A high-precision measurement system for high-frequency weak quantum signals

Abstract

The application relates to a high-precision measurement system for high-frequency weak quantum signals, which comprises a microwave signal source, a first power divider, a normal-temperature attenuator set, a first normal-temperature amplifier, a second power divider, a first frequency mixer, a second frequency mixer, a low-temperature attenuator set, a first low-temperature amplifier, a second low-temperature amplifier, a second normal-temperature amplifier, a third normal-temperature amplifier, a 90-degree hybrid coupler and a cold disc set. The high-precision measurement system for high-frequency weak quantum signals provided by the application adopts low-temperature attenuation, low-temperature amplification and normal-temperature amplification and the like, can suppress thermal noise signals and enhance response signals, and greatly improves the accuracy of quantum device measurement.

Description

Technical Field

[0001] This invention relates to the field of quantum signal measurement, and more specifically to a high-precision measurement system for high-frequency weak quantum signals. Background Technology

[0002] Currently, the measurement of quantum circuits and quantum devices relies on high-frequency weak excitation signals, and the signals are transmitted using standard coaxial microwave half-steel wires.

[0003] In quantum precision measurement experiments, the response signal generated by the excitation signal after passing through the quantum device is extremely weak, making it difficult to measure accurately. Furthermore, at room temperature without any treatment, the interference caused by thermal radiation on the coaxial microwave semi-steel wire can reach approximately 90 μV, far exceeding the nV level of the signal to be measured. Moreover, voltage noise caused by thermal radiation can also enter the device's junction along the coaxial microwave semi-steel wire, significantly interfering with excitation and measurement. Therefore, the voltage fluctuation equivalent to thermal noise is much larger than that of the signal to be measured, making accurate measurement impossible. Thus, a solution is needed to suppress thermal noise and amplify the signal to be measured. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0005] A high-precision measurement system for high-frequency weak quantum signals includes:

[0006] A microwave signal source, wherein the microwave signal source is used to emit microwave signals;

[0007] The first power divider is electrically connected to the microwave signal source at its input terminal. The first power divider is used to split the microwave signal emitted by the microwave signal source into two paths.

[0008] A room temperature attenuator group, wherein the input terminal of the room temperature attenuator group is electrically connected to one output terminal of the first power divider;

[0009] A first ambient temperature amplifier, the input terminal of which is electrically connected to the output terminal of the ambient temperature attenuator group;

[0010] The second power divider is electrically connected to the output of the first ambient temperature amplifier.

[0011] A first mixer and a second mixer, wherein the local oscillator terminals of the first mixer and the second mixer are respectively electrically connected to the two output terminals of the second power divider;

[0012] A low-temperature attenuator group, the input of which is electrically connected to another output of the first power divider, and the output of which is used to electrically connect to a quantum device.

[0013] A first cryogenic amplifier, the input of which is used to electrically connect to the quantum device;

[0014] A second cryogenic amplifier, the input terminal of which is electrically connected to the output terminal of the first cryogenic amplifier;

[0015] The second ambient temperature amplifier has its input terminal electrically connected to the output terminal of the second cryogenic amplifier.

[0016] A third ambient temperature amplifier, wherein the input terminal of the third ambient temperature amplifier is electrically connected to the output terminal of the second ambient temperature amplifier;

[0017] A 90-degree hybrid coupler, wherein the input terminal of the 90-degree hybrid coupler is electrically connected to the output terminal of the third ambient temperature amplifier, and the two output terminals of the 90-degree hybrid coupler are respectively electrically connected to the RF terminal of the first mixer and the RF terminal of the second mixer;

[0018] The cold plate assembly is equipped with the low-temperature attenuator assembly, the first low-temperature amplifier, and the second low-temperature amplifier.

[0019] Preferably, the cold plate group includes five layers of cold plates arranged in parallel at intervals, with the temperature of the cold plates decreasing sequentially from top to bottom.

[0020] Preferably, the temperatures of the five cold plates, from top to bottom, are 77K, 4K, 1K, 0.1K, and 0.01K, respectively.

[0021] Preferably, the high-precision measurement system for high-frequency weak quantum signals further includes:

[0022] A low-temperature anti-interference attenuator is connected in series between the first low-temperature amplifier and the second low-temperature amplifier to isolate the reflected signal between the first low-temperature amplifier and the second low-temperature amplifier.

