Quantum computing circuits and information processing devices

Abstract

The interaction between two of the three or more qubits involved in the many-body interaction has a relatively small impact on the overall many-body interaction. [Solution] The quantum computing circuit comprises a qubit element and a coupler that causes three or more of the qubit elements to interact, wherein the coupler is grounded and has nonlinearity.

Description

[Technical Field]

[0001] This disclosure relates to quantum computing circuits and information processing devices. [Background technology]

[0002] Many-body interactions are sometimes used in quantum computing. For example, Patent Document 1 describes a coupler that connects four qubits using a four-body interaction. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2023 / 248370 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] When three or more qubits interact as a many-body system, the interaction between two of the three or more qubits may influence the many-body interaction. It is preferable to mitigate the influence of the interaction between two qubits on the many-body interaction.

[0005] One example of the purpose of this disclosure is to provide a quantum computing circuit and an information processing device that can solve the above-mentioned problems. [Means for solving the problem]

[0006] According to a first aspect of the present disclosure, a quantum computing circuit comprises a qubit element and a coupler that causes three or more of the qubit elements to interact, wherein the coupler is grounded and has nonlinearity.

[0007] According to a second aspect of the present disclosure, an information processing apparatus includes a quantum computing circuit and control means. The quantum computing circuit includes a qubit element and a coupler that interacts three or more of the qubit elements. The coupler is grounded and has non-linearity. The control means controls the quantum computing circuit to perform quantum computing.

Advantages of the Invention

[0008] According to the present disclosure, it is expected that the influence of the interaction between two qubits among three or more qubits that interact with each other can be made relatively small on the many-body interaction.

Brief Description of the Drawings

[0009] [Figure 1] It is a diagram showing an example of the configuration of an information processing apparatus according to at least one embodiment. [Figure 2] It is a diagram showing a first example of the implementation of many-body coupling in a quantum computing circuit according to at least one embodiment. [Figure 3] It is a diagram showing an example of the implementation of many-body coupling when the coupler is not grounded. [Figure 4] It is a diagram showing an example of a configuration in which two qubit elements 110 are connected without passing through a coupler 120 in at least one embodiment. [Figure 5] It is a diagram showing an example of a configuration in which two qubit elements 110 are connected via a coupler 120. [Figure 6] It is a diagram showing a first example of the configuration of a coupler according to at least one embodiment. [Figure 7] It is a diagram showing a second example of the configuration of a coupler according to at least one embodiment. [Figure 8] It is a diagram showing a third example of the configuration of a coupler according to at least one embodiment. [Figure 9] It is a diagram showing a second example of the implementation of many-body coupling in a quantum computing circuit according to at least one embodiment. [Figure 10]This figure shows an example of an LHZ network using a grounded coupler, according to at least one embodiment. [Figure 11] This figure shows an example of the configuration of a quantum computing circuit according to at least one embodiment. [Figure 12] This figure shows an example of the configuration of an information processing device according to at least one embodiment. [Figure 13] This is a schematic block diagram showing the configuration of a computer according to at least one embodiment. [Modes for carrying out the invention]

[0010] The embodiments will be described below with reference to the drawings. In the following, the dagger symbol will be referred to as: + It is sometimes represented with a superscript +.

[0011] <First Embodiment> Figure 1 shows an example of the configuration of an information processing device according to at least one embodiment. In the configuration shown in Figure 1, the information processing device 1 comprises a quantum computing circuit 100, a control unit 200, and an observation unit 300. The quantum computing circuit 100 comprises a qubit element 110 and a coupler 120.

[0012] Information processing device 1 performs quantum computing. For example, information processing device 1 may perform quantum annealing. Information processing device 1 can also be called a quantum computer. When information processing device 1 performs quantum annealing, it can also be called a quantum annealing machine.

[0013] The quantum computing circuit 100 performs quantum computing according to the control of the control unit 200. The qubit element 110 is an element for representing qubit values. The qubit element 110 may, but is not limited to, be constructed using a Josephson Parametric Oscillator (JPO).

