Coupling circuit and structure and chip and computer thereof

Abstract

The utility model discloses a coupling circuit, a coupling structure, a chip and a computer, and belongs to the field of quantum computing. Wherein the coupling circuit is used for coupling a first quantum bit and a second quantum bit, and comprises a first coupler and a second coupler which are arranged side by side and have a side-by-side direction and are spaced apart. The first coupler has a first preset length, the second coupler has a second preset length, and the first preset length and the second preset length are configured to define an inherent coupling strength of the first quantum bit and the second quantum bit. With the coupler adopted, an ideal coupling effect between bits can be realized under the condition that layout design is reduced.

Description

Technical Field

[0001] This application belongs to the field of quantum information, especially the field of quantum computing technology. In particular, this application relates to a coupling circuit and structure, as well as its chip and computer. Background Art

[0002] Quantum computing is a new computing paradigm that relies on the laws of quantum mechanics to operate quantum information units for computing. A quantum gate (or quantum logic gate) is a basic unit in the computing model of quantum computing, especially in quantum circuits. A quantum gate is the foundation of a quantum circuit and can be understood as the relationship between a logic gate and a digital circuit.

[0003] Specifically, quantum computing is implemented through a quantum computer. As a very promising technical route to achieve universal quantum computing, superconducting quantum computers have many advantages.

[0004] In a superconducting quantum computer, the core component is a superconducting quantum chip, which mainly includes core quantum elements, namely superconducting qubits. Moreover, quantum gates can be single-qubit gates and two-qubit gates, or derivative quantum gates of the two.

[0005] The coupling of two superconducting qubits is the basis for implementing two-qubit gate operations, and the coupling needs to be realized by a certain physical structure. However, as the number of qubits in a quantum chip continues to increase, the difficulty of the coupling configuration scheme between qubits increases significantly. Summary of the Utility Model

[0006] The example of this application provides a coupling circuit and structure, as well as its chip and computer. Applying the coupling circuit scheme to a quantum chip and computer can achieve ideal coupling between two qubits, and can also reduce the space occupied when qubits are coupled, thus helping to integrate more qubits in the quantum chip.

[0007] The solution of the example of this application is implemented through the following content.

[0008] In a first aspect, the example of this application proposes a coupling circuit for coupling a first qubit and a second qubit.

[0009] The coupling circuit includes:

[0010] A first coupler and a second coupler arranged side by side longitudinally and spaced apart in the side-by-side direction;

[0011] The first coupler and the second coupler are configured to be independently coupled to the first qubit and the second qubit at both ends respectively;

[0012] The first coupler has a first preset length determined transversely, the second coupler has a second preset length determined transversely, and the first preset length and the second preset length are configured to define the inherent coupling strength of the first qubit and the second qubit.

[0013] According to some examples of the present application, the first coupler has an adjustable frequency, and the first coupler is configured to change its own frequency so that the first coupler and the second coupler have a modulation coupling strength different from the inherent coupling strength; and / or, the second coupler has a fixed frequency.

[0014] According to some examples of the present application, the first coupler and the second coupler are respectively superconducting qubits;

[0015] and / or, the first coupler and the second coupler have a preset spacing measured in the side-by-side direction.

[0016] According to some examples of the present application, the first coupler is a frequency-tunable superconducting qubit, and the second coupler is a coplanar waveguide resonator.

[0017] According to some examples of the present application, both ends of the first coupler are configured as first coupling parts, both ends of the second coupler are configured as second coupling parts, and the first coupling parts and the second coupling parts have the same shape.

[0018] According to some examples of the present application, the first coupling parts at both ends of the first coupler are symmetrically distributed along the extension direction of the first coupler; the second coupling parts at both ends of the second coupler are symmetrically distributed along the extension direction of the second coupler.

[0019] According to some examples of the present application, the first coupling parts and the second coupling parts are hammer-shaped structures.

[0020] In a second aspect, examples of the present application disclose a superconducting qubit coupling structure, which includes:

[0021] a first qubit and a second qubit; and

[0022] a coupling circuit disposed between the first qubit and the second qubit;

[0023] a first coupler and a second coupler, each independently coupling to the first qubit and the second qubit at both ends respectively.

[0024] In a third aspect, examples of the present application disclose a quantum chip including the foregoing coupling circuit or superconducting qubit coupling structure.

[0025] In a fourth aspect, examples of the present application disclose a quantum computer having the foregoing quantum chip.

[0026] According to the solution disclosed in the present application, a coupling circuit is used in a superconducting quantum chip and a computer to couple two superconducting qubits, so as to meet specific qubit operation requirements. For example, by coupling the qubits, it is possible to allow the construction of a two-qubit quantum logic gate in some examples.

[0027] Preferably, by using the above-mentioned coupling circuit, the coupling distance between two qubits can be shortened, so that it is expected to integrate more qubits within a limited area of the quantum chip, which in turn brings convenience to the layout of various components in the quantum chip and the convenience of design and manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] For a clearer illustration, the drawings required for the description will be briefly introduced below.

