CN117634627A - Waveguide adjustable coupling assembly and quantum computer - Google Patents
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Abstract
The invention relates to the field of bit coupling, and more particularly provides a waveguide tunable coupling assembly and a quantum computer, the waveguide tunable coupling assembly comprising: the device comprises a first qubit, a second qubit, an adjustable coupler, two waveguides coupled together, a first capacitor and a second capacitor, wherein one end of the first qubit is grounded, the other end of the first qubit is respectively connected with the first end of the first capacitor and the first end of the second capacitor, one end of the second qubit is grounded, the other end of the second qubit is respectively connected with the second ends of the first capacitor and the second capacitor, a dielectric layer of the second capacitor is the two waveguides coupled together, and the adjustable coupler is connected with the two waveguides coupled together. The invention uses the waveguide as an intermediate medium to realize long-distance magnetic flux bit coupling, and provides enough physical space for realizing large-scale circuit expansion.
Description
Technical Field
The invention relates to the field of bit coupling, in particular to a waveguide adjustable coupling component and a quantum computer comprising the waveguide adjustable coupling component.
Background
The bit coupling structure of the current design mainly comprises direct coupling of capacitance, coupling by using a resonant cavity and coupling by using a coupler. Since the time of the gate operation is mainly limited by the effective coupling strength between bits, the use of capacitive direct coupling can limit the time of the two-bit gate operation and thus lead to reduced fidelity of the gate operation. The use of a resonant cavity or coupler for bit-to-bit coupling, while enabling fast two-bit gate operation, is also difficult to improve the fidelity of the two-bit gate operation and the large scale circuit expansion.
Based on this, there is still room for improvement in the prior art.
Disclosure of Invention
In view of the above, an object of the embodiments of the present invention is to provide a waveguide tunable coupling assembly, which uses a waveguide as an intermediate medium to realize long-distance magnetic flux bit coupling, so as to provide space for high-fidelity bit reading (e.g., reading a resonant cavity, a Purcell filter), and in addition, increasing the physical distance between bits can reduce the coupling strength between non-adjacent bits, thereby realizing lower crosstalk when the flip-chip (flip-chip) process is used to expand the circuit structure.
Based on the above object, an aspect of an embodiment of the present invention provides a waveguide adjustable coupling assembly, including: the device comprises a first qubit, a second qubit, an adjustable coupler, two waveguides coupled together, a first capacitor and a second capacitor, wherein one end of the first qubit is grounded, the other end of the first qubit is respectively connected with the first end of the first capacitor and the first end of the second capacitor, one end of the second qubit is grounded, the other end of the second qubit is respectively connected with the second ends of the first capacitor and the second capacitor, a dielectric layer of the second capacitor is the two waveguides coupled together, and the adjustable coupler is connected with the two waveguides coupled together.
In some embodiments, the first qubit and the second qubit are comprised of an inductance, a capacitance, and a nonlinear inductance in parallel.
In some embodiments, the first qubit and the second qubit are connected in series by a plurality of josephson junctions to provide inductance.
In some embodiments, the dielectric layer of the first capacitor is an air layer.
In some embodiments, the two waveguides coupled together comprise: a first waveguide, a first end of which is connected to a first end of the second capacitor; and the first end of the second waveguide is connected with the second end of the first waveguide, and the second end of the second waveguide is connected with the second end of the second capacitor.
In some embodiments, the waveguide tunable coupling assembly is configured to: and determining the Hamiltonian amount of the second capacitor according to the Hamiltonian amount of the first quantum bit, the Hamiltonian amount of the second quantum bit, the Hamiltonian amount of the adjustable coupler and the Hamiltonian amounts of the two waveguides coupled together.
In some embodiments, the waveguide tunable coupling assembly is configured to: limiting the first quantum bit and the second quantum bit to the lowest energy level to form a calculation base, determining parasitic coupling strength according to the calculation base, and determining Hamiltonian amount between the first quantum bit and the second quantum bit according to the parasitic coupling strength and the effective transverse coupling strength.
In some embodiments, the waveguide tunable coupling assembly is configured to: calculating a first difference and a first sum of the frequencies of the first qubit and the tunable coupler and a second difference and a second sum of the frequencies of the second qubit and the tunable coupler; calculating a first coupling strength between the first qubit and the tunable coupler, a second coupling strength between the tunable coupler and the second qubit, and a third coupling strength between the first qubit and the second qubit; and determining the effective lateral coupling strength based on the first difference, the first sum, the second difference, the second sum, the first coupling strength, the second coupling strength, and the third coupling strength.