[0014] The coupler 120 causes the qubit elements 110 to interact. In particular, the coupler 120 causes three or more qubit elements 110 to interact in a many-body manner. Here, the interaction of the qubit elements 110 means that the qubit values ​​represented by the qubit elements 110 are correlated. The interaction of the qubit elements 110 can also be called the interaction between the qubit elements 110. The interaction of the qubit elements 110 can also be called the interaction of qubits, or the interaction between qubits. The interaction of the qubit elements 110 can also be called the coupling of qubit elements 110, the coupling between qubit elements 110, the coupling of qubits, or the coupling between qubits.

[0015] The control unit 200 controls the quantum computing circuit 100 to perform quantum computing. For example, the control unit 200 sets parameter values ​​for quantum computing, such as the strength of the many-body coupling by the coupler 120, according to the problem to be solved by quantum computing, such as a combinatorial optimization problem. The control unit 200 also controls the transition of the state of the qubit element 110 (the quantum state in the qubit element 110) by changing the time of the magnetic field input to the qubit element 110. The control unit 200 is an example of a control means.

[0016] The observation unit 300 reads the qubit value as a result of quantum computing. Specifically, after a predetermined time has elapsed since the start of quantum computing, the observation unit 300 observes the output signal of the qubit element 110 to detect the quantum state.

[0017] Figure 2 shows a first example of a many-body coupling implementation in a quantum computing circuit 100. Figure 2 shows an example of a four-body interaction, in which four qubit elements 110 are connected to one coupler 120.

[0018] The qubit element 110 includes a Josephson junction loop 111, an inductor 112, and a capacitor 113. The Josephson junction loop 111 and the capacitor 113 are arranged on a loop. The loop including the Josephson junction loop 111 and the capacitor 113 is also called a resonant loop 114.

[0019] The Josephson junction loop 111 is a superconductor in which a Josephson junction is provided forms a loop (closed circuit). For example, the Josephson junction loop 111 may be a SQUID (Superconducting Quantum Interference Device) which is a loop having two Josephson junctions, but is not limited to this.

[0020] The inductor 112 generates a magnetic field when current flows through it, and applies this magnetic field to the Josephson junction loop 111. By applying a variable-intensity magnetic field to the Josephson junction loop 111, the inductor 112 can make the Josephson junction loop 111 function as a variable inductor (an inductor with variable inductance).

[0021] Capacitor 113 represents the capacitance of the resonant loop 114. The structural capacitor of the resonant loop 114 may function as capacitor 113, or a component designated as capacitor 113 may be provided. The capacitance of capacitor 113 can also be considered as the capacitance of the qubit element 110. The Josephson junction loop 111 functions as a variable inductor, making the resonant loop 114 a loop with a variable resonant frequency. This allows the qubit element 110 to operate as a parametric oscillator.

[0022] Of the resonant loop 114, the two points where the Josephson junction loop 111 and the capacitor 113 are connected in parallel form the ends of the qubit element 110. In Figure 2, the two ends of the qubit element 110 are indicated by points P111 and P112. One of the two ends (the end indicated by point P111) is connected to the coupler 120 via capacitor 130. Capacitor 130 represents the capacitance in the path connecting the qubit element 110 and the coupler 120. Additionally, the other of the two ends (the end indicated by point P112) is grounded.

[0023] The coupler 120 includes a Josephson junction loop 121, an inductor 122, and a capacitor 123. The Josephson junction loop 121 and the capacitor 123 are arranged on a loop. The loop including the Josephson junction loop 121 and the capacitor 123 is also called the resonant loop 124.

[0024] The Josephson junction loop 121 is a superconductor in which a Josephson junction is provided that forms a loop. For example, the Josephson junction loop 121 may be a SQUID, but is not limited to this. Also, in the case of a coupler, the Josephson junction loop 121 may be a single Josephson junction that does not form a loop. That is, the qubit element 110 includes a Josephson junction loop 111, and the coupler 120 may include a single Josephson junction instead of the Josephson junction loop 121. Various nonlinear elements can be used as the Josephson junction loop 121. Because the Josephson junction loop 121 is constructed using nonlinearity, three or more qubit elements 110 can interact with each other.

[0025] Here, the Hamiltonian H of a linear resonator can be expressed as shown in equation (1) using capacitance C, inductance L, charge Q, and magnetic flux Φ.

[0026]

number

[0027] In contrast, the Hamiltonian of a nonlinear resonator includes terms of order 3 or higher of Φ.