[0023] Preferably, the high-precision measurement system for high-frequency weak quantum signals further includes:

[0024] A cryogenic isolator is connected in series between the first cryogenic amplifier and the quantum device to isolate reflected signals between the first cryogenic amplifier and the quantum device.

[0025] Preferably, the first low-temperature amplifier, the second low-temperature amplifier, and the low-temperature anti-interference attenuator are disposed on the second layer of cold plates from top to bottom in the cold plate group, and the low-temperature isolator is disposed on the fourth layer of cold plates from top to bottom in the cold plate group.

[0026] Preferably, the low-temperature attenuator group includes five low-temperature attenuators connected in series, and the five low-temperature attenuators are respectively disposed on the five layers of the cold plate. The attenuation values ​​of the five low-temperature attenuators from the upper layer to the lower layer are -10dB, -20dB, -20dB, -6dB, and -3dB, respectively.

[0027] Preferably, the high-precision measurement system for high-frequency weak quantum signals further includes:

[0028] A first adjustable phase shifter is connected in series between the first power divider and the ambient temperature attenuator group;

[0029] A second adjustable phase shifter is connected in series between the first mixer and the 90-degree hybrid coupler;

[0030] A third adjustable phase shifter is connected in series between the second mixer and the 90-degree mixing coupler.

[0031] Preferably, the high-precision measurement system for high-frequency weak quantum signals further includes:

[0032] A first bandpass filter is connected in series between the second cryogenic amplifier and the second ambient temperature amplifier.

[0033] A second bandpass filter is connected in series between the second ambient temperature amplifier and the third ambient temperature amplifier.

[0034] Preferably, the low-temperature attenuator group, the first low-temperature amplifier, and the second low-temperature amplifier are respectively connected to the cold plate via gold-plated copper sheets.

[0035] The present invention has at least the following beneficial effects:

[0036] The high-precision measurement system for high-frequency weak quantum signals provided in this embodiment adopts measures such as low-temperature attenuation, low-temperature amplification, and room-temperature amplification, which not only suppresses thermal noise signals but also enhances response signals, greatly improving the accuracy of quantum device measurements.

[0037] A low-temperature anti-interference attenuator is connected in series between the first and second low-temperature amplifiers, which can effectively reduce the interference caused by reflected signals.

[0038] A cryogenic isolator is installed between the first cryogenic amplifiers, allowing only high-frequency signals to conduct unidirectionally, thereby effectively suppressing reflected signals from entering the quantum device.

[0039] The input of the first power divider is also connected in series with a first adjustable phase shifter, allowing the measurement personnel to adjust the phase of the reference signal as needed. The two outputs of the 90-degree hybrid coupler are respectively equipped with a second and a third adjustable phase shifter, which can precisely adjust the phase of the two signals according to different conditions, thereby ensuring the orthogonality of the two signals.

[0040] The first and second bandpass filters can filter the response signal after low-temperature amplification, filtering out unwanted frequency components and further improving measurement accuracy.

[0041] Gold-plated copper sheets ensure full thermal contact with the cold plate, improving cooling efficiency. Attached Figure Description

[0042] Figure 1 This is a circuit diagram of a high-precision measurement system for high-frequency weak quantum signals according to an embodiment of the present invention;

[0043] Figure 2 for Figure 1 The low-temperature circuit diagram for section a;

[0044] Figure 3 The changes in the real and imaginary parts of the response signal measured by a high-precision measurement system for high-frequency weak quantum signals under different phases;

[0045] Figure 4 Nyquist curves of response signals measured by a high-precision measurement system for weak high-frequency quantum signals at different phases;

[0046] Figure 5 The amplitude ratio of the reference signal to the response signal in a high-precision measurement system for high-frequency weak quantum signals under different gate voltages;

[0047] Figure 6 The orthogonality phase difference between the reference signal and the response signal in a high-precision measurement system for high-frequency weak quantum signals under different gate voltages;

[0048] Figure reference numerals: 1. Microwave signal source; 2. First power divider; 3. Second power divider; 4. Room temperature attenuator group; 5. First room temperature amplifier; 6. Second room temperature amplifier; 7. Third room temperature amplifier; 8. First mixer; 9. Second mixer; 10. Low temperature attenuator group; 11. First low temperature amplifier; 12. Second low temperature amplifier; 13. 90-degree hybrid coupler; 14. Cold plate group; 15. Quantum device; 16. Low temperature anti-interference attenuator; 17. Low temperature isolator; 18. First adjustable phase shifter; 19. Second adjustable phase shifter; 20. Third adjustable phase shifter; 21. First bandpass filter; 22. Second bandpass filter. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0050] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "connected" or "linked" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up," "down," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship also changes accordingly.

