Noise measurement system and measurement method thereof

Abstract

The invention provides a noise measurement system and a measurement method thereof, the noise measurement system is used for quantum equipment, the quantum equipment comprises refrigeration equipment used for providing an extremely low temperature environment, and the quantum equipment comprises a plurality of superconducting quantum interference devices which are all located in the refrigeration equipment and used for detecting magnetic field signals in the extremely low temperature environment and converting the magnetic field signals into electric signals; the electric signal at least comprises an environment noise signal and an intrinsic magnetic field noise signal of the superconducting quantum interference device; the shielding device is positioned outside one superconducting quantum interference device and is used for shielding an environmental noise signal outside the superconducting quantum interference device; the controller is electrically connected with the superconducting quantum interference devices and used for receiving the electric signals and processing the electric signals so as to determine the environment noise of the refrigeration equipment and the intrinsic magnetic field noise of the superconducting quantum interference devices. By means of the system, accurate measurement of the environment noise and the intrinsic magnetic field noise in the extremely low temperature environment is achieved, and the influence of the environment noise and the intrinsic magnetic field noise on quantum equipment is reduced.

Description

Technical Field

[0001] The present disclosure relates to the field of quantum computing, and in particular to a noise measurement system and a measurement method thereof. Background Art

[0002] Superconducting quantum computing devices operate in extremely low-temperature environments. Superconducting quantum computing devices usually need to be maintained in an extremely low-temperature environment of the mK level to keep the quantum bits in a superconducting state. At the same time, the signals in superconducting quantum computing devices are easily interfered with by the external environment. For example, at extremely low temperatures, tiny magnetic field fluctuations may cause the state of the quantum bits to change dramatically. Therefore, high-precision magnetic field measurement equipment that can detect weak magnetic fields is required to non-destructively detect and adjust the external magnetic field so that the quantum bits can maintain their quantum state as much as possible. Existing magnetic field detection systems usually use induction coils as magnetic probes and use the Hall effect to detect low-temperature magnetic fields. Generally, the magnetic probe is installed on a special test sample rod. The sample rod is inserted into the interior of a low-temperature box, and the signal is read out at room temperature to detect the ambient magnetic field. However, this method cannot be used in the refrigeration equipment (such as a dilution refrigerator) of superconducting quantum computing devices, and the magnetic probe is large in size, resulting in low detection sensitivity.

[0003] Another existing solution is to use a low-temperature superconducting quantum interference device (SQUID) instead of a traditional induction coil as a magnetic probe for magnetic field measurement. However, while the SQUID can detect weak magnetic fields, it is currently mainly used in a high-temperature liquid nitrogen environment at 4.2K. In the extremely low-temperature mK environment of the refrigeration equipment of superconducting quantum computing devices, and when the test signal reaches GHz frequency, the intrinsic magnetic field noise of the detection device, the environmental noise, and the device design parameters will affect the accuracy of the test signal. Therefore, a detection system is urgently needed to detect weak magnetic field noise in extremely low-temperature environments. Summary of the Invention

[0004] The present disclosure provides a noise measurement system and a measurement method thereof, which can accurately measure the ambient noise and the intrinsic magnetic field noise of a superconducting quantum interference device in an extremely low temperature environment, thereby reducing the impact of the ambient noise and the intrinsic magnetic field noise on quantum devices.

[0005] In a first aspect, the present disclosure provides a noise measurement system for a quantum device, wherein the quantum device includes a refrigeration device for providing an extremely low temperature environment, including:

[0006] Multiple superconducting quantum interference devices (SQUIDs) are located within the refrigeration equipment and are used to detect magnetic field signals in an extremely low temperature environment and convert the magnetic field signals into electrical signals; the electrical signals include at least an environmental noise signal and an intrinsic magnetic field noise signal of the SQUIDs;

[0007] a shield, located outside one of the superconducting quantum interference devices, and used for shielding environmental noise signals outside the superconducting quantum interference device;

[0008] The controller is electrically connected to each superconducting quantum interference device and is used to receive an electrical signal and perform signal processing on the electrical signal to determine the environmental noise of the refrigeration equipment and the intrinsic magnetic field noise of the superconducting quantum interference device.

[0009] Optionally, the refrigeration device includes a dilution refrigerator, the dilution refrigerator includes multiple cold plates in different layers, at least two superconducting quantum interference devices are located on the cold plates in the same layer, and the shield is located outside one of the superconducting quantum interference devices in the same layer.

[0010] Optionally, the multiple superconducting quantum interference devices include a first superconducting quantum interference device, a second superconducting quantum interference device, a third superconducting quantum interference device, and a fourth superconducting quantum interference device, the first superconducting quantum interference device, the second superconducting quantum interference device, and the third superconducting quantum interference device are respectively located on cold disks on different layers, the fourth superconducting quantum interference device and the third superconducting quantum interference device are located on a cold disk on the same layer, and the shield is located outside the fourth superconducting quantum interference device;

[0011] The controller is used to receive a first electrical signal generated by the first superconducting quantum interference device, a second electrical signal generated by the second superconducting quantum interference device, a third electrical signal generated by the third superconducting quantum interference device, and a fourth electrical signal generated by the fourth superconducting quantum interference device, and average the first electrical signal, the second electrical signal, and the third electrical signal to determine the environmental noise signal; and determine the intrinsic magnetic field noise signal based on the third electrical signal and the fourth electrical signal.

[0012] Optionally, the system further comprises a flux locking structure;

[0013] The flux locking structure is electrically connected to the superconducting quantum interference device and is used to determine an error signal between the electrical signal and a preset signal, and when the error deviates from the preset error signal, feedback adjustment is performed on the electrical signal to lock the magnetic flux of the superconducting quantum interference device at a preset operating point.

[0014] Optionally, it further includes a base plate and a hanging structure; the superconducting quantum interference device includes a detection coil and a superconducting quantum interference device chip, the detection coil and the superconducting quantum interference device chip are connected by an aluminum wire and are located on the base plate; the base plate and the refrigeration equipment are fixedly connected by the hanging structure;

[0015] The bottom plate is used for fixing the superconducting quantum interference device and transferring heat to the superconducting quantum interference device.

[0016] Optionally, the superconducting quantum interference device chip includes a feedback coil, a superconducting loop and a Josephson junction;

[0017] The feedback coil and the detection coil are connected by aluminum wire, and the Josephson junction is located on the superconducting loop;

[0018] There is a preset spacing between the feedback coil and the superconducting loop to reduce electromagnetic interference.

[0019] Optionally, the superconducting quantum interference device also includes a magnetic shielding cover; the magnetic shielding cover is fixed above the side of the superconducting quantum interference device chip away from the base plate; small holes are provided on both sides of the magnetic shielding cover, the leads of the superconducting loop are electrically connected to the controller through the small holes, and the aluminum wire connects the detection coil to the superconducting quantum interference device chip through the small holes.

[0020] Optionally, the Josephson junction includes a first Josephson junction and a second Josephson junction; the first Josephson junction is located on a side of the superconducting loop close to the feedback coil, and the second Josephson junction is located on a side of the superconducting loop away from the feedback coil;

[0021] The feedback coil is used to couple changes in the external magnetic field to the superconducting loop; the superconducting loop generates an induced current; under the action of the induced current, the critical current of the first Josephson junction and the second Josephson junction changes periodically; the superconducting quantum interference device chip detects the magnetic field signal based on the periodically changing critical current.