[0028] The inductor 122 generates a magnetic field when current flows through it, and applies this magnetic field to the Josephson junction loop 121. By applying a variable-intensity magnetic field to the Josephson junction loop 121, the inductor 122 can make the Josephson junction loop 121 function as a variable inductor.

[0029] Capacitor 123 represents the capacitance of the resonant loop 124. The structural capacitor of the resonant loop 124 may function as capacitor 123, or a component designated as capacitor 123 may be provided. The capacitance represented by capacitor 123 can also be considered as the capacitance of the coupler 120.

[0030] The Josephson junction loop 121 functions as a variable inductor, making the resonant loop 124 a loop with a variable resonant frequency. By adjusting the resonant frequency of the coupler 120 and causing it to interact with each of the qubit elements 110, the four qubit elements 110 can be made to interact as a four-body interaction.

[0031] Of the resonant loop 124, the two points where the Josephson junction loop 121 and the capacitor 123 are connected in parallel form the ends of the coupler 120. In Figure 2, the two ends of the coupler 120 are indicated by points P121 and P122. One of the two ends (indicated by point P121) is connected to the qubit element 110 via a capacitor 130 for each qubit element 110. The other end (indicated by point P122) is grounded.

[0032] In the configuration shown in Figure 2, each of the qubit elements 110 is connected to the coupler 120, and two of the four qubit elements 110 are connected to each other. This connection of two qubit elements 110 creates a two-body interaction between them. In the example shown in Figure 2, there are 4C2 = 6 possible two-body interactions, representing the number of ways to select two of the four qubit elements 110.

[0033] Two-body interactions between qubit elements induce cross-Kerr interactions. Cross-Kerr interactions negatively affect many-body interactions (four-body interactions in the example in Figure 2), such as by altering the resonant frequency of the qubit elements. The Cross-Kerr interaction can be expressed as part of the Hamiltonian shown in equation (2).

[0034]

number

[0035] i and j both represent indices that identify four qubit elements. The qubit element identified by index i is also referred to as qubit element i. H JPO,i This represents the Hamiltonian of each individual qubit element. g is the coupling between the coupler and the qubit element i. gi The coefficient is proportional to the product of (i=1,···,4). g is expressed as shown in equation (3).

[0036]

number

[0037] a + k This indicates a creation operator. a k This indicates the annihilation operator. "hc" is an abbreviation for Hermitian Conjugate, and is a dagger symbol (+ ) shows the equation with the presence or absence swapped. In the case of Equation (2), h.c. is shown as in Equation (4).

[0038] [Number]

[0039] Χ ij is a coefficient proportional to at least the square of the coupling gij between the qubit element i and the qubit element j. Χ ij is shown as in Equation (5).

[0040] [Number]

[0041] In the quantum computing circuit 100, the coupler 120 is grounded in order to reduce the influence of the Cross-Kerr interaction on the four-body interaction.

[0042] FIG. 3 is a diagram showing an example of the implementation of many-body coupling when the coupler is not grounded. Among the parts of FIG. 3, parts having the same functions corresponding to the parts of FIG. 2 are denoted by the same reference numerals (110, 120, 121, 122, 123, 124, 130), and detailed descriptions thereof are omitted here. When distinguishing the four qubit elements 110, they are also denoted as qubit elements 110-1, 110-2, 110-3, and 110-4.

[0043] In the example of FIG. 3, the coupler 120 is not grounded, and the two ends indicated by points P211 and P212 are respectively connected to two qubit elements 110. The coupler 120 is connected to the qubit elements 110-1 and 110-2 at the end indicated by point P211, and is connected to the qubit elements 110-3 and 110-4 at the end indicated by point P212.

[0044] Here, we consider a comparison between the case where two qubit elements 110 are connected without directly passing through the coupler 120, as in the example in Figure 2, and the case where two qubit elements 110 are connected via the coupler 120, as in the connection relationship between qubit elements 110-1 and 110-3 in Figure 3.

[0045] Figure 4 shows an example of a configuration in which two qubit elements 110 are connected without going through a coupler 120. In the example in Figure 4, the paths from each of the two qubit elements 110 and the path from the coupler 120 are connected at point P311. This means that there is a path that connects the two qubit elements 110 without going through the coupler 120. The strength of the interaction between the qubit elements 110 in this case is g. q This is expressed as shown in equation (6).

