Semiconductor quantum dot measurement method, measurement and control system and quantum computer

Abstract

The invention 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 an induction quantum dot to obtain a target working signal when the induction quantum dot is in a reading state; wherein the working signal comprises a first type of synthesis signal which is applied to the grid electrode of the induction quantum dot I and is synthesized by a fixed amplitude direct current signal and a variable amplitude direct current signal; applying the first type of composite signal to the grid electrode of the bit quantum dot, and applying the target working signal to the grid electrode of the induction quantum dot to read the information of the induction quantum dot; wherein the first type of composite signals are used for forming the induction quantum dots and the bit quantum dots below the grid electrode. According to the invention, the measurement efficiency of the semiconductor quantum chip is improved.

Description

Technical Field

[0001] The present application relates to the field of quantum computer technology, and in particular to a semiconductor quantum dot measurement method, a measurement and control system, and a quantum computer. Background Art

[0002] Among the many quantum computing physical systems, silicon-based spin qubits (also known as semiconductor quantum dots) are internationally recognized as one of the physical systems that are expected to achieve scalable, large-scale, and practical universal 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 the potential for application in temperature ranges above 1.5K. Effective measurement of semiconductor quantum dots is a key technology for the practical application of silicon-based spin qubits. Summary of the invention

[0003] The present application provides a semiconductor quantum dot measurement method, a measurement and control system, and a quantum computer, which solve the problem of low measurement efficiency of spin quantum dots in the prior art and improve the measurement efficiency.

[0004] On one hand, the present application provides a method for measuring semiconductor quantum dots, wherein bit quantum dots and sensing quantum dots having mutual coupling are formed on a semiconductor quantum chip, and the method comprises:

[0005] Applying a working signal to the sensing quantum dot to obtain a target working signal when the sensing quantum dot is in a reading state; wherein the working signal comprises a first type of synthetic signal synthesized by a fixed amplitude DC signal and a variable amplitude DC signal applied to a gate of the sensing quantum dot;

[0006] Applying the first type of synthetic signal to the gate of the bit quantum dot, and applying the target working signal to the gate of the sensing quantum dot to read the information of the sensing quantum dot;

[0007] Wherein, the first type of synthetic signal is used to form the sensing quantum dot and the bit quantum dot under the gate.

[0008] In the above method, preferably, the working signal further includes a first microwave signal for measuring the information of the sensing quantum dot, the voltage of the first type of synthetic signal varies within a first preset range, and the target working signal when applying the working signal to the sensing quantum dot to obtain the sensing quantum dot reading state includes:

[0009] Applying the first type of synthetic signal and the first microwave signal to the gate of the sensing quantum dot;

[0010] Obtaining a first curve of a voltage of a second microwave signal output by the gate reflection as a function of a voltage within the first preset range;

[0011] The target working signal is determined according to the first curve.

[0012] In the above method, preferably, determining the target working signal according to the first curve includes:

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

[0014] The first type of synthetic signal whose voltage value is determined to be the target voltage value is the target working signal.

[0015] In the above method, preferably, the working signal further comprises a first DC voltage signal applied to the gate of the sensing quantum dot, and the applying the working signal to the sensing quantum dot to obtain a target working signal when the sensing quantum dot is in a reading state further comprises:

[0016] Traversing the voltage of the first DC voltage signal within a second preset range, applying the first type of synthetic signal and the first microwave signal to the gate of the sensing quantum dot;

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

[0018] The target working signal is determined according to the Coulomb peak phase diagram.

[0019] In the above method, preferably, determining the target working signal according to the Coulomb peak phase diagram comprises:

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

[0021] Determine the first type of synthetic signal whose voltage value is the target voltage value and the first DC voltage signal as the target working signal.

[0022] In the above method, preferably, applying the first type of synthetic signal to the gate of the bit quantum dot and applying the target working signal to the gate of the sensing quantum dot to read the information of the sensing quantum dot includes:

[0023] Applying the first type of synthetic signal to the gate of the bit quantum dot;

[0024] Applying the target working signal and the first microwave signal to the gate of the sensing quantum dot;

[0025] Obtaining information of the sensing quantum dot according to a change in the voltage amplitude of a second microwave signal output by a gate reflection of the sensing quantum dot along with the first type of synthetic signal; or,

[0026] The step of applying the first type of synthetic signal to the gate of the bit quantum dot and applying the target working signal to the gate of the sensing quantum dot to read the information of the sensing quantum dot includes:

[0027] Applying the first type of synthetic signal to the gate of the bit quantum dot;

[0028] Applying the target working signal to the gate of the sensing quantum dot;

[0029] Applying a second DC voltage signal to the drain of the semiconductor quantum chip;

[0030] The information of the sensing quantum dot is obtained according to the change of the signal output by the source of the semiconductor quantum chip with the voltage amplitude of the first type of synthetic signal.

