CN117015224B - Electromagnetic shielding device and system for keeping superconducting state of Josephson junction - Google Patents

Abstract

The invention relates to an electromagnetic shielding device and system for maintaining the superconducting state of the Josephson junction. The device includes at least two concentrically spaced magnetic shielding units. Each magnetic shielding unit includes a cylinder with one end closed and a A removable cover that fits closely at the other end of the cylinder; a non-magnetic isolation layer is provided on the inner wall surface and/or the outer wall surface of the cylinder, and there is at least one non-magnetic isolation layer between adjacent magnetic shielding units; According to the magnetic field strength of the environment around the Josephson junction and the target shielding effectiveness of the electromagnetic shielding device, determine the size of the magnetic shielding unit and the thickness of the non-magnetic isolation layer, and set a vacuum inside each magnetic shielding unit to keep the Josephson junction super guidance status. The electromagnetic shielding device and system provided by the present invention have a simple structure and strong designability, and can stably and effectively realize electromagnetic shielding of the Josephson junction chip.

Description

An electromagnetic shielding device and system that maintains the superconducting state of Josephson junction

Technical field

The invention belongs to the technical field of electromagnetic shielding, and particularly relates to an electromagnetic shielding device and system that maintains the superconducting state of the Josephson junction.

Background technique

The existence of a magnetic field in an area is caused by a magnetic flux source. The magnetic flux source may be the earth, a motor, a transformer, a power line, etc. The strength of the magnetic field at a certain location depends on the magnetic field source and the distance of the location from the magnetic field source. In quantum voltage systems, proper electromagnetic shielding is critical to isolating the Josephson junction chip from these electromagnetic fields. Increasing distance from the source of magnetic field radiation reduces the strength of the shielded magnetic field, so the best way to isolate a chip from a known source of electromagnetic fields is to move the chip out of the electromagnetic field, however this is often not possible. There are many shielding materials that can be used to further reduce the incoming electromagnetic fields. In order to develop and design effective magnetic shielding, one must first measure the magnetic field strength around the area to be shielded and estimate the source of the electromagnetic noise. In a Josephson voltage standard system, it is critical to electromagnetically shield the Josephson junction array chip and maintain very low magnetic noise levels in the vicinity. In liquid helium-free quantum voltage systems, closed cycle refrigeration (CCR) based cooling systems use two-stage 4.2 K Gifford-McMahon (GM) cryogenic coolers and vacuum pumps to achieve operating temperatures; the disadvantages of using these systems are They are a major source of electromechanical noise and are located very close to the Josephson chip. Since the noise source cannot be eliminated or the separation distance significantly increased, magnetic shielding must be carefully designed around the chip to obtain a very low magnetic field region. For example, patent CN101059556A provides a superconducting qubit measurement system, which places the Josephson junction under test in a metal sample box. In particular, the sample box is made of superconducting metal aluminum material. During measurement, the Josephson junction under test and the sample are The box is in a temperature environment of the order of mk, and aluminum will transform into a superconductor after the temperature drops to 1.14k, and it will become a superconducting shielding layer around the Josephson junction under test, which can further reduce the interference of external environmental noise on the sample , although this patent has a certain superconducting shielding effect, it requires continuous cooling of the aluminum, and its shielding effect cannot be guaranteed stably and continuously.

Therefore, how to provide an electromagnetic shielding device with a simple structure, low energy consumption, good electromagnetic shielding effect, and a wide range of application scenarios that can stably and effectively maintain the Josephson junction superconducting state is an urgent technical problem in this field that needs to be solved.

Contents of the invention

In view of the above-mentioned defects in the prior art, the present invention provides an electromagnetic shielding device and system that maintains the superconducting state of the Josephson junction, which can realize electromagnetic shielding of the Josephson junction chip.

The invention provides an electromagnetic shielding device that maintains the superconducting state of the Josephson junction. The device includes at least two concentrically spaced magnetic shielding units, wherein,

Each magnetic shielding unit includes a cylinder with one end closed and a removable cover that tightly fits the other end of the cylinder;

A non-magnetic isolation layer is provided on the inner wall surface and/or the outer wall surface of the cylinder, and there is at least one non-magnetic isolation layer between adjacent magnetic shielding units;

According to the magnetic field strength of the environment around the Josephson junction and the target shielding effectiveness of the electromagnetic shielding device, determine the size of the magnetic shielding unit and the thickness of the non-magnetic isolation layer, and set a vacuum inside each magnetic shielding unit to keep the Josephson junction super guidance status.

