Apparatus and method with frequency tuning

Abstract

Apparatuses and methods with frequency tuning are disclosed. A superconducting device includes: a frequency tunable device including a first conductive pad and a second conductive pad connected to each other by a Josephson junction; a ferromagnetic structure disposed at a predetermined distance from the first conductive pad and the second conductive pad; a control line under the ferromagnetic structure; and a control circuit configured to control a resonant frequency of the frequency adjustable device by controlling a current flowing through the control line.

Description

[0001] This application claims the benefit of Korean Patent Application No. 10-2023-0104932 filed on August 10, 2023, in the Korean Intellectual Property Office, and Korean Patent Application No. 10-2023-0162464 filed on November 21, 2023, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference in their entirety for all purposes. Technical Field

[0002] The following description relates to a frequency tunable device and a superconducting device including the frequency tunable device. Background Art

[0003] A quantum computer may be a computing machine that uses quantum mechanical phenomena (such as quantum superposition and quantum entanglement) as an operating principle for performing data processing. A unit element or the information itself that can store information using the principles of quantum mechanics is called a quantum bit (qubit), which can be used as the basic unit of information in a quantum computer.

[0004] Qubits can be implemented in various ways, such as photon qubits, ion trap qubits, topological qubits, and superconducting qubits. Summary of the invention

[0005] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

[0006] In one or more general aspects, a superconducting device includes: a frequency tunable device including a first conductive pad and a second conductive pad connected to each other through a Josephson junction; a ferromagnetic structure disposed at a predetermined distance from the first conductive pad and the second conductive pad; a control line located below the ferromagnetic structure; and a control circuit configured to control a resonant frequency of the frequency tunable device by controlling a current flowing through the control line.

[0007] The frequency tunable device may include one or both of a tunable qubit coupler and a tunable qubit.

[0008] The control circuit may be configured to flip the magnetization arrangement direction of the ferromagnetic structure by applying a current exceeding a predetermined threshold to the control line to induce a spin-orbit torque (SOT) phenomenon in the ferromagnetic structure.

[0009] In order to apply the current exceeding the predetermined threshold, the control circuit may be configured to apply the current exceeding the predetermined threshold in the form of a pulse only once.

[0010] To apply the current exceeding the predetermined threshold, the control circuit may be configured to: apply the current exceeding the predetermined threshold in a direction opposite to the current direction during the formation of the magnetization arrangement direction to flip the formed magnetization arrangement direction of the ferromagnetic structure.

[0011] The control circuit may be configured to change the magnetic flux of the frequency tunable device based on the flipping of the magnetization alignment direction.

[0012] The control circuit may be configured to obtain the resonant frequency corresponding to the changed magnetic flux using a model defining a relationship between the magnetic flux and the resonant frequency.

[0013] In order to control the resonant frequency, the control circuit may be configured to control the resonant frequency to be in two states including coupling-on and coupling-off.

[0014] To control the resonant frequency, the control circuit may be configured to control the resonant frequency to be a coupling-on frequency by setting the resonant frequency of the frequency tunable device to be similar to the resonant frequency of the coupled qubit.

[0015] The frequency tunable device may include two Josephson junctions, and the ferromagnetic structure is located between the two Josephson junctions or on the outside of one of the two Josephson junctions.

[0016] The ferromagnetic structure can be formed to have a structure with broken horizontal symmetry.

[0017] The ferromagnetic structure may have a diameter of 50 nanometers or more and 5 micrometers or less.

[0018] The first conductive pad and the second conductive pad may be made of a superconducting material.

[0019] The control line may be disposed parallel to a longitudinal direction of the first conductive pad and the second conductive pad.

[0020] The control wire may be made of heavy metal.

[0021] The control lines, ferromagnetic structures and frequency tunable devices may be stacked from bottom to top.

[0022] In one or more general aspects, a method for controlling the resonant frequency of a frequency tunable device using a superconducting device, the superconducting qubit-based device comprising a frequency tunable device, a ferromagnetic structure, and a control line, the frequency tunable device comprising a first conductive pad and a second conductive pad connected to each other via a Josephson junction, the ferromagnetic structure being disposed at a predetermined distance from the first conductive pad and the second conductive pad, the control line being located below the ferromagnetic structure, the method comprising: applying a current to the control line; flipping a magnetization arrangement direction of the ferromagnetic structure; changing a magnetic flux of the frequency tunable device; and controlling the resonant frequency of the frequency tunable device.

[0023] The frequency tunable device may include one or both of a tunable qubit coupler and a tunable qubit.

[0024] The step of switching the magnetization arrangement direction may include switching the magnetization arrangement direction of the ferromagnetic structure by applying a current exceeding a predetermined threshold to the control line to induce a SOT phenomenon in the ferromagnetic structure.

[0025] In one or more general aspects, a superconducting device includes: a frequency tunable device including two Josephson junctions, wherein a ferromagnetic structure is located between the two Josephson junctions or on the outside of one of the two Josephson junctions; the ferromagnetic structure; and a control line, wherein the resonant frequency of the frequency tunable device is changed by flipping the magnetization arrangement direction of the ferromagnetic structure by applying a current exceeding a predetermined threshold to the control line.

[0026] Other features and aspects will be apparent from the following detailed description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1A is a diagram illustrating a structure of a quantum computer chip according to one or more embodiments.

[0028] Figure 1B is a circuit diagram showing a frequency fixing device.

[0029] Figure 1C is a circuit diagram showing a frequency tunable device.

[0030] Figure 1D is a circuit diagram used to describe the resonant frequency control of a tunable qubit coupler.

[0031] Figure 2A and Figure 2B is a diagram illustrating a structure of a superconducting device including a tunable qubit coupler according to one or more embodiments.

[0032] Figure 2C and Figure 2D is a diagram illustrating a ferromagnetic structure according to one or more embodiments.

