CN115632712B

CN115632712B - Signal separator and measuring system, method and device for quantum bit state

Info

Publication number: CN115632712B
Application number: CN202211520791.1A
Authority: CN
Inventors: 李红珍; 张新; 李辰; 姜金哲; 徐哲
Original assignee: Suzhou Inspur Intelligent Technology Co Ltd
Current assignee: Suzhou Inspur Intelligent Technology Co Ltd
Priority date: 2022-11-30
Filing date: 2022-11-30
Publication date: 2023-03-21
Anticipated expiration: 2042-11-30
Also published as: CN115632712A

Abstract

The embodiment of the application provides a signal separator and a measuring system, a method and a device of a quantum bit state, wherein the method comprises the following steps: converting the initial sweep frequency signal into an initial resonance signal and inputting the initial resonance signal into a quantum dot device to be measured; acquiring a target resonance signal returned by the quantum dot device; separating a target signal of a target frequency component from the target resonance signal, wherein the target frequency component is a frequency associated with a charge tunneling event within the quantum dot device; and detecting the dispersion frequency shift of the target signal. By the method and the device, the problem of low accuracy in measuring the silicon-based spin qubit state in a dispersion reading mode is solved, and the effect of improving the accuracy in measuring the silicon-based spin qubit state in the dispersion reading mode is achieved.

Description

Signal separator and measuring system, method and device for quantum bit state

Technical Field

The embodiment of the application relates to the field of silicon-based devices, in particular to a signal separator, and a system, a method and a device for measuring a quantum bit state.

Background

At present, the spin state of a qubit cannot be directly measured due to the intrinsic properties of the silicon-based spin qubit, and the prior art generally performs equivalent measurement on the qubit by means of charge sensing or dispersion readout. However, for the dispersion readout mode, the measurement process is easily interfered by signal noise, such as: in the mode of dispersion reading, if the measurement signal carrying spin qubit state information is in a high-temperature operation mode, background noise can gradually submerge the measurement signal, and the readout visibility is reduced by coulomb peak thermal broadening, so that the detected Rabi oscillation (Rabi oscillation) V-shaped pattern for judging the qubit state is directly blurred, and the accuracy and the measurement efficiency of the qubit state measurement are influenced.

Aiming at the problems that the accuracy of measuring the state of the silicon-based spin qubit in a dispersion readout mode is low and the like in the related art, an effective solution is not provided yet.

Disclosure of Invention

The embodiment of the application provides a signal separator and a measuring system, a method and a device of a quantum bit state, and aims to at least solve the problem that the accuracy of measuring a silicon-based spin quantum bit state in a dispersion reading mode in the related art is low.

According to an embodiment of the present application, there is provided a signal splitter including: a first straight waveguide, a second straight waveguide and a ring waveguide,

the first straight waveguide is connected with the second straight waveguide through the annular waveguide;

the annular waveguide includes: the waveguide comprises a first semi-annular waveguide, a second semi-annular waveguide, a first transmission waveguide and a second transmission waveguide, wherein the first semi-annular waveguide is embedded into the first straight waveguide to form a first coupling region, the second semi-annular waveguide is embedded into the second straight waveguide to form a second coupling region, the first transmission waveguide is connected between the first semi-annular waveguide and the second semi-annular waveguide to form a first transmission region, and the second transmission waveguide is connected between the second semi-annular waveguide and the first semi-annular waveguide to form a second transmission region;

the length parameter of the annular waveguide is determined according to a target frequency component of chromatic dispersion frequency shift in the measurement process of the state of the silicon-based spin qubit;

the signal separator is configured to separate a target signal of the target frequency component from the received signal.

In one exemplary embodiment, the first transmission waveguide and the second transmission waveguide are each a serpentine-shaped waveguide, wherein,

the first transmission waveguide comprises a first number of first meandering periods connected in series, the first meandering periods comprising a first partial ring segment, a first straight line segment, a first semi-ring segment, a second straight line segment, and a second partial ring segment connected in series;

the second transmission waveguide comprises a second number of second meandering periods connected in sequence, the second meandering periods comprising a third partial ring segment, a third straight segment, a second semi-ring segment, a fourth straight segment, and a fourth partial ring segment connected in sequence;

the first number may be the same as or different from the second number.

In an exemplary embodiment, the first number is the same as the second number, the radii of the first and second semi-toroidal waveguides are the same, the radii of the first, second, third, fourth, first and second semi-toroidal segments are the same, and the lengths of the first, second, third and fourth straight segments are the same.

According to another embodiment of the present application, there is provided a system for measuring a quantum bit state, including: a signal source, a signal converter, a signal separator and a detector, wherein,

the signal source is connected with the signal converter, the signal converter is also connected between the quantum dot device to be measured and the signal separator, and the signal separator is connected with the detector;

the signal source is used for transmitting an initial frequency sweep signal to the signal converter;

the signal converter is used for converting the initial frequency sweep signal into an initial resonance signal, inputting the initial resonance signal to the quantum dot device, and transmitting a target resonance signal returned by the quantum dot device to the signal separator;

the signal separator is configured to separate a target signal of a target frequency component from the target resonance signal, where the target frequency component is a frequency associated with a charge tunneling event within the quantum dot device;

the detector is configured to detect a chromatic dispersion frequency shift occurring in the target signal, where the occurrence of the chromatic dispersion frequency shift in the signal output by the signal converter indicates that the tunneling charge event has occurred in the quantum dot device, and the tunneling charge event is used to characterize a silicon-based spin quantum bit state in the quantum dot device.

In an exemplary embodiment, the signal separator includes: a microring resonator, wherein the microring resonator comprises: a first straight waveguide, a second straight waveguide and a ring waveguide,

the first straight waveguide is connected with the second straight waveguide through the annular waveguide, an input port of the first straight waveguide is connected with the signal converter, and an output port of the second straight waveguide is connected with the detector;

the target frequency component is a resonance condition of the micro-ring resonator;

the micro-ring resonator is used for inputting the target resonance signal from the input port and outputting the target signal meeting the resonance condition from the output port.

In one exemplary embodiment, the resonance frequency of the micro-ring resonator is within a dispersion frequency shift range of the signal converter, and the full width half maximum of the micro-ring resonator is less than the bandwidth of the signal converter.

In one exemplary embodiment, the annular waveguide includes: a first semi-annular waveguide, a second semi-annular waveguide, a first transmission waveguide, and a second transmission waveguide, wherein,

the first semi-ring waveguide is embedded into the first straight waveguide to form a first coupling region, the second semi-ring waveguide is embedded into the second straight waveguide to form a second coupling region, the first transmission waveguide is connected between the first semi-ring waveguide and the second semi-ring waveguide to form a first transmission region, and the second transmission waveguide is connected between the second semi-ring waveguide and the first semi-ring waveguide to form a second transmission region;

the length parameter of the annular waveguide is determined from the target frequency component.

the first transmission waveguide comprises a first number of first meandering periods connected in series;

the second transmission waveguide includes a second number of second meandering periods connected in series;

the first number is the same as or different from the second number.

In one exemplary embodiment, the first meandering period includes a first partial loop segment, a first straight segment, a first semi-loop segment, a second straight segment, and a second partial loop segment connected in series;

the second meandering period includes a third partial loop segment, a third straight segment, a second semi-loop segment, a fourth straight segment, and a fourth partial loop segment connected in sequence.

In one exemplary embodiment, the detector includes: an amplifier and an IQ mixer, wherein,

the amplifier is connected between the signal separator and the IQ mixer;

the IQ mixer is used for outputting a resonance peak of the target signal; and detecting the chromatic dispersion frequency shift of the target signal according to the harmonic peak.