Further, the magnetic shielding unit is a cylinder and is arranged vertically. It can avoid the influence of the earth's magnetic field on the electromagnetic shielding device and destroy its magnetic shielding effect.

Furthermore, the inner cavity diameter of the magnetic shielding unit with the smallest inner diameter is 15 to 20 cm, that is, the inner cavity diameter of the innermost magnetic shielding unit is 15 to 20 cm.

Further, the outer diameter of each magnetic shielding unit is determined, specifically including:

,

Among them, B is the magnetic flux density of the magnetic shielding unit, D is the outer diameter of the magnetic shielding unit, H ₀ is the magnetic field intensity of the environment around the magnetic shielding unit in Oersted units, d" is the thickness of the magnetic shielding unit, α is Magnetic flux density coefficient.

Preferably, α is 1.25, that is, the size of each magnetic shielding unit satisfies the following relationship:

.

Furthermore, the magnetic shielding unit is made of highly magnetically permeable alloy, specifically MuMetal material, and the non-magnetic isolation layer includes oxygen-free copper (OFHC copper).

Further, the non-magnetic isolation layer is provided on the inner wall surface and/or the outer wall surface of the magnetic shielding unit, and the thickness of each non-magnetic isolation layer is the same, and the thickness of each magnetic shielding unit is the same;

Determination of the thickness of the non-magnetic isolation layer includes:

The target shielding effectiveness of the electromagnetic shielding device is obtained according to the magnetic field strength of the environment around the electromagnetic shielding device and the critical magnetic field of the Josephson junction;

According to the inner diameter and outer diameter of each magnetic shielding unit, the outer diameter or inner diameter of the non-magnetic isolation layer provided on each magnetic shielding unit is obtained;

According to the inner diameter, outer diameter and magnetic permeability of each magnetic shielding unit, and the outer diameter, inner diameter, relative magnetic permeability and electrical conductivity of each non-magnetic isolation layer, each magnetic shielding unit and each non-magnetic isolation layer are obtained The shielding effectiveness;

According to the corresponding relationship between the thickness of each magnetic shielding unit and the inner diameter and outer diameter, the corresponding relationship between the thickness of each non-magnetic isolation layer and the inner diameter and outer diameter, the target shielding effectiveness of the electromagnetic shielding device, and the corresponding relationship between each magnetic shielding unit and each The shielding effectiveness of each non-magnetic isolation layer is obtained by obtaining the thickness of each non-magnetic isolation layer;

Further, the thickness of each non-magnetic isolation layer satisfies the following relationship:

,

In the formula, d' is the thickness of each non-magnetic isolation layer, _{outside r', i} is the outer diameter of the i-th non-magnetic isolation layer, _{inside r', i} is the inner diameter of the i-th non-magnetic isolation layer, and n is The number of layers of non-magnetic isolation layer, μ ₀ is the vacuum magnetic permeability, μ ₁ is the relative magnetic permeability of the non-magnetic isolation layer, ω is the angular frequency of the magnetic field, is the conductivity of the non-magnetic isolation layer, y is the imaginary part, d" is the thickness of each magnetic shielding unit, _{outside r", j} is the outer diameter of the jth magnetic shielding unit, _{inside r", j} is the jth magnetic shielding unit The inner diameter of the magnetic shielding unit, m is the number of magnetic shielding units, m≤n, μ ₂ is the magnetic permeability of the magnetic shielding unit, a', b', a", b" are all constants, H is the surrounding area of the electromagnetic shielding device The magnetic field strength of the environment, B _c is the critical magnetic field.

Further, the non-magnetic isolation layer is formed by magnetron sputtering;

Among them, the action time of the DC power supply, the action time of the high-power pulse power supply and the action time of the ion source are regarded as one cycle, and a non-magnetic isolation layer with a predetermined thickness is formed on the inner wall surface and/or the outer wall surface of the magnetic shielding unit through multiple cycles.

Furthermore, the action time of DC power supply, high-power pulse power supply and ion source in each cycle are 20~40min, 200~300min, and 6~8min respectively.

In a second aspect, a Josephson voltage system is also provided, and the system includes:

The above-mentioned electromagnetic shielding device for maintaining the superconducting state of the Josephson junction;

A Josephson junction chip is located inside the electromagnetic shielding device and has a Josephson junction. The Josephson junction chip is at least located at the geometric center of the two concentrically spaced magnetic shielding units.