[0033] FIG. 3A to FIG. 3D is a circuit diagram illustrating magnetic field and flux through a tunable qubit coupler according to the magnetization alignment direction of a ferromagnetic structure according to one or more embodiments.

[0034] FIG. 4A to FIG. 4B is a circuit diagram illustrating magnetic field and flux through a tunable qubit coupler according to the magnetization alignment direction of a ferromagnetic structure according to one or more embodiments.

[0035] Figure 5A and Figure 5B is a graph showing the relationship between application of current and resonance frequency over time.

[0036] FIG. 6A to FIG. 6D is a diagram illustrating a process of manufacturing a superconducting device according to one or more embodiments.

[0037] Figure 7 is a flow chart illustrating a method of controlling the resonant frequency of a tunable qubit coupler using a superconducting device according to one or more embodiments.

[0038] Throughout the drawings and detailed description, unless otherwise described, the same drawing reference numerals will be understood to refer to the same elements, features, and structures. The relative sizes and depictions of these elements may be exaggerated for clarity, illustration, and convenience. DETAILED DESCRIPTION

[0039] The following specific embodiments are provided to help the reader obtain a comprehensive understanding of the method, device and / or system described herein. However, after understanding the disclosure of the application, various changes, modifications and equivalents of the method, device and / or system described herein will be clear. For example, the sequence in the operation described herein and / or the sequence of operation are only examples, and are not limited to those sequences set forth herein, but except for the sequence in the operation that must occur in a specific order and / or the sequence of operation, it can be changed as it will be clear after understanding the disclosure of the application. As another example, except that at least a portion of the sequence in the sequence in the sequence in the operation and / or the operation must occur in order (e.g., a specific order), the sequence in the sequence in the operation and / or the operation can be performed in parallel. In addition, for greater clarity and simplicity, the description of features known after understanding the disclosure of the application can be omitted.

[0040] Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. Advantages and features of the present invention and methods of implementing the present invention will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. Throughout the specification, the same reference numerals denote the same elements.

[0041] Although terms such as "first", "second" and "third" or A, B, (a), (b), etc. may be used herein to describe various components, components, regions, layers or parts, these components, components, regions, layers or parts are not limited by these terms. Each of these terms is not used to define, for example, the essence, order or sequence of the corresponding component, component, region, layer or part, but is only used to distinguish the corresponding component, component, region, layer or part from other components, components, regions, layers or parts. Therefore, without departing from the teachings of the examples, the first component, first component, first region, first layer or first part referred to in the examples described herein may also be referred to as the second component, second component, second region, second layer or second part.

[0042] The terms used herein are only used to describe various examples and are not used to limit disclosure. Unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. As a non-limiting example, the terms "comprise", "include" and "have" indicate the presence of stated features, quantities, operations, components, elements and / or combinations thereof, but do not exclude the presence or addition of one or more other features, quantities, operations, components, elements and / or combinations thereof, or optionally the presence of optional stated features, quantities, operations, components, elements and / or combinations thereof. In addition, although one embodiment may elaborate that the terms "comprise", "include" and "have" indicate the presence of stated features, quantities, operations, components, elements and / or combinations thereof, other embodiments may have one or more of the stated features, quantities, operations, components, elements and / or combinations thereof that do not exist.

[0043] In the following description, when a constituent element is disposed “on” or “under” another constituent element, the constituent element may be merely directly on or under the other constituent element, or be above or below the other constituent element in a non-contact manner.

[0044] As used herein, the term "and / or" includes any one of the associated listed items and any combination of any two or more. Unless the corresponding description and embodiments require that such a list (e.g., "at least one of A, B, and C") be interpreted as having a conjunctive meaning, the phrases "at least one of A, B, and C," "at least one of A, B, or C," etc. are intended to have a disjunctive meaning, and these phrases "at least one of A, B, and C," "at least one of A, B, or C," etc. also include examples in which one or more of each of A, B, and / or C may exist (e.g., any combination of one or more of each of A, B, and C).

[0045] Unless otherwise indicated herein, the operations constituting the method may be performed in any suitable order. Unless otherwise stated, the use of any and all languages ​​(e.g., "such as") provided herein is intended only to explain the disclosed technical spirit in detail and is not intended to limit the scope of the disclosure.

[0046] Unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as those commonly understood by those skilled in the art to which the present disclosure belongs based on the understanding of the disclosure of the present application. Unless explicitly defined as such herein, terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant field and the disclosure of the present application, and should not be interpreted in an idealized or overly formalized meaning.

[0047] Throughout the specification, when a component or element is described as being "on", "connected to", "bonded to" or "joined to" another component, element or layer, it may be directly (e.g., in contact with) "on", "connected to", "bonded to" or "joined to" the other component, element or layer, or one or more other components, elements or layers may reasonably be present in between. When a component or element is described as being "directly on", "directly connected to", "directly joined to" or "directly joined to" another component, element or layer, there may be no other components, elements or layers in between. Similarly, expressions such as "between" and "immediately between" and "adjacent to" and "immediately adjacent to" may also be interpreted as described above.

[0048] As used herein, the term "and / or" includes any one of the associated listed items and any combination of any two or more. Unless the corresponding description and embodiments require that such a list (e.g., "at least one of A, B, and C") be interpreted as having a conjunctive meaning, the phrases "at least one of A, B, and C," "at least one of A, B, or C," etc. are intended to have a disjunctive meaning, and these phrases "at least one of A, B, and C," "at least one of A, B, or C," etc. also include examples in which one or more of each of A, B, and / or C may exist (e.g., any combination of one or more of each of A, B, and C).