[0051] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0052] like Figure 1-2As shown, an embodiment of the present invention provides a high-precision measurement system for high-frequency weak quantum signals, including a microwave signal source 1, a first power divider 2, a second power divider 3, a room temperature attenuator group 4, a first room temperature amplifier 5, a second room temperature amplifier 6, a third room temperature amplifier 7, a first mixer 8, a second mixer 9, a low temperature attenuator group 10, a first low temperature amplifier 11, a second low temperature amplifier 12, a 90-degree hybrid coupler 13, and a cold plate group 14. Microwave signal source 1 is used to emit microwave signals; the input terminal of the first power divider 2 is electrically connected to the microwave signal source 1, and the first power divider 2 is used to split the microwave signal emitted by the microwave signal source 1 into two paths; the input terminal of the room temperature attenuator group 4 is electrically connected to one output terminal of the first power divider 2; the input terminal of the first room temperature amplifier 5 is electrically connected to the output terminal of the room temperature attenuator group 4; the input terminal of the second power divider 3 is electrically connected to the output terminal of the first room temperature amplifier 5; the local oscillator terminals of the first mixer 8 and the second mixer 9 are respectively electrically connected to the two output terminals of the second power divider 3; the input terminal of the low temperature attenuator group 10 is electrically connected to the other output terminal of the first power divider 2, and the output terminal of the low temperature attenuator group 10 is used to electrically connect to the output terminal of the first power divider 2. The quantum device 15 is included; the input terminal of the first cryogenic amplifier 11 is electrically connected to the quantum device 15; the input terminal of the second cryogenic amplifier 12 is electrically connected to the output terminal of the first cryogenic amplifier 11; the input terminal of the second ambient temperature amplifier 6 is electrically connected to the output terminal of the second cryogenic amplifier 12; the input terminal of the third ambient temperature amplifier 7 is electrically connected to the output terminal of the second ambient temperature amplifier 6; the input terminal of the 90-degree hybrid coupler 13 is electrically connected to the output terminal of the third ambient temperature amplifier 7, and the two output terminals of the 90-degree hybrid coupler 13 are respectively electrically connected to the RF terminal of the first mixer 8 and the RF terminal of the second mixer 9; the cold plate assembly 14 is equipped with a cryogenic attenuator assembly 10, a first cryogenic amplifier 11, and a second cryogenic amplifier 12.

[0053] The high-precision measurement system for high-frequency weak quantum signals in this embodiment is a zero-beat detection system that measures the amplified signal. A microwave signal source 1 outputs a high-frequency microwave signal; this signal is split into two paths by a first power divider 2. One path serves as a reference signal, and the other as the excitation signal for the quantum device 15. The reference signal passes through a room-temperature attenuator group 4 and a first room-temperature amplifier 5. The room-temperature attenuator group 4 attenuates the thermal noise signal at room temperature, and the first room-temperature amplifier 5 amplifies the reference signal. The amplified reference signal then passes through a second power divider 3, which splits it into two paths. These two paths then enter the local oscillator terminals of the first mixer 8 and the second mixer 9, respectively. The excitation signal passes through the cryogenic attenuator group 10 and enters the quantum device 15, where the cryogenic attenuator group 10 attenuates the thermal noise signal on the line. After passing through the quantum device 15, the excitation signal generates a response signal, which is amplified by the first cryogenic amplifier 11 and the second cryogenic amplifier 12. The amplified response signal is further amplified by the second room temperature amplifier 6 and the third room temperature amplifier 7. Then, the response signal enters the input terminal of the 90-degree hybrid coupler 13, which splits the response signal into two paths with equal magnitude and a 90-degree phase difference. Finally, the two signals enter the RF terminals of the first mixer 8 and the second mixer 9, respectively, and are coupled with the reference signals of the two local oscillators. Synchronous correlation detection is achieved using the cross-correlation principle to extract the test signal with the same frequency as the reference signal. Among them, the microwave signal source 1 can be an Agilent 8648D with a frequency range of 9kHz-4000MHz; the first power divider 2 can be a Picosecond Pulse Labs model 5350 with an attenuation of -6dB and a frequency band of DC-40GHz; the first ambient temperature amplifier 5 can be a He250 with a gain of 42dB and a frequency band of 1GHz–4GHz; the first mixer 8 and the second mixer 9 can be Miteq DM0104L with a frequency band of 1GHz–4GHz; the second ambient temperature amplifier 6 can be an F497 with a gain of 30dB and a frequency band of 0.1GHz–6GHz; the third ambient temperature amplifier 7 can be a He200 with a gain of 42dB and a frequency band of 1GHz–4GHz; and the 90-degree hybrid coupler 13 can be an RF-LAMBDA RFHB01G02GVT with a frequency band of 1GHz–2GHz and an attenuation of -6dB.