[0029] Figure 1 It is a schematic structural diagram of qubits on a quantum chip in the related art;

[0030] Figure 2 It is a schematic structural diagram of the relative distribution of the quantum circuit and the ground plane in the example of the present application;

[0031] Figure 3 It records Figure 2 the schematic structural diagram of the quantum circuit in

[0032] Figure 4 It is a schematic structural diagram of the relative distribution of the quantum circuit and the ground plane in the example of the present application;

[0033] Figure 5 It records Figure 4 the schematic structural diagram of the quantum circuit in

[0034] Figure 6 It discloses the structure of a superconducting qubit constructed based on the quantum circuit shown in Figure 3 ;

[0035] Figure 7 It shows Figure 3 a schematic structural diagram of the position where a superconducting qubit constructed based on the quantum circuit shown in is coupled to other superconducting qubits;

[0036] Figure 8 It discloses three quantum circuit schematic structural diagrams different from the quantum circuits shown in the examples of the present application Figure 2 and Figure 5 ;

[0037] Figure 9 It discloses a schematic structural diagram of two qubits in the examples of the present application being coupled to each other through a coupling circuit composed of two couplers;

[0038] Figure 10 Schematic structural diagram of a coupling circuit in an example of the present application;

[0039] Figure 11 Schematic diagram of the equivalent circuit of a DC superconducting quantum interference device in an example of the present application;

[0040] Figure 12 Schematic diagrams of two arrangement methods of the coupling circuit in an example of the present application are disclosed;

[0041] Figure 13 Schematic diagram of the distribution structure of the coupling circuit (providing a coupler between qubits) and the quantum circuit (providing qubit capacitance) in qubits arranged in a one-dimensional matrix in an example of the present application;

[0042] Figure 14 Schematic diagram of the distribution structure of the coupling circuit (providing a coupler between qubits) and the quantum circuit (providing qubit capacitance) in qubits arranged in a two-dimensional matrix (only one qubit is shown in the figure) in an example of the present application.

[0043] Description of reference numerals:

[0044] 101 - Ground plane; 102 - Quantum circuit; 102a - Quantum circuit;

[0045] 1021 - Main body; 1022 - Protrusion; 1023 - Hammer-shaped part;

[0046] 1021a - Main body; 1022a - Protrusion; 1023a - Hammer-shaped part;

[0047] 201 - Josephson junction;

[0048] 300 - Coupling circuit;

[0049] 301 - First coupler; 3011 - First coupling part;

[0050] 302 - Second coupler; 3021 - Second coupling part. Detailed implementation manners

[0051] The pursuit of computing power and general-purpose quantum computers has led to an increasing number of qubits integrated on superconducting quantum chips. Therefore, the number of qubits in quantum chips has experienced development from several, dozens, and hundreds, and currently, the integration goals are gradually approaching thousands and even millions of qubits. Facing the increasing demand for the number of qubits in quantum chips, great pressure is faced in aspects such as the layout design, manufacturing process, and chip packaging of superconducting quantum chips.

[0052] This application mainly focuses on the optimization and improvement of the layout design of qubits. For superconducting quantum chips, one of the difficulties in their design lies in the fact that the chip includes multiple structures, such as the qubits themselves, and their peripheral structures - various circuits and components for qubit control and readout operations. In addition, in order to achieve specific logic gates and other purposes, it is often necessary to couple different qubits. These characteristics bring considerable complexity to the design of the chip layout.

[0053] Among these designs, an important factor is the structure of the qubit. Currently, the more commonly used qubit structure is the Transmon - type qubit (transmon qubit). Its shape resembles a "+" shape and is composed of a cross - shaped capacitor and a superconducting quantum interference device (Superconducting Quantum Interference Device, abbreviated as squid) connected to the end of one branch of the capacitor.

[0054] Among them, the superconducting quantum interference device (squid) contains one or more Josephson junctions; a Josephson junction is a device that includes two electrodes and a thin insulating potential barrier layer separating the two electrodes, and the materials of these two electrodes can exhibit superconducting characteristics at their own critical temperature or below this critical temperature.

[0055] The Transmon qubit (transmon qubit) has a shape resembling a "+" shape and is composed of a cross - shaped capacitor and a superconducting quantum interference device (Superconducting Quantum Interference Device, abbreviated as squid) connected to the end of one branch of the capacitor. Among them, the superconducting quantum interference device (squid) contains one or more Josephson junctions; a Josephson junction is a device that includes two electrodes and a thin insulating potential barrier layer separating the two electrodes, and the materials of these two electrodes can exhibit superconducting characteristics at their own critical temperature or below this critical temperature.

[0056] In the above - mentioned qubit system, there are various circuit structures with different functions around the qubit. For example, a readout resonator and a coupler for coupling connections between qubits.