[0031] The method as described above, preferably, before applying a working signal to the sensing quantum dot to obtain a target working signal when the sensing quantum dot is in a reading state, further comprises:

[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] On the other hand, the present application provides a semiconductor quantum dot measurement and control system for measuring bit quantum dots and sensing quantum dots with mutual coupling formed on a semiconductor quantum chip, the system comprising:

[0034] A first measurement module is 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 reading state; wherein the working signal applied to the sensing quantum dot includes a first type of synthetic signal synthesized by a fixed amplitude DC signal and a variable amplitude DC signal applied to a gate of the sensing quantum dot;

[0035] A second measurement module is used to apply the first type of synthetic signal to the gate of the bit quantum dot, and apply a target working signal to the gate of the sensing quantum dot to read the information of the sensing quantum dot;

[0036] Wherein, the first type of synthetic signal is used to form the sensing quantum dot and the bit quantum dot under the gate.

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

[0038] A DC voltage source, used for outputting the fixed amplitude DC signal;

[0039] An arbitrary waveform generator, used for outputting the variable amplitude DC signal;

[0040] The radio frequency source is used to output a first microwave signal.

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

[0042] In the system as 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 collect 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 segment or the falling segment of the triangular wave signal or the sawtooth wave signal.

[0043] On the other hand, the present application provides a quantum computer, which uses any of the above-mentioned semiconductor quantum dot measurement methods to test quantum dots on a semiconductor quantum chip, or uses any of the above-mentioned semiconductor quantum dot systems to test quantum dots on a semiconductor quantum chip.

[0044] Compared with the prior art, the present application proposes a method for measuring semiconductor quantum dots, by applying a first type of synthetic signal to the gate of a semiconductor quantum chip to form a sensing quantum dot and a bit quantum dot under the gate, the first type of synthetic signal is synthesized by a fixed amplitude DC signal and a variable amplitude DC signal, wherein 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, so that the first type of synthetic signal applied to the gate responds quickly, so that the sensing quantum dots and the bit quantum dots respond faster with the first type of synthetic signal, thereby improving the measurement efficiency of the sensing quantum dots.

[0045] In addition, both the sensing quantum dots and the bit quantum dots use the first type of synthetic signals, which ensures the synchronization of the voltage responses of the sensing quantum dots and the bit quantum dots, lays the foundation for realizing the measurement of the bit quantum dots through the measurement of the sensing quantum dots and guarantees the measurement effect of the bit quantum dots, and helps to realize the scalable and large-scale practical realization of quantum computers based on silicon-based spin quantum bits; secondly, through the synthesis of fixed amplitude and variable amplitude, the voltage amplitude of the first type of synthetic signal is higher, which meets the needs of testing the sensing quantum dots.

[0046] The present application provides a semiconductor quantum dot measurement and control system and a quantum computer including the above-mentioned semiconductor quantum dot measurement method, and therefore has the same beneficial effects, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0049] Figure 3 A schematic diagram of a process for measuring semiconductor quantum dots provided in an embodiment of the present application;

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

[0051] Figure 5 A schematic diagram of a fixed amplitude DC signal and a variable amplitude DC signal synthesized according to an embodiment of the present application;

[0052] Figure 6 A schematic diagram of a process for determining a target working signal provided in an embodiment of the present application;

[0053] Figure 7 A schematic diagram of a process for determining a target working signal according to a first curve provided in an embodiment of the present application;

[0054] Figure 8 A flowchart of another flowchart of a flowchart of a flowchart of determining a target working signal provided in an embodiment of the present application;

[0055] Fig. 9 A schematic diagram of a process for determining a target working signal according to a Coulomb peak phase diagram provided in an embodiment of the present application;

[0056] Fig.10 A specific schematic diagram of a Coulomb peak phase diagram provided in an embodiment of the present application;

[0057] Fig.11 A schematic diagram of a process for measuring a sensing quantum dot provided in an embodiment of the present application;

[0058] Fig.12 A schematic diagram of another process for measuring sensing quantum dots provided in an embodiment of the present application;

[0059] Fig.13 A schematic diagram of a signal transmission link including an impedance matching unit provided in an embodiment of the present application;

[0060] Fig.14 A schematic diagram of a flow chart of adjusting an impedance matching circuit provided in an embodiment of the present application;

[0061] Fig.15A schematic diagram of the composition of a semiconductor quantum dot measurement and control system provided in an embodiment of the present application.

[0062] In the reference numerals:

[0063] 1-substrate, 3-impedance matching circuit;

[0064] 11-drain, 12-source, 21-barrier gate, 22-pumping gate, 23-accumulation gate, 10-first measurement module, 20-second measurement module;

[0065] The first barrier gate-211, the second barrier gate-212. DETAILED DESCRIPTION

[0066] In order to enable those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of this application. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application, and cannot be interpreted as limitations on the present application.

[0067] In the description of the present application, it should be understood that the terms "center", "up", "down", "left", "right", etc., indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present application.