Further, a temperature sensor and a magnetic field sensor are provided in the electromagnetic shielding device, and the temperature sensor and the magnetic field sensor are placed close to the Josephson junction chip.

Furthermore, the Josephson voltage system also includes a controller that adjusts the ambient temperature around the magnetic shielding unit, and a connector located on the magnetic shielding unit with the largest inner diameter. The connector can be disconnected from the temperature sensor and magnetic field sensor respectively from the controller. Connection.

Further, the system includes: when the temperature result detected by the temperature sensor is not greater than the critical temperature of the Josephson junction chip, the connector is connected to the controller, and the controller adjusts the temperature of the environment around the magnetic shielding unit according to the temperature result detected by the temperature sensor. , when the temperature result detected by the temperature sensor is greater than the critical temperature of the Josephson junction chip, the connector is disconnected from the controller.

Further, the controller adjusts the temperature of the environment around the magnetic shielding unit based on the temperature result detected by the temperature sensor, which also includes:

Obtain the current temperature results detected by the temperature sensor and the temperature results within a predetermined time period;

According to the temperature result detected by the temperature sensor, the temperature change rate is obtained;

According to the temperature change rate, the temperature change state in the magnetic shielding unit is obtained;

According to the temperature change status, current temperature result and temperature threshold, adjust the ambient temperature around the magnetic shielding unit to the preset value.

Among them, the temperature change state includes heating, constant and cooling states;

According to the temperature change status, current temperature results and temperature threshold, adjust the ambient temperature around the magnetic shielding unit to the preset value, including:

When the temperature change state is a heating state and the current temperature result is less than the temperature threshold, and when the temperature change state is a cooling state and the current temperature result is greater than the temperature threshold, adjust the ambient temperature around the magnetic shielding unit to remain unchanged;

When the temperature change state is a heating state and the current temperature result is not less than the temperature threshold, and when the temperature change state is a constant temperature state and the current temperature result is greater than the temperature threshold, reduce the ambient temperature around the magnetic shielding unit;

When the temperature change state is a constant temperature or cooling state, and the current temperature result is not greater than the temperature threshold, adjust the ambient temperature around the magnetic shielding unit to a predetermined temperature; preferably, the predetermined temperature is 4K.

The invention provides an electromagnetic shielding device and system for maintaining the superconducting state of the Josephson junction, which at least includes the following beneficial effects:

Compared with a single magnetic shielding unit, the present invention can achieve continuous shielding by arranging at least two magnetic shielding units. The multiplication effect through successive shields provides significant magnetic field attenuation and prevents saturation of the shield. And by setting up a non-magnetic isolation layer that cooperates with the magnetic shielding unit, the magnetic shielding of the Josephson junction chip can be jointly achieved. Among them, the magnetic shielding unit and the non-magnetic isolation layer are used to shield the low-frequency magnetic field and the high-frequency magnetic field in the surrounding environment respectively, thereby improving the application scenarios of the electromagnetic shielding device and improving the magnetic shielding effect on the Josephson junction chip.

By disposing the Josephson junction chip at the geometric center of the magnetic shielding unit, the magnetic field around the Josephson junction chip can be made uniform and symmetrical, and the influence of the magnetic field on the Josephson junction chip can be minimized.

By selecting the appropriate size of the magnetic shielding unit and non-magnetic isolation layer, it is possible to ensure that the inner vacuum, temperature and magnetic shielding meet predetermined requirements while reducing costs.

Description of the drawings

Figure 1 shows a schematic diagram of an electromagnetic shielding device that maintains the superconducting state of the Josephson junction according to an embodiment of the present invention;

Figure 2 shows a schematic diagram of a Josephson voltage system according to an embodiment of the present invention.

Explanation of reference signs: 10-electromagnetic shielding device, 11-magnetic shielding unit, 2-Josephson junction chip, 3-magnetic field sensor, 4-temperature sensor, 5-connector, 6-controller.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, optional embodiments of the present invention are described in detail below with reference to the accompanying drawings.

In the Josephson junction, the binding energy of Cooper's electrons is very small and is very sensitive to any external excitation source. The presence of an external magnetic field exerts a torque on the electron spins, which tends to destroy these Cooper pairs, and as the Cooper pairs separate into individual electrons, the Josephson junction becomes a normal conductor or "non-superconductor." Cooper pairs break when the magnetic field is above a specific value associated with superconducting materials; this magnetic field value is called the critical magnetic field and depends on the material involved.