In some embodiments, the waveguide tunable coupling assembly is configured to: calculating the first coupling strength, the second coupling strength, and the third coupling strength from the capacitance of the first qubit, the capacitance of the second qubit, the capacitance between the first qubit and the tunable coupler, the capacitance between the second qubit and the tunable coupler, and the capacitance between the first qubit and the second qubit; calculating a third sum of the reciprocal of the first difference and the reciprocal of the second difference, calculating a fourth sum of the reciprocal of the first sum and the reciprocal of the second sum, and calculating a difference of the third sum and the fourth sum; calculating a first product of the first coupling strength and the second coupling strength, calculating a second product of the first product and the difference value, and dividing the second product by two to obtain an intermediate result; and taking the sum of the intermediate result and the third coupling strength as the effective lateral coupling strength.
In another aspect of the invention, a quantum computer is presented that includes a waveguide tunable coupling assembly comprising:
a first qubit, a second qubit, a tunable coupler, two waveguides coupled together, a first capacitor and a second capacitor,
the first qubit has one end grounded, the other end connected to the first ends of the first capacitor and the second capacitor respectively, the one end grounded of the second qubit, the other end connected to the second ends of the first capacitor and the second capacitor respectively, the dielectric layer of the second capacitor is the two waveguides coupled together, and the adjustable coupler is connected to the two waveguides coupled together.
The invention has at least the following beneficial technical effects: the use of waveguides as intermediate media to achieve long-range magnetic flux bit coupling can provide space for high-fidelity bit reading (e.g., reading resonator, purcell filter), and in addition, increasing the physical distance between bits can reduce the coupling strength between non-neighboring bits to achieve lower crosstalk when expanding circuit structures using flip-chip technology.
Drawings
In order to more clearly illustrate the embodiments of the invention or the technical solutions in the prior art, the drawings that are necessary for the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the following description are only some embodiments of the invention and that other embodiments may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of an embodiment of a waveguide tunable coupling assembly provided by the present invention;
FIG. 2 is a graph showing the variation of coupling strength with distance between two bits according to the present invention;
FIG. 3 is a graph showing the variation of effective transverse coupling strength with coupler frequency provided by the present invention;
fig. 4 is a schematic diagram of a quantum computer provided by the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the following embodiments of the present invention will be described in further detail with reference to the accompanying drawings.
It should be noted that, in the embodiments of the present invention, all the expressions "first" and "second" are used to distinguish two entities with the same name but different entities or different parameters, and it is noted that the "first" and "second" are only used for convenience of expression, and should not be construed as limiting the embodiments of the present invention, and the following embodiments are not described one by one.
Quantum computers have shown the ability to surpass classical computers in dealing with complex problems such as chemical molecular potential analysis, materials science, and bulk decomposition. This capability is mainly manifested in a great reduction in both consumption of resources and time. The time of quantum devices with medium scale is stepped into at present, so that a plurality of simple algorithm demonstration and quantum simulation can be performed on the platform. While there are many choices for the type of superconducting qubit, current platforms rely primarily on conventional ground tranmons. The use of this type of bit has several drawbacks: is more sensitive to dielectric loss and less non-resonant. This may be a type of replacement for trans, since the Fluxonium bit better overcomes both of these disadvantages. First, the lower operating frequency of the Fluxonium bit makes itself less sensitive to dielectric losses, and in addition, the non-harmonics can reach the order of GHz at the operating point, most importantly, the decoherence time exceeds the order of ms. With this type of bit and adjustable coupling structure, a single bit gate, two bits exceeding 99.9% can be realized, but currently large scale expansion of this type is difficult.
The present invention proposes to use a waveguide as an intermediate medium to achieve long-range magnetic flux bit coupling. This approach may provide space for high fidelity bit reading (e.g., reading resonator, purcell filter), and additionally, increasing the physical distance between bits may reduce the coupling strength between non-neighboring bits to achieve lower crosstalk when expanding the circuit structure with flip-chip technology.
Embodiments of a waveguide tunable coupling assembly are presented. Fig. 1 is a schematic diagram of an embodiment of a waveguide tunable coupling assembly provided by the present invention. As shown in fig. 1, an embodiment of the present invention includes the following components:
a first qubit 1, a second qubit 2, a tunable coupler 3, two waveguides 5 coupled together, a first capacitance and a second capacitance 4,
the first qubit 1 has one end grounded, the other end of the first qubit 1 is respectively connected with the first ends of the first capacitor and the second capacitor 4, one end of the second qubit 2 is grounded, the other end of the second qubit 2 is respectively connected with the second ends of the first capacitor and the second capacitor 4, the dielectric layer of the second capacitor 4 is the two waveguides 5 coupled together, and the adjustable coupler 3 is connected with the two waveguides 5 coupled together.