[0022] In a second aspect, the present disclosure provides a noise measurement method for a quantum device, comprising:

[0023] receiving a first electrical signal generated by the first superconducting quantum interference device, a second electrical signal generated by the second superconducting quantum interference device, a third electrical signal generated by the third superconducting quantum interference device, and a fourth electrical signal generated by the fourth superconducting quantum interference device;

[0024] The environmental noise of the refrigeration device in the quantum device and the intrinsic magnetic field noise of the superconducting quantum interference device are determined according to the first electrical signal, the second electrical signal, the third electrical signal and the fourth electrical signal.

[0025] Optionally, determining the ambient noise of the refrigeration equipment and the intrinsic magnetic field noise of the superconducting quantum interference device according to the first electrical signal, the second electrical signal, the third electrical signal, and the fourth electrical signal includes:

[0026] averaging the first electrical signal, the second electrical signal, and the third electrical signal to determine the environmental noise;

[0027] Intrinsic magnetic field noise is determined based on the third electrical signal and the fourth electrical signal.

[0028] Optionally, the first electrical signal includes a first hold electrical signal and a first shut-off electrical signal, the second electrical signal includes a second hold electrical signal and a second shut-off electrical signal, the third electrical signal includes a third hold electrical signal and a third shut-off electrical signal, and the fourth electrical signal includes a fourth hold electrical signal and a fourth shut-off electrical signal;

[0029] The method also includes:

[0030] Locking the magnetic fluxes of the first superconducting quantum interference device, the second superconducting quantum interference device, the third superconducting quantum interference device, and the fourth superconducting quantum interference device at a preset operating point;

[0031] When controlling the superconducting quantum interference device to turn on the input signal, the first holding electrical signal, the second holding electrical signal, the third holding electrical signal and the fourth holding electrical signal are received;

[0032] When controlling the superconducting quantum interference device to turn off the input signal, a first turn-off electrical signal, a second turn-off electrical signal, a third turn-off electrical signal and a fourth turn-off electrical signal are received.

[0033] Optionally, averaging the first electrical signal, the second electrical signal, and the third electrical signal to determine the ambient noise includes:

[0034] averaging the first held electrical signal, the second held electrical signal, and the third held electrical signal to determine a held environmental noise signal;

[0035] Averaging the first closing electrical signal, the second closing electrical signal, and the third closing electrical signal to determine a closing ambient noise signal;

[0036] The ambient noise is determined by comparing the ambient noise signal with the ambient noise signal kept on and the ambient noise signal turned off.

[0037] Optionally, determining intrinsic magnetic field noise according to the third electrical signal and the fourth electrical signal includes:

[0038] determining to maintain an intrinsic magnetic field noise signal according to the third maintained electrical signal and the fourth maintained electrical signal;

[0039] determining to turn off the intrinsic magnetic field noise signal according to the third turn-off electrical signal and the fourth turn-off electrical signal;

[0040] The intrinsic magnetic field noise signal is maintained and the intrinsic magnetic field noise signal is turned off to determine the intrinsic magnetic field noise.

[0041] The present disclosure comprises a plurality of superconducting quantum interference devices (SQUIDs) disposed in a refrigeration device of a superconducting quantum computing device, with a shield disposed externally on one of the SQUIDs. The refrigeration device provides an extremely low temperature environment, wherein each SQUID is exposed to the extremely low temperature environment. Within the extremely low temperature environment, each SQUID detects microwave signals such as surrounding magnetic fields and converts the detected magnetic field signals into electrical signals. The electrical signals include the ambient magnetic field signal and the intrinsic magnetic field noise signal of the SQUID. Since the shield disposed externally on one of the SQUIDs shields the ambient noise signal outside the SQUID, the electrical signal generated by the SQUID includes at least the intrinsic magnetic field noise signal. A controller is electrically connected to each SQUID to receive the electrical signals generated by each SQUID and perform signal processing on the received electrical signals to obtain the ambient noise of the refrigeration device and the intrinsic magnetic field noise of the SQUID.

[0042] The noise measurement system is used to set up an external shield in an extremely low-temperature environment to shield the ambient noise signal of one superconducting quantum interference device. The superconducting quantum interference device is used to detect the magnetic field signal in the extremely low-temperature environment and convert it into an electrical signal. The electrical signals generated by the remaining unshielded superconducting quantum interference devices and the electrical signals generated by the superconducting quantum interference device that shields the ambient noise signal are processed. This achieves accurate measurement of the ambient noise of the refrigeration equipment and the intrinsic magnetic field noise of the superconducting quantum interference device, reducing the impact of the ambient noise and intrinsic magnetic field noise on the quantum device.

[0043] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0045] Figure 1 A schematic structural diagram of a noise measurement system provided in an embodiment of the present disclosure;

[0046] Figure 2 A schematic diagram of the structural relationship between a dilution refrigerator and a noise measurement system provided in an embodiment of the present disclosure;

[0047] Figure 3 A schematic structural diagram of a superconducting quantum interference device provided in an embodiment of the present disclosure;

[0048] Figure 4 A schematic structural diagram of a superconducting quantum interference device chip provided in an embodiment of the present disclosure;

[0049] Figure 5 A flow chart of a noise measurement method provided in an embodiment of the present disclosure;

[0050] Figure 6 A flowchart of another noise measurement method provided by an embodiment of the present disclosure;

[0051] Figure 7 A flow chart of another noise measurement method provided in an embodiment of the present disclosure;

[0052] Figure 8 A flowchart of another noise measurement method provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0053] In order to enable those skilled in the art to better understand the solutions of the present disclosure, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the embodiments described are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present disclosure.

[0054] It should be noted that the terms "first", "second", etc. in the specification and claims of the present disclosure and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present disclosure described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0055] The present disclosure provides a noise measurement system for a quantum device, wherein the quantum device includes a refrigeration device for providing an extremely low temperature environment, and comprises: a plurality of superconducting quantum interference devices (SQUIDs) located within the refrigeration device, configured to detect magnetic field signals in the extremely low temperature environment and convert the magnetic field signals into electrical signals; the electrical signals comprising at least an ambient noise signal and an intrinsic magnetic field noise signal of the SQUIDs; a shield located outside one of the SQUIDs, configured to shield the ambient noise signal outside the SQUID; and a controller electrically connected to each SQUID, configured to receive the electrical signals and perform signal processing on the electrical signals to determine the ambient noise of the refrigeration device and the intrinsic magnetic field noise of the SQUIDs. The noise measurement system is used to set up an external shield in an extremely low-temperature environment to shield the ambient noise signal of one superconducting quantum interference device. The superconducting quantum interference device is used to detect the magnetic field signal in the extremely low-temperature environment and convert it into an electrical signal. The electrical signals generated by the remaining unshielded superconducting quantum interference devices and the electrical signals generated by the superconducting quantum interference device that shields the ambient noise signal are processed. This achieves accurate measurement of the ambient noise of the refrigeration equipment and the intrinsic magnetic field noise of the superconducting quantum interference device, reducing the impact of the ambient noise and intrinsic magnetic field noise on the quantum device.