[0068] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0069] The spin state information of silicon-based spin qubits is indirectly read by using the charge-spin conversion mechanism, with the help of the charge state change in the adjacent single-electron transistor. There are currently two mainstream measurement schemes that are more popular internationally: (1) Traditional transport measurement, which uses the transport current to detect the change of weak resistance signals in the single-electron transistor; (2) RF reflection reading technology, which introduces an "impedance converter" circuit between the single-electron transistor and the measurement reading link, thereby constructing an impedance matching network that can provide real-time feedback on the change of the conductivity state in the single-electron transistor.

[0070] Single-electron transistors and spin qubits are usually formed by controlling the potential of the two-dimensional electron gas under the gate by a voltage signal applied by the gate; then a measurement signal is applied to test the charge state of the single-electron transistor. When testing spin qubits with the help of single-electron transistors, the voltage signal applied to the gate changes linearly within a preset range. The applicant has found that if a voltage source is used to provide a linearly changing DC voltage signal, each time the voltage source adjusts the output voltage, it needs to go through the voltage establishment, voltage stabilization and voltage maintenance time to ensure the stability of the DC voltage signal output to the gate.

[0071] The applicant has found that when the voltage signal to be applied has a high precision requirement when it changes linearly, the voltage source takes a long time to provide a voltage signal that changes linearly within a preset range, which directly affects the efficiency of testing single-electron transistors, that is, the measurement efficiency of spin quantum bits is very low. The present application proposes a method for quickly measuring spin quantum bits.

[0072] As attached Figure 1 The schematic diagram of reading the gated silicon-based spin quantum bit of the prior art is shown, 1 is the substrate of the semiconductor quantum chip, the electrode 11 and the electrode 12 are respectively the drain and the source formed on the opposite sides of the substrate, which are used to apply a DC voltage excitation signal to form a transport channel of the two-dimensional electron gas, and the electrode 21 and the electrode 22 are both gate electrodes, which are used to apply a DC voltage signal to adjust the electric potential of the two-dimensional electron gas to form a bit quantum dot in the channel, or to form an induction quantum dot for reading the bit quantum dot; in addition, the electrode 23 corresponding to the induction quantum dot is also used to apply a radio frequency signal to read the induction quantum dot to obtain the information of the bit quantum dot.

[0073] Attached Figure 2 This is a cross-sectional schematic diagram of electrodes of two quantum dots formed on a substrate. The electrode structures of the two quantum dots are exactly the same, both 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 sensing quantum dot, the gate of the corresponding sensing quantum dot and the gate of the corresponding bit quantum dot both need to apply a DC voltage signal to form the sensing quantum dot and the bit quantum dot. In addition, when using RF reflection reading technology, it is also necessary to apply an RF reading signal to the gate of the sensing quantum dot, and when using traditional transport measurement, the drain needs to apply an excitation signal.

[0075] As attached Figure 3 As shown, in an embodiment of the present application, a measurement method for measuring semiconductor quantum dots is provided, wherein bit quantum dots and sensing quantum dots having mutual coupling are formed on a semiconductor quantum chip, and the method comprises:

[0076] Step S10: applying a working signal to the sensing quantum dot to obtain a target working signal when the sensing quantum dot is in a reading state; wherein the working signal includes a first type of synthetic signal applied to a gate of the sensing quantum dot and synthesized by a fixed amplitude DC signal and a variable amplitude DC signal.

[0077] Combined with Figure 2 As shown, the sensing quantum dot is used as a reading detector of the bit quantum dot, and the information of the bit quantum dot is obtained by reading the sensing quantum dot. In combination with the 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 reading 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 a sensing quantum dot, wherein the working signal is a synthetic signal, including a fixed amplitude DC signal and a variable amplitude DC signal, and the voltage amplitude of the synthesized first type of synthetic signal is variable, and varies within a preset voltage range. By applying the first type of synthetic signal with a variable voltage amplitude to the gate of the sensing quantum dot and reading it, information about the change of the voltage amplitude of the read signal with the first type of synthetic signal can be obtained, and then the target voltage value of the first type of synthetic signal when the change value of the read signal is the largest is determined based on the changed information, and the working signal is updated to the target working signal based on the target voltage value. When the target working signal is applied to the gate of the sensing quantum dot, the sensing quantum dot is most sensitive to changes, making the measurement of the bit quantum dot more sensitive.

[0079] Combined with Figure 4 and attached Figure 5 As shown, in this embodiment, a fixed amplitude DC signal and a variable amplitude DC signal are synthesized to obtain a first type of synthesized signal with a linear voltage value; Figure 4 The fixed amplitude DC signal and the variable amplitude DC signal are respectively exemplified, wherein the voltage value of the fixed amplitude DC signal is fixed, and the voltage amplitude of the variable amplitude DC signal is variable. The voltage variation curve of the first type of synthesized signal after synthesis is shown in the attached figure. Figure 5 As shown, it can be found that the change in the voltage value of the first type of synthetic signal corresponds to the change in the voltage amplitude of the variable amplitude DC signal. For example, the voltage value of the fixed amplitude DC signal is 3V, the voltage amplitude of the variable amplitude DC signal is {-1.5V, 1.5V}, and the voltage amplitude of the first type of synthetic signal after synthesis is {1.5V, 4.5V}. The voltage amplitude changes linearly in both the rising and falling sections, which is used to meet the requirements of the voltage signal for manipulating the sensing quantum dots or bit quantum dots.