[0054] This system employs a cold plate assembly 14, on which the circuitry directly connected to the quantum device 15 is mounted. The cold plate assembly 14 provides an ultra-low temperature environment for the circuitry, thereby suppressing voltage noise caused by thermal radiation. To further enhance the suppression of thermal noise, a low-temperature attenuator assembly 10 is also connected in series in the circuitry. The low-temperature attenuator assembly 10 effectively attenuates thermal noise signals.

[0055] The excitation signal is typically set relatively large to ensure that the signal entering the quantum device 15 after a series of attenuations meets the requirements of linear response. After passing through the quantum device 15, the excitation signal will be further attenuated, typically by about -60dB. Therefore, the equivalent voltage of the response signal will reach the nanovolt level. If the response signal at this point directly enters the room temperature circuit, it will be completely masked by thermal noise and cannot be effectively measured. Therefore, the response signal must be amplified at low temperature. In this system, a first low-temperature amplifier 11 and a second low-temperature amplifier 12 are connected in series at the output of the quantum device 15, with a gain of about 35dB. The thermal noise signal at room temperature is negligible compared to the response signal after low-temperature amplification. Therefore, after the response signal enters the low-temperature circuit, a second room-temperature amplifier 6 and a third room-temperature amplifier 7 can be added to further amplify it. At this point, although the thermal noise signal will be amplified, it will have little impact on the response signal.

[0056] The high-precision measurement system for high-frequency weak quantum signals provided in this embodiment adopts measures such as low-temperature attenuation, low-temperature amplification, and room-temperature amplification, which not only suppresses thermal noise signals but also enhances response signals, greatly improving the measurement accuracy of quantum device 15.

[0057] In this embodiment, the cold plate group 14 includes five layers of cold plates arranged in parallel and spaced apart, with the temperature of the cold plates decreasing sequentially from top to bottom. The temperatures of the five cold plates can be set from top to bottom to 77K, 4K, 1K, 0.1K, and 0.01K.

[0058] In this embodiment, the high-precision measurement system for high-frequency weak quantum signals also includes a low-temperature anti-interference attenuator 16. The low-temperature anti-interference attenuator 16 is connected in series between the first low-temperature amplifier 11 and the second low-temperature amplifier 12 to isolate the reflected signal between the first low-temperature amplifier 11 and the second low-temperature amplifier 12.

[0059] Impedance mismatch may occur between the first cryogenic amplifier 11 and the second cryogenic amplifier 12. In this case, reflected signals will appear between the first cryogenic amplifier 11 and the second cryogenic amplifier 12, thus interfering with the amplification effect of the response signal. Connecting a cryogenic anti-interference attenuator 16 in series between the two can effectively reduce the interference caused by the reflected signals.

[0060] In this embodiment, the high-precision measurement system for high-frequency weak quantum signals also includes a cryogenic isolator 17. The cryogenic isolator 17 is connected in series between the first cryogenic amplifier 11 and the quantum device 15 to isolate the reflected signal between the first cryogenic amplifier 11 and the quantum device 15.

[0061] Reflected signals may occur between the first cryogenic amplifier 11 and the second cryogenic amplifier 12 and may also enter the quantum device 15. The cryogenic isolator 17 only allows high-frequency signals to conduct unidirectionally, thereby effectively suppressing reflected signals from entering the quantum device 15.

[0062] In this embodiment, the first low-temperature amplifier 11, the second low-temperature amplifier 12, and the low-temperature anti-interference attenuator 16 are disposed on the second layer of cold plates from top to bottom in the cold plate group 14, and the low-temperature isolator 17 is disposed on the fourth layer of cold plates from top to bottom in the cold plate group 14.