[0057] The circuit structure also includes a drive control signal line (XY - Control Line, also known as the xy control line or pulse regulation signal line) for performing XY rotation operations on the qubit. By applying a drive voltage signal in the circuit, the qubit can be excited to transition; it is associated with the qubit through capacitive coupling.

[0058] The circuit structure also includes a circuit structure for performing a Z-rotation operation on the qubit, which is completed by a control signal line near the superconducting quantum interference device (SQUID); it is called a flux control signal line (Z-Control Line, also known as the z control signal line or the frequency control signal line). As mentioned above, the flux control signal line is arranged near the superconducting quantum interference device (SQUID), and its excitation current is inductively coupled to the superconducting quantum interference device (SQUID) through a magnetic field.

[0059] It should be noted that both the flux control signal line and the drive control line can be used to control the qubit, but their control forms and purposes are essentially different.

[0060] Among them, the drive control signal line applies a pulse to the qubit in the form of an electric field, and this pulse causes the energy level of the qubit to transition.

[0061] The signal transmitted by the flux control signal line will generate a magnetic field and apply it to the superconducting quantum interference device (SQUID) region. At the same time, the magnetic flux passing through the superconducting quantum interference device (SQUID) region can cause a change in the critical current of the SQUID. This change in the critical current leads to a change in the frequency of the tunable qubit, that is, the frequency of the qubit can be controlled by the signal transmitted by the flux control signal line.

[0062] Figure 1 It is a schematic diagram of the structure of qubits arranged on a quantum chip in the related art.

[0063] Combined with Figure 1 As shown, the structure of the qubit often adopts a single capacitor grounded to the ground, and a superconducting quantum interference device with one end grounded and the other end connected to the capacitor. And this capacitor is often a cross-shaped parallel plate capacitor.

[0064] Refer to Figure 1 As shown, the cross-shaped capacitor plate Cq (i.e., the qubit capacitor) is surrounded by a ground plane (GND), and there is a gap (usually an air gap, insulating) between the cross-shaped capacitor plate Cq and the ground plane (GND).

[0065] One end of the superconducting quantum interference device is connected to the end of one capacitor arm of the cross-shaped capacitor plate Cq (such as the first end mentioned later), and the other end is connected to the ground plane (GND).

[0066] Since the first end of the cross-shaped capacitor plate Cq is usually used to connect the superconducting quantum interference device, the second end is used to couple with the reading resonant cavity. The other two ends of the cross-shaped capacitor plate Cq are used to couple with adjacent quantum bits to achieve bit expansion. A certain space is usually reserved near the first end and the second end for arranging microwave transmission lines such as drive control signal lines and flux control signal lines. Similarly, a certain space is usually reserved near the resonant cavity for arranging the reading signal transmission line coupled with the resonant cavity.

[0067] The above-mentioned form of quantum bits are usually arranged in a one-dimensional linear structure, which occupies a large space on the chip and is not conducive to the deployment of large-scale bits.

[0068] In the quantum bit, as mentioned above, it is mainly composed of a capacitor and a Josephson junction. And the size of the Josephson junction is relatively small compared to the capacitor, so the coupling, readout and other operations of the bit are optimized and improved in this application. And considering that the size and shape of the capacitor in the bit also affect the key characteristic parameters such as the intrinsic frequency of the quantum bit and the coupling strength between quantum bits. Therefore, the scheme of this application also helps to conveniently adjust the performance parameters of the designed bit and is easy to manufacture and implement.

[0069] As far as the applicant knows, the hardware of the capacitor used to construct the superconducting quantum bit equivalent circuit in the current superconducting quantum chip is implemented as a distributed capacitor, and can be specifically manufactured as a metal plate on the surface of the substrate. For example, the metal plate is disconnected from the ground plane to form a ground capacitor.

[0070] For different quantum bit structures, different bit capacitors can be formed by designing metal plates with different structural forms.

[0071] Currently, there are several types of bit capacitors in practice.

[0072] Cross capacitor

[0073] A cross capacitor is a capacitor device whose hardware form is similar to the Chinese character "十".

[0074] The cross capacitor has four coupling ports, which facilitate the mutual coupling between bits, reading resonant cavities, and control circuits.

[0075] When a cross-shaped capacitor is connected to a Josephson junction, superconducting quantum bits in the form of Transmon and Xmon can be formed.

[0076] As mentioned above, this form of superconducting quantum bits can be used to construct a one-dimensional chain-like bit arrangement architecture, such as Figure 1 As shown in the figure, Cq represents the cross capacitor.

[0077] In practice, the applicant has found that when qubits constructed especially based on the above-mentioned cross capacitors are adjusted in size to change qubit performance or operability, it will bring great changes to the qubit structure. For example, it will significantly change the positions of Josephson junctions and each coupling port. Due to the existence of the coupling relationship between the qubit and other qubits and components, various circuits, components, and sizes in the chip will change correspondingly, thus bringing huge complexity and workload to the preliminary design, large-scale integration, and electromagnetic simulation of superconducting qubits.