[0056] Specifically, Figure 1 This is a schematic diagram of the structure of a noise measurement system provided by an embodiment of the present disclosure. Since the source of noise in a superconducting quantum computing device is magnetic field noise, the noise detection of the present invention is targeted at the magnetic field noise detection of a superconducting quantum interferometer. In other words, this embodiment can be used to accurately measure the intrinsic magnetic field noise of a superconducting quantum interferometer and the environmental noise of the refrigeration equipment in a quantum device in an extremely low temperature mK environment, thereby reducing the impact of environmental noise and intrinsic magnetic field noise on the quantum device. Figure 1 As shown, the noise measurement system is used for a quantum device, which includes a refrigeration device 1 for providing an extremely low temperature environment. The noise measurement system includes: multiple superconducting quantum interference devices 2, all located in the refrigeration device 1, for detecting magnetic field signals in the extremely low temperature environment and converting the magnetic field signals into electrical signals; the electrical signals include at least environmental noise signals and intrinsic magnetic field noise signals of the superconducting quantum interference devices 2; a shielding device 3, located outside one of the superconducting quantum interference devices 2, for shielding environmental noise signals outside the superconducting quantum interference device 2; a controller 4, electrically connected to each superconducting quantum interference device 2, for receiving electrical signals and performing signal processing on the electrical signals to determine the environmental noise of the refrigeration device 1 and the intrinsic magnetic field noise of the superconducting quantum interference device 2.

[0057] Refrigeration equipment 1 is an instrument capable of providing a cryogenic environment. Refrigeration equipment 1 may include, but is not limited to, a dilution refrigerator, a pulse tube refrigerator, liquid nitrogen, or a custom cryogenic chamber. Refrigeration equipment 1 is used to provide a cryogenic environment, which can range from 20mK to 800mK.

[0058] Superconducting quantum interference device (SQUID) 2 is a flux-sensitive element based on superconducting flux quantization and Josephson effect, which can detect extremely weak magnetic field changes. It can be understood that the superconducting quantum interference device 2 is used to detect magnetic flux changes. When the external magnetic field changes, the magnetic flux passing through the superconducting quantum interference device 2 will also change accordingly, thereby causing the physical quantity (such as critical current or inductance) inside the superconducting quantum interference device 2 to change. Therefore, the superconducting quantum interference device 2 is configured to detect the magnetic field signal of the external environment, convert the magnetic field signal into an electrical signal, and perform signal processing. In some embodiments of the present disclosure, the number of multiple superconducting quantum interference devices 2 may include at least three, and the position of each superconducting quantum interference device 2 is different. The specific position can be determined according to the specific instrument of the refrigeration equipment 1.

[0059] Shield 3 is used to block external environmental noise signals. Shield 3 is located outside one of the SQUIDs 2 and blocks only the external environmental noise signals of that SQUID 2, minimizing the environmental noise signals detected by that SQUID 2. The noise is primarily intrinsic magnetic field noise. Shield 3 can be shaped, but not limited to, a cube, a rectangular parallelepiped, or a cylinder, and can be switched on and off freely. This is not a limitation.

[0060] The controller 4 is a core control unit, which is used to receive and process electrical signals, and determine the ambient noise of the refrigeration equipment 1 and the intrinsic magnetic field noise of the superconducting quantum interference device 2 according to the signal processing results.

[0061] Specifically, when measuring noise in an ultra-low temperature environment, multiple superconducting quantum interference devices (SQUIDs) 2 are installed on a refrigeration device 1, and a shield 3 is installed outside one of the SQUIDs 2. When the refrigeration device 1 is in operation, it can be lowered to a desired ultra-low temperature and maintained at that temperature to provide an ultra-low temperature environment. In this ultra-low temperature environment, each SQUID 2 detects the surrounding microwave magnetic field signal and converts the detected magnetic field signal into an electrical signal for subsequent signal processing. After each SQUID 2 generates an electrical signal, the electrical signal includes at least an ambient magnetic field signal and an intrinsic magnetic field noise signal of the SQUID 2. Since a shield 3 is provided outside one of the SQUIDs 2, the shield 3 shields the ambient noise signal outside the SQUID 2. Therefore, the electrical signal generated by the SQUID 2 mainly includes the intrinsic magnetic field noise signal. The controller 4 is electrically connected to each SQUID 2 via a cryogenic cable, receives the electrical signal generated by each SQUID 2, and processes the received electrical signal to obtain the ambient noise of the refrigeration equipment 1 and the intrinsic magnetic field noise of the SQUID 2. The controller 4 can determine the ambient noise based on the electrical signals generated by the remaining two SQUIDs 2 without the shield 3, and can determine the intrinsic magnetic field noise based on the electrical signal generated by the SQUID 2 with the shield 3 and the electrical signal generated by one of the SQUIDs 2 without the shield 3. The specific determination method can be set according to the time situation and is not limited here.

[0062] The noise measurement system disclosed herein comprises multiple superconducting quantum interference devices (SQUIDs) disposed within a refrigeration device, with a shield disposed externally on one of the SQUIDs. When the refrigeration device operates in an extremely low-temperature environment, each SQUID is in the extremely low-temperature environment. Within the extremely low-temperature environment, each SQUID detects microwave signals, such as the surrounding magnetic field, and converts the detected magnetic field signals into electrical signals. The electrical signals include the ambient magnetic field signal and the intrinsic magnetic field noise signal of the SQUID. Because the shield disposed externally on one of the SQUIDs shields the ambient noise signal outside the SQUID, the electrical signal generated by the SQUID includes the intrinsic magnetic field noise signal. A controller is electrically connected to each SQUID, receives the electrical signals generated by each SQUID, and processes the received electrical signals to obtain the ambient noise and the intrinsic magnetic field noise of the SQUID.

[0063] The noise measurement system is designed to accurately measure the ambient noise of the refrigeration equipment and the intrinsic magnetic field noise of the superconducting quantum interference device by setting a shield in an extremely low-temperature environment to shield the ambient noise signal of one superconducting quantum interference device. The superconducting quantum interference device is then used to detect the magnetic field signal in the extremely low-temperature environment and convert it into an electrical signal. The electrical signals generated by the remaining unshielded superconducting quantum interference devices and the electrical signals generated by the superconducting quantum interference device that shields the ambient noise signal are processed, thereby reducing the impact of the ambient noise and the intrinsic magnetic field noise on the quantum device.

[0064] In some embodiments of the present disclosure, Figure 2 This is a structural diagram of the positional relationship between a dilution refrigerator and a noise measurement system provided in an embodiment of the present disclosure, with reference to Figure 2 As shown, the refrigeration device 1 includes a dilution refrigerator 11, which includes multiple cold plates 111 on different layers. At least two superconducting quantum interference devices 2 are located on the cold plates 111 on the same layer. The shield 3 is located outside one of the superconducting quantum interference devices 2 on the same layer to shield noise signals around the superconducting quantum interference device 2.

[0065] The multiple superconducting quantum interference devices 2 include a first superconducting quantum interference device 200, a second superconducting quantum interference device 210, a third superconducting quantum interference device 220 and a fourth superconducting quantum interference device 230. The first superconducting quantum interference device 200, the second superconducting quantum interference device 210 and the third superconducting quantum interference device 220 are located on different layers of the cold plate 111, the third superconducting quantum interference device 220 and the fourth superconducting quantum interference device 230 are located on the same layer of the cold plate 111, and the shield 3 is located outside the fourth superconducting quantum interference device 230; the controller 4 is used to receive a first electrical signal generated by the first superconducting quantum interference device 200, a second electrical signal generated by the second superconducting quantum interference device 210, a third electrical signal generated by the third superconducting quantum interference device 220 and a fourth electrical signal generated by the fourth superconducting quantum interference device 230, and average the first electrical signal, the second electrical signal and the third electrical signal to determine the environmental noise signal; and determine the intrinsic magnetic field noise signal based on the third electrical signal and the fourth electrical signal.