[0080] In addition, Figure 4 and attached Figure 5 The curve diagrams of the fixed amplitude DC signal, the variable amplitude DC signal, and the first type of synthetic signal in the example are only examples. In specific measurements, 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 needs and will not be repeated 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 by the DC voltage source and the variable amplitude DC signal output by the arbitrary waveform generator are synthesized, so that the first type of synthetic signal applied to the gate of the sensing quantum dot is also a linearly varying voltage signal, and the voltage amplitude is relatively high, which meets the requirements for testing the sensing quantum dot. In addition, the DC voltage source outputs a fixed value voltage signal, and the arbitrary waveform generator can directly output a triangular wave signal, which has a fast response, and thus generates a fast response of the first type of synthetic signal, which can improve the measurement efficiency of the sensing quantum dot.

[0082] Step S20: applying the first type of synthetic signal to the gate of the bit quantum dot, and applying 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 the bit quantum dot and the sensing quantum dot are the same. The first type of synthetic signal is also applied to the gate of the bit quantum dot to form the bit quantum dot; and the first type of synthetic signal has a fast response, so that the bit quantum dot also responds quickly to the first type of synthetic signal, and when the bit quantum dot is measured through the sensing quantum dot, the measurement efficiency can also be improved. In addition, after determining the target working signal applied to the gate of the sensing quantum dot through step S10, the signal applied to the gate of the sensing quantum dot is updated to the target working signal, ensuring the measurement sensitivity of the sensing quantum dot and improving the measurement accuracy.

[0084] Combined with Figure 1 and attached Figure 2As shown, when the sensing quantum dots are measured using radio frequency reflection reading technology, a microwave signal for reading needs to be applied to the gate of the sensing quantum dots, wherein the microwave signal for reading is applied to the gate 23 and the first type of synthetic signal is applied to the gate 22.

[0085] In this embodiment, the working signal also includes a first microwave signal for measuring the information of the sensing quantum dots. The voltage of the first type of synthetic signal varies within a first preset range. For example, the voltage of the variable amplitude DC signal varies within 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 corresponding voltage amplitude of the first type of synthetic signal after synthesis varies within the range of {1.5V, 4.5V}.

[0086] As attached Figure 6 As shown, the step S10 of applying a working signal to the sensing quantum dot to obtain a target working signal when the sensing quantum dot is in a reading state includes:

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

[0088] The first type of synthetic signal is applied to the gate corresponding to the sensing quantum dot to form the sensing quantum dot under the gate, and a first microwave signal is applied to another gate to measure the sensing quantum dot. The first microwave signal is usually provided by a radio frequency source.

[0089] Step S102: obtaining a first curve showing a change in voltage of a second microwave signal output by the gate reflection as a function of a voltage within the first preset range.

[0090] The measurement of the sensing quantum dot is a reflection measurement, that is, after applying the first microwave signal to the gate of the sensing quantum dot, the gate will reflect and output a second microwave signal carrying the quantum dot information. Among them, the voltage of the first type of synthetic signal changes within the first preset range, and the one-to-one correspondence between the voltage of the second microwave signal and the voltage within the first preset range can be obtained by measurement. After traversing the voltage within the first preset range, several groups of one-to-one corresponding data are obtained, and the first curve is obtained by processing the several groups of data.

[0091] Step S103: determining the target working signal according to the first curve.

[0092] The first curve represents the relationship between the voltage of the reflected output second microwave signal and the voltage within the first preset range, and can also represent the sensitivity of the sensing quantum dots. The voltage within the first preset range when the sensing quantum dots in the first curve change most sensitively can be selected and determined as the target voltage of the first type of synthetic signal.

[0093] When determining the target working signal in the above step S103, the Figure 7 As shown, determining the target working signal according to the first curve includes:

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

[0095] Step S1032: Determine that the first type of synthetic signal having a voltage value equal to the target voltage value is the target working signal.

[0096] Through the first curve, a data point when the voltage change value of the second microwave signal is the largest can be determined. This data point represents that the sensing quantum dot is most sensitive to the first type of synthetic signal. By determining the voltage within the first preset range corresponding to this data point, the target voltage value of the first type of synthetic signal can be determined. The first type of synthetic signal that determines this target voltage value is the target working signal applied to the gate of the sensing quantum dot, ensuring the measurement sensitivity of the bit quantum dot measured by the sensing quantum dot.