Superconducting states cannot exist in magnetic fields greater than the critical magnetic field, even at absolute zero. This critical magnetic field is closely related to the critical temperature of the superconductor, which in turn is related to the band gap. Critical temperature and critical field are parameters that represent the amount of energy that can be supplied to a material in a way that begins to interfere with the superconducting mechanism. According to the Meissner effect, the essence of a superconductor is a repulsive magnetic field, but this is true only when the external magnetic field does not exceed its critical magnetic field. The critical magnetic field value is usually established at 0 K. As the temperature increases, the magnetic field value gradually decreases until it reaches zero at the superconducting critical temperature. The critical magnetic field (B _c ) at any temperature (T) below the critical temperature is given by:

,

where B _c (0) is the magnetic field required to suppress superconductivity at 0 K, and T _c is the critical temperature of the material. The Josephson junction is highly sensitive to any magnetic field and is susceptible to magnetic fields as low as a few Gauss.

Referring to Figure 1, in order to achieve magnetic shielding of the Josephson junction chip 2, the present invention provides an electromagnetic shielding device 10 that maintains the superconducting state of the Josephson junction. The device includes at least two concentrically spaced magnetic shielding units. 11, among which,

Each magnetic shielding unit 11 includes a cylinder with one end closed and a detachable cover that tightly fits the other end of the cylinder;

A non-magnetic isolation layer is provided on the inner wall surface and/or the outer wall surface of the cylinder, and there is at least one non-magnetic isolation layer between adjacent magnetic shielding units 11;

According to the magnetic field strength of the environment around the Josephson junction and the target shielding effectiveness of the electromagnetic shielding device 10, the size of the magnetic shielding unit 11 and the thickness of the non-magnetic isolation layer are determined, and each magnetic shielding unit 11 is set to a vacuum to maintain the Josephson junction. Sen junction superconducting state.

The number and size of the magnetic shielding units 11 in the electromagnetic shielding device 10 of the present invention can be selected according to the environmental parameters of the actual application scenario. For example, when the magnetic field intensity of the surrounding environment of the electromagnetic shielding device 10 is relatively high, a larger number of magnetic shielding units 11 can be installed. For the magnetic shielding unit 11, a hierarchical structure formed by a certain thickness of the magnetic shielding unit 11 and a non-magnetic isolation layer can also be selected to achieve electromagnetic shielding in the current environment. The non-magnetic isolation layer includes OFHC copper material (oxygen-free copper), which can further improve the magnetic isolation effect. In order to improve the shielding effect, the inner cavity diameter of the magnetic shielding unit 11 needs to be as small as possible, because attenuation is inversely proportional to the diameter, and the size of the magnetic shielding is calculated based on the approximate value of the environmental field and the expected level of flux density. Preferably, the inner cavity diameter of the two magnetic shielding units 11 is 15~20cm, so that on the basis of shielding based on specific materials, by selecting an appropriate diameter range, the electromagnetic shielding device 10 of the present invention has better magnetic shielding. Effect. Specifically, by selecting an appropriate size of the magnetic shielding unit 11, the present invention can ensure that the inner vacuum degree, temperature and magnetic shielding meet predetermined requirements on the basis of reducing costs. For example, when the inner cavity diameter of the inner magnetic shielding unit 11 is greater than 20 cm, although it can have a better shielding effect, due to its larger diameter, the cost of the magnetic shielding unit 11 increases, and it is also prone to difficulty in installation. . When the inner cavity diameter of the inner magnetic shielding unit 11 is less than 15cm, although it is easy to install and requires low cost, the smaller size of the magnetic shielding unit 11 cannot make the internal environment vacuum, temperature and magnetic shielding reach the predetermined effect.