[0066] Among them, the dilution refrigerator 11 is a refrigeration device that uses the phase change characteristics of helium isotope mixed liquid to achieve an extremely low temperature environment. Its principle is based on 3 He and 4 Phase separation phenomenon of He mixture at low temperature. When the temperature is lower than a certain temperature value, such as 0.86K, 3 He and 4 The He mixture will separate into concentrated phase and diluted phase. 3When He atoms pass through the phase interface from the concentrated phase into the dilute phase, they absorb a large amount of heat, thereby achieving refrigeration. The cold plate 111 is an important component of the dilution refrigerator 11. It is located in the low temperature area of ​​the dilution refrigerator 11 and is used to provide a stable low temperature platform. Figure 2 The dilution refrigerator 11 includes a plurality of cold plates 111 at different layers. The cold plates 111 at different layers are used to set up various superconducting quantum interference devices 2. In some embodiments of the present disclosure, the plurality of superconducting quantum interference devices 2 include a first superconducting quantum interference device 200, a second superconducting quantum interference device 210, a third superconducting quantum interference device 220, and a fourth superconducting quantum interference device 230. The first superconducting quantum interference device 200 is located on the topmost cold plate 111, the second superconducting quantum interference device 210 is located on the middle cold plate 111, the third superconducting quantum interference device 220 and the fourth superconducting quantum interference device 230 are located on the bottommost cold plate 111, and the shield 3 is located outside the fourth superconducting quantum interference device 230.

[0067] Specifically, the controller 4 receives a first electrical signal generated by the first superconducting quantum interference device 200, a second electrical signal generated by the second superconducting quantum interference device 210, and a third electrical signal generated by the third superconducting quantum interference device 220, all of which include an environmental noise signal and an intrinsic magnetic field noise signal. The controller 4 averages the first electrical signal, the second electrical signal, and the third electrical signal to obtain the environmental noise signal of the dilution refrigerator 11, thereby reducing the impact of the environmental noise of the magnetic field in the cavity of the dilution refrigerator 11 on the test signal. The controller 4 also receives a third electrical signal generated by the third superconducting quantum interference device 220, which is located on the same layer, and a fourth electrical signal generated by the fourth superconducting quantum interference device 230, which is externally provided with a shield 3. By comparing, analyzing, and processing the data of the third electrical signal and the fourth electrical signal, the controller can determine the intrinsic magnetic field noise of the superconducting quantum interference device 2, thereby reducing the impact of the intrinsic magnetic field noise in the superconducting quantum interference device. It is understandable that before the controller 4 measures the ambient noise and intrinsic magnetic field noise, the dilution refrigerator 11 operates at an extremely low temperature, and at the same time ensures that other external devices and signal sources are turned off. After the dilution refrigerator 11 operates stably, the controller 4 and other measuring devices are turned on to receive and process the electrical signals generated by each superconducting quantum interference device 2 to ensure test accuracy.

[0068] refer to Figure 2 , Figure 2There are four superconducting quantum interference devices 2, which are arranged on the third, fourth, and fifth cold plates, and two superconducting quantum interference devices 2 are arranged on the fifth cold plate. Except for the structure on the top layer of the refrigeration equipment 1, the cold plates in the refrigeration equipment 1 are arranged in the following order from top to bottom: the first cold plate, the second cold plate, the third cold plate, the fourth cold plate, and the fifth cold plate. That is, the four superconducting quantum interference devices 2 are arranged on the third to fifth cold plates, and a shield 3 is provided on the outside of one of the superconducting quantum interference devices 2 on the fifth cold plate. The controller 4 averages the three electrical signals generated by the superconducting quantum interference devices 2 on the three different layers to obtain the environmental noise signal of the dilution refrigerator 11; and determines the intrinsic magnetic field noise of the superconducting quantum interference devices 2 based on the electrical signals generated by the two superconducting quantum interference devices 2 on the fifth layer. Furthermore, the temperatures of different cold plates 111 vary, decreasing as they are positioned downwards. The fifth cold plate has the lowest temperature. In some embodiments of the present disclosure, the temperature of the third cold plate 111 is 800 mK, the temperature of the fourth cold plate 111 is 200 mK, and the temperature of the fifth cold plate 111 is 10 mK. These temperatures are merely examples, and those skilled in the art may determine the temperature of each cold plate 111 based on actual needs. This is not intended to be limiting. It is understood that the environmental noise detected by the superconducting quantum interference device 2 is the environmental noise surrounding a quantum device at an extremely low temperature, such as the environmental noise surrounding a quantum chip at 20 mK. Specifically, the quantum chip can be placed on the fifth cold plate 111, and the superconducting quantum interference device 2 can be placed above the quantum chip, so that the superconducting quantum interference device 2 detects the environmental noise surrounding the quantum chip in an extremely low temperature environment.

[0069] Continue to refer Figure 2 The noise measurement system also includes a flux locking structure (not shown in the figure); the flux locking structure is electrically connected to the superconducting quantum interference device 2, and is used to determine the error between the electrical signal and the preset signal, and when the error deviates from the preset error signal, feedback adjustment is performed on the electrical signal to lock the magnetic flux of the superconducting quantum interference device 2 at a preset operating point.

[0070] Among them, the flux locking structure (FLL) locks the magnetic flux within the superconducting quantum interference device 2 at a certain operating point through feedback, thereby achieving linear conversion between magnetic flux and voltage. Specifically, after the superconducting quantum interference device 2 generates an electrical signal, the flux locking structure receives the electrical signal and, based on the error between the electrical signal and a preset signal, adjusts the bias current or magnetic field applied to the superconducting quantum interference device 2 when the error deviates from the preset error signal, achieving feedback regulation to offset the magnetic flux fluctuations caused by external signal interference and ensure that the magnetic flux of the superconducting quantum interference device 2 is locked near the preset operating point.

[0071] In some embodiments of the present disclosure, Figure 3 A schematic diagram of the structure of a superconducting quantum interference device provided by the embodiment of the present disclosure, referring to Figure 3 As shown, the noise measurement system also includes a base plate 23 and a hanging structure (not shown in the figure), the superconducting quantum interference device 2 includes a detection coil 21 and a superconducting quantum interference device chip 22, the detection coil 21 and the superconducting quantum interference device chip 22 are connected by an aluminum wire 24 and are located on the base plate 23; the base plate 23 is fixedly connected to the refrigeration equipment 1 through the hanging structure; the base plate 23 is used to fix the superconducting quantum interference device 2 and transfer heat to the superconducting quantum interference device 2.