[0078] In view of the above understanding and the current situation, in the examples of this application, the applicant has proposed a new quantum capacitor, which can be used as a capacitor to construct superconducting qubits.

[0079] In the example, the quantum circuit includes a main body part, a convex part, and a hammer-shaped part (or can also be described as a T-shaped part). The three parts in the quantum circuit can be integrally formed. For example, they are manufactured into an integral structure through a coating process - for example, forming the pattern of the layout of the quantum circuit through photolithography, and then forming the quantum circuit through processes such as evaporation coating and lift-off.

[0080] In this quantum circuit, the contour of the main body part is a continuous ring or a discontinuous ring with a discontinuous part.

[0081] The number of convex parts is one or at least two. Therefore, the quantum circuit can include multiple convex parts. These multiple convex parts are connected to the edge of the main body part and extend outward from the main body part. Specifically, the convex part can be connected at a selected position with a continuous ring; or, the convex part is connected at the position of the discontinuous part of the discontinuous ring.

[0082] The number of hammer-shaped parts is one or at least two. Therefore, the quantum circuit can include multiple hammer-shaped parts. These multiple hammer-shaped parts are connected to the edge of the main body part and extend outward from the main body part. Specifically, the hammer-shaped part can be connected at a selected position with a continuous ring; or, the hammer-shaped part is connected at the position of the discontinuous part of the discontinuous ring.

[0083] Moreover, the convex part and the hammer-shaped part are spaced apart. In particular, the extension length of the hammer-shaped part is greater than that of the convex part.

[0084] Therefore, in some examples, the overall shape of this quantum circuit is roughly like a round cake, and multiple protruding structures with different structural forms are formed from the edge.

[0085] In the illustrated embodiment of the present application, the protruding portion extends substantially in a straight line shape. However, in other examples, the extending shape of the protruding portion can be selected as a curve or a bent line shape. By selecting different extending shapes, a balance can be achieved in multiple aspects such as the space occupation of the protruding portion and the adjustment of the bit capacitance value of the superconducting qubit. For example, the extending shape of the changing region can be adjusted to more conveniently adjust the capacitance value. For example, when a longer protruding portion is required to adjust the capacitance of the qubit, it can be designed in a curved manner, thereby reducing the space occupation of the protruding portion in the chip and facilitating the integration of more superconducting qubits in the chip.

[0086] As a planar circuit, the periphery of the quantum circuit can be surrounded by a ground plane. Therefore, in specific manufacturing, a metal layer can be selected to be fabricated on the surface of the substrate. Then, by patterning the metal layer, a pattern of the quantum circuit is formed (holes exposing the substrate surface are formed in the metal layer), and then coating and stripping are performed. Alternatively, in specific manufacturing, a metal layer can be selected to be fabricated on the surface of the substrate. Then, an opening exposing the substrate surface is formed by etching the metal layer, and then the quantum circuit is fabricated within the opening.

[0087] In the above manufacturing scheme, the remaining portion of the metal layer can serve as the ground plane of the quantum circuit, and it can be known that the quantum circuit does not directly contact the ground plane, that is, there is a gap between the ground plane 101 and the quantum circuit 102. Please refer to Figure 2 . This gap provides a non-direct electrical connection between the ground plane 101 and the quantum circuit 102, and can also be used to adjust the capacitance value of the bit capacitor as mentioned later, and can also be used to configure the Josephson junction that constitutes the superconducting qubit.

[0088] In the quantum circuit, the main body portion 1021 provides its main area, while the areas of the protruding portion 1022 and the hammer-shaped portion 1023 are relatively small, as Figure 3 shown. Therefore, when the quantum circuit is used as the bit capacitor in the superconducting qubit, the main body portion serves as the main body providing the capacitance value of the bit capacitor, while the protruding portion can be used to make relatively finer adjustments to the capacitance value. That is, the area of the main body portion is larger than the area of the hammer-shaped portion, and the area of the hammer-shaped portion is larger than the area of the protruding portion.

[0089] In Figure 2 and Figure 3 the structure shown, the contour of the main body portion 102 of the quantum circuit 102 is a continuous ring. There are 6 protruding portions 1022 therein. In Figure 2 , there are two hammer-shaped portions 1023 provided. In other examples, the number of the protruding portions and the hammer-shaped portions can be selected according to the design of the required capacitance value, and the arrangement manner can also be selected.

[0090] For example, among them, on the basis of the direction shown, the two hammer-shaped parts 1023 are arranged in the vertical direction. Taking the main body part 1021 as a disc shape with a circular contour as an example, the number of hammer-shaped parts is two, and they are distributed at both ends in the diameter direction of the main body part. In other examples, the number of hammer-shaped parts is two, and they can also be distributed in two radial directions of the main body part that are at right angles, as shown in Figure 3 Figure (2) of Figure 8 . Of course, they can also be distributed at other angles.