[0046]

number

[0047] The symbol "∝" indicates proportionality. C c This indicates the capacitance of capacitor 130. That is, C c This indicates the capacitance of the path. C g This indicates the capacitance of capacitor 123. That is, C g This indicates the capacitance of coupler 120. C q This indicates the capacitance of capacitor 113. That is, C q This shows the capacitance of the qubit element 110. g q This refers to the coupling g between the qubit element i and the qubit element j described above. ij This corresponds to a compilation of the above.

[0048] The strength of the interaction between the qubit element 110 and the coupler 120 g g This is expressed as shown in equation (7).

[0049]

number

[0050] g g This refers to the coupling g between the aforementioned coupler and the qubit element i. gi This corresponds to a compilation of the above. Assuming the proportionality constant is the same in the case of equation (6) and the case of equation (7), the strength of the interaction between the qubit elements 110 is g. q The strength of the interaction between the qubit element 110 and the coupler 120 is g. g The relationship is shown in equation (8).

[0051]

number

[0052] Capacitance C of qubit element 110 q The capacitance C of the path is c It is thought to be about 100 times stronger. Therefore, the strength of the interaction between the qubit elements 110 is g q This is the strength of the interaction g between the qubit element 110 and the coupler 120. g It is about 1 / 100th of that. Thus, in the configuration shown in the example in Figure 4, the strength of the interaction between the qubit elements 110 is g. q This is the strength of the interaction g between the qubit element 110 and the coupler 120. g It can be considered sufficiently small compared to [another factor].

[0053] Figure 5 shows an example of a configuration in which two qubit elements 110 are connected via a coupler 120. In the example in Figure 5, the coupler 120 is connected to the paths from the qubit elements 110 at each of the two ends indicated by points P411 and P412. This connects the two qubit elements 110 via the coupler 120. The strength of the interaction between the qubit elements 110 in this case is g. q This is shown in equation (9).

[0054]

number

[0055] The strength of the interaction between the qubit element 110 and the coupler 120 g g This is expressed as in equation (7) above, similar to the case in Figure 4. Assuming the proportionality constant is the same in the case of equation (3) and the case of equation (4), the strength of the interaction between the qubit elements 110 is g. q The strength of the interaction between the qubit element 110 and the coupler 120 is g. g The relationship is shown in equation (10).

[0056]

number

[0057] Capacitance C of qubit element 110 q And the capacitance C of the coupler 120 g and are approximately equal (C q ≒C g ) If so, the strength of the interaction between the qubit elements 110 is g q The strength of the interaction between the qubit element 110 and the coupler 120 is g. g These can be considered to be approximately equal.

[0058] The four-body interaction mediated by the coupler 120 can be understood as being realized through the interaction between the coupler 120 and each of the four qubit elements 110. Therefore, the strength of the four-body interaction is considered to be proportional to the strength of the interaction between the qubit elements 110 and the coupler 120.

[0059] Based on this, and a comparison between the case in Figure 4 and the case in Figure 5, it is expected that in the configuration of Figure 2, where the coupler 120 is grounded, the influence of the interaction between the qubit elements 110 on the four-body interaction can be reduced to about 1 / 100th compared to the configuration of Figure 3, where the coupler 120 is not grounded.

[0060] As described above, the Josephson junction loop 121 of the coupler 120 may be a SQUID, but is not limited to this. Figure 6 shows a first example of the configuration of the coupler 120. In the example in Figure 6, the Josephson junction loop 121 is constructed using a SQUID. As described above, a SQUID is a loop having two Josephson junctions. A Josephson junction is also called a Josephson junction 125. As shown in the example in Figure 6, the Josephson junction loop 121 constructed using SQUIDs is also referred to as Josephson junction loop 121a. The coupler 120 in which the Josephson junction loop 121 is constructed using SQUIDs is also referred to as coupler 120a.

[0061] Figure 7 shows a second example of the configuration of the coupler 120. In the example in Figure 7, the Josephson junction loop 121 is configured as a loop having three or more Josephson junctions 125. Figure 7 shows an example where the Josephson junction loop 121 has three Josephson junctions 125. However, the Josephson junction loop 121 may have four or more Josephson junctions 125. Also, the number of Josephson junctions on the left side of the Josephson junction loop 121b in Figure 7 is not limited to one, and multiple Josephson junctions may be provided.