[0072] The detection coil 21 is used to sense changes in the external magnetic field. When the external magnetic field changes, an induced current is generated in the coil. The superconducting quantum interference device chip 22 is a superconducting quantum interference device that can convert magnetic fields into voltage, thereby achieving high-sensitivity detection of magnetic fields. The superconducting quantum interference device chip 22 includes two superconducting junctions, an input junction and an output junction. When an external magnetic field is applied to the input junction, the magnetic flux changes, causing the current in the output junction to change, thereby causing a change in the potential difference. This effect can be used to measure the magnetic field. The base plate 23 provides physical support and electrical connections to ensure stable operation of each device. In some embodiments of the present disclosure, the hanging structure is fixed to the refrigeration equipment 1 via screw holes. The hanging structure includes two layers: the upper layer is used to place and fix the base plate 23 to achieve a fixed connection between the two; the lower layer can be used to place the quantum chip or magnetic chip so that the superconducting quantum interference device 2 is located above the quantum chip or magnetic chip. In addition, the base plate 23 is used to transfer heat to the superconducting quantum interference device 2. The aluminum wire 24 is a connecting wire used to connect the detection coil 21 and the superconducting quantum interference device chip 22 .

[0073] In some embodiments of the present disclosure, reference Figure 3 The superconducting quantum interference device chip 22 includes a feedback coil 221, a superconducting loop 222 and a Josephson junction 223; the feedback coil 221 is connected to the detection coil 21 through an aluminum wire 24, the Josephson junction 223 is located on the superconducting loop 222, and there is a preset gap between the feedback coil 221 and the superconducting loop 222 to reduce electromagnetic interference.

[0074] Feedback coil 221 provides feedback to adjust the sensitivity and response of the SQUID. Superconducting loop 222, the core component of SQUID 2, is made of superconducting materials and can detect magnetic field changes with extreme sensitivity. A key component of superconducting loop 222 is the Josephson junction 223, formed by a very thin insulating layer between two superconductors. This allows current to flow without voltage, enabling the SQUID to detect weak magnetic fields.

[0075] In some embodiments of the present disclosure, the superconducting quantum interference device 2 also includes a magnetic shielding cover 25; the magnetic shielding cover 25 is fixed to the superconducting quantum interference device chip 22 and is above the side away from the base plate 23; small holes are provided on both sides of the magnetic shielding cover 25, and the leads of the superconducting loop 222 are electrically connected to the controller 4 through the small holes, and the aluminum wire 24 connects the detection coil 21 to the superconducting quantum interference device chip 22 through the small holes.

[0076] Figure 4 A schematic diagram of the structure of a superconducting quantum interference device chip provided by the embodiment of the present disclosure, referring to Figure 4 As shown, the Josephson junction 223 includes a first Josephson junction 2231 and a second Josephson junction 2232; the first Josephson junction 2231 is located on a side of the superconducting loop 222 close to the feedback coil 221, and the second Josephson junction 2232 is located on a side of the superconducting loop 222 away from the feedback coil 221; the feedback coil 221 is used to couple changes in the external magnetic field to the superconducting loop 222; the superconducting loop 222 generates an induced current; under the action of the induced current, the critical current of the first Josephson junction 2231 and the second Josephson junction 2232 changes periodically; the superconducting quantum interferometer chip 22 detects the magnetic field signal according to the periodically changing critical current.

[0077] Among them, the magnetic shield 25 is used to shield the interference of the external magnetic field on the superconducting quantum interference device chip 22, ensuring the accuracy and sensitivity of the test signal. The material of the magnetic shield 25 includes but is not limited to metal niobium. According to the Meissner effect, under the action of the magnetic shield 25, the influence of the external electromagnetic field can be shielded, further reducing the impact of environmental noise fluctuations on the test signal, and improving the test accuracy. The shape of the magnetic shield 25 can include but is not limited to a cube, a rectangular parallelepiped or a cylinder, etc., which is not limited here. In addition, the superconducting quantum interference device chip 22 can be a double-junction DC superconducting quantum interference device chip.

[0078] Specifically, taking a double-junction DC superconducting quantum interference device chip as an example, when the external magnetic field B changes, the detection coil 21 senses the magnetic field change and transmits it to the feedback coil 221 of the superconducting quantum interference device chip 22 via the aluminum wire 24. The feedback coil 221 couples the change in the external magnetic field to the superconducting loop 222. The superconducting loop 222 generates an induced current I when the external magnetic field changes. This induced current I is generated in the superconducting loop 222 due to the feedback coil 221 coupling the change in the external magnetic field. Because both the first and second Josephson junctions 2231 and 2232 are located on the superconducting loop 222, the magnetic flux of the first and second Josephson junctions 2231 and 2232 changes under the influence of the induced current, converting the changing magnetic field signal into a shielding current Is or a magnetic flux passing through the superconducting loop 222. These currents or magnetic fluxes are highly sensitive and can detect very weak magnetic field changes. The shielding current Is circulates in the superconducting loop 222 and, in combination with the resistor R, creates a potential difference in the output voltage V of the SQUID chip. This results in periodic variations in the critical current Ic flowing through the first and second Josephson junctions 2231 and 2232, further causing periodic oscillations in the voltage-flux curve or current-flux curve of the SQUID 2, with the period of the oscillation being one flux quantum Φ0. Based on these periodic oscillations, the SQUID chip 22 detects extremely minute magnetic field signals, converts them into electrical signals, and transmits them to the controller 4 via the leads of the superconducting loop 222. The controller 4 then amplifies and detects the electrical signals in the form of power spectrum density or flux noise density, thereby achieving noise measurement.

[0079] In some embodiments of the present disclosure, the superconducting quantum interference device is a strongly nonlinear device, and the parameter β C Indicates the damping degree of the Josephson junction or the hysteresis degree of the IV curve. At extremely low temperatures of the mK level, in order to improve the damping, the parameter β C It is set to be less than 0.5 to adapt to the working environment temperature at the mK level, thereby improving the stability and measurement accuracy of the superconducting quantum interference device 2.

[0080] The leads of the superconducting loop 222 include an aluminum core, an insulating layer, and an electromagnetic signal shielding layer from the inside out. The aluminum core is used to transmit electrical signals. The insulating layer is located on the outside of the aluminum core to prevent current leakage and ensure the effective transmission of electrical energy or signals. The insulating layer includes but is not limited to materials such as polyethylene (PE), polyvinyl chloride (PVC), and cross-linked polyethylene (XLPE). These materials not only provide electrical insulation, but also have certain heat resistance and chemical corrosion resistance. The electromagnetic signal shielding layer is used to prevent external electromagnetic interference from entering the inner layer, and at the same time prevent the inner layer signal from radiating outward, thereby avoiding interference with other devices. The electromagnetic signal shielding layer is made of woven copper mesh or copper foil (aluminum) and is grounded to achieve electromagnetic shielding function. In addition, the aluminum wire 24 includes at least an aluminum core.

[0081] In some embodiments of the present disclosure, Figure 5 A flow chart of a noise measurement method provided in an embodiment of the present disclosure, the noise measurement method is used for quantum devices, reference Figure 2 and Figure 5 As shown, before introducing the method of the present application, it is necessary to briefly explain the system structure involved. In the present disclosure, the refrigeration equipment includes a dilution refrigerator, which includes multiple cold plates on different layers; the multiple superconducting quantum interference devices include a first superconducting quantum interference device, a second superconducting quantum interference device, a third superconducting quantum interference device, and a fourth superconducting quantum interference device. The first superconducting quantum interference device, the second superconducting quantum interference device, and the third superconducting quantum interference device are respectively located on cold plates on different layers, the fourth superconducting quantum interference device and the third superconducting quantum interference device are located on the same cold plate, and the shield is located outside the fourth superconducting quantum interference device. Figure 2 The superconducting quantum interference devices 2 include four superconducting quantum interference devices 2, namely the first superconducting quantum interference device 200, the second superconducting quantum interference device 210, the third superconducting quantum interference device 220 and the fourth superconducting quantum interference device 230, which are arranged on the third cold plate, the fourth cold plate and the fifth cold plate; two superconducting quantum interference devices 2 are arranged on the fifth cold plate, and a shield 3 is arranged outside one of the superconducting quantum interference devices 2 on the fifth cold plate, that is, the fourth superconducting quantum interference device 230 and the third superconducting quantum interference device 220 are located on the same cold plate 111, and the shield 3 is located outside the fourth superconducting quantum interference device 230.