[0049] The features described herein may be embodied in different forms and should not be construed as being limited to the examples described herein. On the contrary, the examples described herein are provided to illustrate only some of the many possible ways in which it will be clear to implement the methods, devices and / or systems described herein after understanding the disclosure of the present application. The use of the term "may" herein with respect to an example or embodiment (e.g., what may be included or implemented with respect to an example or embodiment) indicates that there is at least one example or embodiment that includes or implements such a feature, and all examples are not limited thereto. The term "example" or "embodiment" is used herein with the same meaning (e.g., the phrase "in one example" has the same meaning as "in one embodiment", and "one or more examples" has the same meaning as "in one or more embodiments").

[0050] Figure 1A is a diagram illustrating a structure of a quantum computer chip according to one or more embodiments. Figure 1B is a circuit diagram showing a frequency fixed device (e.g., a fixed qubit or a fixed qubit coupler), and Figure 1C is a circuit diagram showing a frequency tunable device (eg, a tunable qubit or a tunable qubit coupler).

[0051] Reference Figure 1A , inside the quantum computer chip 10, there are a plurality of qubits 11 and a qubit coupler 15 that connects the qubits to each other. The qubit coupler 15 can be used to perform quantum entanglement and other interactions between qubits. In the quantum computer chip 10, when there are two or more qubits 11, the qubit coupler 15 can be used to facilitate the interaction between these qubits.

[0052] The qubits 11 can be classified into fixed qubits with a fixed resonant frequency and tunable qubits with a tunable resonant frequency. Similarly, the qubit couplers 15 can be classified into fixed qubit couplers with a fixed resonant frequency and tunable qubit couplers with an adjustable resonant frequency.

[0053] Fixed qubits and fixed qubit couplers may be formed, for example, using a capacitor 20 and a Josephson junction 25 (e.g., as Figure 1B On the other hand, the tunable qubit and the tunable qubit coupler can be formed, for example, using a capacitor 30 and two Josephson junctions 35 (e.g., as shown in Figure 1C ).

[0054] For example, a qubit and a coupler may have the same structure, and they may be selected and used as a qubit or a coupler according to the purpose.

[0055] In addition, the tunable qubit can set a desired or determined resonant frequency by tuning the resonant frequency, and the tunable qubit coupler can control the on / off of quantum entanglement of the qubit by tuning the resonant frequency to two different values.

[0056] In the following embodiments using ferromagnetic structures, utilizing two magnetization states within the ferromagnetic material (e.g., alignment in the upward direction and alignment in the downward direction) can make a tunable qubit coupler more useful than a tunable qubit. Therefore, as a non-limiting example, the description will focus on a tunable qubit coupler.

[0057] Figure 1D is a circuit diagram used to describe the resonant frequency control of a tunable qubit coupler.

[0058] A fixed qubit coupler may maintain a fixed resonant frequency that must closely match the resonant frequency of the coupled qubits to enable interaction between the qubits. In this example, due to the fixed resonant frequency of the coupler, the coupled qubits may always participate in interaction with each other.

[0059] In contrast, a tunable qubit coupler can tune the resonant frequency to enable significant interaction between qubits (e.g., coupling on) or to minimize interaction between qubits (e.g., coupling off). For example, a tunable qubit coupler can be configured to increase qubit interaction (e.g., coupling on) by tuning the resonant frequency of the coupler to closely match the resonant frequency of the coupled qubits (e.g., the absolute value of the difference between the resonant frequency of the coupler and the resonant frequency of the coupled qubits can be less than a predetermined threshold). Conversely, a tunable qubit coupler can also be configured to significantly reduce qubit interaction (e.g., coupling off) by setting the resonant frequency of the coupler to be different from the resonant frequency of the coupled qubits (e.g., the absolute value of the difference between the resonant frequency of the coupler and the resonant frequency of the coupled qubits can be greater than or equal to a predetermined threshold).

[0060] That is, tunable qubit couplers can freely enable and disable interactions between qubits, allowing for more efficient quantum computing compared to fixed qubit couplers.

[0061] Reference Figure 1D, a typical tunable qubit coupler 100 can use a separate control line 110 adjacent to the coupler for resonant frequency control. When a control current (e.g., a bias current) 115 is applied to the control line through a control circuit, a magnetic field 120 can be generated around the control line (e.g., a magnetic field 120 is generated in a vertical upward direction (⊙) according to Ampere's right-hand screw law). The generated magnetic field 120 can change the magnetic flux passing through the coupler, and the resonant frequency can be changed accordingly. For example, by adjusting the amplitude and direction of the control current, the resonant frequency of the coupler can be controlled.

[0062] However, typical tunable qubit coupler 100 has disadvantages in that a relatively high constant control current of several milliamperes (mA) may need to be continuously applied when the qubit coupler operates, a separate cryogenic electronic device may be required to apply a direct current (DC) control current, and magnetic noise (flux noise) and crosstalk caused by the DC current may destroy stable quantum computing.

[0063] Figure 2A and Figure 2B is a diagram illustrating a structure of a superconducting device including a tunable qubit coupler according to one or more embodiments.

[0064] Reference Figure 2A and Figure 2B , the superconducting device 200 may include a tunable qubit coupler 210 , a ferromagnetic structure 220 , a control line 230 , and a control circuit 240 .

[0065] The tunable qubit coupler 210 may be located between qubits and may be used as a coupler that can turn on / off the interaction between qubits by adjusting the resonant frequency. It may include a first conductive pad 211 and a second conductive pad 212 connected to each other via a Josephson junction 213.

[0066] The Josephson effect may refer to a phenomenon in which a current flows through a thin insulator when the thin insulator is placed between, for example, two superconducting materials. The Josephson junction 213 may represent a weak connection between two superconducting materials combined with an insulator. In this example, in addition to the insulator, various types of metals may be used as materials for the weak connection to form the Josephson junction 213.