In one exemplary embodiment, the signal converter includes: a gate reflectometer, or, equivalently, an LC resonator.

According to another embodiment of the present application, there is provided a method for measuring a quantum bit state, including:

converting the initial sweep frequency signal into an initial resonance signal and inputting the initial resonance signal into a quantum dot device to be measured;

acquiring a target resonance signal returned by the quantum dot device;

separating a target signal of a target frequency component from the target resonance signal, wherein the target frequency component is a frequency associated with a charge tunneling event within the quantum dot device;

and detecting a chromatic dispersion frequency shift of the target signal, wherein the chromatic dispersion frequency shift of the separated signal indicates that the charge tunneling event occurs in the quantum dot device, and the charge tunneling event is used for representing a silicon-based spin quantum bit state in the quantum dot device.

In one exemplary embodiment, the separating the target signal of the target frequency component from the target resonance signal includes:

extracting a signal of a target frequency component from the target resonance signal to obtain a reference signal;

and performing signal enhancement on the reference signal to obtain the target signal.

separating the target signal of the target frequency component from the target resonance signal by a microring resonator, wherein the microring resonator includes: the micro-ring resonator comprises a first straight waveguide, a second straight waveguide and a ring waveguide, wherein the first straight waveguide is connected with the second straight waveguide through the ring waveguide, an input port of the first straight waveguide is used for inputting the target resonance signal, an output port of the second straight waveguide is used for outputting the target signal meeting the resonance condition of the micro-ring resonator, and the resonance condition is the target frequency component.

In one exemplary embodiment, before the separating the target signal of the target frequency component from the target resonance signal by the microring resonator, the method further includes:

determining a length parameter of the annular waveguide according to the target frequency component, wherein the annular waveguide comprises: the waveguide fiber coupler comprises a first semi-annular waveguide, a second semi-annular waveguide, a first transmission waveguide and a second transmission waveguide, wherein the first semi-annular waveguide is embedded into a first straight waveguide to form a first coupling area, the second semi-annular waveguide is embedded into a second straight waveguide to form a second coupling area, the first transmission waveguide is connected between the first semi-annular waveguide and the second semi-annular waveguide to form a first transmission area, and the second transmission waveguide is connected between the second semi-annular waveguide and the first semi-annular waveguide to form a second transmission area.

In an exemplary embodiment, the determining the length parameter of the annular waveguide according to the target frequency component includes:

acquiring a dispersion frequency shift range of a signal converter, wherein the signal converter is used for converting charge tunneling events in the quantum dot device into dispersion frequency shift of signals;

selecting the target frequency component from the dispersion frequency shift range according to the material property of the micro-ring resonator as the resonant frequency of the micro-ring resonator, wherein the full width at half maximum of the micro-ring resonator with the resonant frequency is smaller than the bandwidth of the signal converter;

calculating the waveguide length of the annular waveguide according to the target frequency component;

determining the radius of a semi-annular waveguide, the radius of an annular section, the length of a straight line section and the number of winding cycles as the length parameters according to the waveguide length and the deployment information of the micro-ring resonator;

the first transmission waveguide and the second transmission waveguide are both waveguides with a winding shape, the first transmission waveguide comprises a first number of first winding cycles which are connected in sequence, the second transmission waveguide comprises a second number of second winding cycles which are connected in sequence, the first number is the same as or different from the second number, the first winding cycle comprises a first partial ring section, a first straight line section, a first semi-ring section, a second straight line section and a second partial ring section which are connected in sequence, and the second winding cycle comprises a third partial ring section, a third straight line section, a second semi-ring section, a fourth straight line section and a fourth partial ring section which are connected in sequence;

wherein the radius of the semi-circular waveguide is the radius of the first semi-circular waveguide and the second semi-circular waveguide, the radius of the circular segment is the radius of the first partial circular segment, the radius of the second partial circular segment, the radius of the third partial circular segment, the radius of the fourth partial circular segment, the radius of the first semi-circular segment and the radius of the second semi-circular segment, the length of the straight segment is the length of the first straight segment, the length of the second straight segment, the length of the third straight segment and the length of the fourth straight segment, and the number of winding cycles is the sum of the first number and the second number.

According to another embodiment of the present application, there is provided a quantum bit state measurement apparatus including:

the input module is used for converting the initial sweep frequency signal into an initial resonance signal and inputting the initial resonance signal to the quantum dot device to be measured;

the acquisition module is used for acquiring a target resonance signal returned by the quantum dot device;

a separation module configured to separate a target signal of a target frequency component from the target resonance signal, wherein the target frequency component is a frequency associated with a charge tunneling event within the quantum dot device;

and a detection module, configured to detect a chromatic dispersion frequency shift occurring in the target signal, where the chromatic dispersion frequency shift occurring in the separated signal indicates that the charge tunneling event occurs in the quantum dot device, and the charge tunneling event is used to characterize a silicon-based spin qubit state in the quantum dot device.

According to a further embodiment of the application, there is also provided a computer-readable storage medium having a computer program stored thereon, wherein the computer program is arranged to perform the steps of any of the above method embodiments when executed.

According to yet another embodiment of the present application, there is also provided an electronic device, comprising a memory in which a computer program is stored and a processor arranged to run the computer program to perform the steps of any of the above method embodiments.

According to the method and the device, the initial sweep frequency signal is converted into the initial resonance signal through the signal converter and is input to the quantum dot device, the target resonance signal returned by the quantum dot device is transmitted to the signal separator, and the target signal of the target frequency component is separated from the target resonance signal through the signal separator. Therefore, the problem of low accuracy of measuring the state of the silicon-based spin qubit in a dispersion readout mode can be solved, and the effect of improving the accuracy of measuring the state of the silicon-based spin qubit in the dispersion readout mode can be achieved.

Drawings

FIG. 1 is a first schematic diagram of a signal splitter according to an embodiment of the present application;

FIG. 2 is a second schematic diagram of a signal splitter according to an embodiment of the present application;

FIG. 3 is a schematic diagram of a signal splitter in accordance with an alternative embodiment of the present application;

FIG. 4 is a first schematic diagram of a qubit state measurement system according to an embodiment of the present application;

FIG. 5 is a second schematic diagram of a qubit state measurement system according to an embodiment of the present application;

FIG. 6 is a schematic diagram of an operating state of a microring resonator according to an embodiment of the present application;

FIG. 7 is a third schematic diagram of a qubit state measurement system according to an embodiment of the present application;

FIG. 8 is a fourth schematic diagram of a qubit state measurement system according to an embodiment of the present application;

FIG. 9 is a schematic diagram of detecting chromatic dispersion shift by a harmonic peak according to an embodiment of the present application;

FIG. 10 is a schematic diagram of a measurement circuit for qubit states for silicon-based spin qubit dispersion readout in accordance with an embodiment of the present application;

FIG. 11 is a flow chart of a method of measuring qubit states in accordance with an embodiment of the application;

fig. 12 is a block diagram of a qubit state measurement device according to an embodiment of the application.

Detailed Description

Embodiments of the present application will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.

Silicon-based spin qubits are a type of qubit that is confined in silicon-based quantum dots, typically isotopically purified, using spin-encoding ²⁸ The Si (i.e. silicon element) epitaxial layer is used as a bearing material, and provides restraint when a voltage bias is applied to the grid, so that a potential well structure with the size of only tens of nanometers (Nanometer) can be formed at a specific position of a heterogeneous interface or a channel surface under the grid, and the potential well structure is called a quantum dot. Generally, by means of external magnetic field and microwave pulse excitation, silicon-based spin qubit inversion can be precisely regulated and controlled, thereby realizing various gate operations. Currently, both single bit and two bit gate fidelity have exceeded 99% fault tolerance thresholds. The measurement of the flip state of the Si-based spin qubit by dispersive readout can be the point-to-point tunneling phenomenon generated when the Si-based spin qubit is flippedThe element exhibits a dispersive frequency shift of the swept frequency microwave, which is thus revealed by the detection device.