[0082] The noise measurement method includes:

[0083] S110: Receive a first electrical signal generated by the first superconducting quantum interference device, a second electrical signal generated by the second superconducting quantum interference device, a third electrical signal generated by the third superconducting quantum interference device, and a fourth electrical signal generated by the fourth superconducting quantum interference device.

[0084] Among them, when receiving the electrical signal of the superconducting quantum interference device, the electrical signals generated by the four superconducting quantum interference devices are received, namely the first electrical signal generated by the first superconducting quantum interference device, the second electrical signal generated by the second superconducting quantum interference device, the third electrical signal generated by the third superconducting quantum interference device, and the fourth electrical signal generated by the fourth superconducting quantum interference device. The receiving method may include but is not limited to receiving by setting a circuit structure or a logic algorithm, thereby providing a basis for subsequently determining the environmental noise and intrinsic magnetic field noise based on the received electrical signals.

[0085] S120: Determine, based on the first electrical signal, the second electrical signal, the third electrical signal, and the fourth electrical signal, the environmental noise of the refrigeration device in the quantum device and the intrinsic magnetic field noise of the superconducting quantum interference device.

[0086] Specifically, based on the received first electrical signal, second electrical signal, third electrical signal, and fourth electrical signal, by performing signal processing on the first electrical signal, the second electrical signal, the third electrical signal, and the fourth electrical signal, the ambient noise of the refrigeration device in the quantum device and the intrinsic magnetic field noise of the superconducting quantum interference device can be determined.

[0087] It is understood that before measuring ambient noise and intrinsic magnetic field noise, the dilution refrigerator is first cooled to an extremely low temperature environment, while ensuring that other external devices and signal sources are turned off. After stable operation, the room temperature controller and other measuring equipment are turned on. After stable operation, the electrical signals generated by each superconducting quantum interference device are received and processed to ensure test accuracy. In addition, to ensure that the superconducting quantum interference device can detect changes in the external magnetic field with optimal sensitivity and linear response, before receiving the electrical signal, the magnetic flux of the superconducting quantum interference device is ensured to be locked near the preset operating point. Under this premise, the electrical signal generated by the superconducting quantum interference device is received, ensuring the accuracy of the electrical signal, thereby achieving high-sensitivity measurement of the electrical signal.

[0088] The noise measurement method of the disclosed embodiment receives a first electrical signal generated by a first superconducting quantum interference device (SQUID), a second electrical signal generated by a second SQUID, a third electrical signal generated by a third SQUID, and a fourth electrical signal generated by a fourth SQUID. Based on the first, second, third, and fourth electrical signals, the method determines the ambient noise of the refrigeration device and the intrinsic magnetic field noise of the SQUID in the quantum device. This method accurately measures the ambient noise of the refrigeration device and the intrinsic magnetic field noise of the SQUID, reducing the impact of these noises on the quantum device.

[0089] In some embodiments of the present disclosure, Figure 6 This is a flow chart of another noise measurement method provided by an embodiment of the present disclosure. For details not yet fully described in the present disclosure, please refer to the above embodiments and will not be repeated here. Figure 6 As shown, the noise measurement method includes:

[0090] S210: Receive a first electrical signal generated by the first superconducting quantum interference device, a second electrical signal generated by the second superconducting quantum interference device, a third electrical signal generated by the third superconducting quantum interference device, and a fourth electrical signal generated by the fourth superconducting quantum interference device.

[0091] S220 : Average the first electrical signal, the second electrical signal, and the third electrical signal to determine environmental noise.

[0092] S230 : Determine intrinsic magnetic field noise according to the third electrical signal and the fourth electrical signal.

[0093] Specifically, when determining environmental noise, the first electrical signal generated by a first superconducting quantum interference device (SQUID), a second electrical signal generated by a second SQUID, and a third electrical signal generated by a third SQUID located on different layers are received, wherein each of the first, second, and third electrical signals includes an environmental noise signal and an intrinsic magnetic field noise signal. The first, second, and third electrical signals are averaged to obtain internal environmental noise data for the dilution refrigerator, thereby reducing the impact of the environmental noise in the dilution refrigerator cavity magnetic field on the test signal. When determining intrinsic magnetic field noise, the third electrical signal generated by a third SQUID located on the same layer and a fourth electrical signal generated by a fourth SQUID with an external shield are received. By comparing, analyzing, and processing the relevant data of the third and fourth electrical signals, the intrinsic magnetic field noise of the SQUID can be determined. The determined intrinsic magnetic field noise can then be used in other magnetic field studies with signal sources to reduce the impact of the SQUID intrinsic magnetic field noise.

[0094] The noise measurement method of the disclosed embodiment receives a first electrical signal generated by a first superconducting quantum interference device, a second electrical signal generated by a second superconducting quantum interference device, a third electrical signal generated by a third superconducting quantum interference device, and a fourth electrical signal generated by a fourth superconducting quantum interference device; averages the first, second, and third electrical signals to determine ambient noise; and determines intrinsic magnetic field noise based on the third and fourth electrical signals. Using this method, by receiving and processing the electrical signals generated by each superconducting quantum interference device, accurate measurement of both ambient noise and intrinsic magnetic field noise is achieved.

[0095] In another disclosed embodiment, Figure 7 A flowchart of another noise measurement method provided in an embodiment of the present disclosure further includes the following steps before step S110, in which a first electrical signal generated by a first superconducting quantum interference device, a second electrical signal generated by a second superconducting quantum interference device, a third electrical signal generated by a third superconducting quantum interference device, and a fourth electrical signal generated by a fourth superconducting quantum interference device are received:

[0096] The magnetic fluxes of the first superconducting quantum interference device, the second superconducting quantum interference device, the third superconducting quantum interference device and the fourth superconducting quantum interference device are all locked at a preset working point.

[0097] Furthermore, step S110, receiving the first electrical signal generated by the first superconducting quantum interference device, the second electrical signal generated by the second superconducting quantum interference device, the third electrical signal generated by the third superconducting quantum interference device, and the fourth electrical signal generated by the fourth superconducting quantum interference device further includes:

[0098] When controlling the superconducting quantum interference device to turn on the input signal, the first holding electrical signal, the second holding electrical signal, the third holding electrical signal and the fourth holding electrical signal are received;

[0099] When controlling the superconducting quantum interference device to turn off the input signal, a first turn-off electrical signal, a second turn-off electrical signal, a third turn-off electrical signal and a fourth turn-off electrical signal are received.

[0100] For details not yet provided in this embodiment, please refer to the above embodiments and will not be described again here.