The first qubit 1 and the second qubit 2 are Fluxonium bits and the tunable coupler 3 is a transmon type coupler. The existing mainstream superconducting qubit is transmon. Wherein the transmon takes two states with/without electron shock excitation (plasmon) in the circuit as '0' and '1' of the quantum bit, has a simple structure that only one to two Josephson tunneling junctions are needed, and is insensitive to electric noise. While Fluxonium is a bit of "0" and "1" of the flux quanta in a superconducting ring circuit. In addition, fluxonium uses magnetic fields as a way of quantum information storage, is not only insensitive to electrical noise, but also has greatly reduced sensitivity to dielectric loss compared with tranmon, so that it is a qubit with stronger resistance to external noise interference. Meanwhile, fluxonium is a quantum bit which is closer to two energy levels, and when the high-speed operation between 0 and 1 is realized, the fluxonium is less easy to transition to other energy levels except 0 and 1, so that quantum operation with higher precision can be performed.
A waveguide is a device that transfers energy from one location to another. The waveguide is able to bind energy in a hollow metal, which greatly reduces losses during energy transmission, rather than radiating energy directly into the whole space as an antenna would. A waveguide can be understood as an antenna with particularly strong directivity, where energy can only propagate in the waveguide and not elsewhere.
A waveguide is a closed structure with a cavity formed between two parallel metal plates. When an electromagnetic wave passes through the waveguide, it is repeatedly reflected between the metal plates, thereby forming a waveguide mode. The waveguide can transmit high-frequency electromagnetic signals in a certain range and is widely applied to the fields of wireless communication, radar, microwave ovens and the like. Waveguides can be classified into different types such as rectangular waveguides, cylindrical waveguides, coaxial waveguides, and the like. Each waveguide type has different characteristics and application scenarios.
The basic features of the waveguide include the following aspects:
(1) Mode: there are a number of different modes in the waveguide that can transmit electromagnetic wave signals in the waveguide;
(2) The port: two ends of the waveguide are usually provided with a port for inputting or outputting electromagnetic wave signals into or from the waveguide;
(3) Impedance: the impedance of the waveguide is an important parameter, and has direct influence on the transmission characteristic and the application effect of the waveguide;
(4) Bandwidth: the larger the bandwidth of the waveguide, the wider the electromagnetic wave frequency range that can be transmitted.
In addition to the basic features, the waveguide has several important feature parameters:
(1) Cut-off frequency: the waveguide cannot transmit electromagnetic waves below a certain frequency;
(2) Mode power: the electromagnetic wave power distribution of different modes is different and needs to be selected according to actual requirements;
(3) Diffraction loss: when electromagnetic waves pass through the edge of the waveguide, diffraction occurs, so that certain energy loss is caused;
(4) Attenuation coefficient: since the waveguide has a certain energy loss, the attenuation coefficient needs to be considered to evaluate its transmission effect.
In some embodiments, the first qubit and the second qubit are comprised of an inductance, a capacitance, and a nonlinear inductance in parallel.
In some embodiments, the first qubit and the second qubit are connected in series by a plurality of josephson junctions to provide inductance.
The Fluxonium bit is formed by connecting about 100 Josephson junctions in series to provide an inductance E L E in parallel with J Is smaller than the E of Josephson junction providing inductance J· . The first qubit and the second qubit are simply illustrated in fig. 1 as a parallel connection of an inductance, a capacitance and a nonlinear inductance.
Josephson junction (Josephson junction), or superconducting tunnel junction. Typically a structure consisting of two superconductors sandwiched by some sort of very thin barrier layer (thickness less than or equal to the coherence length of the Cooper electron pair), such as an S (superconductor) -I (semiconductor or insulator) -S (superconductor) structure, abbreviated SIS. In which superconducting electrons can tunnel from one side through a semiconductor or insulator film to the other side. However, in practice, it is not necessary to take the form of a tunnel junction, as long as two weakly coupled superconductors (with a coupling region size less than or equal to the coherence length of the Cooper electron pair) can form a Josephson junction.
In some embodiments, the dielectric layer of the first capacitor is an air layer.