An embodiment of the present application provides a signal splitter, and fig. 1 is a schematic diagram of a signal splitter according to an embodiment of the present application, as shown in fig. 1, the signal splitter 102 includes: a first straight waveguide 104, a second straight waveguide 106 and a ring waveguide 108,

the first straight waveguide 104 is connected with the second straight waveguide 106 through the annular waveguide 108;

the annular waveguide 108 includes: a first semi-ring waveguide 110, a second semi-ring waveguide 112, a first transmission waveguide 114 and a second transmission waveguide 116, wherein the first semi-ring waveguide 110 is embedded in the first straight waveguide 104 to form a first coupling region, the second semi-ring waveguide 112 is embedded in the second straight waveguide 106 to form a second coupling region, the first transmission waveguide 114 is connected between the first semi-ring waveguide 110 and the second semi-ring waveguide 112 to form a first transmission region, and the second transmission waveguide 116 is connected between the second semi-ring waveguide 112 and the first semi-ring waveguide 110 to form a second transmission region;

the length parameter of the annular waveguide 108 is determined according to a target frequency component of chromatic dispersion frequency shift during the measurement of the state of the silicon-based spin qubit;

the signal separator 102 is configured to separate a target signal of the target frequency component from the received signal.

Through the device, the signal separator with the structure can separate the target signal of the target frequency component from the received signal, the target frequency component is the frequency associated with the charge tunneling event in the quantum dot device, which is equivalent to filtering out the influence of the noise part in the target resonance signal on the detection result, and only the dispersion frequency shift of the target signal of the frequency part associated with the charge tunneling event in the quantum dot device is detected, so that the silicon-based spin quantum bit state in the quantum dot device is detected more accurately. Therefore, the problem of low accuracy of measuring the state of the silicon-based spin qubit in a dispersion readout mode can be solved, and the effect of improving the accuracy of measuring the state of the silicon-based spin qubit in the dispersion readout mode can be achieved.

Optionally, in this embodiment, the signal separator may not only separate the target signal of the target frequency component, but also enhance the target signal, so that the result of measuring the state of the silicon-based spin qubit in a dispersion readout manner is more accurate.

Alternatively, in the present embodiment, each of the waveguides may be, but not limited to, formed of a low refractive index cladding layer (e.g., silica) and a high refractive index core layer (e.g., silicon nitride) when viewed in a cross section.

Alternatively, in this embodiment, the two straight waveguides may be, but are not limited to being, arranged in parallel and at a distance on a silicon substrate, and the two semi-annular waveguides may be, but are not limited to being, antisymmetrically close to the straight waveguides with cladding layers partially embedded in the straight waveguide cladding layers, forming the first coupling region and the second coupling region.

In an exemplary embodiment, fig. 2 is a second schematic diagram of a signal splitter according to an embodiment of the present application, and as shown in fig. 2, the first transmission waveguide 114 and the second transmission waveguide 116 are both waveguides with a serpentine shape, wherein the first transmission waveguide 114 includes a first number of first serpentine periods 202 connected in sequence, and the first serpentine periods 202 include a first partial ring segment 204, a first straight line segment 206, a first semi-ring segment 208, a second straight line segment 210, and a second partial ring segment 212 connected in sequence; the second transmission waveguide 116 comprises a second number of second meandering periods 214 connected in series, the second meandering periods 214 comprising a third partial loop segment 216, a third straight segment 218, a second half-loop segment 220, a fourth straight segment 222, and a fourth partial loop segment 224 connected in series; the first number may be the same as or different from the second number.

In an alternative embodiment, an example of the structure of the signal splitter is provided, and fig. 3 is a schematic diagram of a signal splitter according to an alternative embodiment of the present application, and as shown in fig. 3, a ring waveguide is designed in a combination of a "semi-ring waveguide + a meandering waveguide" to accommodate an increase in length due to a decrease in frequency from a visible light frequency band to a microwave frequency band.

The signal separator uses one input and two outputs. The input end is an In port, and the reflected signal transmitted by the front stage is input into the signal separator. The output ends are respectively a Through port and a Drop port, all reflected signal power under the condition that no charge tunneling event between points occurs and most reflected signal power during the period that charge tunneling events between points occur are output from the Through port, only a reflected signal component with a small part of frequency resonance during the period that charge tunneling events between points occur is output from the Drop port after resonance enhancement. The two paths of output signals respectively enter an IQ mixer through an amplifier, and only the measurement signals are reserved after demodulation. If the reflected signal output from the Drop port continues to have two strong frequency responses within a narrow band, it indicates that the auxiliary quantum dot has an inter-dot charge tunneling event.

An embodiment of the present application further provides a system for measuring a qubit state, and fig. 4 is a first schematic diagram of the system for measuring a qubit state according to the embodiment of the present application, and as shown in fig. 4, the system includes: a signal source 402, a signal converter 404, a signal separator 406 and a detector 408, wherein the signal source 402 is connected with the signal converter 404, the signal converter 404 is further connected between a quantum dot device 410 to be measured and the signal separator 406, and the signal separator 406 is connected with the detector 408;

the signal source 402 is configured to transmit an initial frequency sweep signal to the signal converter 404;

the signal converter 404 is configured to convert the initial frequency sweep signal into an initial resonance signal, input the initial resonance signal to the quantum dot device 410, and transmit a target resonance signal returned by the quantum dot device 410 to the signal separator 406;

the signal splitter 406 is configured to split a target signal of a target frequency component from the target resonance signal, where the target frequency component is a frequency associated with a charge tunneling event in the quantum dot device 410;

the detector 408 is configured to detect a chromatic dispersion frequency shift of the target signal, where the chromatic dispersion frequency shift of the signal output by the signal converter 404 indicates that the tunneling charge event occurs in the quantum dot device 410, and the tunneling charge event is used to characterize a silicon-based spin qubit state in the quantum dot device 410.

Through the system, the initial sweep frequency signal is converted into the initial resonance signal through the signal converter and is input into the quantum dot device, the target resonance signal returned by the quantum dot device is transmitted to the signal separator, and the target signal of the target frequency component is separated from the target resonance signal through the signal separator. Therefore, the problem of low accuracy of measuring the state of the silicon-based spin qubit in a dispersion readout manner can be solved, and the effect of improving the accuracy of measuring the state of the silicon-based spin qubit in a dispersion readout manner can be achieved.

Alternatively, in the present embodiment, the quantum dot device may be, but not limited to, a silicon-based quantum dot device, and the silicon-based quantum dot device may be classified into SiMOS, si/SiGe, FDSOI, finFET, and the like according to different constraint strategies. The Silicon metal-oxide-semiconductor is a Silicon metal-oxide-semiconductor, which is a kind of quantum dot device manufactured in a laboratory, and the quantum dots are formed in the Si semiconductor (near the Si-SiO2 interface). Si/SiGe, siGe heterojunction, is another type of lab-fabricated quantum dot device where quantum dots are formed in Si wells (near the Si-SiGe barrier interface). FDSOI is a Fully depleted Silicon On Insulator (SOI), which is a traditional semiconductor structure manufactured in industry and can be used as a quantum dot device, and the quantum dot is located at the corner where a source drain and a gate contact. The FinFET is a Fin field-effect transistor, which is a traditional semiconductor structure manufactured in industry and can also be used as a quantum dot device, and the quantum dot is positioned on the upper surface of a contact between a source drain and a grid. SimOS and Si/SiGe use laboratory fabrication to generate electron spin coded qubits, FDSOI and FinFET use industrial production line fabrication to generate hole spin coded qubits.