[0097] Continue as attached Figure 1 and attached Figure 2 As shown, the gates forming the sensing quantum dot and the bit quantum dot include three gates, among which the one in the middle is the pump gate and the ones on both sides are the barrier gates. To form the sensing quantum dot and the bit quantum dot, it is necessary not only to apply the first type of synthetic signal to the pump gate, but also to apply the first DC voltage signal to the barrier gate. The voltage value of the first DC voltage signal and the voltage value of the first type of synthetic signal both affect the reaction sensitivity of the sensing quantum dot. Therefore, the voltage values ​​of the first DC voltage signal and the first type of synthetic signal need to be adjusted to the target value.

[0098] Therefore, combined with the Figure 8 As shown, in this embodiment, applying a working signal to the sensing quantum dot to obtain a target working signal when the sensing quantum dot is in a reading state also includes:

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

[0100] In step S101-step S102, the voltage value of the applied first type of synthetic signal varies within a preset range, and the voltage of the first DC voltage signal applied to the gate of the sensing quantum dot varies within a second preset range. The first microwave signal is applied to the gate of the sensing quantum dot, and the second microwave signal reflected and output by the gate can be measured by a measuring device.

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

[0102] As attached Figure 2 As shown, the barrier gate of the inductive quantum dot includes a first barrier gate 211 and a second barrier gate 212. When a first DC voltage signal is applied to the gate for traversal in step S111, the first DC voltage signal applied to the first barrier gate 211 and the second barrier gate 212 can be applied and traversed separately.

[0103] Specifically, the first DC voltage signal applied to the first barrier gate 211 is first set to a voltage signal of a preset value, the first DC voltage signal applied to the second barrier gate 212 is traversed within a third preset range, and steps S111-S112 are repeated to obtain a Coulomb peak phase diagram. Then, the preset value of the first DC voltage signal applied to the first barrier gate 211 is adjusted, the first DC voltage signal applied to the second barrier gate 212 is traversed within the third preset range, and steps S111-S112 are repeated to obtain another Coulomb peak phase diagram.

[0104] Repeat the preset value of the first DC voltage signal applied to the barrier gate 211 in step S111-step S112 to traverse within the second preset range, and then combine the first DC voltage signal applied to the second barrier gate 212 to traverse within the third preset range to obtain a plurality of Coulomb peak phase diagrams. According to the plurality of Coulomb peak phase diagrams, the target voltage values ​​of the first DC voltage signals respectively applied to the first barrier gate 211 and the second barrier gate 212 can be determined to ensure a higher sensitivity of the sensing quantum dot.

[0105] Step S113: determining the target working signal according to the Coulomb peak phase diagram.

[0106] Specifically, the information about the state change of the sensing quantum dot can be obtained through the voltage of the second microwave signal in the Coulomb peak phase diagram. Fig. 9 As shown, in this embodiment, determining the target working signal according to the Coulomb peak phase diagram includes:

[0107] Step S1131: determining a target voltage value of the first type of synthetic signal and a 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 synthetic signal whose voltage value is 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 of the voltage of the second microwave signal output by the gate reflection of the sensing quantum dot with the voltage value of the first DC voltage signal and the voltage value of the first type of synthetic signal. The information of the state change of the sensing quantum dot can be obtained through the voltage of the second microwave signal in the Coulomb peak phase diagram. The state in which the state change of the sensing quantum dot is most sensitive corresponds to the maximum change value of the 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 synthetic signal when the voltage change value of the second microwave signal in the Coulomb peak phase diagram is the maximum are determined as the target voltage values, and the voltages of the first DC voltage signal and the first type of synthetic signal applied to the gate of the sensing quantum dot are updated.

[0110] Combined with Fig.10 The Coulomb peak phase diagram in the three-dimensional image style shown in the figure is attached. Fig.10 In the figure, the horizontal axis U3 represents the voltage value of the first type of synthetic signal, and 2.5V-4.5V corresponds to the voltage value of the first preset range; the vertical axis U4 on the left represents the voltage value of the first DC voltage signal, and 0V-3V corresponds to the voltage value of the second preset range; the vertical axis on the right represents the voltage value of the second microwave signal. The brighter the white area in the three-dimensional graph, the larger the voltage value of the corresponding second microwave signal. Through the Coulomb peak phase diagram, the target voltage values ​​of the first DC voltage signal and the first type of synthetic signal can be obtained when the voltage change of the second microwave signal is obvious.

[0111] As attached Fig.11 As shown, after determining the target working signal applied to the sensing quantum dot, this embodiment provides a method for reading the sensing quantum dot using the radio frequency reflection reading technology, wherein 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 the information of the sensing quantum dot, including:

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

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

[0114] Step S203: obtaining information of the sensing quantum dot according to the change in the voltage amplitude of the second microwave signal output by the gate reflection of the sensing quantum dot along with the first type of synthetic signal.

[0115] Specifically, a first type of synthetic signal is first applied to the gate on the semiconductor quantum chip to form a bit quantum dot under the gate; and a target working signal is applied to the gate of the sensing quantum dot to generate a sensing quantum dot under the gate. Combined with the above description, the measurement sensitivity of the sensing quantum dot generated by the target working signal is higher; 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 about the voltage of a second microwave signal reflected and output by the gate of the sensing quantum dot as the voltage amplitude of the first type of synthetic signal changes, thereby obtaining information about the sensing quantum dot, and obtaining information about the bit quantum dot through the information about the sensing quantum dot.