[0062] As shown in the example in Figure 7, a Josephson junction loop 121 having three or more Josephson junctions 125 is also referred to as a Josephson junction loop 121b. A coupler 120 in which the Josephson junction loop 121 has three or more Josephson junctions 125 is also referred to as a coupler 120b. A coupler with such a configuration may have negative nonlinearity depending on the strength of the magnetic field generated by the magnetic field applying means (e.g., inductor 122). In that case, it can be canceled out by the positive nonlinearity of the qubit element, reducing the undesirable crossker effect.

[0063] Here, if the Josephson junction loop 121 is constructed using a SQUID, additional operations such as signal application are required to make an odd number of qubit elements 110 interact, such as a three-body interaction or a five-body interaction. In contrast, since the Josephson junction loop 121 is constructed as a loop having three or more Josephson junctions, it is expected that an odd number of qubit elements 110 can be made to interact with relatively high precision without the need for additional operations.

[0064] Figure 8 shows a third example of the configuration of the coupler 120. In the example in Figure 8, the Josephson junction loop 121 is constructed using a combination of two loops. Each of the two loops is also referred to as loop L11 and L12. In addition, in the example in Figure 8, the Josephson junction loop 121 has four Josephson junctions 125. Each of the four Josephson junctions 125 is also referred to as Josephson junction 125a, 125b, 125c, and 125d.

[0065] Of the four Josephson junctions 125, Josephson junction 125a is included only in loop L11 of loops L11 and L12. Josephson junctions 125b and 125c are common Josephson junctions 125 to loops L11 and L12. That is, Josephson junctions 125b and 125c are included in both loops L11 and L12. Josephson junction 125d is included only in loop L12 of loops L11 and L12.

[0066] However, a Josephson junction loop 121 may consist of three or more loops. The number of Josephson junctions 125 in a Josephson junction loop 121 containing multiple loops is not limited to a specific number. Each loop may have a Josephson junction 125 that is included only in that loop, and there may also be a Josephson junction 125 that is common to multiple loops. As shown in the example in Figure 8, a Josephson junction loop 121 containing multiple loops is also referred to as a Josephson junction loop 121c. A coupler 120 having a Josephson junction 125 containing multiple loops in the Josephson junction loop 121 is also referred to as a coupler 120c.

[0067] Since the Josephson junction loop 121 is configured as a loop having three or more Josephson junctions, it is expected that an odd number of qubit elements 110 can be interacted with relatively high precision. Furthermore, since the Josephson junction loop 121 is configured using a combination of multiple loops, the magnetic field applied to each loop can be adjusted, and it is expected that the interaction of the qubit elements 110 can be executed with relatively high precision.

[0068] The coupler 120 is grounded, but the qubit element 110 does not necessarily have to be grounded.

[0069] Figure 9 shows a second example of the implementation of many-body coupling in the quantum computing circuit 100. In Figure 9, parts that have the same function as those in Figure 2 are denoted by the same reference numerals (110, 111, 112, 113, 114, 120, 121, 122, 123, 124, 130), and detailed explanations are omitted here. Also, point P511 in Figure 9 corresponds to point P111 in Figure 2, point P521 corresponds to point P121, and point P522 corresponds to point P122.

[0070] The configuration shown in Figure 9 differs from the configuration shown in Figure 2 in that each of the qubit elements 110 is not grounded. In all other respects, the configuration shown in Figure 9 is the same as the configuration shown in Figure 2. Because the qubit element 110 is not grounded, energy leakage from the qubit element 110 is reduced, which is expected to increase the internal Q-factor (become higher) and extend the time during which the coherent state can be maintained.

[0071] A longer time for the qubit element 110 to maintain a coherent state increases the time for which a bit value (qubit value) can be read from the qubit element 110. A longer time for which a bit value can be read from the qubit element 110 can also be described as a longer qubit lifetime.

[0072] Now, let's consider the case where neither the qubit element 110 nor the coupler 120 is grounded. In this case, the four-body interaction by the coupler 120 becomes more susceptible to the influence of other circuits, and the accuracy of the four-body interaction may decrease. For example, if one or more of the qubit elements 110 that are subject to the four-body interaction by the first coupler 120 are also subject to the four-body interaction by the second coupler 120, the four-body interaction by the first coupler 120 may become more susceptible to the influence of the four-body interaction by the second coupler 120.