Optionally, in this embodiment, the signal source may be, but is not limited to, any signal source capable of emitting a frequency sweep signal, such as: the signal source may include, but is not limited to, a voltage source and a microwave source, which are combined by a biaser to emit a swept frequency microwave as an initial swept frequency signal to the signal converter. Alternatively, the signal source may be, but is not limited to, a single device capable of emitting swept frequency microwaves.

Optionally, in this embodiment, the various signals may be, but are not limited to, microwave signals.

Optionally, in this embodiment, occurrence of a dispersion frequency shift in a signal output by the signal converter indicates occurrence of a charge tunneling event in the quantum dot device, and the charge tunneling event further characterizes a silicon-based spin quantum bit state in the quantum dot device, so that the quantum bit state can be measured by detecting the dispersion frequency shift occurring in the target signal.

In an exemplary embodiment, fig. 5 is a second schematic diagram of a qubit state measurement system according to an embodiment of the application, and as shown in fig. 5, the demultiplexer 406 includes: a microring resonator 502, wherein the microring resonator 502 comprises: a first straight waveguide 504, a second straight waveguide 506 and a ring waveguide 508, wherein the first straight waveguide 504 is connected with the second straight waveguide 506 through the ring waveguide 508, an input port 510 of the first straight waveguide 504 is connected with the signal converter 404, and an output port 512 of the second straight waveguide 506 is connected with the detector 408; the target frequency component is a resonance condition of the microring resonator 502;

the micro-ring resonator 502 is configured to input the target resonance signal from the input port 510, and output the target signal satisfying the resonance condition from the output port 512.

Optionally, in this embodiment, the microring resonator is a silicon-based photonic device. Structurally, the micro-ring resonator is formed by coupling annular waveguides and straight waveguides, wherein one annular waveguide or a plurality of annular waveguides can be connected in parallel or in series to form an array, and one straight waveguide or two straight waveguides are called as All-pass type or Add-drop type.

Optionally, in this embodiment, the micro-ring resonator is an Add-drop micro-ring resonator, where a resonant frequency of the Add-drop micro-ring resonator is a target frequency component; the first straight waveguide is an upper straight waveguide of the Add-drop type micro-ring resonator, and the input port is an In port of the upper straight waveguide; the second straight waveguide is a lower straight waveguide of the Add-Drop type micro-ring resonator, and the input port is a Drop port of the lower straight waveguide.

The micro-ring resonator has the advantages of low cost, small volume, compact structure and high on-chip integration level, and is used as a filter in the embodiment. The filter is divided into four types of low-pass, high-pass, band-pass and band-stop according to the frequency of the passed signal, the micro-ring resonator belongs to a notch filter in the band-stop filter, and specific frequency components with very narrow bandwidth in the light wave transmitted on the straight waveguide can be absorbed into the annular waveguide, so that the filtering effect is realized. Fig. 6 is a schematic diagram of an operating state of a micro-ring resonator according to an embodiment of the present application, and as shown in fig. 6, the micro-ring resonator uses an Add-drop type structure and is composed of two straight waveguides and a ring waveguide, where the ring waveguide is divided into four functional regions: the first coupling area is close to the upper straight waveguide, the second coupling area is close to the lower straight waveguide, and the first transmission area and the second transmission area are arranged between the first coupling area and the second coupling area. When a microwave signal f is input from an In port of the upper straight waveguide and is transmitted to the first coupling region, part of microwave power is coupled into the ring, and the rest of microwave power is output from a high port. The microwaves coupled into the ring reach the second coupling region through the first transmission region, coupling occurs again, part of microwave power is coupled to the Drop straight waveguide and is output from the Drop port, and the rest power returns to the first coupling region through the second transmission region.

According to the resonance condition of the micro-ring resonator, if the optical path difference of a certain specific wavelength component of the microwave signal transmitted in the ring waveguide for one circle is integral multiple of the wavelength,

that is to

Representing the effective refractive index, L being the total length of the annular waveguide, m representing the number of resonant stages,

the resonance wavelength corresponding to the order is called as the resonance frequency), resonance strengthening occurs in the first coupling region, and as a result, the power of the resonance frequency in the annular waveguide is increased, and the power of the resonance frequency output by the Drop end of the lower path is also increased. If no loss exists in the transmission process, the operation is repeated for many times, the resonant frequency is output from the Drop port of the down-path straight waveguide, and the separation of the resonant frequency and other frequency components is realized.

In an exemplary embodiment, the resonance frequency of the micro-ring resonator is within a dispersive frequency shift range of the signal converter, and the full width at half maximum of the micro-ring resonator is less than the bandwidth of the signal converter.

Optionally, in this embodiment, the notch characteristic of the micro-ring resonator is utilized to absorb and output the frequency response associated with the charge tunneling event between the points, and taking the signal converter as an LC resonator as an example, the micro-ring resonator meets the following two requirements: the resonance frequency of the micro-ring resonator is in the dispersion frequency shift range of the LC resonator, and the full width at half maximum of the micro-ring resonator is far smaller than the bandwidth of the LC resonator.

In an exemplary embodiment, fig. 7 is a schematic diagram three of a qubit state measurement system according to an embodiment of the application, and as shown in fig. 7, the annular waveguide 508 includes: a first semi-annular waveguide 702, a second semi-annular waveguide 704, a first transmission waveguide 706 and a second transmission waveguide 708, wherein the first semi-annular waveguide 702 is embedded in the first straight waveguide 504 to form a first coupling region, the second semi-annular waveguide 704 is embedded in the second straight waveguide 506 to form a second coupling region, the first transmission waveguide 706 is connected between the first semi-annular waveguide 702 and the second semi-annular waveguide 704 to form a first transmission region, and the second transmission waveguide 708 is connected between the second semi-annular waveguide 704 and the first semi-annular waveguide 702 to form a second transmission region; the length parameter of the annular waveguide 508 is determined from the target frequency component.

Optionally, in this embodiment, the shape and arrangement of each transmission waveguide may be changed according to requirements.

Alternatively, in the present embodiment, the length parameter of the annular waveguide may include, but is not limited to, the length, curvature, and the like of each portion in the annular waveguide. Such as: the radius of each semi-circular waveguide, the radius of the circular portion of each transmission waveguide, the length of the linear portion, and the like.

In one exemplary embodiment, the first transmission waveguide and the second transmission waveguide are both serpentine-shaped waveguides, wherein the first transmission waveguide includes a first number of first serpentine periods connected in series; the second transmission waveguide includes a second number of second meandering periods connected in series; the first number may be the same as or different from the second number.

Alternatively, in this embodiment, by forming the serpentine-like arrangement structure in the first transmission region and the second transmission region by using the above-mentioned waveguide having a serpentine shape with a certain number of serpentine periods, it is possible to form signal transmission on the one hand and save the area occupied by the structure on the other hand.

In one exemplary embodiment, the first meandering period includes a first partial loop segment, a first straight segment, a first semi-loop segment, a second straight segment, and a second partial loop segment connected in series; the second meandering period includes a third partial loop segment, a third straight segment, a second semi-loop segment, a fourth straight segment, and a fourth partial loop segment connected in sequence.

Optionally, in this embodiment, the first partial ring segment, the second partial ring segment, the third partial ring segment, and the fourth partial ring segment are all quarter ring segments.