[0116] In addition, the voltage amplitude of the first synthetic signal applied to the gate of the bit quantum dot in step S201 is variable and varies within a preset voltage range; when the voltage amplitude of the first synthetic signal applied to the gate of the bit quantum dot changes, the state of the bit quantum dot will also change, and the adjacent sensing quantum dots can sensitively sense the changes in the bit quantum dots, and obtain the information of the bit quantum dots by measuring the sensing quantum dots.

[0117] It should be added that when the above-mentioned radio frequency reflection reading technology is used to read the sensing quantum dots, the first microwave signal used for reading is transmitted through the attached Figure 2 The accumulation gate 23 is applied, and the measured second microwave signal is also collected by the accumulation gate 23.

[0118] As attached Fig.12 As shown, after determining the target working signal applied to the sensing quantum dot, this embodiment provides a method for reading the sensing quantum dot using the current transport test technology, wherein 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 the information of the sensing quantum dot, including:

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

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

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

[0122] Step S214: obtaining information of the sensing quantum dot according to the change in the voltage amplitude of the first type of synthetic signal with the signal output by the source of the semiconductor quantum chip.

[0123] When the sensing quantum dots are tested by current transport measurement, steps S211-S212 are the same as steps S201-S202, both of which are used to form bit quantum dots under the gate to which the first type of synthetic signal is applied, and to apply a target working signal to the gate of the sensing quantum dots to generate sensing quantum dots under the gate. Combined with the above description, the measurement sensitivity of the sensing quantum dots generated by the target working signal is higher.

[0124] When measuring after forming the bit quantum dot and the highly sensitive sensing quantum dot, a second DC voltage signal is applied to the drain of the semiconductor quantum chip, wherein the second DC voltage signal is measured as an excitation signal, and the information of the voltage of the signal output by the source changing with the voltage amplitude of the first type of synthetic signal is collected through the measuring device, thereby obtaining the information of the sensing quantum dot, and obtaining the information of the bit quantum dot through the information of the sensing quantum dot.

[0125] In this embodiment, whether the measurement is performed using the RF reflection reading technology of step S201-step S203 or the current transport method of step S211-step S214, the bit quantum dots and the sensing quantum dots are formed by the first type of synthetic signal. Combined with the above description, the response is fast when the first type of synthetic signal is used, and the response of the bit quantum dots and the sensing quantum dots is fast, which can greatly improve the measurement efficiency of the sensing quantum dots.

[0126] In this embodiment, when the fixed amplitude DC signal and the variable amplitude DC signal in the first synthetic 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 the positive and negative range. The fixed amplitude DC signal is output by a DC voltage source, and the variable amplitude DC signal is output by an arbitrary waveform generator; for the DC voltage source, a DC signal with a higher voltage amplitude can be output, and for the arbitrary waveform generator, a voltage signal with a relatively low voltage amplitude is output to ensure that the output voltage signal is within the rated range. In addition, for the arbitrary waveform generator to output a voltage signal with a preset variable amplitude range, it generally varies within the positive and negative range to ensure that the power consumption of the arbitrary waveform generator is low.

[0127] Combined with Figure 4 and attached Figure 5 As shown, for 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}, so that the voltage amplitude of the first type of synthesized signal is {1.5V, 4.5V}. The voltage amplitude of the fixed amplitude DC signal can also be set to 3.5V, and the range of the variable amplitude DC signal can be set to {-1V, 1V}, so that the voltage amplitude of the first type of synthesized signal is {2.5V, 4.5V}.

[0128] The variation range of the voltage amplitude of the first type of synthetic signal can be determined according to the measurement sensitivity of the sensing quantum dots. Fig.10 In the Coulomb peak phase diagram of the example, the voltage amplitude variation range of the first type of synthetic signal on the horizontal axis can be set to {2.5V, 4.5V}, or {3V, 4.5V} or {3.5V, 5V}, which can sensitively respond to the voltage variation of the second microwave signal output by 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 synthetic signal, and is set according to the variation within the positive and negative range; and then the voltage amplitude of the fixed amplitude DC signal is set.

[0129] When the RF reading reflection technology is used for measurement, an impedance matching unit is provided on the signal transmission link between the RF source and the semiconductor quantum chip, and the state of the sensing quantum dot is read by the impedance matching unit to obtain the information of the bit quantum dot. Before step S201, the step of adjusting the resonant frequency of the impedance matching circuit to make the impedance matching circuit resonate with the sensing quantum dot is also included, so that the impedance matching circuit is in a reading sensitive state.

[0130] Specifically, the frequency of the impedance matching circuit is adjustable. The resonance frequency of the impedance matching circuit can be adjusted to achieve the best resonance effect between the impedance matching circuit and the sensing quantum dots. At this time, the impedance matching circuit is most sensitive to the reading of the sensing quantum dots. When the charge of the sensing quantum dots changes slightly, it can also be measured through the impedance matching circuit. The frequency of the impedance matching circuit is determined as the reading frequency at this resonance frequency, thereby improving the measurement sensitivity of the sensing quantum dots.