[0073] In contrast, because the coupler 120 is grounded, even when the qubit element 110 is not grounded, the four-body interaction by the coupler 120 becomes relatively less susceptible to the influence of other circuits. As a result, the four-body interaction by the coupler 120 is expected to be relatively high-precision.

[0074] Figure 10 shows an example of a network using a grounded coupler. In the configuration shown in Figure 10, the network 400 comprises an oscillator 410, indicated by a circle, and a coupler 420, indicated by a square (diamond). Network 400 corresponds to an example of quantum computing circuit 100. Oscillator 410 corresponds to an example of qubit element 110. Coupler 420 corresponds to an example of coupler 120.

[0075] The oscillator 410 has positive nonlinearity. Coupler 420 has negative nonlinearity. In the configuration shown in Figure 10, oscillators 410 with positive nonlinearity and couplers 420 with negative nonlinearity are alternately connected and spread out in two dimensions. Specifically, oscillators 410 with positive nonlinearity and couplers 420 with negative nonlinearity are alternately arranged and connected in both the vertical and horizontal directions. As a result, the oscillator 410 and the coupler 420 efficiently cancel out the nonlinearity, and the cross-car effect is canceled out.

[0076] Here, the vertical and horizontal directions correspond to examples of the first and second directions. The structure of network 400 can be described as a mesh-like structure in which oscillators 410 and couplers 420 are alternately connected in both the first and second directions. Figure 10 shows an example where there are 10 oscillators 410 and 6 couplers 420. However, the number of oscillators 410 and couplers 420 in the network 400 are not limited to a specific number. Furthermore, while Figure 10 shows an example where the network 400 has a triangular shape, similar to the network used in the LHZ method, the shape of the network 400 is not limited to a specific shape and can be configured in various ways, extending in two dimensions.

[0077] In this way, by alternately connecting oscillators with positive nonlinearity and couplers with negative nonlinearity and spreading them out in two dimensions, it is possible to construct a large-scale multi-bit network while maintaining a structure that cancels out the crosscar effect. The magnitude (absolute value) of the nonlinearity of the oscillator 410 and the magnitude of the nonlinearity of the coupler 420 may be the same. This allows for particularly efficient cancellation of the nonlinearities. Furthermore, even if the nonlinearity of the oscillator 410 is negative and the nonlinearity of the coupler 420 is positive, the nonlinearities cancel each other out, resulting in the cancellation of the crossker effect.

[0078] As described above, the coupler 120 is a grounded, nonlinear coupler that interacts three or more qubit elements 110. According to the quantum computing circuit 100, the coupler 120 has nonlinearity, which allows three or more qubit elements 110 to interact.

[0079] Furthermore, according to the quantum computing circuit 100, it is expected that the grounding of the coupler 120 will reduce the influence of the interaction between two of the three or more qubits involved in the many-body interaction on the many-body interaction. In other words, according to the quantum computing circuit 100, it is expected that the coupler 120 will reduce the influence of the interaction between two of the three or more qubit elements 110 involved in the many-body interaction on the many-body interaction.

[0080] Furthermore, the coupler 120 interacts with three or more ungrounded qubit elements 110. According to the quantum computing circuit 100, since the qubit element 110 is not grounded, it is expected that the time during which bit values ​​can be read from the qubit element 110 will be relatively long. Furthermore, according to the quantum computing circuit 100, since the coupler 120 is grounded, it is less susceptible to the influence of other circuits, and it is expected that the coupler 120 will be able to interact with three or more qubit elements 110 with relatively high precision.

[0081] Furthermore, the coupler 120 interacts with the four qubit elements 110. According to the quantum computing circuit 100, quantum computing can be performed using various quantum computing methods that utilize four-body interactions, such as quantum annealing using the LHZ method.

[0082] Furthermore, the sign of the nonlinearity between the coupler 120 (e.g., coupler 420) and the qubit element 110 (e.g., oscillator 410) is different. According to the quantum computing circuit 100, nonlinearity cancellation occurs between the coupler 120 and the qubit element 110, thereby canceling out the cross-kar effect.