Alternatively, in the present embodiment, the structures in the first transmission waveguide and the second transmission waveguide are regularly and symmetrically arranged by the configuration of the parameters.

In an exemplary embodiment, fig. 8 is a fourth schematic diagram of a qubit state measurement system according to an embodiment of the application, and as shown in fig. 8, the detector 408 includes: an amplifier 802 and an IQ mixer 804, wherein the amplifier 802 is connected between the signal separator 406 and the IQ mixer 804; the IQ mixer 804 is configured to output a formant of the target signal; and detecting the chromatic dispersion frequency shift of the target signal according to the harmonic peak.

Optionally, in this embodiment, the chromatic dispersion shift occurring in the target signal may be detected by, but is not limited to, a harmonic peak, and fig. 9 is a schematic diagram of detecting the chromatic dispersion shift by the harmonic peak according to an embodiment of the present application, as shown in fig. 9: when the target signal is subjected to dispersion frequency shift, the resonance peak is shifted, that is, if the resonance peak is shifted, the target signal can be determined to be subjected to dispersion frequency shift.

Optionally, in this embodiment, the dispersion readout uses a Gate-reflectometer (GR), where the GR is essentially an LC resonator, and can represent an inter-point tunneling event as a dispersive frequency shift of swept-frequency microwaves, and does not involve an embedded charge sensor, so that the method has an obvious scalability advantage, is more robust to Temperature, and can operate at a Temperature of K magnitude (kelvin Temperature).

Optionally, in this embodiment, the gate reflectometer may include, but is not limited to, a patch inductor and a gate parasitic capacitance, and includes an auxiliary quantum dot that acts as a variable impedance load for the resonator. Such as: the auxiliary quantum dot is positioned on the quantum dot device and defined by the grid of the quantum dot device, the chip inductor is positioned on a Printed Circuit Board (PCB) for fixing the quantum dot device, and the chip inductor and the auxiliary quantum dot are connected through lead bonding.

Optionally, in this embodiment, when the bias gate DC voltage of the quantum dot device causes the charge in the quantum dot of the quantum dot device to undergo spin-selective inter-dot tunneling, the additional quantum capacitance associated with the charge transition causes the signal converter to undergo dispersion frequency shift.

Optionally, in this embodiment, an amplifier and an IQ mixer may be connected to the Though port of the micro-ring resonator to detect a resonance peak of a signal output from the Though port. Fig. 10 is a schematic diagram of a measurement circuit for a qubit state for si-based spin qubit dispersion readout according to an embodiment of the present application, where, as shown In fig. 10, a gate reflectometer equivalent LC resonator is connected to a quantum dot device, a voltage source and a microwave source are used as signal sources to provide swept-frequency microwaves for the LC resonator and the quantum dot device through a biaser, a directional coupler transmits a return signal to an In port of a micro-ring resonator, a drop port of the micro-ring resonator is connected to one set of an amplifier and an IQ mixer, and a Though port of the micro-ring resonator is connected to the other set of the amplifier and the IQ mixer.

Aiming at a dispersion reading scheme, starting from an improved measuring circuit, an Add-drop type micro-ring resonator branch is introduced, a certain frequency component in a reflected signal, which is subjected to dispersion frequency shift, is resonantly enhanced and absorbed into a ring waveguide, and the frequency component is output from a drop end. And weakening the thermal broadening influence of background noise on the frequency component by utilizing the trap characteristic of the micro-ring resonator, and judging whether a spin-related point-to-point charge tunneling event occurs according to whether frequency response occurs at drop end output.

In this embodiment, a method for measuring a qubit state operated in the mobile terminal is provided, and fig. 11 is a flowchart of a method for measuring a qubit state according to an embodiment of the present application, where as shown in fig. 11, the flowchart includes the following steps:

step S1102, converting the initial sweep frequency signal into an initial resonance signal and inputting the initial resonance signal into a quantum dot device to be measured;

step S1104, obtaining a target resonance signal returned by the quantum dot device;

step S1106, separating a target signal of a target frequency component from the target resonance signal, wherein the target frequency component is a frequency associated with a charge tunneling event in the quantum dot device;

step S1108, detecting a chromatic dispersion frequency shift of the target signal, where the chromatic dispersion frequency shift of the separated signal indicates that the charge tunneling event occurs in the quantum dot device, and the charge tunneling event is used to characterize a silicon-based spin qubit state in the quantum dot device.

Through the steps, the initial sweep frequency signal is converted into the initial resonance signal and is input to the quantum dot device, the target resonance signal returned by the quantum dot device is obtained, and then the target signal of the target frequency component is separated from the target resonance signal, and the dispersion frequency shift detection is performed on the target signal of the target frequency component, wherein the target frequency component is the frequency associated with the charge tunneling event in the quantum dot device, which is equivalent to filtering the influence of the noise part in the target resonance signal on the detection result, and only the dispersion frequency shift generated on the target signal of the frequency part associated with the charge tunneling event in the quantum dot device is detected, so that the silicon-based spin quantum bit state in the quantum dot device is detected more accurately. Therefore, the problem of low accuracy of measuring the state of the silicon-based spin qubit in a dispersion readout mode can be solved, and the effect of improving the accuracy of measuring the state of the silicon-based spin qubit in the dispersion readout mode can be achieved.

In the technical solution provided in step S1102, the initial frequency sweep signal may be, but is not limited to, frequency sweep microwave, and may be, but is not limited to, frequency sweep microwave synthesized by a voltage signal emitted from a voltage source and a microwave signal emitted from a microwave source through a bias device. Or swept-frequency microwaves emitted by a signal source.

Optionally, in this embodiment, the initial resonance signal may be, but is not limited to, a result of resonance of the initial frequency sweep signal at the resonant frequency of the grid reflectometer and the grid reflectometer.

Optionally, in this embodiment, a charge tunneling event may occur, but is not limited to, in the quantum dot device, and the quantum dot device may be excited by an external magnetic field and a microwave pulse, so as to implement precise control of silicon-based spin qubit inversion and various gate operations, which may include, but is not limited to: siMOS, si or SiGe, FDSOI, and FinFET, among others.

In the technical solution provided in step S1104, the target resonance signal may be obtained according to, but not limited to, a tunneling event between dots of the quantum dot device, for example: and the capacitance of the signal converter is +2 (positive 2), the additional capacitance generated by the tunneling event between the dots during the quantum dot period is-1 (negative 1), the additional capacitance generated by the tunneling event between the dots during the quantum dot period is superposed with the capacitance of the signal converter, the total capacitance is reduced, the frequency is increased, and the target resonance signal returned by the signal converter is obtained.

In the technical solution provided in step S1106, the target frequency component is a frequency associated with a charge tunneling event in a quantum dot device. That is, the target frequency component may be, but is not limited to being, determined according to a frequency associated with occurrence of a charge tunneling event.

Optionally, in this embodiment, a method for determining a target frequency component is provided, where a dispersion frequency shift range of a signal converter is used as the dispersion frequency shift range

The target frequency component is

For example, the target frequency component is

The dispersion frequency shift range that must fall within the signal converter is

That is, the frequency shift range according to the dispersion of the signal converter is

I.e. the target frequency component can be determined

。

In one exemplary embodiment, the target signal of the target frequency component may be separated from the target resonance signal by, but is not limited to: extracting a signal of a target frequency component from the target resonance signal to obtain a reference signal; and performing signal enhancement on the reference signal to obtain the target signal.