The magnetic shielding unit 11 is made of alloy material with high magnetic permeability. Since magnetic fields can neither be generated nor eliminated, the purpose of the magnetic shielding unit 11 is to redistribute the magnetic field in such a way that an area of zero or very low magnetic field is generated around the Josephson junction chip 2 to be shielded. The high permeability material shields the area where the Josephson junction chip 2 is located by pulling the magnetic field toward itself and away from the Josephson junction chip 2 to be shielded. When the present invention implements electromagnetic shielding through the magnetic shielding unit 11, the material of the magnetic shielding unit 11 is selected so that it has a better shielding effect. Preferably, the magnetic shielding unit 11 of the present invention is made of MuMetal material. MuMetal shields have the ability to absorb magnetic energy and produce very high attenuation by concentrating the magnetic field within the MuMetal shield itself, making these shielding alloys the material of choice for reducing low-frequency electromagnetic interference (EMI). Since the operating environment of the Josephson junction chip 2 has higher requirements, the magnetic shielding effect needs to meet predetermined requirements. Therefore, by manufacturing two concentrically spaced magnetic shielding units 11 with high magnetic permeability metal, a magnetic shielding unit 11 is manufactured for the Josephson junction chip 2 Enclosures in extremely low magnetic field regions. Because the magnetic field source is very strong and close to the Josephson junction chip 2, the multiplication effect of the continuous shield provides significantly greater magnetic field attenuation and prevents saturation of the shield compared to a single magnetic shield of equivalent wall thickness.

For the electromagnetic shielding of the Josephson junction chip 2 in different scenarios, the optimal size of the magnetic shielding unit 11 can be selected by analyzing the setting environment to complete the electromagnetic shielding of the Josephson junction chip 2 . Specifically, the size of each magnetic shielding unit 11 is calculated based on the approximate value of the environmental field and the expected level of flux density. The size determination of the magnetic shielding unit 11 may specifically include:

,

Where, B is the flux density of the magnetic shielding unit, D is the diameter of the magnetic shielding unit, H ₀ is the ambient field in Oersted units, and d" is the thickness of the magnetic shielding unit.

The non-magnetic isolation layer of the present invention is provided on the inner wall surface and/or the outer wall surface of the magnetic shielding unit, and the thickness of each non-magnetic isolation layer is the same, and the thickness of each magnetic shielding unit is the same;

Determination of the thickness of each non-magnetic isolation layer includes:

The target shielding effectiveness of the electromagnetic shielding device 10 is obtained according to the magnetic field strength of the environment around the electromagnetic shielding device 10 and the critical magnetic field of the Josephson junction;

According to the inner diameter and outer diameter of each magnetic shielding unit, the outer diameter or inner diameter of the non-magnetic isolation layer provided on each magnetic shielding unit is obtained;

According to the inner diameter, outer diameter and magnetic permeability of each magnetic shielding unit, and the outer diameter, inner diameter, relative magnetic permeability and electrical conductivity of each non-magnetic isolation layer, each magnetic shielding unit and each non-magnetic isolation layer are obtained The shielding effectiveness;

According to the corresponding relationship between the thickness of each magnetic shielding unit and the inner diameter and outer diameter, the corresponding relationship between the thickness of each non-magnetic isolation layer and the inner diameter and outer diameter, the target shielding effectiveness of the electromagnetic shielding device 10, and each magnetic shielding unit and The shielding effectiveness of each non-magnetic isolation layer is obtained by obtaining the thickness of each non-magnetic isolation layer;

Among them, the thickness of each non-magnetic isolation layer satisfies the following relationship:

,

In the formula, d' is the thickness of each non-magnetic isolation layer, _{outside r', i} is the outer diameter of the i-th non-magnetic isolation layer, _{inside r', i} is the inner diameter of the i-th non-magnetic isolation layer, and n is The number of layers of the non-magnetic isolation layer, μ ₀ is the vacuum permeability, μ ₁ is the relative permeability of the non-magnetic isolation layer, and the relative permeability is the ratio of the magnetic permeability of the non-magnetic isolation layer to the vacuum permeability, ω is the angular frequency of the magnetic field, is the conductivity of the non-magnetic isolation layer, y is the imaginary part, d" is the thickness of each magnetic shielding unit, _{outside r", j} is the outer diameter of the jth magnetic shielding unit, _{inside r", j} is the jth magnetic shielding unit The inner diameter of the magnetic shielding unit, m is the number of magnetic shielding units, m≤n, i=1,2,3,...,n, j=1,2,3,...,m, μ ₂ is the magnetic The magnetic permeability of the shielding unit, a', b', a", b" are all constants, H is the magnetic field intensity of the environment around the electromagnetic shielding device 10, and B _c is the critical magnetic field. The present invention is based on each magnetic shielding unit and The thickness of each non-magnetic isolation layer is limited, so that on the basis of meeting the electromagnetic shielding requirements of the current application environment, the excessive use of magnetic shielding units and non-magnetic isolation layers during structural design can be minimized, which can reduce the electromagnetic shielding device of the present invention. 10 cost, with high economic effect.