[0091] For the convex parts, all the convex parts (described as a whole with multiple convex parts) include at least one convex group. As the name implies, a convex group is composed of a plurality of convex parts. Therefore, there are at least two convex parts in the convex group. In Figure 3 , the convex parts are positioned accordingly according to the distribution of the two hammer-shaped parts.

[0092] For example, Figure 3 the six convex parts 1022 in

[0093] are evenly divided into two convex groups—for the convenience of discussion, they are respectively denoted as the first convex group and the second convex group, and each group has three convex parts; in other examples, the number of convex parts in each convex group can also be different. The three convex parts in the same group are arranged at intervals in sequence, and the distance between adjacent two is the same—for example, the convex group includes at least three convex parts and is arranged in an equally spaced circular shape. Among them, the first convex group is on the left in the vertical direction, and the second convex group is on the right in the vertical direction.

[0094] In other words, when the number of hammer-shaped parts is two and they are distributed at both ends of the diameter of the main body part, multiple convex parts (such as six) include two convex groups. Each convex group has at least two convex parts (such as three), and the two convex groups are located on both sides of the vertical direction perpendicular to the diameter defined by the two hammer-shaped parts.

[0094] In Figure 2 and Figure 3 the shown examples, the convex parts 1022 and the hammer-shaped parts 1023 are distributed at equal intervals along a roughly circular circumference. However, in other examples of the present application, the convex parts and the hammer-shaped parts can also be distributed non-equidistantly.

[0095] Another quantum circuit is also disclosed in the examples of the present application, as shown in Figure 4 . In Figure 4 , a quantum circuit 102a surrounded by a ground plane 101 is disclosed—that is, the quantum circuit 102a is located in the gap defined by the edge contour of the ground plane.

[0096] For the quantum circuit 102a, its main body 1021a forms a structure similar to a polygon; for example, it can be described as having a discontinuous ring shape. In Figure 5 For the discontinuous ring shape, the corresponding main body 1021a has 8 segments, and a discontinuous part is formed between two adjacent segments. Correspondingly, the protruding part 1022a and the hammer-shaped part 1023a are respectively connected to the positions of different discontinuous parts.

[0097] Figure 5 A schematic diagram of the main body of a quantum circuit having a substantially ring structure is disclosed. Figure 8 Figure (3) in Figure 4 and Figure 5 and Figure 8 In the structures shown in Figure (3) in

[0098] Since the main body of the quantum circuit (a capacitor serving as a qubit) has an internal void defined by its contour in the structures shown in Figure (3) in

[0099] In the quantum circuit 102a, similar to the aforementioned quantum circuit 102, the protruding part 1022a and the hammer-shaped part 1023a can play the role and effect of adjusting the capacitance value of the bit capacitor. For example, the capacitance value of the bit capacitor can be adjusted by the length of these structures extending outward from the main body, or the distance between the end of these structures far from the main body in the extending direction and the ground plane, or a combination of the two.

[0100] When adjusting the capacitance value of the bit capacitor, appropriate differences can be made in the extension lengths of the respective protruding parts; for example, the lengths of some protruding parts are larger, while the lengths of the remaining protruding parts are smaller, as shown in Figure (1) in Figure 8 In addition, the widths of the protruding parts can also be selected. These adjustments to the protruding parts can also be applied to the adjustments of the hammer-shaped parts, which will not be elaborated here.

[0101] Based on the above-mentioned quantum circuit, an example of the present application also discloses a superconducting qubit. The superconducting qubit includes the above-mentioned quantum circuit. Based on the composition of the superconducting qubit, if the aforementioned quantum circuit is a qubit capacitor, the qubit may further include a Josephson junction, thereby forming an equivalent nonlinear oscillation circuit with the capacitor. Based on the need to adjust the qubit frequency, the Josephson junction can be constructed in a superconducting quantum interference device (SQUID); and the superconducting quantum interference can have multiple Josephson junctions, such as at least two Josephson junctions. In an example, the superconducting qubit may also have a superconducting quantum interference device with a single Josephson junction.

[0102] In a nonlinear oscillation circuit, there is a nonlinear element. That is, the superconducting qubit has a nonlinear element, which can be provided by the above-mentioned Josephson junction. In a specific hardware implementation example, the superconducting qubit includes a nonlinear element, one end of the nonlinear element is grounded, and the other end is connected to a protrusion. For example, based on Figure 2 the quantum circuit described in Figure 6 the connection method between two Josephson junctions 201 and qubit 102 is described.