[0067] The first conductive pad 211 and the second conductive pad 212 may each be formed of a superconducting material and disposed on the substrate 250. In this example, both the first conductive pad 211 and the second conductive pad 212 may be formed of the same superconducting material or different superconducting materials. The superconducting material may include at least one of aluminum (Al), niobium (Nb), indium (In), α-tantalum (α-Ta), titanium (Ti), lead (Pb), vanadium (V), and / or compounds thereof (e.g., NbN, NbTiN, TiN, or VN), but is not limited thereto.

[0068] The ferromagnetic structure 220 may be disposed at a predetermined distance from the first conductive pad 211 and the second conductive pad 212 .

[0069] A ferromagnetic material may refer to a material in which the magnetic moments or magnetizations of atoms are arranged in a particular direction even in the absence of an external magnetic field. The magnetization in a ferromagnetic material may be oriented in a particular preferred direction, which is referred to as magnetic anisotropy. For example, in the example of a ferromagnetic film, when the ferromagnetic film has perpendicular magnetic anisotropy, the magnetization of the ferromagnetic film may be preferably arranged in a vertical direction (e.g., +Z axis direction or -Z axis direction). When the ferromagnetic film has in-plane magnetic anisotropy, the magnetization may be preferably arranged in a horizontal direction (e.g., XY plane direction).

[0070] The ferromagnetic structure 220 may have the characteristics of a ferromagnetic material (ferromagnet), and may be formed of a ferromagnet (e.g., Co, CoFeB, (CoNi)n, (CoPt)n, etc.), not only in its pure form, but also in a heterojunction structure having a ferromagnet and a heavy metal (e.g., platinum (Pt), tantalum (Ta), palladium (Pd), tungsten (W), ruthenium (Ru), etc.), and even having an antiferromagnetic material (e.g., an antiferromagnet). The type of the ferromagnetic structure 220 is not limited thereto.

[0071] The diameter of the ferromagnetic structure 220 may be in the range of tens of nanometers to several micrometers (eg, from 50 nm to 5 μm), and there is no limitation on the shape of the ferromagnetic structure 220 , which may include a cylindrical shape, a cuboid, a rectangle, and the like.

[0072] Reference Figure 2A , the tunable qubit coupler 210 includes two Josephson junctions 213, and the ferromagnetic structure 220 may be located between the two Josephson junctions 213. Figure 2B, the ferromagnetic structure 220 may be located on the outside of one of the Josephson junctions 213 that is adjacent to the control circuit 240. In this example, the ferromagnetic structure 220 may be disposed, for example, at a distance ranging from tens of nanometers to hundreds of nanometers from the first conductive pad 211, the second conductive pad 212, and / or the Josephson junction 213 to allow the magnetic flux of the tunable qubit coupler 210 to be changed. The arrangement of the ferromagnetic structure 220 is not limited to this example.

[0073] The control line 230 may be a wire through which a control current flows under the control of the control circuit 240, and may be located below the ferromagnetic structure 220. The control line 230 may be disposed between the first conductive pad 211 and the second conductive pad 212 in parallel with the longitudinal direction of the first conductive pad 211 and the second conductive pad 212, and connected to the control circuit 240 (e.g., Figure 2A Additionally or alternatively, the control line 230 may be located at a predetermined distance from the first conductive pad 211 and the second conductive pad 212 and connected to the control circuit 240 (eg, as shown in FIG. 2 ). Figure 2B ).

[0074] The control line 230 may be made of a material exhibiting a significant spin Hall effect, such as Ta, Pt, Pd, W, Ru, etc., but is not limited to these materials. The size of the control line 230 may be in the range of, for example, tens of nanometers to tens of micrometers.

[0075] Control circuit 240 may be connected to control line 230 and may control the current flowing through control line 230 , thereby adjusting the resonant frequency of tunable qubit coupler 210 .

[0076] First, the control circuit 240 may induce a spin-orbit torque (SOT) phenomenon in the ferromagnetic structure 220 by applying a current to the control line 230 , thereby reversing the magnetization alignment direction of the ferromagnetic structure 220 .

[0077] The spin-orbit torque (SOT) phenomenon may refer to a phenomenon in which when a current exceeding a predetermined threshold is applied to a double layer consisting of a heavy metal and a ferromagnetic structure, the current applies a torque to the magnetization of the ferromagnetic structure, thereby causing magnetization switching. For example, the control circuit 240 may induce the SOT phenomenon in the ferromagnetic structure 220 located above the control line 230 by applying a current exceeding a predetermined threshold to the control line 230, thereby flipping the magnetization arrangement direction by 180 degrees (such as from vertically upward to downward or from vertically downward to upward).

[0078] In order to reverse the formed magnetization alignment direction of the ferromagnetic structure, the control circuit 240 may apply a current exceeding a predetermined threshold in a direction opposite to the current direction during the formation of the magnetization alignment direction.

[0079] Return to reference Figure 2A , when current flows through the control line 230 in the direction A and induces the SOT phenomenon in the ferromagnetic structure 220 to form a vertically upward magnetization arrangement direction, the control circuit 240 may apply a current exceeding a predetermined threshold value to the control line 230 in the opposite direction A'. As a result, the SOT phenomenon may be induced, and the magnetization arrangement direction may be flipped to a vertically downward direction. Information about the current direction based on the magnetization arrangement direction and the predetermined threshold value may be stored in an internal or external storage unit, and the control circuit 240 may apply the current using the stored information.

[0080] In this example, the ferromagnetic structure 220 may break the horizontal symmetry in order to flip the magnetization arrangement direction via the SOT phenomenon according to the direction of the current applied to the ferromagnetic structure 220. For this purpose, a separate form may be used for the ferromagnetic structure 220. Alternatively, an external factor (such as a magnetic field) may be applied to the ferromagnetic structure 220.

[0081] Figure 2C and Figure 2D is a diagram illustrating a ferromagnetic structure with broken horizontal symmetry according to one or more embodiments.