[0083] Furthermore, the absolute value of the nonlinearity is the same for both the qubit element 110 and the coupler 120. According to the quantum computing circuit 100, the cancellation of nonlinearities occurs particularly efficiently.

[0084] Furthermore, the qubit elements 110 and the couplers 120 are alternately connected in both the first and second directions. According to the quantum computing circuit 100, it is possible to construct a network while maintaining a structure that cancels out the cross-ker effect. For example, according to the quantum computing circuit 100, it is possible to construct a large-scale multi-bit network while maintaining a structure that cancels out the cross-ker effect.

[0085] <Second Embodiment> Figure 11 shows an example of the configuration of a quantum computing circuit according to at least one embodiment. In the configuration shown in Figure 11, the quantum computing circuit 610 comprises a qubit element 611 and a coupler 612 that interacts three or more qubit elements 611. The coupler 612 is grounded and has nonlinearity.

[0086] According to the quantum computing circuit 610, the coupler 612 has nonlinearity, which allows three or more qubit elements 611 to interact. Furthermore, according to the quantum computing circuit 610, it is expected that the grounding of the coupler 612 will reduce the influence of the interaction between two of the three or more qubits involved in the many-body interaction on the many-body interaction. In other words, according to the quantum computing circuit 610, it is expected that the coupler 612 will reduce the influence of the interaction between two of the three or more qubit elements 611 involved in the many-body interaction on the many-body interaction.

[0087] <Third Embodiment> Figure 12 shows an example of the configuration of an information processing device according to at least one embodiment. As shown in Figure 12, the information processing device 620 comprises a quantum computing circuit 621 and a control unit 624. The quantum computing circuit 621 comprises a qubit element 622 and a coupler 623 that interacts three or more qubit elements 622. The coupler 623 is grounded and has nonlinearity. The control unit 624 controls the quantum computing circuit 621 to perform quantum computing. The control unit 624 is an example of a control means.

[0088] According to the information processing device 620, the coupler 623 has nonlinearity, which allows three or more qubit elements 622 to interact. Furthermore, according to the information processing device 620, it is expected that the grounding of the coupler 623 will reduce the influence of the interaction between two of the three or more qubits involved in the many-body interaction on the many-body interaction. In other words, according to the information processing device 620, it is expected that the interaction between two of the three or more qubit elements 622 involved in the many-body interaction will reduce the influence of the interaction between two of the qubit elements 622 on the many-body interaction.

[0089] Figure 13 is a schematic block diagram showing the configuration of a computer according to at least one embodiment. In the configuration shown in Figure 13, the computer 700 comprises a CPU 710, a main memory 720, an auxiliary memory 730, an interface 740, a non-volatile recording medium 750, and a quantum device 760.

[0090] The above-described information processing device 1 or a part thereof may be implemented in a computer 700. In that case, the quantum computing circuit 100 may be used as the quantum device 760. The operation of the control unit 200 and the observation unit 300 may be stored in the auxiliary storage device 730 in the form of a program. The CPU 710 reads the program from the auxiliary storage device 730, loads it into the main memory 720, and executes the above processing according to the program. The CPU 710 also reserves a memory area in the main memory 720 for the control unit 200 and the observation unit 300 to perform processing according to the program. Furthermore, the interface 740 outputs control signals to the quantum device 760 and reads signals output by the quantum device 760, in accordance with the control of the CPU 710. The interface 740 also has a port for the non-volatile recording medium 750, and reads information from the non-volatile recording medium 750 and writes information to the non-volatile recording medium 750. Communication between the information processing device 1 and other devices is performed by the interface 740 having a communication function and performing communication according to the control of the CPU 710. Interaction between the information processing device 1 and the user is performed by the interface 740 having an input device and an output device, presenting information to the user via the output device and accepting user operations via the input device according to the control of the CPU 710.

[0091] One or more of the above-mentioned programs may be recorded on the non-volatile recording medium 750. In this case, the interface 740 may read the program from the non-volatile recording medium 750. The CPU 710 may then either directly execute the program read by the interface 740, or temporarily save it in the main memory 720 or auxiliary memory 730 before executing it.