[0103] For two mutually coupled superconducting qubits, based on Figure 6 the superconducting qubit example shown in Figure 7 it is possible to couple with other superconducting qubits through the edge position of the main body of the quantum circuit. For example, configure a coupler so that the coupler is distributed in a region (such as

[0104] as shown in Figure 7 the coupling region shown) defined by two adjacent protrusions and the edge of the main body therebetween, thereby realizing capacitive coupling. Figure 7 As shown in

[0105] When there are 6 protrusions 1022 and two hammer-shaped parts 103 and they are distributed in the manner described in the figure, the number of coupling regions can be 8,

[0106] only 1 is marked in . It should be noted that two mutually coupled superconducting qubits can choose to couple through a coupling region. The selection basis can be, for example, the arrangement, attitude of each adjacent superconducting qubit, or the layout of a set of multiple qubits, etc.

[0105] Through the quantum circuit with the above structural design form, it can provide a large operating space for the design, layout, and integration of superconducting qubits, thus bringing great convenience to the layout design. The specific structure, size, etc. of the quantum circuit can be obtained through electromagnetic simulation, and the specific structure and size can be corrected or changed according to the simulation results.

[0106] Moreover, since the capacitance value can be adjusted by regulating the number, position, and size of the protrusions and hammer-shaped parts in the quantum circuit, etc., without major modifications, different scenarios can be simulated and layout designs can be achieved at a relatively lower cost.

[0107] Based on the above superconducting qubits, a quantum chip including the aforementioned quantum circuit or superconducting qubit can also be constructed in this application. In the quantum chip, in addition to having the aforementioned quantum circuit or superconducting qubit, corresponding structures for reading and controlling superconducting qubits, such as the aforementioned control lines and read lines, can also be provided.

[0108] Furthermore, a quantum computer can be constructed using the above quantum chip. Considering the superconducting qubit system, a refrigeration device (such as a dilution refrigerator) and classical computer devices are configured in the quantum computer.

[0109] To implement a more complex circuit, the first qubit and the second qubit can be coupled. Therefore, a coupling circuit 300 is also disclosed in the examples of this application.

[0110] The coupling circuit 300 includes a first coupler 301 and a second coupler 302. In the examples of this application, the first coupler and the second coupler are used instead of using a single first coupler or a single second coupler. In this way, the problem that a single first coupler or a single second coupler has a too large length, which occupies a large space on the chip and is not conducive to the layout of other components and the integration of more qubits, can be avoided.

[0111] That is, when using a single first coupler or a single second coupler alone, a relatively large length of the corresponding coupler is required to achieve a certain coupling strength.

[0112] However, when using the first coupler and the second coupler simultaneously, the first coupler and the second coupler can be shortened respectively. In this way, the lengths of the first coupler and the second coupler are shorter, thus reducing the space occupation.

[0113] Due to the advantage of small space occupation, using the first coupler and the second coupler disclosed in the examples of this application in the quantum chip can effectively utilize the surface space of the chip, reduce the space occupation, and thus facilitate leaving more space for other structures. Therefore, the use of the above coupling circuit helps to integrate more qubits in the quantum chip, which can play a positive role in improving the quantum computer.

[0114] In the example, the first coupler and the second coupler are arranged side by side and spaced apart in the side-by-side direction. The first coupler and the second coupler are open-circuited with respect to each other. In some examples, in order to avoid potential mutual influence between the two couplers, the first coupler and the second coupler can be provided with a preset spacing measured in the side-by-side direction. This preset spacing can be, for example, a distance sufficient to prevent mutual interference of bit-occurring signals. For the convenience of description, it can be defined that the first coupler and the second coupler are arranged side by side in the longitudinal direction (such as the vertical direction), and the lengths of the subsequent-mentioned couplers, namely the first preset length of the first coupler and the second preset length of the second coupler, are correspondingly determined by measurement in the transverse direction (such as the horizontal direction).

[0115] The first coupler and the second coupler are each configured to be independently coupled to the first qubit and the second qubit at both ends, as Figure 9 shown. Among them, the bit and the coupler can be coupled by means of capacitive coupling. It should be noted that Figure 9 only the approximate relative positional relationship between the first coupler and the second coupler, and the first qubit and the second qubit is schematically shown. In actual design and manufacturing, it can be adjusted as needed without special limitations.

[0116] In particular, in the example, the first coupler has a first preset length, the second coupler has a second preset length, and the first preset length and the second preset length are configured to define the inherent coupling strength between the first qubit and the second qubit.

[0117] That is, the coupling strength can be adjusted by the lengths of the first coupler and the second coupler. Therefore, it should be understood that the capacitance value can be adjusted by changing the coupler length, and correspondingly, it is associated with the coupling between the bits. In short, by increasing the number of couplers, the adverse change in the coupling strength caused by the change in the coupler size (such as the length reduction) can be offset to meet the coupling strength requirements between the bits.

[0118] The inherent coupling strength therein means the coupling strength that can be achieved between the first qubit and the second qubit determined by the structural dimensions of the first coupler and the second coupler.

