantum dot is obtained based on the change in voltage amplitude of the signal output from the source of the semiconductor quantum chip as a function of the first type of synthesized signal.

7. The method according to any one of claims 1-6, characterized in that, Before applying an operating signal to the sensing quantum dot to obtain the target operating signal when the sensing quantum dot reads out, the method further includes: The voltage amplitude of the fixed amplitude DC signal is preset to be greater than the maximum voltage amplitude of the variable amplitude DC signal.

8. A measurement and control system for semiconductor quantum dots, characterized in that, The system for measuring mutually coupled qubit quantum dots and sensed quantum dots formed on a semiconductor quantum chip includes: The first measurement module is used to apply a working signal to the sensing quantum dot to obtain the target working signal when the sensing quantum dot is in the readout state; wherein, applying a working signal to the sensing quantum dot includes a first type of composite signal applied to a gate of the sensing quantum dot, which is composed of 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 to read the information of the sensing quantum dot; The first type of synthesized signal is used to form the inductive quantum dot and the bit quantum dot below the gate.

9. The system as described in claim 8, characterized in that, The first measurement module includes: 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; Radio frequency source, used to output the first microwave signal.

10. The system as described in claim 8, characterized in that, The second measurement module includes a signal acquisition card, used to acquire the second microwave signal output from the gate of the sensing quantum dot or the signal output from the source of the semiconductor quantum chip.

11. The system as claimed in claim 10, characterized in that, The variable amplitude DC signal includes a triangular wave signal or a sawtooth wave signal. The signal acquisition card is used to acquire the second microwave signal or current signal 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.

12. A quantum computer, characterized in that, The quantum dots on the semiconductor quantum chip are tested using the measurement method for semiconductor quantum dots as described in any one of claims 1-7, or using the system for semiconductor quantum dots as described in any one of claims 8-11.

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