[0092] Alternatively, the processing of each unit may be performed by recording a program for executing all or part of the processing performed by the control unit 200 and the observation unit 300 on a computer-readable recording medium, and then loading and executing the program recorded on this recording medium into a computer system. The term "computer system" here includes hardware such as the operating system (OS) and peripheral devices. Furthermore, "computer-readable recording media" refers to portable media such as flexible disks, magneto-optical disks, ROMs (Read Only Memory), CD-ROMs (Compact Disc Read Only Memory), and storage devices such as hard disks built into computer systems. The above-mentioned program may be intended to implement only a part of the functions described above, and may also be able to implement the above-mentioned functions in combination with programs already recorded in the computer system.

[0093] Although the present disclosure has been described above with reference to embodiments, the present disclosure is not limited to the embodiments described above. Various modifications to the structure and details of the present disclosure can be made as understandable to those skilled in the art within the scope of the present disclosure. Furthermore, the embodiments described above may be combined with other embodiments as appropriate.

[0094] Some or all of the above embodiments may also be described as follows, but are not limited to the following:

[0095] (Note 1) A qubit element and A coupler for interacting three or more of the aforementioned qubit elements, Equipped with, The coupler is grounded and has nonlinearity. Quantum computing circuit.

[0096] (Note 2) The coupler causes three or more of the ungrounded qubit elements to interact. The quantum computing circuit described in Appendix 1.

[0097] (Note 3) The coupler interacts the four qubit elements, The quantum computing circuit described in Appendix 1 or Appendix 2.

[0098] (Note 4) The sign of the nonlinearity between the coupler and the qubit element is different. A quantum computing circuit as described in any one of the appendices 1 to 3.

[0099] (Note 5) The absolute value of the nonlinearity is the same for the qubit element and the coupler. The quantum computing circuit described in Appendix 4.

[0100] (Note 6) In both the first and second directions, the qubit elements and the couplers are alternately connected. The quantum computing circuit described in Appendix 4 or Appendix 5.

[0101] (Note 7) Equipped with a quantum computing circuit and control means, The aforementioned quantum computing circuit is A qubit element and A coupler for interacting three or more of the aforementioned qubit elements, Equipped with, The coupler is grounded and has nonlinearity. The control means controls the quantum computing circuit to perform quantum computing. Information processing device.

[0102] (Note 8) The coupler causes three or more of the ungrounded qubit elements to interact. The information processing device described in Appendix 7.

[0103] (Note 9) The coupler interacts the four qubit elements, The information processing device described in Appendix 7 or Appendix 8.

[0104] (Note 10) The sign of the nonlinearity between the coupler and the qubit element is different. A quantum computing circuit as described in any one of the appendices 7 through 9.

[0105] (Note 11) The absolute value of the nonlinearity is the same for the qubit element and the coupler. The quantum computing circuit described in Appendix 10.

[0106] (Note 12) In both the first and second directions, the qubit elements and the couplers are alternately connected. The quantum computing circuit described in Appendix 10 or Appendix 11. [Explanation of symbols]

[0107] 1,620 Information Processing Equipment 100, 610, 621 quantum calculation circuit 110, 611, 622 qubit elements 111, 121 Josephson junction loop 112, 122 inductors 113, 123, 130 Capacitors 114, 124 Resonant Loops 125 Josephson junction 120, 612, 623 combiner 200, 624 Control Unit 300 Observation Unit 400 Networks 410 Oscillator 420 Combiner

Claims

1. A qubit element and A coupler for interacting three or more of the aforementioned qubit elements, Equipped with, The coupler is grounded and has nonlinearity. Quantum computing circuit.

2. The coupler interacts three or more of the ungrounded qubit elements. The quantum computing circuit according to claim 1.

3. The coupler interacts the four qubit elements, A quantum computing circuit according to claim 1 or claim 2.

4. The sign of the nonlinearity between the coupler and the qubit element is different. The quantum computing circuit according to claim 1.

5. The absolute value of the nonlinearity is the same for the qubit element and the coupler. The quantum computing circuit according to claim 4.

6. In both the first and second directions, the qubit elements and the couplers are alternately connected. The quantum computing circuit according to claim 4.

7. Equipped with a quantum computing circuit and control means, The aforementioned quantum computing circuit is A qubit element and A coupler for interacting three or more of the aforementioned qubit elements, Equipped with, The coupler is grounded and has nonlinearity. The control means controls the quantum computing circuit to perform quantum computing. Information processing device.

Images