The non-magnetic isolation layer in the embodiment of the present invention is formed by magnetron sputtering; wherein, the action time of the DC power supply, the action time of the high-power pulse power supply and the action time of the ion source are one cycle, and the magnetic shielding unit is formed through multiple cycles. The inner wall surface and/or the outer wall surface form a non-magnetic isolation layer with a predetermined thickness. Furthermore, the action time of DC power supply, high-power pulse power supply and ion source in each cycle are 20~40min, 200~300min, and 6~8min respectively.

As shown in Figure 2, the present invention also provides a Josephson voltage system, which includes:

The above-mentioned electromagnetic shielding device 10 that maintains the superconducting state of the Josephson junction;

The Josephson junction chip 2 is located inside the electromagnetic shielding device 10 and has a Josephson junction.

By disposing the Josephson junction chip 2 inside the electromagnetic shielding device 10 , the electromagnetic shielding of the Josephson junction chip 2 can be achieved by the electromagnetic shielding device 10 . Moreover, by setting the material, size, and structure of the electromagnetic shielding device 10 as described above, the electromagnetic shielding effect on the Josephson junction chip 2 is improved.

In order to improve the shielding effect on the Josephson junction chip 2 of the Josephson voltage system of the present invention, the Josephson junction chip 2 can be arranged at the geometric center of two concentrically spaced magnetic shielding units 11 . The magnetic field around the Josephson junction chip 2 can be made uniform and symmetrical, and the influence of the magnetic field on the Josephson junction chip 2 can be minimized.

The magnetic shielding unit 11 is very effective in preventing any type of low frequency magnetic noise from entering the magnetically shielded enclosure. A low magnetic field enclosure is created by a physical boundary of magnetic shielding that separates and isolates the internal volume, but it should be ensured that there are no sources of magnetic fields within the chamber. In an operating Josephson junction system, there is a potential magnetic field source near Josephson junction chip 2 (located outside the magnetic shielding unit). In addition, in order to monitor the working conditions of the Josephson junction chip 2 , a temperature sensor 4 and a magnetic field sensor 3 can also be provided in the electromagnetic shielding device 10 , and the temperature sensor 4 and the magnetic field sensor 3 are arranged close to the Josephson junction chip 2 . By monitoring the temperature and magnetic field size, the shielding effect of the electromagnetic shielding device 10 can be judged, thereby ensuring the working device of the Josephson junction chip 2 inside it. Furthermore, the Josephson voltage system also includes a controller 6 that adjusts the ambient temperature around the magnetic shielding unit, and a connector 5 located on the magnetic shielding unit with the largest inner diameter. The connector 5 connects the temperature sensor 4 and the magnetic field sensor 3 to the control unit respectively. 6 disconnectable connections. Among them, the connector 5 will have different connection effects at different temperatures. Specifically, when the temperature result detected by the temperature sensor 4 is not greater than the critical temperature of the Josephson junction chip 2, the connector 5 is connected to the controller 6, and the controller 6. Adjust the temperature of the environment around the magnetic shielding unit according to the temperature result detected by the temperature sensor 4. When the temperature result detected by the temperature sensor 4 is greater than the critical temperature of the Josephson junction chip 2, the connector 5 is disconnected from the controller 6.

Among them, the controller adjusts the temperature of the environment around the magnetic shielding unit according to the temperature result detected by the temperature sensor 4, and also includes:

Obtain the current temperature result detected by the temperature sensor 4 and the temperature result within a predetermined time period;

According to the temperature result detected by the temperature sensor 4, the temperature change rate is obtained;

According to the temperature change rate, the temperature change state in the magnetic shielding unit is obtained;

According to the temperature change status, current temperature result and temperature threshold, adjust the ambient temperature around the magnetic shielding unit to the preset value.