[0082] Reference Figure 2C When the ferromagnetic structure 220 is formed by bonding the antiferromagnetic material 222 to the top of the ferromagnetic material 221 above the control line 230, the antiferromagnetic material 222 can generate a local horizontal (X direction) magnetic field 260 on the ferromagnetic material 221, destroying the horizontal (X direction) symmetry of the ferromagnetic structure 220. Figure 2D , even when the thickness (Y direction) of the ferromagnetic structure 220 itself varies horizontally (X direction), this can destroy the horizontal (X direction) symmetry of the ferromagnetic structure 220. However, the shape of the ferromagnetic structure 220 that destroys the horizontal symmetry is not limited to these examples.

[0083] In addition, the control circuit 240 can flip the magnetization arrangement direction by applying a current exceeding a predetermined threshold value only once to the control line 230. Since the magnetization of the ferromagnetic structure 220 remains unchanged even when the external magnetic field is eliminated, the control circuit 240 can flip the magnetization arrangement direction by applying a current exceeding a predetermined threshold value only once without continuous application, and the flipped magnetization arrangement direction can be maintained. In this example, the control circuit 240 can apply the current exceeding the predetermined threshold value, for example, in the form of pulses.

[0084] Then, the control circuit 240 may change the magnetic flux of the tunable qubit coupler 210 based on the flipping of the magnetization alignment direction of the ferromagnetic structure 220 .

[0085] FIG. 3A to FIG. 3D is a circuit diagram illustrating magnetic field and flux through a tunable qubit coupler according to the magnetization alignment direction of a ferromagnetic structure according to one or more embodiments. FIG. 3A to FIG. 3D Show Figure 2A One or more embodiments of the ferromagnetic structure 220 are located between Josephson junctions 213 in a superconducting device.

[0086] Reference FIG. 3A to FIG. 3B , when the control circuit 240 applies current to the control line 230 to align the magnetization of the ferromagnetic structure 220 along the vertical upward direction (⊙) 310, the ferromagnetic structure 220 may emit a magnetic field 320 in the vertical upward direction, similar to a bar magnet with the north pole facing vertically upward. As a result, a magnetic flux 330 in the vertical upward direction may be formed in the tunable qubit coupler 210.

[0087] Reference FIG. 3C to FIG. 3D When the control circuit 240 applies current to the control line 230, the magnetization of the ferromagnetic structure 220 is vertically downward. When aligned at 340, ferromagnetic structure 220 may emit a magnetic field 350 in a vertically downward direction, similar to a bar magnet with its north pole facing vertically downward. As a result, magnetic flux 360 in a vertically downward direction may be formed in tunable qubit coupler 210.

[0088] FIG. 4A to FIG. 4B is a circuit diagram illustrating magnetic field and flux through a tunable qubit coupler according to the magnetization alignment direction of a ferromagnetic structure according to one or more embodiments. FIG. 4A to FIG. 4B Show Figure 2B One or more embodiments of the ferromagnetic structure 220 are located outside the Josephson junction 213 in the superconducting device.

[0089] Reference Figure 4A , when current flows through the control line 230 to align the magnetization of the ferromagnetic structure 220 along the vertical upward direction (⊙) 410, the ferromagnetic structure 220 may emit a magnetic field 430 in the vertical upward direction from its top, similar to a bar magnet with the north pole pointing vertically upward. The emitted magnetic field 430 may pass through the space between the Josephson junctions of the tunable qubit coupler 210 and bend downward toward the lower part of the ferromagnetic structure 220 in a parabolic trajectory, and finally form a magnetic flux 420 in the vertical downward direction in the tunable qubit coupler 210.

[0090] Reference Figure 4B When current flows through the control line 230, the magnetization of the ferromagnetic structure 220 moves vertically downward. When aligned with 440, ferromagnetic structure 220 may emit magnetic field 460 in a vertical downward direction, similar to a bar magnet with its north pole facing vertically downward. Emitted magnetic field 460 may bend upward toward the top of ferromagnetic structure 220 in a parabolic trajectory and pass through the space between the Josephson junctions of tunable qubit coupler 210, ultimately forming magnetic flux 450 in the vertical upward direction in tunable qubit coupler 210.

[0091] Next, the control circuit 240 may obtain the resonant frequency corresponding to the magnetic flux that changes according to the magnetization arrangement direction using a model that defines the relationship between the magnetic flux and the resonant frequency.

[0092] The resonant frequency of the coupler may change with the magnetic flux passing through the coupler. Therefore, a model defining the relationship between the resonant frequency and the magnetization may be generated. The control circuit 240 may use the generated model to obtain the resonant frequency based on the magnetization generated according to the magnetization arrangement direction. The model defining the relationship between the resonant frequency and the magnetic flux may be pre-constructed by regression analysis or machine learning and stored in an internal or external storage device. The control circuit 240 may use the stored model to obtain the resonant frequency based on the magnetic flux.

[0093] At this time, the control circuit 240 may control the resonant frequency to be in one of the following two states: coupling-on and coupling-off.

[0094] In the ferromagnetic structure 220 including ferromagnetic material, due to the characteristics of the ferromagnetic material, when the magnetization alignment direction remains unchanged due to the application of current exceeding a predetermined threshold, the amplitude of the magnetic field can remain constant over time. Therefore, the magnetization of the tunable qubit coupler 210 can remain constant, resulting in a constant resonant frequency.

[0095] When the magnetization arrangement direction of the ferromagnetic structure 220 according to the above-described embodiment has only two directions (e.g., a vertical upward direction and a vertical downward direction) due to flipping, there may be only two constant resonant frequencies. One of these values ​​may be used as a coupling-on frequency for forming a qubit interaction, and the other may be used as a coupling-off frequency for not forming a qubit interaction. In this example, a resonant frequency similar to the resonant frequency of a qubit coupled to a tunable qubit coupler (e.g., the absolute value of the difference between the resonant frequency of the tunable qubit coupler and the resonant frequency of the coupled qubit may be less than a predetermined threshold) may be used as a coupling-on frequency, and a resonant frequency relatively different from the resonant frequency of the coupled qubit (e.g., the absolute value of the difference between the resonant frequency of the tunable qubit coupler and the resonant frequency of the coupled qubit may be greater than or equal to a predetermined threshold) may be used as a coupling-off frequency.