[0101] refer to Figure 2 and Figure 7 As shown, the noise measurement method includes:

[0102] S310: Lock the magnetic fluxes of the first superconducting quantum interference device, the second superconducting quantum interference device, the third superconducting quantum interference device, and the fourth superconducting quantum interference device at a preset operating point.

[0103] The preset operating point is the SQUID's highest sensitivity point and is a constant operating point. Specifically, the magnetic flux of the first, second, third, and fourth SQUIDs is locked at the preset operating point, stabilizing their measurement states before subsequent signal reception and processing.

[0104] S320 , when controlling the superconducting quantum interference device to turn on the input signal, receiving the first holding electrical signal, the second holding electrical signal, the third holding electrical signal, and the fourth holding electrical signal.

[0105] S330: When controlling the superconducting quantum interference device to turn off the input signal, a first turn-off electrical signal, a second turn-off electrical signal, a third turn-off electrical signal, and a fourth turn-off electrical signal are received.

[0106] The input signal is an external signal used to drive and control the operation of the superconducting quantum interference device. For example, the input signal may include but is not limited to a bias current signal, a modulation signal, and a feedback signal. The first hold signal is the signal generated by the first superconducting quantum interference device when the input signal is turned on, the second hold signal is the signal generated by the second superconducting quantum interference device when the input signal is turned on, the third hold signal is the signal generated by the third superconducting quantum interference device when the input signal is turned on, and the fourth hold signal is the signal generated by the fourth superconducting quantum interference device when the input signal is turned on. The first shut-down signal is the signal generated by the first superconducting quantum interference device when the input signal is turned off, the second shut-down signal is the signal generated by the second superconducting quantum interference device when the input signal is turned off, the third shut-down signal is the signal generated by the third superconducting quantum interference device when the input signal is turned off, and the fourth shut-down signal is the signal generated by the fourth superconducting quantum interference device when the input signal is turned off.

[0107] Specifically, when controlling the SQUID to turn on an input signal, the received electrical signals include a first holding electrical signal generated by the first SQUID, a second holding electrical signal generated by the second SQUID, a third holding electrical signal generated by the third SQUID, and a fourth holding electrical signal generated by the fourth SQUID. When the SQUID holds the input signal, it is in normal operating mode and can respond to tiny changes in magnetic flux. Therefore, the received first, second, third, and fourth holding electrical signals all include ambient noise signals and intrinsic magnetic field noise signals. When controlling the SQUID to turn off an input signal, the received signals include a first shut-off electrical signal generated by the first SQUID, a second shut-off electrical signal generated by the second SQUID, a third shut-off electrical signal generated by the third SQUID, and a fourth shut-off electrical signal generated by the fourth SQUID. When the superconducting quantum interference device is controlled to turn off the input signal, it is almost unable to respond to changes in the external magnetic field. Therefore, the received first shutdown electrical signal, second shutdown electrical signal, third shutdown electrical signal and fourth shutdown electrical signal only include environmental noise signals and intrinsic magnetic field noise signals.

[0108] S340 , average the first held electrical signal, the second held electrical signal, and the third held electrical signal to determine a held environmental noise signal.

[0109] Specifically, after receiving the first hold electrical signal, the second hold electrical signal, and the third hold electrical signal, the first hold electrical signal, the second hold electrical signal, and the third hold electrical signal are averaged to obtain a hold environmental noise signal. The hold environmental noise signal is an environmental noise signal obtained when controlling the superconducting quantum interference device to turn on the input signal.

[0110] S350: Average the first off electrical signal, the second off electrical signal, and the third off electrical signal to determine a closed ambient noise signal.

[0111] Specifically, after receiving the first, second, and third shutdown electrical signals, the first, second, and third shutdown electrical signals are averaged to obtain a shutdown ambient noise signal. The shutdown ambient noise signal is the ambient noise signal obtained when controlling the superconducting quantum interference device to turn off the input signal.

[0112] S360: Compare the maintained ambient noise signal and the turned-off ambient noise signal to determine the ambient noise;

[0113] Specifically, to ensure the accuracy of the ambient noise, after obtaining the ambient noise holding signal and the ambient noise turning off signal, this embodiment compares and analyzes the obtained ambient noise holding signal and the ambient noise turning off signal to determine the ambient noise of the superconducting quantum interference device.

[0114] S370: Determine intrinsic magnetic field noise according to the third electrical signal and the fourth electrical signal.

[0115] The noise measurement method of the embodiment of the present disclosure achieves accurate determination of environmental noise by receiving various electrical signals both when the input signal is turned on and when the input signal is turned off, and performing signal processing and comparative analysis on each electrical signal based on the various electrical signals.

[0116] In other embodiments of the present disclosure, Figure 8 This is a flow chart of another noise measurement method provided by an embodiment of the present disclosure. For details not yet fully described in this embodiment, please refer to the above embodiments and will not be repeated here.

[0117] refer to Figure 2 and Figure 8 As shown, the noise measurement method includes:

[0118] S410: Lock the magnetic fluxes of the first superconducting quantum interference device, the second superconducting quantum interference device, the third superconducting quantum interference device, and the fourth superconducting quantum interference device at a preset operating point.

[0119] S420: When the superconducting quantum interference device is controlled to start the input signal, the first holding electrical signal, the second holding electrical signal, the third holding electrical signal, and the fourth holding electrical signal are received.

[0120] S430: When controlling the superconducting quantum interference device to turn off the input signal, a first turn-off electrical signal, a second turn-off electrical signal, a third turn-off electrical signal, and a fourth turn-off electrical signal are received.

[0121] S440: Average the first electrical signal, the second electrical signal, and the third electrical signal to determine environmental noise.

[0122] S450: Determine to maintain an intrinsic magnetic field noise signal according to the third maintained electrical signal and the fourth maintained electrical signal.

[0123] Specifically, after receiving the third hold electrical signal and the fourth hold electrical signal, the third hold electrical signal and the fourth hold electrical signal are compared and analyzed to obtain a hold intrinsic magnetic field noise signal, wherein the hold intrinsic magnetic field noise signal is an intrinsic magnetic field noise signal obtained when the input signal is held.

[0124] S460: Determine whether to turn off the intrinsic magnetic field noise signal according to the third turn-off electrical signal and the fourth turn-off electrical signal.

[0125] Specifically, after receiving the third and fourth shutdown electrical signals, the third and fourth shutdown electrical signals are compared and analyzed to obtain a shutdown intrinsic magnetic field noise signal, wherein the shutdown intrinsic magnetic field noise signal is an intrinsic magnetic field noise signal obtained when the input signal is turned off.

[0126] S470 : Compare the intrinsic magnetic field noise signal maintained and the intrinsic magnetic field noise signal turned off to determine the intrinsic magnetic field noise.

[0127] Specifically, to ensure the accuracy of the intrinsic magnetic field noise, after obtaining the intrinsic magnetic field noise signal and the intrinsic magnetic field noise signal, this embodiment compares and analyzes the intrinsic magnetic field noise signal and the intrinsic magnetic field noise signal, thereby ultimately determining the intrinsic magnetic field noise of the superconducting quantum interference device.

[0128] The noise measurement method of the embodiment of the present disclosure achieves accurate determination of intrinsic magnetic field noise by receiving various electrical signals both when the input signal is turned on and when the input signal is turned off, and performing signal processing and analysis on each electrical signal based on the various electrical signals.