Temperature change states include heating, constant temperature and cooling states;

According to the temperature change status, current temperature results and temperature threshold, adjust the ambient temperature around the magnetic shielding unit to the preset value, including:

When the temperature change state is a heating state and the current temperature result is less than the temperature threshold, and when the temperature change state is a cooling state and the current temperature result is greater than the temperature threshold, adjust the ambient temperature around the magnetic shielding unit to remain unchanged;

When the temperature change state is a heating state and the current temperature result is not less than the temperature threshold, and when the temperature change state is a constant temperature state and the current temperature result is greater than the temperature threshold, reduce the ambient temperature around the magnetic shielding unit;

When the temperature change state is a constant temperature or cooling state, and the current temperature result is not greater than the temperature threshold, adjust the ambient temperature around the magnetic shielding unit to a predetermined temperature; preferably, the predetermined temperature is 4K.

The embodiment of the present disclosure provides an electromagnetic shielding device 10 that maintains the superconducting state of the Josephson junction. The system includes a processor and a memory. The processor implements the functions of the above embodiment by executing computer instructions in the memory.

It should be noted that the computer-readable medium mentioned above in the present disclosure may be a computer-readable signal medium or a computer-readable storage medium, or any combination of the above two. The computer-readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or device, or any combination thereof. More specific examples of computer readable storage media may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard drive, random access memory (RAM), read only memory (ROM), removable Programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination of the above. In this disclosure, a computer-readable storage medium may be any tangible medium that contains or stores a program for use by or in connection with an instruction execution system, apparatus, or device. In the present disclosure, a computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code therein. Such propagated data signals may take many forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. A computer-readable signal medium may also be any computer-readable medium other than a computer-readable storage medium that can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device . Program code embodied on a computer-readable medium may be transmitted using any suitable medium, including but not limited to: wire, optical fiber cable, RF (radio frequency), etc., or any suitable combination of the foregoing.

The above-mentioned computer-readable medium may be included in the above-mentioned electronic device; it may also exist independently without being assembled into the electronic device. Computer program code for performing the operations of the present disclosure may be written in one or more programming languages, including object-oriented programming languages such as Java, Smalltalk, C++, and conventional A procedural programming language, such as the "C" language or similar programming language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server; In situations involving remote computers, the remote computer can be connected to the user's computer through any kind of network, including a local area network (AN) or a wide area network (WAN), or it can be connected to an external computer (such as an Internet service provider through the Internet). ).

The flowcharts and block diagrams in the figures illustrate the architecture, functionality, and operations of possible implementations of systems, methods, and computer program products according to various embodiments of the present disclosure. In this regard, each block in the flowchart or block diagram may represent a module, segment, or portion of code that contains one or more logic functions that implement the specified executable instructions. It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown one after another may actually execute substantially in parallel, or they may sometimes execute in the reverse order, depending on the functionality involved. It will also be noted that each block of the block diagram and/or flowchart illustration, and combinations of blocks in the block diagram and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or operations. , or can be implemented using a combination of specialized hardware and computer instructions.

The units involved in the embodiments of the present disclosure can be implemented in software or hardware. Among them, the name of a unit does not constitute a limitation on the unit itself under certain circumstances.

The above describes the preferred embodiments of the present invention, which are intended to make the spirit of the present invention clearer and easier to understand. They are not intended to limit the present invention. All modifications, substitutions, and improvements can be made within the spirit and principles of the present invention. , should be included in the scope of protection summarized by the appended claims of the present invention.

Claims (9)