[0096] Figure 5A and Figure 5Bis a graph showing the relationship between application of current and resonance frequency over time.

[0097] Reference Figure 5A and Figure 5B , the control circuit 240 can obtain the coupling-on frequency F1 by controlling the current (e.g., applying a current exceeding the threshold in the form of pulses 510). Similarly, the control circuit 240 can obtain the coupling-off frequency F2 by applying a current exceeding the threshold in the form of pulses 520 in the opposite direction. For example, the control circuit 240 can apply a current in the form of pulses only when a change in the coupling state is determined as needed.

[0098] According to the above embodiments, the control circuit 240 can induce SOT in the ferromagnetic structure 220 by applying a predetermined current to the control line 230, thereby flipping the magnetization arrangement direction of the ferromagnetic structure 220. The control circuit 240 can also change the magnetic flux of the tunable qubit coupler 210 according to the flipping of the magnetization arrangement direction, and use a model that defines the relationship between the magnetic flux and the resonant frequency to obtain the resonant frequency corresponding to the changed magnetic flux. That is, the control circuit 240 of one or more embodiments can ultimately control the resonant frequency of the tunable qubit coupler 210 by controlling the current.

[0099] According to one embodiment, a superconducting device including a tunable qubit coupler may exist in a layered structure. For example, the superconducting device may be formed into a layered structure in which control wires, ferromagnetic structures, and frequency tunable devices (e.g., tunable qubit couplers) are stacked from bottom to top.

[0100] FIG. 6A to FIG. 6D is a diagram illustrating a process of manufacturing a superconducting device according to one or more embodiments.

[0101] Reference FIG. 6A to FIG. 6D First, the control line 230 may be disposed on the substrate 610 (eg Fig. 6A ), and the ferromagnetic structure 220 may be disposed on top of the control line 230 (as shown in Figure 6B Then, an insulating layer 620 made of an insulating material (such as Figure 6C ), and finally a tunable qubit coupler 210 (as shown in Fig.6D ).

[0102] As described above, the tunable qubit coupler and the tunable qubit as a frequency tunable device can have the same structure, so they can be selected as a coupler or a qubit according to the desired use. Therefore, the above embodiments can be used as a tunable qubit.

[0103] For example, a ferromagnetic structure may be placed between the positive conductive pads of the tunable qubit and at a predetermined distance from the Josephson junction. A control line may be disposed below the ferromagnetic structure, and a current flowing through the control line may be controlled by a control circuit to adjust the resonant frequency of the tunable qubit.

[0104] A typical tunable qubit coupler may be driven by a volatile control method in which a continuous control current needs to be applied to maintain a desired resonant frequency. Such a typical tunable qubit coupler may be inefficient in terms of energy consumption and may result in reduced reliability of the measured resonant frequency due to noise (e.g., magnetic noise) and crosstalk caused by the control current, thereby correspondingly resulting in reduced stability of quantum computing. In addition, for a typical tunable qubit coupler, a separate cryogenic electronic device (e.g., a cryogenic DC line) may be required to supply the control current.

[0105] In contrast to typical tunable qubit couplers, according to one or more embodiments that use a magnetic field generated by a ferromagnetic structure to control the resonant frequency of a tunable qubit coupler, the magnetization alignment direction of the ferromagnetic structure can remain constant, and therefore, the resonant frequency of the coupler can also remain constant. Therefore, a continuous control current supply is not required.

[0106] In order to change the resonant frequency, the apparatus and method of one or more embodiments need to apply a current exceeding the threshold value only once (for example, in the form of a pulse) (non-volatile control method). In this way, the apparatus and method of one or more embodiments can reduce problems related to noise and crosstalk caused by continuous control current supply, reduce the cost and complexity associated with the need for separate electronic devices, and enable relatively stable resonant frequency control.

[0107] Figure 7 is a flow chart illustrating a method of controlling the resonant frequency of a tunable qubit coupler using a superconducting device according to one or more embodiments. Operations 710 to 740 described below may be referred to as follows Figure 7 The operations are performed in the order and manner shown and described, but the order of one or more of the operations may be changed, one or more of the operations may be omitted, and / or two or more of the operations may be performed in parallel or simultaneously without departing from the spirit and scope of the example embodiments described herein.

[0108] Figure 7 According to Figure 1 to Fig.6D One or more embodiments of a method of controlling the resonant frequency of a tunable qubit coupler of an embodiment of the present invention are provided. To avoid redundancy, a brief description is provided.

[0109] In this example, the superconducting device may include a frequency tunable device (e.g., a tunable qubit coupler and / or a tunable qubit) having a first conductive pad and a second conductive pad connected by a Josephson junction, a ferromagnetic structure disposed at a predetermined distance from the first conductive pad and the second conductive pad, and a control line located below the ferromagnetic structure. The ferromagnetic structure may be formed in a structure in which horizontal symmetry is broken.

[0110] First, the superconducting device may apply current to a control wire in 710 .

[0111] The control line may be made of heavy metal and may be arranged parallel to the longitudinal direction of the first and second conductive pads, or spaced apart from the first and second conductive pads by a predetermined distance. In this example, the superconducting device may apply a current exceeding a predetermined threshold to the control line in the form of a pulse only once.

[0112] When a current is applied to the control line in 710, the superconducting device may flip the magnetization arrangement direction of the ferromagnetic structure in 720. For example, the superconducting device may induce a SOT phenomenon in the ferromagnetic structure by applying a current exceeding a predetermined threshold to the control line, thereby flipping the magnetization arrangement direction of the ferromagnetic structure. In this example, the superconducting device may flip the magnetization arrangement direction by applying a current exceeding a predetermined threshold in a direction opposite to the current direction during the formation of the magnetization arrangement direction.