[0063] In this embodiment, the low-temperature attenuator group 10 includes five low-temperature attenuators connected in series. The five low-temperature attenuators are respectively disposed on five layers of cold plates, and the attenuation values ​​of the five low-temperature attenuators from the top layer to the bottom layer are -10dB, -20dB, -20dB, -6dB, and -3dB, respectively. Each attenuator uses a copper sheet as a heat sink to make sufficient thermal contact with the cold plate it is on, effectively achieving attenuation of temperature-induced noise signals.

[0064] In this embodiment, the high-precision measurement system for high-frequency weak quantum signals further includes a first adjustable phase shifter 18, a second adjustable phase shifter 19, and a third adjustable phase shifter 20. The first adjustable phase shifter 18 is connected in series between the first power divider 2 and the room-temperature attenuator group 4; the second adjustable phase shifter 19 is connected in series between the first mixer 8 and the 90-degree hybrid coupler 13; and the third adjustable phase shifter 20 is connected in series between the second mixer 9 and the 90-degree hybrid coupler 13.

[0065] The zero-beat detection system requires that the response signals entering the first mixer 8 and the second mixer 9 be 90 degrees out of phase and have the same amplitude. To achieve this, the line lengths and attenuation values ​​from the two outputs of the 90-degree hybrid coupler 13 to the two mixers must be identical. To ensure this requirement is met under various conditions, the system incorporates a second adjustable phase shifter 19 and a third adjustable phase shifter 20 at the two outputs of the 90-degree hybrid coupler 13, respectively, allowing for precise phase adjustment. Fine-tuning of the phases of the two signals under different conditions ensures their orthogonality. Additionally, a first adjustable phase shifter 18 is connected in series at the input of the first power divider 2, allowing the measurement operator to adjust the phase of the reference signal as needed. The first adjustable phase shifter 18, the second adjustable phase shifter 19, and the third adjustable phase shifter 20 can be of model SMP2018C, with a bandwidth of DC–18GHz.

[0066] In this embodiment, the high-precision measurement system for high-frequency weak quantum signals further includes a first bandpass filter 21 and a second bandpass filter 22. The first bandpass filter 21 is connected in series between the second cryogenic amplifier 12 and the second ambient temperature amplifier 6; the second bandpass filter 22 is connected in series between the second ambient temperature amplifier 6 and the third ambient temperature amplifier 7. The first bandpass filter 21 and the second bandpass filter 22 can filter the response signal after cryogenic amplification, filtering out unwanted frequency components and further improving measurement accuracy. The first bandpass filter 21 and the second bandpass filter 22 can be selected from the Mini-circuits ZX75BP-1500+, with a frequency band of 1.35GHz–1.65GHz.

[0067] In this embodiment, the low-temperature attenuator assembly 10, the first low-temperature amplifier 11, and the second low-temperature amplifier 12 are connected to the cold plate via gold-plated copper sheets. The gold-plated copper sheets ensure sufficient thermal contact with the cold plate, improving the cooling effect.

[0068] Figure 3-4 The figure shows the simple harmonic oscillation curves (a) and Nyquist plots (b) of the response signals X and Y obtained by fixing the gate voltage of a quantum device, continuously changing the phase of the local oscillator terminal, and thus changing the phase φI. Figure 3 The two signals are fitted with sine and cosine functions respectively to obtain specific amplitude and phase curves. Figure 4 The Nyquist plot is close to a circle, indicating that the orthogonality and amplitude of the two response signals are close to the theoretical case.

[0069] Figure 5-6 The amplitude ratio of the real part X to the imaginary part Y of the measured response signal under different gate voltages and the phase deviation from orthogonality are presented. It can be seen that throughout the entire gate voltage range, the amplitude ratio satisfies X / Y = 1.03 ± 0.025, and the difference in phase orthogonality is within ± 2 degrees. Therefore, this system can meet the requirements for high-frequency quantum transport measurement in nanocircuits.

[0070] The above embodiments are used to further illustrate the present invention, but do not limit the present invention to these specific embodiments. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be understood as falling within the protection scope of the present invention.