Optionally, in this embodiment, by extracting and enhancing the signal of the target frequency component, not only the chromatic dispersion and frequency shift of the signal of the target frequency component can be detected in a targeted manner, but also the signal-to-noise ratio of the signal can be improved, so that the detection process is more accurate and the efficiency is higher.

OptionallyIn this embodiment, a method for extracting a target signal is provided, taking the example of extracting the target signal through a micro-ring resonator, according to the resonance condition of the micro-ring resonator, if the optical path difference of a certain wavelength component of a microwave signal transmitted in a ring waveguide for one circle is an integral multiple of the wavelength, that is, the optical path difference is an integral multiple of the wavelength

（

Which represents the effective refractive index of the light,

is the total length of the ring-shaped waveguide,

the number of the resonance stages is represented,

the resonance wavelength corresponding to the order, and the frequency corresponding to the resonance wavelength is referred to as a resonance frequency), resonance intensification occurs at this time, and as a result, the resonance frequency power in the annular waveguide of the microring resonator increases, and the output resonance frequency power also increases. If no loss occurs in the transmission process, the resonant frequency is output from the port all the time in such a way that the resonant frequency is separated from other frequency components.

In one exemplary embodiment, the target signal of the target frequency component may be separated from the target resonance signal by, but is not limited to: separating the target signal of the target frequency component from the target resonance signal by a microring resonator, wherein the microring resonator includes: the micro-ring resonator comprises a first straight waveguide, a second straight waveguide and a ring waveguide, wherein the first straight waveguide is connected with the second straight waveguide through the ring waveguide, an input port of the first straight waveguide is used for inputting the target resonance signal, an output port of the second straight waveguide is used for outputting the target signal meeting the resonance condition of the micro-ring resonator, and the resonance condition is the target frequency component.

Optionally, in this embodiment, the resonance condition of the micro-ring resonator is the target frequency component, so as to separate the target signal of the target frequency component from the target resonance signal.

In an exemplary embodiment, before the target signal of the target frequency component is separated from the target resonance signal by the microring resonator, the annular waveguide may be formed by, but not limited to: determining a length parameter of the annular waveguide according to the target frequency component, wherein the annular waveguide comprises: the waveguide coupler comprises a first semi-annular waveguide, a second semi-annular waveguide, a first transmission waveguide and a second transmission waveguide, wherein the first semi-annular waveguide is embedded into a first straight waveguide to form a first coupling area, the second semi-annular waveguide is embedded into a second straight waveguide to form a second coupling area, the first transmission waveguide is connected between the first semi-annular waveguide and the second semi-annular waveguide to form a first transmission area, and the second transmission waveguide is connected between the second semi-annular waveguide and the first semi-annular waveguide to form a second transmission area.

Alternatively, in the present embodiment, the length parameter of the annular waveguide may be, but is not limited to, determined according to the target frequency component.

Alternatively, in the present embodiment, the coupling region may be, but is not limited to, formed by embedding a half-ring waveguide into a straight waveguide, which may be, but is not limited to, used for controlling the full width at half maximum of the resonance peak.

Alternatively, in this embodiment, the transmission region is formed by a waveguide of a meandering shape, which may be used, but not limited to, for controlling the resonance frequency.

In one exemplary embodiment, the length parameter of the annular waveguide may be determined from the target frequency component by, but is not limited to: acquiring a dispersion frequency shift range of a signal converter, wherein the signal converter is used for converting charge tunneling events in the quantum dot device into dispersion frequency shift of signals; selecting the target frequency component from the dispersion frequency shift range according to the material property of the micro-ring resonator as the resonant frequency of the micro-ring resonator, wherein the full width at half maximum of the micro-ring resonator with the resonant frequency is smaller than the bandwidth of the signal converter; calculating the waveguide length of the annular waveguide according to the target frequency component; determining the radius of a semi-annular waveguide, the radius of an annular section, the length of a straight line section and the number of winding cycles as the length parameters according to the waveguide length and the deployment information of the micro-ring resonator; the first transmission waveguide and the second transmission waveguide are both waveguides with a winding shape, the first transmission waveguide comprises a first number of first winding cycles which are connected in sequence, the second transmission waveguide comprises a second number of second winding cycles which are connected in sequence, the first number is the same as or different from the second number, the first winding cycle comprises a first partial ring section, a first straight line section, a first semi-ring section, a second straight line section and a second partial ring section which are connected in sequence, and the second winding cycle comprises a third partial ring section, a third straight line section, a second semi-ring section, a fourth straight line section and a fourth partial ring section which are connected in sequence; wherein the radius of the semi-circular waveguide is the radius of the first semi-circular waveguide and the second semi-circular waveguide, the radius of the circular segment is the radius of the first partial circular segment, the radius of the second partial circular segment, the radius of the third partial circular segment, the radius of the fourth partial circular segment, the radius of the first semi-circular segment and the radius of the second semi-circular segment, the length of the straight segment is the length of the first straight segment, the length of the second straight segment, the length of the third straight segment and the length of the fourth straight segment, and the number of winding cycles is the sum of the first number and the second number.

Optionally, in this embodiment, the signal converter is configured to convert a charge tunneling event in the quantum dot device into a dispersive frequency shift of the signal. The signal converter may be, but is not limited to, a GR or an LC resonator equivalent to GR.

Optionally, in this embodiment, the dispersion frequency shift range of the signal converter may be determined according to different tunneling states, such as: in order to distinguish different tunneling states in actual measurement, the sweep frequency microwave is fixed

Time integration is performed on the dispersion frequency shift during the occurrence of the tunneling event to obtain the phase response:

wherein

Is the quality factor of the LC resonator. Obtaining additional quantum capacitance from phase response

The range of dispersion shifts can be obtained in reverse.

In an alternative embodiment, a method is provided for obtaining a dispersion shift range of a signal converter without interpoint charge tunneling

Refers to the plunger gate parasitic capacitance defining the auxiliary quantum dots

The natural resonant frequency of the LC resonator is then:

wherein,

is the inductance of the patch inductor.

Causing additional quantum capacitance associated with charge transitions when charge tunneling between dots occurs

The capacitor C comprises a parasitic capacitor

And quantum capacitor

The resonant frequency of the LC resonator becomes:

the LC resonance frequency can be seen to undergo a dispersive frequency shift. Once the tunneling event is complete, the resonant frequency of the LC resonator returns to the natural resonant frequency for a duration determined by the charge mobility and the effective noise temperature, typically on the order of ms (millisec). In order to distinguish different tunneling states in actual measurement, the sweep frequency microwave is fixed

。

Optionally, in this embodiment, the resonant frequency of the micro-ring resonator may be, but is not limited to, within a dispersion frequency shift range of the signal converter, such as: the dispersion frequency shift range of the signal converter is

For example, the resonant frequency of the micro-ring resonator is at the dispersive frequency shift of the LC resonator

Within the range.

Optionally, in this embodiment, the full width at half maximum of the micro-ring resonator may be, but is not limited to, smaller than the bandwidth of the signal converter.

In an alternative embodiment, a method for obtaining the full width at half maximum of a micro-ring resonator is provided, where the full width at half maximum of the micro-ring resonator without dispersion is:

wherein alpha is the amplitude loss factor of a microwave signal transmitted along the annular waveguide for one circle,

the transmission coefficients of the first and second coupling regions respectively,

which represents the effective refractive index of the light,

is the total length of the annular waveguide, m represents the number of resonant stages,

the resonant wavelength corresponding to the order, i.e., the frequency corresponding to the resonant wavelength, is the resonant frequency.