[0131] Combined with Fig.13 As shown, the impedance matching circuit 3 includes an inductor, and a first adjustable capacitor and a second adjustable capacitor electrically connected to both ends of the inductor. Specifically, the impedance matching circuit 3 adopts an LC impedance matching network of an inductor and a capacitor, and selects a first adjustable capacitor and a second adjustable capacitor with adjustable capacitance values.

[0132] Combined with Fig.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 located at the reading frequency includes:

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

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

[0135] Step S22: applying a fourth DC voltage signal and a first microwave signal to the gate of the sensing quantum dot and obtaining an S21 curve showing that the attenuation value of the reflected signal varies with the voltage value of the third DC voltage signal.

[0136] The fourth DC voltage signal is used to form the sensing quantum dot, and the first microwave signal is used to read the information of the sensing quantum dot. When the voltage value of the third DC voltage signal is adjusted, the resonant frequency of the impedance matching circuit will change, and the reflected signal output by the gate reflection of the sensing quantum dot read by the impedance matching circuit will also change. Specifically, the attenuation value of the reflected signal will change with the voltage value of the third DC voltage signal, and the reflected signal can be collected by the measuring device to obtain the S21 curve of the attenuation value change. In this embodiment, the measuring device can be a vector network analyzer.

[0137] Step S23: Determine the voltage value corresponding to the trough position of the S21 curve as the third target voltage. The S21 curve is used to characterize the attenuation value of the reflected signal. At the trough position of the S21 curve, the impedance matching circuit has the highest response sensitivity to the sensing quantum dot pair. The corresponding voltage value at this time is determined as the third target voltage, which is the voltage value of the third DC voltage signal.

[0138] Step S24: Apply a third DC voltage of the third target voltage to the first adjustable capacitor and the second adjustable capacitor so that the frequency of the impedance matching circuit is at the reading frequency. The S21 curve of the reflection signal output by the gate reflection of the sensing quantum dot is obtained through steps S21-S23 to determine the third target voltage when the impedance matching circuit has the best response sensitivity, and apply a third DC voltage signal with a voltage value of the third target voltage to the first adjustable capacitor and the second adjustable capacitor, and adjust the frequency of the impedance matching circuit to the reading frequency to ensure that the reading of the sensing quantum dot is at the best sensitivity.

[0139] As attached Fig.15As shown, based on the same application concept, the embodiment of the present application also provides a semiconductor quantum dot measurement and control system for measuring bit quantum dots and sensing quantum dots formed on a semiconductor quantum chip with mutual coupling, and 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 reading state; wherein the working signal applied to the sensing quantum dot includes a first type of synthetic signal synthesized by 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 synthetic signal to the gate of the bit quantum dot, and apply a 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 synthetic signal is used to form the sensing quantum dot and the bit quantum dot under 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, which are used to output a first type of synthetic 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, which are used to process and analyze 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, which are used to output the first type of synthetic 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, which are used to process and analyze the read signal 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 the 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, and various signal amplifiers, etc., which are used to collect the second microwave signal output by the gate of the sensing quantum dot or the signal output by 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 collect 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 segment or the falling segment of the triangular wave signal or the sawtooth wave signal.

[0145] When the voltage value of the variable amplitude DC signal is the rising waveform of a triangular wave signal or a sawtooth wave signal, the voltage signal applied to the pump gate of the bit quantum dot steps from a small voltage to a large voltage; when the voltage value of the variable amplitude DC signal is the falling waveform of a triangular wave signal or a sawtooth wave signal, the voltage signal applied to the pump gate of the bit quantum dot steps from a large voltage to a small voltage; when a signal acquisition card is used to measure the reflected signal output by the pump gate of the bit quantum dot, multiple measurements are performed and the average value is taken; when the variable amplitude DC signal applied to the bit gate is selected as a complete rising segment or falling segment, the voltage value of the second microwave signal during the rising segment or falling segment is collected, which can improve the measurement accuracy of the voltage of the second microwave signal.

[0146] Based on the same application concept, an embodiment of the present application also provides a quantum computer, which uses any of the above-mentioned semiconductor quantum dot measurement methods to test the quantum dots on the semiconductor quantum chip, or uses any of the above-mentioned semiconductor quantum dot systems to test the quantum dots on the semiconductor quantum chip.

[0147] In the description of this specification, the description with reference to the terms "some embodiments" or "examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples described in this specification.

[0148] The above are only preferred embodiments of the present application and do not have any limiting effect on the present application. Any technical personnel in the relevant technical field, without departing from the scope of the technical solution of the present application, may make any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present application, which shall be deemed as the content of the technical solution of the present application and still fall within the protection scope of the present application.