[0129] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions of this disclosure can be achieved, and this document is not limited here.

[0130] The above specific embodiments do not constitute a limitation on the scope of protection of this disclosure. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this disclosure shall be included within the scope of protection of this disclosure.

Claims

1. A noise measurement system for a quantum device, wherein the quantum device includes a refrigeration device for providing an extremely low temperature environment, characterized in that: include: Multiple superconducting quantum interference devices, all located in the refrigeration equipment, are used to detect magnetic field signals in the extremely low temperature environment and convert the magnetic field signals into electrical signals; the electrical signals at least include environmental noise signals and intrinsic magnetic field noise signals of the superconducting quantum interference devices; a shield, located outside one of the superconducting quantum interference devices, for shielding environmental noise signals outside the superconducting quantum interference device; A controller is electrically connected to each of the superconducting quantum interference devices, and is used to receive the electrical signal and perform signal processing on the electrical signal to determine the ambient noise of the refrigeration equipment and the intrinsic magnetic field noise of the superconducting quantum interference device.

2. The noise measurement system according to claim 1, wherein The refrigeration equipment includes a dilution refrigerator, which includes multiple cold plates in different layers. At least two superconducting quantum interference devices are located on the cold plates in the same layer, and the shield is located outside one of the superconducting quantum interference devices in the same layer.

3. The noise measurement system according to claim 2, characterized in that The multiple superconducting quantum interference devices include a first superconducting quantum interference device, a second superconducting quantum interference device, a third superconducting quantum interference device, and a fourth superconducting quantum interference device, wherein the first superconducting quantum interference device, the second superconducting quantum interference device, and the third superconducting quantum interference device are respectively located on the cold disks of different layers, the fourth superconducting quantum interference device and the third superconducting quantum interference device are located on the cold disk of the same layer, and the shield is located outside the fourth superconducting quantum interference device; The controller is used to receive a first electrical signal generated by the first superconducting quantum interference device, a second electrical signal generated by the second superconducting quantum interference device, a third electrical signal generated by the third superconducting quantum interference device, and a fourth electrical signal generated by the fourth superconducting quantum interference device, and average the first electrical signal, the second electrical signal, and the third electrical signal to determine the environmental noise signal; and determine the intrinsic magnetic field noise signal based on the third electrical signal and the fourth electrical signal.

4. The noise measurement system according to claim 3, wherein: Also included is a flux locking structure; The flux locking structure is electrically connected to the superconducting quantum interference device and is used to determine the error between the electrical signal and a preset signal, and when the error deviates from the preset error signal, perform feedback adjustment on the electrical signal to lock the magnetic flux of the superconducting quantum interference device at a preset operating point.

5. The noise measurement system according to claim 1, wherein: It also includes a base plate and a hanging structure; the superconducting quantum interference device includes a detection coil and a superconducting quantum interference device chip, the detection coil and the superconducting quantum interference device chip are connected by an aluminum wire and are located on the base plate; the base plate and the refrigeration device are fixedly connected by the hanging structure; The bottom plate is used for fixing the superconducting quantum interference device and transferring heat to the superconducting quantum interference device.

6. The noise measurement system according to claim 5, characterized in that The superconducting quantum interference device chip includes a feedback coil, a superconducting loop and a Josephson junction; The feedback coil is connected to the detection coil via the aluminum wire, and the Josephson junction is located on the superconducting loop; There is a preset interval between the feedback coil and the superconducting loop to reduce electromagnetic interference.

7. The noise measurement system according to claim 6, characterized in that The superconducting quantum interference device also includes a magnetic shield; the magnetic shield is fixed above the side of the superconducting quantum interference device chip away from the base plate; small holes are provided on both sides of the magnetic shield, the leads of the superconducting loop are electrically connected to the controller through the small holes, and the aluminum wire connects the detection coil to the superconducting quantum interference device chip through the small holes.

8. The noise measurement system according to claim 6, wherein: The Josephson junction includes a first Josephson junction and a second Josephson junction; the first Josephson junction is located on a side of the superconducting loop close to the feedback coil, and the second Josephson junction is located on a side of the superconducting loop away from the feedback coil; The feedback coil is used to couple changes in the external magnetic field to the superconducting loop; the superconducting loop generates an induced current; under the action of the induced current, the critical current of the first Josephson junction and the second Josephson junction changes periodically; the superconducting quantum interference device chip detects the magnetic field signal based on the periodically changing critical current.

9. A noise measurement method for a quantum device, characterized in that: include: receiving a first electrical signal generated by the first superconducting quantum interference device, a second electrical signal generated by the second superconducting quantum interference device, a third electrical signal generated by the third superconducting quantum interference device, and a fourth electrical signal generated by the fourth superconducting quantum interference device; The environmental noise of a refrigeration device in the quantum device and the intrinsic magnetic field noise of a superconducting quantum interference device are determined according to the first electrical signal, the second electrical signal, the third electrical signal, and the fourth electrical signal.

10. The noise measurement method according to claim 9, characterized in that: Determining the environmental noise of the refrigeration equipment and the intrinsic magnetic field noise of the superconducting quantum interference device according to the first electrical signal, the second electrical signal, the third electrical signal, and the fourth electrical signal includes: averaging the first electrical signal, the second electrical signal, and the third electrical signal to determine the environmental noise; The intrinsic magnetic field noise is determined according to the third electrical signal and the fourth electrical signal.

11. The noise measurement method according to claim 10, characterized in that: The first electrical signal includes a first hold electrical signal and a first shut-off electrical signal, the second electrical signal includes a second hold electrical signal and a second shut-off electrical signal, the third electrical signal includes a third hold electrical signal and a third shut-off electrical signal, and the fourth electrical signal includes a fourth hold electrical signal and a fourth shut-off electrical signal; The method further comprises: Locking the magnetic fluxes of the first superconducting quantum interference device, the second superconducting quantum interference device, the third superconducting quantum interference device, and the fourth superconducting quantum interference device at a preset operating point; When controlling the superconducting quantum interference device to turn on the input signal, the first holding electrical signal, the second holding electrical signal, the third holding electrical signal and the fourth holding electrical signal are received; When controlling the superconducting quantum interference device to turn off the input signal, the first turn-off electrical signal, the second turn-off electrical signal, the third turn-off electrical signal, and the fourth turn-off electrical signal are received.

12. The noise measurement method according to claim 11, characterized in that: Averaging the first electrical signal, the second electrical signal, and the third electrical signal to determine the environmental noise includes: averaging the first held electrical signal, the second held electrical signal, and the third held electrical signal to determine a held environmental noise signal; Averaging the first shut-off electrical signal, the second shut-off electrical signal, and the third shut-off electrical signal to determine a shut-off ambient noise signal; The maintained ambient noise signal and the disabled ambient noise signal are compared to determine the ambient noise.

13. The noise measurement method according to claim 11, characterized in that: Determining the intrinsic magnetic field noise according to the third electrical signal and the fourth electrical signal includes: determining to maintain an intrinsic magnetic field noise signal according to the third maintained electrical signal and the fourth maintained electrical signal; determining to turn off the intrinsic magnetic field noise signal according to the third turn-off electrical signal and the fourth turn-off electrical signal; The intrinsic magnetic field noise is determined by comparing the maintained intrinsic magnetic field noise signal with the disabled intrinsic magnetic field noise signal.

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