Optionally, in this embodiment, the waveguide length of the annular waveguide may be calculated according to the target frequency component, such as: if the optical path difference of a certain wavelength component of the microwave signal transmitted in the ring waveguide for one circle is an integral multiple of the wavelength, that is

（

is the resonant wavelength corresponding to the order, and the frequency corresponding to the resonant wavelength is called the resonant frequency).

The relation between the resonance frequency of the mth resonance series and the total length of the annular waveguide is as follows:

where c represents the speed of light.

Optionally, in this embodiment, the lengths of the parts of the signal converter may be determined according to, but not limited to, the resonance frequency of the signal splitter, such as: assuming that the resonant frequency of the LC resonator (i.e., the signal converter) is fixed, the resonant frequency of the micro-ring resonator (i.e., the signal splitter) is selected to be within the dispersion frequency shift range of the LC resonator (typically larger than the order of kHz), and the total length of the combination "half-ring waveguide + meandering waveguide" is determined (the number of resonant stages may be 1, when the total length is minimum). After the two semicircular waveguide lengths are removed, the remaining lengths are equally distributed to the first transmission region and the second transmission region.

In an alternative embodiment, a determination process of the length parameter is provided, with the circuit parameter of GR: chip inductor inductance L =400nH, parasitic capacitance

=890fF, resulting in a resonance frequency of the LC resonator

=266.744MHz, quality factor Q =38; observed phase response Δ Φ =2.2mrad, calculated to give additional quantum capacitance

= 0.016fF, the dispersion shift can be estimated

Approximately 266.747MHz, i.e. 3kHz offset to the high frequency, for example:

assuming that the cladding and core materials are silicon dioxide and silicon nitride, respectively, the refractive indices are n (silicon dioxide) =1.5 and n (silicon nitride) =2.5, respectively, due to the effective refractive indices

Varies with frequency, and is fixed here

≈2。

Selecting resonant frequencies of micro-ring resonators

=266.746MHz, assuming an amplitude loss factor α =

Coefficient of transmission

Full width at half maximum

And the design requirements are met.

According to the resonant frequency

The total length L =397.629mm for the "half-ring waveguide + meandered waveguide" combination is calculated. To arrange the combination on a 2cm x 2cm chip, the coupling region radius r1=0.01mm for a half-circular waveguide, r2=0.4mm for a circular segment in a meandering waveguide, s2=7.779mm for a straight segment length, 22 cycles of the meandering, and an overall occupied area of 1.809cm x 1.762cm can be taken. The peripheral remaining chip area may be used to distribute two straight waveguides as well as ports.

Through the above description of the embodiments, those skilled in the art can clearly understand that the method according to the above embodiments can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware, but the former is a better implementation mode in many cases. Based on such understanding, the technical solutions of the present application may be embodied in the form of a software product, which is stored in a storage medium (e.g., ROM/RAM, magnetic disk, optical disk) and includes instructions for enabling a terminal device (e.g., a mobile phone, a computer, a server, or a network device) to execute the method according to the embodiments of the present application.

In this embodiment, a device for measuring a quantum bit state is further provided, and the device is used to implement the foregoing embodiments and preferred embodiments, and details of which have been already described are not repeated. As used below, the term "module" may be a combination of software and/or hardware that implements a predetermined function. Although the means described in the embodiments below are preferably implemented in software, an implementation in hardware, or a combination of software and hardware is also possible and contemplated.

Fig. 12 is a block diagram of a qubit state measurement device according to an embodiment of the application, the device comprising, as shown in fig. 12:

an input module 1202, configured to convert the initial frequency sweep signal into an initial resonance signal and input the initial resonance signal to the quantum dot device to be measured;

an obtaining module 1204, configured to obtain a target resonance signal returned by the quantum dot device;

a separating module 1206, configured to separate a target signal of a target frequency component from the target resonance signal, wherein the target frequency component is a frequency associated with a charge tunneling event in the quantum dot device;

a detecting module 1208, configured to detect a chromatic dispersion shift of the target signal, where the chromatic dispersion shift of the separated signal indicates that the charge tunneling event occurs in the quantum dot device, and the charge tunneling event is used to characterize a silicon-based spin quantum bit state in the quantum dot device.

By the device, the initial sweep frequency signal is converted into the initial resonance signal and is input to the quantum dot device, the target resonance signal returned by the quantum dot device is obtained, and then the target signal of the target frequency component is separated from the target resonance signal, and the dispersion frequency shift detection is performed on the target signal of the target frequency component, wherein the target frequency component is the frequency associated with the charge tunneling event in the quantum dot device, which is equivalent to filtering the influence of the noise part in the target resonance signal on the detection result, and only the dispersion frequency shift generated on the target signal of the frequency part associated with the charge tunneling event in the quantum dot device is detected, so that the silicon-based spin quantum bit state in the quantum dot device is more accurately detected. Therefore, the problem of low accuracy of measuring the state of the silicon-based spin qubit in a dispersion readout mode can be solved, and the effect of improving the accuracy of measuring the state of the silicon-based spin qubit in the dispersion readout mode can be achieved.

In an exemplary embodiment, the separation module includes:

an extraction unit, configured to extract a signal of a target frequency component from the target resonance signal to obtain a reference signal;

and the enhancement unit is used for carrying out signal enhancement on the reference signal to obtain the target signal.

In an exemplary embodiment, the separation module is configured to:

In one exemplary embodiment, the apparatus further comprises:

a determining module, configured to determine a length parameter of the annular waveguide according to the target frequency component, where the annular waveguide includes: the waveguide coupler comprises a first semi-annular waveguide, a second semi-annular waveguide, a first transmission waveguide and a second transmission waveguide, wherein the first semi-annular waveguide is embedded into a first straight waveguide to form a first coupling area, the second semi-annular waveguide is embedded into a second straight waveguide to form a second coupling area, the first transmission waveguide is connected between the first semi-annular waveguide and the second semi-annular waveguide to form a first transmission area, and the second transmission waveguide is connected between the second semi-annular waveguide and the first semi-annular waveguide to form a second transmission area.

In an exemplary embodiment, the determining module includes:

an obtaining unit, configured to obtain a dispersion frequency shift range of a signal converter, where the signal converter is configured to convert a charge tunneling event in the quantum dot device into a dispersion frequency shift of a signal;

a selecting unit, configured to select the target frequency component from the dispersion frequency shift range according to a material property of the micro-ring resonator, as a resonant frequency of the micro-ring resonator, where a full width at half maximum of the micro-ring resonator having the resonant frequency is smaller than a bandwidth of the signal converter;

a calculation unit configured to calculate a waveguide length of the annular waveguide according to the target frequency component;

the determining unit is used for determining the radius of a semi-annular waveguide, the radius of an annular section, the length of a straight line section and the number of winding cycles as the length parameters according to the waveguide length and the deployment information of the micro-ring resonator; wherein the first transmission waveguide and the second transmission waveguide are both waveguides having a meandering shape, the first transmission waveguide includes a first number of first meandering periods connected in sequence, the second transmission waveguide includes a second number of second meandering periods connected in sequence, the first number is the same as or different from the second number, the first meandering period includes a first ring segment, a first straight line segment, and a second ring segment connected in sequence, the first ring segment and the second ring segment have an opposite annular orientation, the second meandering period includes a third ring segment, a second straight line segment, and a fourth ring segment connected in sequence, and the third ring segment and the fourth ring segment have an opposite annular orientation; wherein the radius of the semi-circular waveguide is the radius of the first semi-circular waveguide and the second semi-circular waveguide, the radius of the circular segment is the radius of the first circular segment, the radius of the second circular segment, the radius of the third circular segment and the radius of the fourth circular segment, the length of the straight line segment is the length of the first straight line segment and the second straight line segment, and the number of winding cycles is the sum of the first number and the second number.