[0119] And correspondingly further, when one or both of the first coupler and the second coupler have variable / adjustable performance such that the coupling strength between the first qubit and the second qubit can be adjusted, then the adjusted coupling strength between the first qubit and the second qubit at this time can be described as the modulated coupling strength. And it can be known that the numerical values of the inherent coupling strength and the modulated coupling strength are usually not equal. This will be further elaborated later.

[0120] The first coupler and the second coupler mentioned above can be implemented as capacitors, resonators, qubits (frequency-tunable or non-frequency-tunable), etc. During specific manufacturing, a metal thin film can be deposited on the substrate surface and then subjected to on-demand and specific structural adjustments (such as patterning through photolithography).

[0121] For example, in some examples, depending on the specific implementation of the two couplers, the first coupler has a tunable frequency. Therefore, the first coupler is configured to change its own frequency so that the first coupler and the second coupler have a modulated coupling strength different from the inherent coupling strength. The second coupler can be designed to have a fixed frequency.

[0122] In some other examples, the first coupler and the second coupler can be specifically implemented as superconducting qubits respectively. Or, in some other examples, the first coupler is a frequency-tunable superconducting qubit and the second coupler is a coplanar waveguide resonator.

[0123] As the structure for coupling the coupler and the qubit, both ends of the first coupler are configured as the first coupling parts, and both ends of the second coupler are configured as the second coupling parts. Therefore, the first coupling part is coupled to the first qubit, and the second coupler is coupled to the second qubit.

[0124] In some examples, the first coupling parts at both ends of the first coupler are symmetrically distributed along the extension direction of the first coupler; the second coupling parts at both ends of the second coupler are symmetrically distributed along the extension direction of the second coupler. Further, the first coupling part and the second coupling part can have the same shape. For example, both are respectively set as hammer-shaped structures.

[0125] As a specific example, Figure 10 The structural schematic diagram of a coupling circuit in the examples of the present application is disclosed.

[0126] As shown in Figure 10 the figure, there are a first coupler 101 and a second coupler 102.

[0127] The second coupler 302 has an extension length in the left-to-right direction (such as the horizontal direction) shown in Figure 10 the figure, and a second coupling part 3021 in the shape of a hammer is formed at each end respectively, and a second main body part is located between the two second coupling ends. The second main body part is an elongated strip structure, and the ends on the left and right sides "expand / bulge" to form second coupling parts 3021 with a larger cross-sectional area. The second coupling part 3021 shown in this figure can be configured as a resonator.

[0128] The first coupler 301 has an extension length in Figure 10The extension length in the left-to-right direction (such as the horizontal direction) as shown, and at both ends, a first coupling portion 3011 of a hammer-shaped structure is formed respectively, and a first main body portion between the two second coupling ends. The first main body portion is an elongated strip-shaped structure, and at the ends on the left and right sides, it "expands / dilates" to form the first coupling portion 3011 with a larger cross-sectional area.

[0129] As Figure 10 shown, the first coupler and the second coupler have a spacing in the vertical direction ( Figure 10 represented by d), and this spacing can be appropriately adjusted, such as increased or decreased, according to the difference in the coupling positions of the couplers.

[0130] In addition, the main body portion between the two ends of the two couplers can also be appropriately and selectively locally expanded (i.e., the cross-sectional area is increased) to meet different parameter requirements. Or, a spiral structure is formed in a local area, etc.

[0131] And, Figure 10 in Figure 12 shown, the two couplers are horizontally placed. In other examples, the two can also be vertically placed or obliquely arranged, as

[0132] shown. Figure 10 Specifically, in the structure shown, the first coupler 301 is implemented as a qubit - formed by the parallel connection of a Josephson junction (not shown) and a capacitor. For the convenience of grounding the Josephson junction and the need for function implementation, the first coupler 301 protrudes from a roughly middle region to form a connection portion 3012. When using the second coupler in the chip, through the two superconducting electrodes of the Josephson junction, they are respectively connected to the ground and the connection portion 3012.

[0133] It should be noted that, Figure 10 in

[0134] only the example structures of the two coupler structures are given. Figure 11 According to whether the frequency of the qubit formed by the first coupler 302 is adjustable, the number and layout form of the Josephson junctions in its composition can be adjusted. Based on an example selection of its adjustable frequency, the Josephson junction can be provided in the form of a Direct-Current Superconducting Quantum Interference Device (abbreviated as DC-SQUID). It has a structure as Figure 11a connection part 3012 (represented by a solid circle) to the first coupler and is connected to the ground plane. The interface therein can be specifically implemented as a pad.

[0135] In the above-mentioned coupling circuit 300 and the quantum circuit (a capacitor as a qubit), an example of the present application also discloses a superconducting qubit coupling structure.