Claims

1. A method for measuring semiconductor quantum dots, characterized in that: A method for forming mutually coupled bit quantum dots and sensing quantum dots on a semiconductor quantum chip includes: Applying a working signal to the sensing quantum dot to obtain a target working signal when the sensing quantum dot is in a reading state; wherein the working signal comprises a first type of synthetic signal synthesized by a fixed amplitude DC signal and a variable amplitude DC signal applied to a gate of the sensing quantum dot; Applying the first type of synthetic signal to the gate of the bit quantum dot, and applying 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 synthetic signal is used to form the sensing quantum dot and the bit quantum dot under the gate.

2. The method according to claim 1, characterized in that The working signal also includes a first microwave signal for measuring information of the sensing quantum dot, the voltage of the first type of synthetic signal varies within a first preset range, and the target working signal when applying the working signal to the sensing quantum dot to obtain the sensing quantum dot reading state includes: Applying the first type of synthetic signal and the first microwave signal to the gate of the sensing quantum dot; Obtaining a first curve of a voltage of a second microwave signal output by the gate reflection as a function of a voltage within the first preset range; The target working signal is determined according to the first curve.

3. The method according to claim 2, characterized in that The determining the target working signal according to the first curve includes: Determine a target voltage value of the first type of synthetic signal when the voltage change value in the first curve is the largest; The first type of synthetic signal whose voltage value is determined to be the target voltage value is the target working signal.

4. The method according to claim 2, characterized in that The working signal further includes a first DC voltage signal applied to the gate of the sensing quantum dot, and the target working signal when the sensing quantum dot is applied with the working signal to obtain the sensing quantum dot reading state also includes: Traversing the voltage of the first DC voltage signal within a second preset range, applying the first type of synthetic signal and the first microwave signal to the gate of the sensing quantum dot; Obtaining a Coulomb peak phase diagram of a voltage of a second microwave signal output by the gate reflection as a function of a voltage within the first preset range and a voltage within the second preset range; The target working signal is determined according to the Coulomb peak phase diagram.

5. The method according to claim 4, characterized in that The step of determining the target working signal according to the Coulomb peak phase diagram includes: Determine a target voltage value of the first type of synthetic signal and a target voltage value of the first DC voltage signal when the voltage change value in the Coulomb peak phase diagram is the largest; Determine the first type of synthetic signal whose voltage value is the target voltage value and the first DC voltage signal as the target working signal.

6. The method according to claim 1, characterized in that The step of applying the first type of synthetic signal to the gate of the bit quantum dot and applying the target working signal to the gate of the sensing quantum dot to read the information of the sensing quantum dot includes: Applying the first type of synthetic signal to the gate of the bit quantum dot; Applying the target working signal and the first microwave signal to the gate of the sensing quantum dot; Obtaining information of the sensing quantum dot according to a change in the voltage amplitude of a second microwave signal output by a gate reflection of the sensing quantum dot along with the first type of synthetic signal; or, The step of applying the first type of synthetic signal to the gate of the bit quantum dot and applying the target working signal to the gate of the sensing quantum dot to read the information of the sensing quantum dot includes: Applying the first type of synthetic signal to the gate of the bit quantum dot; Applying the target working signal to the gate of the sensing quantum dot; Applying a second DC voltage signal to the drain of the semiconductor quantum chip; The information of the sensing quantum dot is obtained according to the change of the signal output by the source of the semiconductor quantum chip with the voltage amplitude of the first type of synthetic signal.

7. The method according to any one of claims 1 to 6, characterized in that: Before applying a working signal to the sensing quantum dot to obtain a target working signal when the sensing quantum dot is in a reading state, 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 semiconductor quantum dot measurement and control system, characterized in that: The system measures the bit quantum dots and the sensing quantum dots with mutual coupling formed on the semiconductor quantum chip, and includes: A first measurement module is 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 reading state; wherein the working signal applied to the sensing quantum dot includes a first type of synthetic signal synthesized by a fixed amplitude DC signal and a variable amplitude DC signal applied to a gate of the sensing quantum dot; A second measurement module is used to apply the first type of synthetic signal to the gate of the bit quantum dot, and apply a 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 synthetic signal is used to form the sensing quantum dot and the bit quantum dot under the gate.

9. The system according to claim 8, characterized in that The first measurement module comprises: A DC voltage source, used for outputting the fixed amplitude DC signal; An arbitrary waveform generator, used for outputting the variable amplitude DC signal; The radio frequency source is used to output a first microwave signal.

10. The system according to claim 8, characterized in that The second measurement module includes a signal acquisition card for acquiring a second microwave signal output by the gate of the sensing quantum dot or a signal output by the source of the semiconductor quantum chip.

11. The system according to claim 10, characterized in that The variable amplitude DC signal includes a triangular wave signal or a sawtooth wave signal, and the signal acquisition card is used to collect 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 segment or the 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 semiconductor quantum dot measurement method as described in any one of claims 1 to 7, or the quantum dots on the semiconductor quantum chip are tested using the semiconductor quantum dot system as described in any one of claims 8 to 11.

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