Claims

1. A high-precision measurement system for high-frequency weak quantum signals, characterized in that, include: A microwave signal source (1) is used to emit microwave signals; The first power divider (2) is electrically connected to the microwave signal source (1) at its input terminal. The first power divider (2) is used to split the microwave signal emitted by the microwave signal source (1) into two paths. A room temperature attenuator group (4) is provided, the input of which is electrically connected to one output of the first power divider (2). The first ambient temperature amplifier (5) is electrically connected to the output of the ambient temperature attenuator group (4). The second power divider (3) is electrically connected to the output of the first ambient temperature amplifier (5). The first mixer (8) and the second mixer (9) are electrically connected to the two output terminals of the second power divider (3), respectively. A low-temperature attenuator group (10) is provided, the input of which is electrically connected to the other output of the first power divider (2), and the output of which is electrically connected to the quantum device (15). A first cryogenic amplifier (11) is provided, the input of which is used to electrically connect to the quantum device (15); The second cryogenic amplifier (12) is electrically connected to the output of the first cryogenic amplifier (11). The second ambient temperature amplifier (6) is electrically connected to the output of the second low temperature amplifier (12). The third ambient temperature amplifier (7) is electrically connected to the output terminal of the second ambient temperature amplifier (6). A 90-degree hybrid coupler (13) is provided. The input terminal of the 90-degree hybrid coupler (13) is electrically connected to the output terminal of the third ambient temperature amplifier (7). The two output terminals of the 90-degree hybrid coupler (13) are electrically connected to the RF terminal of the first mixer (8) and the RF terminal of the second mixer (9), respectively. The cold plate assembly (14) is provided with the low temperature attenuator assembly (10), the first low temperature amplifier (11), and the second low temperature amplifier (12).

2. The high-precision measurement system for high-frequency weak quantum signals according to claim 1, characterized in that, The cold plate group (14) includes five layers of cold plates arranged in parallel and spaced apart, with the temperature of the cold plates decreasing sequentially from top to bottom.

3. The high-precision measurement system for high-frequency weak quantum signals according to claim 2, characterized in that, The temperatures of the five cold plates, from top to bottom, are 77K, 4K, 1K, 0.1K, and 0.01K, respectively.

4. The high-precision measurement system for high-frequency weak quantum signals according to claim 1 or 3, characterized in that, Also includes: A low-temperature anti-interference attenuator (16) is connected in series between the first low-temperature amplifier (11) and the second low-temperature amplifier (12) to isolate the reflected signal between the first low-temperature amplifier (11) and the second low-temperature amplifier (12).

5. The high-precision measurement system for high-frequency weak quantum signals according to claim 4, characterized in that, Also includes: A cryogenic isolator (17) is connected in series between the first cryogenic amplifier (11) and the quantum device (15) to isolate the reflected signal between the first cryogenic amplifier (11) and the quantum device (15).

6. The high-precision measurement system for high-frequency weak quantum signals according to claim 5, characterized in that, The first low-temperature amplifier (11), the second low-temperature amplifier (12), and the low-temperature anti-interference attenuator (16) are disposed on the second layer of cold plates from top to bottom of the cold plate group (14), and the low-temperature isolator (17) is disposed on the fourth layer of cold plates from top to bottom of the cold plate group (14).

7. The high-precision measurement system for high-frequency weak quantum signals according to claim 6, characterized in that, The low-temperature attenuator group (10) includes five low-temperature attenuators (10) connected in series. The five low-temperature attenuators (10) are respectively arranged on the five layers of the cold plate. The attenuation values ​​of the five low-temperature attenuators (10) from the upper layer to the lower layer are -10dB, -20dB, -20dB, -6dB and -3dB, respectively.

8. The high-precision measurement system for high-frequency weak quantum signals according to claim 1, characterized in that, Also includes: The first adjustable phase shifter (18) is connected in series between the first power divider (2) and the room temperature attenuator group (4); The second adjustable phase shifter (19) is connected in series between the first mixer (8) and the 90-degree hybrid coupler (13); The third adjustable phase shifter (20) is connected in series between the second mixer (9) and the 90-degree hybrid coupler (13).

9. The high-precision measurement system for high-frequency weak quantum signals according to claim 1, characterized in that, Also includes: A first bandpass filter (21) is connected in series between the second low-temperature amplifier (12) and the second room-temperature amplifier (6); The second bandpass filter (22) is connected in series between the second ambient temperature amplifier (6) and the third ambient temperature amplifier (7).

10. The high-precision measurement system for high-frequency weak quantum signals according to claim 1, characterized in that, The low-temperature attenuator group (10), the first low-temperature amplifier (11), and the second low-temperature amplifier (12) are respectively connected to the cold plate via gold-plated copper sheets.

Images