[0136] It includes: a first qubit and a second qubit; and a coupling circuit disposed between the first qubit and the second qubit; and a first coupler and a second coupler, each independently coupling to the first qubit and the second qubit at both ends, as Figure 13 shown.

[0137] Therefore, according to the arrangement positions of two coupled superconducting qubits, Figure 10 and Figure 12 a coupling circuit in the arrangement manner can be used to couple two superconducting qubits. For example, Figure 13 for the two qubits shown in Figure 10 the coupling circuit in Figure 7 is used for coupling. Since the quantum circuit 102 has multiple coupling regions shown in Figure 10 and the coupling region can be fitted and coupled with the first coupling part 3011 and the second coupling part 3021 of the coupler identified in Figure 13 Therefore, according to the distribution of the coupling regions in the quantum circuit 102, any selected number of coupling circuits can be configured to realize various arrangement structures of superconducting qubits, so as to realize different bit distribution topologies. For example, it can be a one-dimensional linear arrangement (for example, adopting the arrangement manner shown in Figure 14 ), a two-dimensional array arrangement (for example, adopting the arrangement manner shown in

[0138] Furthermore, on this basis, a quantum chip or its extended product, namely a quantum computer, can be constructed.

[0139] Combined with the foregoing quantum circuit and coupling circuit, the space of the chip can be effectively utilized in the quantum chip, the layout design can be significantly improved, and it is convenient to integrate bits in the chip, thus playing a positive role in realizing a large-scale bit quantum chip.

[0140] The embodiments described above with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be construed as a limitation of the present application.

[0141] To make the objectives, technical solutions and advantages of the embodiments of this application clearer, one or more embodiments are described below with reference to the accompanying drawings. Among them, like reference numerals are used throughout the text to refer to like components. In the above description, for the purpose of explanation, many specific details are set forth in order to provide a more thorough understanding of one or more embodiments. However, it is obvious that in various cases, one or more embodiments can be practiced without these specific details, and the various embodiments can be combined and cross-referenced with each other on the premise of not being contradictory.

[0142] It should be noted that the terms "first", "second", etc. in the description and claims of this application and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments of this application described here can be implemented in an order other than those illustrated or described here.

[0143] In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that comprises a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or are inherent to these processes, methods, products or devices.

[0144] The structure, features and effects of this application have been described in detail based on the embodiments shown in the drawings above. The above are only the preferred embodiments of this application, but this application does not limit the scope of implementation by the drawings shown. Any changes made according to the concept of this application, or equivalent embodiments modified to equivalent changes, should still be within the protection scope of this application as long as they do not exceed the spirit covered by the description and the drawings.

Claims

1. A coupling circuit for coupling a first quantum bit and a second quantum bit, characterized in that: The coupling circuit comprises: A first coupler and a second coupler are arranged side by side in the longitudinal direction and are spaced apart in the side-by-side direction, wherein the first coupler and the second coupler are configured to be independently coupled to the first qubit and the second qubit at two ends thereof; The first coupler has a first preset length determined in a lateral direction, the second coupler has a second preset length determined in a lateral direction, and the first preset length and the second preset length are configured to define an intrinsic coupling strength of the first quantum bit and the second quantum bit.

2. The coupling circuit according to claim 1, characterized in that: The first coupler has an adjustable frequency, and the first coupler is configured to change its own frequency so that the first coupler and the second coupler have a modulation coupling strength different from the inherent coupling strength; And / or, the second coupler has a fixed frequency.

3. The coupling circuit according to claim 1, characterized in that: The first coupler and the second coupler are superconducting qubits respectively; And / or, the first coupler and the second coupler have a preset spacing measured in the side-by-side direction.

4. The coupling circuit according to claim 1, characterized in that: The first coupler is a frequency-adjustable superconducting quantum bit, and the second coupler is a coplanar waveguide resonant cavity.

5. The coupling circuit according to claim 4, characterized in that: Both ends of the first coupler are configured as first coupling parts, and both ends of the second coupler are configured as second coupling parts, and the first coupling part and the second coupling part have the same shape.

6. The coupling circuit according to claim 5, characterized in that: The first coupling parts at both ends of the first coupler are symmetrically distributed along the extension direction of the first coupler; the second coupling parts at both ends of the second coupler are symmetrically distributed along the extension direction of the second coupler.

7. The coupling circuit according to claim 5 or 6, characterized in that: The first coupling portion and the second coupling portion are hammer-shaped structures.

8. A coupling structure, characterized in that: include: A first quantum bit and a second quantum bit; as well as The coupling circuit according to any one of claims 1 to 7, arranged between the first quantum bit and the second quantum bit; The first coupler and the second coupler are independently coupled to the first quantum bit and the second quantum bit at two ends respectively.

9. A chip, characterized in that: The coupling circuit comprises the coupling circuit according to any one of claims 1 to 7, or the coupling structure according to claim 8.

10. A computer, characterized in that: Comprising the chip as claimed in claim 9.

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