It should be noted that, the above modules may be implemented by software or hardware, and for the latter, the following may be implemented, but not limited to: the modules are all positioned in the same processor; alternatively, the modules are respectively located in different processors in any combination.

Embodiments of the present application further provide a computer-readable storage medium having a computer program stored therein, wherein the computer program is configured to perform the steps in any of the above method embodiments when executed.

In an exemplary embodiment, the computer-readable storage medium may include, but is not limited to: various media capable of storing computer programs, such as a usb disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a removable hard disk, a magnetic disk, or an optical disk.

Embodiments of the present application further provide an electronic device comprising a memory having a computer program stored therein and a processor configured to execute the computer program to perform the steps in any of the above method embodiments.

In an exemplary embodiment, the electronic device may further include a transmission device and an input/output device, wherein the transmission device is connected to the processor, and the input/output device is connected to the processor.

For specific examples in this embodiment, reference may be made to the examples described in the above embodiments and exemplary embodiments, and details of this embodiment are not repeated herein.

It will be apparent to those skilled in the art that the various modules or steps of the present application described above may be implemented using a general purpose computing device, they may be centralized on a single computing device or distributed across a network of multiple computing devices, and they may be implemented using program code executable by the computing devices, such that they may be stored in a memory device and executed by the computing devices, and in some cases, the steps shown or described may be performed in an order different than that described herein, or they may be separately fabricated into separate integrated circuit modules, or multiple ones of them may be fabricated into a single integrated circuit module. Thus, the present application is not limited to any specific combination of hardware and software.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the principle of the present application shall be included in the protection scope of the present application.

Claims

1. A signal splitter, comprising: a first straight waveguide, a second straight waveguide and a ring waveguide,

the annular waveguide includes: the waveguide comprises a first semi-annular waveguide, a second semi-annular waveguide, a first transmission waveguide and a second transmission waveguide, wherein the first semi-annular waveguide is embedded in the first straight waveguide to form a first coupling region, the second semi-annular waveguide is embedded in the second straight waveguide to form a second coupling region, the first transmission waveguide is connected between the first semi-annular waveguide and the second semi-annular waveguide to form a first transmission region, the second transmission waveguide is connected between the second semi-annular waveguide and the first semi-annular waveguide to form a second transmission region, and the first transmission waveguide and the second transmission waveguide are both waveguides with winding shapes;

2. Signal splitter according to claim 1,

the first number may be the same as or different from the second number.

3. The signal splitter of claim 2, wherein the first number is the same as the second number, wherein the radii of the first and second semi-toroidal waveguides are the same, wherein the radii of the first, second, third, fourth partial toroidal segments are the same, wherein the radii of the first, second, third, and fourth partial toroidal segments are the same, and wherein the lengths of the first, second, third, and fourth linear segments are the same.

4. A system for measuring the state of a qubit, comprising: a signal source, a signal converter, a signal separator and a detector, wherein,

the detector is configured to detect a chromatic dispersion frequency shift of the target signal, where the chromatic dispersion frequency shift of the signal output by the signal converter indicates that the charge tunneling event occurs in the quantum dot device, and the charge tunneling event is used to characterize a silicon-based spin quantum bit state in the quantum dot device;

wherein the signal separator includes: a microring resonator, wherein the microring resonator comprises: a first straight waveguide, a second straight waveguide and a ring waveguide,

5. The system of claim 4, wherein the resonant frequency of the microring resonator is within a dispersive frequency shift range of the signal converter and a full width half maximum of the microring resonator is less than a bandwidth of the signal converter.

6. The system of claim 4, wherein the annular waveguide comprises: a first semi-annular waveguide, a second semi-annular waveguide, a first transmission waveguide, and a second transmission waveguide, wherein,

the first semi-ring waveguide is embedded in the first straight waveguide to form a first coupling area, the second semi-ring waveguide is embedded in the second straight waveguide to form a second coupling area, the first transmission waveguide is connected between the first semi-ring waveguide and the second semi-ring waveguide to form a first transmission area, and the second transmission waveguide is connected between the second semi-ring waveguide and the first semi-ring waveguide to form a second transmission area;

7. The system of claim 6, wherein the first transmission waveguide and the second transmission waveguide are each a serpentine-shaped waveguide, wherein,

the first transmission waveguide includes a first number of first meandering periods connected in series;

the first number is the same as or different from the second number.

8. The system of claim 7, wherein the first serpentine period comprises a first partial loop segment, a first straight segment, a first semi-loop segment, a second straight segment, and a second partial loop segment connected in series;

9. The system of claim 8, wherein the first number is the same as the second number, wherein the first and second semi-toroidal waveguides have the same radius, wherein the first, second, third, fourth, first, second, third, and fourth semi-toroidal segments have the same radius, and wherein the first, second, third, and fourth linear segments have the same length.

10. The system of claim 4, wherein the detector comprises: an amplifier and an IQ mixer, wherein,

the amplifier is connected between the signal separator and the IQ mixer;

11. The system of claim 4, wherein the signal converter comprises: a gate reflectometer, or, equivalently, an LC resonator.

12. A method for measuring a qubit state, the method being applied to the qubit state measurement system of any one of claims 4 to 11, the method comprising:

acquiring a target resonance signal returned by the quantum dot device;

separating a target signal of a target frequency component from the target resonance signal, wherein the target frequency component is a frequency associated with a charge-tunneling event within the quantum dot device;

13. The method of claim 12, wherein said separating the target signal of the target frequency component from the target resonance signal comprises:

14. The method of claim 12, wherein said separating the target signal of the target frequency component from the target resonance signal comprises:

15. The method of claim 14, wherein before the separating the target signal of the target frequency component from the target resonance signal by the microring resonator, the method further comprises:

determining a length parameter of the annular waveguide according to the target frequency component, wherein the annular waveguide comprises: the waveguide coupler comprises a first semi-annular waveguide, a second semi-annular waveguide, a first transmission waveguide and a second transmission waveguide, wherein the first semi-annular waveguide is embedded into a first straight waveguide to form a first coupling area, the second semi-annular waveguide is embedded into a second straight waveguide to form a second coupling area, the first transmission waveguide is connected between the first semi-annular waveguide and the second semi-annular waveguide to form a first transmission area, and the second transmission waveguide is connected between the second semi-annular waveguide and the first semi-annular waveguide to form a second transmission area.

16. The method of claim 15, wherein said determining a length parameter of the annular waveguide from the target frequency component comprises:

17. An apparatus for measuring a qubit state, comprising:

a detection module, configured to detect a chromatic dispersion frequency shift occurring in the target signal, where the chromatic dispersion frequency shift occurring in the separated signal indicates that the charge tunneling event occurs in the quantum dot device, and the charge tunneling event is used to characterize a silicon-based spin qubit state in the quantum dot device;

wherein the separation module is configured to: separating the target signal of the target frequency component from the target resonance signal by a microring resonator, wherein the microring resonator includes: the micro-ring resonator comprises a first straight waveguide, a second straight waveguide and a ring waveguide, wherein the first straight waveguide is connected with the second straight waveguide through the ring waveguide, an input port of the first straight waveguide is used for inputting the target resonance signal, an output port of the second straight waveguide is used for outputting the target signal meeting the resonance condition of the micro-ring resonator, and the resonance condition is the target frequency component.

18. A computer-readable storage medium, in which a computer program is stored, which computer program, when being executed by a processor, carries out the steps of the method according to any one of claims 12 to 16.

19. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the steps of the method as claimed in any of claims 12 to 16 are implemented by the processor when executing the computer program.