[0113] When the magnetization arrangement direction of the ferromagnetic structure is flipped in 720, the superconducting device may change the magnetic flux of the tunable qubit coupler according to the flipped magnetization arrangement direction of the ferromagnetic structure in 730, and may control the resonant frequency of the tunable qubit coupler in 740. For example, the superconducting device may use a model that defines the relationship between the magnetic flux and the resonant frequency to obtain the resonant frequency corresponding to the magnetic flux changed according to the magnetization arrangement direction. In this example, the superconducting device may control the resonant frequency to be in one of the following two states: coupling on and coupling off.

[0114] The description herein includes reference to FIGS. 1 to Figure 7The described quantum computer chip, qubit, qubit coupler, capacitor, Josephson junction, control line, superconducting device, first conductive pad, second conductive pad, ferromagnetic structure, control circuit, substrate, ferromagnetic material, insulating layer, quantum computer chip 10, qubit 11, qubit coupler 15, capacitor 20, Josephson junction 25, capacitor 30, Josephson junction 35, tunable qubit coupler 100, control line 110, superconducting device 200, tunable qubit coupler 210, first conductive pad 211, second conductive pad 212, Josephson junction 213, ferromagnetic structure 220, control line 230, control circuit 240, substrate 250, antiferromagnetic material 222, ferromagnetic material 221, substrate 610, insulating layer 620 are implemented by hardware components or represent hardware components. As described above, or in addition to the above description, examples of hardware components that can be used to perform the operations described in this application include, where appropriate, controllers, sensors, generators, drivers, memories, comparators, arithmetic logic units, adders, subtractors, multipliers, dividers, integrators, and any other electronic components configured to perform the operations described in this application. In other examples, one or more hardware components that perform the operations described in this application are implemented by computing hardware (e.g., by one or more processors or computers). A processor or computer may be implemented by one or more processing elements (such as logic gate arrays, controllers and arithmetic logic units, digital signal processors, microcomputers, programmable logic controllers, field programmable gate arrays, programmable logic arrays, microprocessors, or any other device or combination of devices configured to respond and execute instructions in a limited manner to achieve desired results). In one example, a processor or computer includes or is connected to one or more memories storing instructions or software executed by a processor or computer. Hardware components implemented by a processor or computer may execute instructions or software (such as an operating system (OS) and one or more software applications running on the OS) to perform the operations described in this application. Hardware components can also access, manipulate, process, create and store data in response to the execution of instructions or software. For simplicity, the singular term "processor" or "computer" can be used in the description of the examples described in this application, but in other examples, multiple processors or computers can be used, or the processor or computer can include multiple processing elements, or multiple types of processing elements, or both. For example, a single hardware component or two or more hardware components can be implemented by a single processor, or two or more processors, or a processor and a controller. One or more hardware components can be implemented by one or more processors or a processor and a controller, and one or more other hardware components can be implemented by one or more other processors or another processor and another controller. One or more processors or a processor and a controller can implement a single hardware component or two or more hardware components.As described above, or in addition to the description above, the example hardware components may have any one or more of different processing configurations, examples of which include a single processor, independent processors, parallel processors, single instruction single data (SISD) multiprocessing, single instruction multiple data (SIMD) multiprocessing, multiple instruction single data (MISD) multiprocessing, and multiple instruction multiple data (MIMD) multiprocessing.

[0115] In Figures 1 to Figure 7 1 to 1 Figure 7 The methods discussed for performing the operations described in this application are performed by computing hardware (e.g., by one or more processors or computers), which is implemented as executing instructions (e.g., computer or processor / processing device readable instructions) or software as described above to perform the operations performed by the methods described in this application. For example, a single operation or two or more operations may be performed by a single processor, or two or more processors, or a processor and a controller. One or more operations may be performed by one or more processors or a processor and a controller, and one or more other operations may be performed by one or more other processors or another processor and another controller. One or more processors or a processor and a controller may perform a single operation or two or more operations.

[0116] Instructions or software for controlling computing hardware (e.g., one or more processors or computers) to implement hardware components and perform methods as described above may be written as computer programs, code segments, instructions, or any combination thereof, for individually or collectively instructing or configuring one or more processors or computers to operate as a machine or special-purpose computer to perform operations performed by the hardware components and methods as described above. In one example, the instructions or software include machine code (such as machine code generated by a compiler) directly executed by one or more processors or computers. In another example, the instructions or software include high-level code executed by one or more processors or computers using an interpreter. The instructions or software may be written in any programming language based on the block diagrams and flow charts shown in the accompanying drawings and the corresponding descriptions herein, and the block diagrams and flow charts shown in the accompanying drawings and the corresponding descriptions herein disclose algorithms for performing operations performed by the hardware components and methods as described above.

[0117] Instructions or software for controlling computing hardware (e.g., one or more processors or computers) to implement hardware components and perform the methods described above, and any associated data, data files, and data structures, may be recorded, stored, or fixed in or on one or more non-transitory computer-readable storage media, and are therefore not signals themselves. As described above, or in addition to the above description, examples of non-transitory computer-readable storage media include any one or more of the following: read-only memory (ROM), random access programmable read-only memory (PROM), electrically erasable programmable read-only memory (EEPROM), random access memory (RAM), dynamic random access memory (DRAM), static random access memory (SRAM), flash memory, non-volatile memory, CD-ROM, CD-R, CD+R, CD-RW, CD+RW, DVD-ROM, DVD-R, DVD+R, DVD-RW, DVD+RW, DVD-RAM, BD-ROM, BD-R, BD-R LTH, BD-RE, Blu-ray or optical disk storage device, hard disk drive (HDD), solid state drive (SSD), flash memory, card memory (such as, multimedia card or micro card (for example, secure digital (SD) or extreme digital (XD))), magnetic tape, floppy disk, magneto-optical data storage device, optical data storage device, hard disk, solid state disk and any other device, any other device is configured to store instructions or software and any associated data, data files and data structures in a non-transitory manner and provide instructions or software and any associated data, data files and data structures to one or more processors or computers so that one or more processors or computers can execute the instructions. In one example, the instructions or software and any associated data, data files and data structures are distributed on a networked computer system so that the instructions and software and any associated data, data files and data structures are stored, accessed and executed in a distributed manner by one or more processors or computers.