1. An electromagnetic shielding device that maintains the superconducting state of the Josephson junction, characterized in that the device includes at least two concentrically spaced magnetic shielding units, wherein, Each magnetic shielding unit includes a cylinder with one end closed and a detachable cover that closely fits the other end of the cylinder; a non-magnetic isolation layer is provided on the inner and/or outer wall of the cylinder, and There is at least one non-magnetic isolation layer between adjacent magnetic shielding units; According to the magnetic field strength of the environment around the Josephson junction and the target shielding effectiveness of the electromagnetic shielding device, determine the size of the magnetic shielding unit and the thickness of the non-magnetic isolation layer, and set a vacuum inside each magnetic shielding unit to keep the Josephson junction super conductive state; the inner cavity diameter of the magnetic shielding unit with the smallest inner diameter is 15~20cm; the thickness of each magnetic shielding unit is the same, and the outer diameter of each magnetic shielding unit is determined, including: ; Among them, B is the magnetic flux density of the magnetic shielding unit, D is the outer diameter of the magnetic shielding unit, H ₀ is the magnetic field intensity of the environment around the magnetic shielding unit in Oersted units, d" is the thickness of the magnetic shielding unit, α is Magnetic flux density coefficient; The thickness of each non-magnetic isolation layer is the same. The determination of the thickness of the non-magnetic isolation layer includes: The target shielding effectiveness of the electromagnetic shielding device is obtained according to the magnetic field strength of the environment around the electromagnetic shielding device and the critical magnetic field of the Josephson junction; the non-magnetic isolation layer provided on each magnetic shielding unit is obtained according to the inner diameter and outer diameter of each magnetic shielding unit. The outer diameter or inner diameter; according to the corresponding relationship between the thickness of each magnetic shielding unit and the inner diameter and outer diameter, the corresponding relationship between the thickness of each non-magnetic isolation layer and the inner diameter and outer diameter, the inner diameter and outer diameter of each magnetic shielding unit and magnetic permeability, the outer diameter, inner diameter, relative magnetic permeability and electrical conductivity of each non-magnetic isolation layer, and the target shielding effectiveness of the electromagnetic shielding device to obtain the thickness of each non-magnetic isolation layer. 2. The electromagnetic shielding device for maintaining the superconducting state of the Josephson junction as claimed in claim 1, wherein the magnetic shielding unit is made of a highly permeable alloy, and the non-magnetic isolation layer includes oxygen-free copper. 3. The electromagnetic shielding device for maintaining the superconducting state of the Josephson junction as claimed in claim 1, wherein the thickness of each non-magnetic isolation layer satisfies the following relationship: ; In the formula, d' is the thickness of each non-magnetic isolation layer, _{outside r', i} is the outer diameter of the i-th non-magnetic isolation layer, _{inside r', i} is the inner diameter of the i-th non-magnetic isolation layer, and n is The number of layers of non-magnetic isolation layer, μ ₀ is the vacuum magnetic permeability, μ ₁ is the relative magnetic permeability of the non-magnetic isolation layer, ω is the angular frequency of the magnetic field, is the conductivity of the non-magnetic isolation layer, y is the imaginary part, d" is the thickness of each magnetic shielding unit, _{outside r", j} is the outer diameter of the jth magnetic shielding unit, _{inside r", j} is the jth magnetic shielding unit The inner diameter of the magnetic shielding unit, m is the number of magnetic shielding units, μ ₂ is the magnetic permeability of the magnetic shielding unit, a', b', a", b" are all constants, H is the magnetic field strength of the environment around the electromagnetic shielding device , B _c is the critical magnetic field. 4. The electromagnetic shielding device for maintaining the superconducting state of the Josephson junction according to claim 1, wherein the non-magnetic isolation layer is formed by magnetron sputtering; Among them, the action time of the DC power supply, the action time of the high-power pulse power supply and the action time of the ion source are regarded as one cycle, and a non-magnetic isolation layer with a predetermined thickness is formed on the inner wall surface and/or the outer wall surface of the magnetic shielding unit through multiple cycles. 5. The electromagnetic shielding device for maintaining the Josephson junction superconducting state as claimed in claim 4, characterized in that the DC power supply action time, the high-power pulse power supply action time and the ion source action time in each cycle are 20 to 40 minutes respectively. ,200~300min, 6~8min. 6. A Josephson voltage system, characterized in that the system includes: The electromagnetic shielding device maintaining the superconducting state of the Josephson junction according to any one of claims 1 to 5; A Josephson junction chip is located inside the electromagnetic shielding device and has a Josephson junction. The Josephson junction chip is located at the geometric center of at least two concentrically spaced magnetic shielding units. 7. The Josephson voltage system according to claim 6, wherein a temperature sensor and a magnetic field sensor are provided in the electromagnetic shielding device, and the temperature sensor and the magnetic field sensor are provided close to the Josephson junction chip. 8. The Josephson voltage system as claimed in claim 7, characterized in that the Josephson voltage system further includes a controller that adjusts the ambient temperature around the magnetic shielding unit, and a connector located on the magnetic shielding unit with the largest inner diameter. The device connects the temperature sensor and magnetic field sensor to the controller in a detachable manner. 9. The Josephson voltage system according to claim 8, wherein when the temperature result detected by the temperature sensor is not greater than the critical temperature of the Josephson junction chip, the connector is connected to the controller, and the controller detects the temperature according to the temperature detected by the temperature sensor. The temperature result adjusts the temperature of the environment around the magnetic shielding unit. When the temperature result detected by the temperature sensor is greater than the critical temperature of the Josephson junction chip, the connector is disconnected from the controller.