[0118] Although the present disclosure includes specific examples, it will be clear after understanding the disclosure of the present application that various changes in form and detail may be made in these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are considered to be descriptive only and not for limiting purposes. The description of features or aspects in each example is considered to be applicable to similar features or aspects in other examples. Suitable results may be achieved if the described techniques are performed in a different order, and / or if components in the described systems, architectures, devices, or circuits are combined in different ways, and / or replaced or supplemented by other components or their equivalents.

[0119] Therefore, the scope of the disclosure includes the claims and their equivalents in addition to the disclosure above and all the accompanying drawings (that is, all changes within the scope of the claims and their equivalents should be construed as being included in the disclosure).

Claims

1. A superconducting device, comprising: A frequency tunable device including a first conductive pad and a second conductive pad connected to each other via a Josephson junction; a ferromagnetic structure disposed at a predetermined distance from the first conductive pad and the second conductive pad; a control line, located below the ferromagnetic structure; as well as The control circuit is configured to control the resonant frequency of the frequency tunable device by controlling the current flowing through the control line.

2. The superconducting device according to claim 1, wherein: The frequency tunable device includes one or both of a tunable qubit coupler and a tunable qubit.

3. The superconducting device according to claim 1, wherein: The control circuit is configured to flip the magnetization arrangement direction of the ferromagnetic structure by applying a current exceeding a predetermined threshold to the control line to induce a spin-orbit torque phenomenon in the ferromagnetic structure.

4. The superconducting device according to claim 3, wherein: In order to apply the current exceeding the predetermined threshold, the control circuit is configured to apply the current exceeding the predetermined threshold in the form of a pulse only once.

5. The superconducting device according to claim 4, wherein: To apply the current exceeding the predetermined threshold, the control circuit is configured to: apply the current exceeding the predetermined threshold in a direction opposite to the current direction during the formation of the magnetization arrangement direction to flip the formed magnetization arrangement direction of the ferromagnetic structure.

6. The superconducting device according to claim 3, wherein: The control circuit is configured to change the magnetic flux of the frequency tunable device based on the flipping of the magnetization arrangement direction.

7. The superconducting device according to claim 6, wherein: The control circuit is configured to obtain a resonant frequency corresponding to the changed magnetic flux using a model defining a relationship between the magnetic flux and the resonant frequency.

8. The superconducting device according to claim 3, wherein: To control the resonance frequency, the control circuit is configured to control the resonance frequency to be in one of two states including coupling-on and coupling-off.

9. The superconducting device according to claim 8, wherein: To control the resonant frequency, the control circuit is configured to control the resonant frequency to a coupling-on frequency by setting the resonant frequency of the frequency tunable device to be similar to the resonant frequency of the coupled qubit.

10. The superconducting device according to any one of claims 1 to 9, wherein: The frequency tunable device includes two Josephson junctions, and the ferromagnetic structure is located between the two Josephson junctions or on the outside of one of the two Josephson junctions.

11. The superconducting device according to any one of claims 1 to 9, wherein: The ferromagnetic structure is formed to have a structure with broken horizontal symmetry.

12. The superconducting device according to any one of claims 1 to 9, wherein: A magnetic field is applied to the ferromagnetic structure to break the horizontal symmetry.

13. The superconducting device according to any one of claims 1 to 9, wherein: The first conductive pad and the second conductive pad are made of a superconducting material.

14. The superconducting device according to any one of claims 1 to 9, wherein: The control line is disposed parallel to a longitudinal direction of the first conductive pad and the second conductive pad.

15. The superconducting device according to any one of claims 1 to 9, wherein: The control wire is made of heavy metal.

16. The superconducting device according to any one of claims 1 to 9, wherein: The control lines, ferromagnetic structures and frequency tunable devices are stacked from bottom to top.

17. A method for controlling the resonant frequency of a frequency tunable device using a superconducting device, the superconducting device comprising a frequency tunable device, a ferromagnetic structure and a control line, the frequency tunable device comprising a first conductive pad and a second conductive pad connected to each other through a Josephson junction, the ferromagnetic structure being arranged at a predetermined distance from the first conductive pad and the second conductive pad, and the control line being located below the ferromagnetic structure, the method comprising: applying current to the control wire; Flip the magnetization direction of the ferromagnetic structure; varying the magnetic flux of the frequency tunable device; as well as Controlling the resonant frequency of the frequency tunable device.

18. The method according to claim 17, wherein: The frequency tunable device includes one or both of a tunable qubit coupler and a tunable qubit.

19. The method according to claim 18, wherein: The step of switching the magnetization arrangement direction includes switching the magnetization arrangement direction of the ferromagnetic structure by applying a current exceeding a predetermined threshold to a control line to induce a spin-orbit torque phenomenon in the ferromagnetic structure.

20. A superconducting device, comprising: A frequency tunable device comprising two Josephson junctions, wherein a ferromagnetic structure is located between the two Josephson junctions or on the outside of one of the two Josephson junctions; ferromagnetic structures; and Control line, The resonant frequency of the frequency tunable device is changed by applying a current exceeding a predetermined threshold to a control line to flip the magnetization arrangement direction of the ferromagnetic structure.

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