In some embodiments, the two waveguides 5 coupled together comprise: a first waveguide 51, a first end of the first waveguide 51 being connected to a first end of the second capacitor 4; a second waveguide 52, a first end of the second waveguide 52 being connected to a second end of the first waveguide 51, and a second end of the second waveguide 52 being connected to a second end of the second capacitor 4.
In some embodiments, the waveguide tunable coupling assembly is configured to: and determining the Hamiltonian amount of the second capacitor according to the Hamiltonian amount of the first quantum bit, the Hamiltonian amount of the second quantum bit, the Hamiltonian amount of the adjustable coupler and the Hamiltonian amounts of the two waveguides coupled together.
In some embodiments, the waveguide tunable coupling assembly is configured to: limiting the first quantum bit and the second quantum bit to the lowest energy level to form a calculation base, determining parasitic coupling strength according to the calculation base, and determining Hamiltonian amount between the first quantum bit and the second quantum bit according to the parasitic coupling strength and the effective transverse coupling strength.
The lowest two states of each Fluxonium bit form a computation basis {00, 01, 10, 11}. After modeling the structure, and correspondingly simplifying the coupling capacitance, the Hamiltonian amount of the system is as follows:
H＝H 1 +H 2 +H c +H v
wherein H is 1 And H 2 Hamiltonian amount representing the first quantum bit and Hamiltonian amount representing the second quantum bit, respectively, H C Hamiltonian quantity, H, representing an adjustable coupler v Representing the hamiltonian of two waveguides coupled together. After limiting the energy levels of the first and second qubits to the lowest energy level, the effective hamiltonian amount between the first and second qubits is:
wherein g xx And xi zz The effective transverse coupling strength and the ZZ parasitic coupling strength are respectively. The ZZ parasitic coupling strength is defined as ζ zz ＝E 11 -E 10 -E 01 +E 00 。
In some embodiments, the waveguide tunable coupling assembly is configured to: calculating a first difference and a first sum of the frequencies of the first qubit and the tunable coupler and a second difference and a second sum of the frequencies of the second qubit and the tunable coupler; calculating a first coupling strength between the first qubit and the tunable coupler, a second coupling strength between the tunable coupler and the second qubit, and a third coupling strength between the first qubit and the second qubit; and determining the effective lateral coupling strength based on the first difference, the first sum, the second difference, the second sum, the first coupling strength, the second coupling strength, and the third coupling strength.
In some embodiments, the waveguide tunable coupling assembly is configured to: the first coupling strength, the second coupling strength, and the third coupling strength are calculated from the capacitance of the first qubit, the capacitance of the second qubit, the capacitance between the first qubit and the tunable coupler, the capacitance between the second qubit and the tunable coupler, and the capacitance between the first qubit and the second qubit.
In some embodiments, the waveguide tunable coupling assembly is configured to: calculating a third sum of the reciprocal of the first difference and the reciprocal of the second difference, calculating a fourth sum of the reciprocal of the first sum and the reciprocal of the second sum, and calculating a difference of the third sum and the fourth sum; calculating a first product of the first coupling strength and the second coupling strength, calculating a second product of the first product and the difference value, and dividing the second product by two to obtain an intermediate result; and taking the sum of the intermediate result and the third coupling strength as the effective lateral coupling strength.
The coupling strength between bits and couplers can be calculated according to the following formula:
wherein C is 1c Representing the capacitance between the first qubit 1 and the tunable coupler 3, C 2c Representing the capacitance between the first qubit 2 and the tunable coupler 3, C 12 Representing the capacitance between the first qubit 1 and the second qubit 2, C 1 Capacitance representing first qubit 1, C 2 Capacitance representing second qubit 2, C c Representing the capacitance, ω, of the adjustable coupler 3 1 Represents the frequency, ω, of the first qubit 1 2 Representing the frequency, ω, of the first qubit 2 c Representing the frequency of the adjustable coupler 3.
In addition, since the distance between the first qubit and the second qubit is changed, it can be considered that only C is changed in the changing process 1c ，C 2c ，C 12 And the coupling strength can be approximated by the definition of capacitance inversely proportional to the distance d. So that the coupling strength can be obtained as a function of the distance between two bits. Fig. 2 is a schematic diagram showing the variation of coupling strength with the distance between two bits according to the present invention. The coupling strength when d=d0 is selected to be g0, and the coupling strength calculation of other distances is performed. Such asAs shown in fig. 2, even if the distance is increased by 0.5 times the original distance, the coupling strength can be ensured to be 0.6 times or more.
The frequencies of the two Fluxonium bits are chosen to be ω, respectively 1 ＝0.3GHz，ω 2 The direct coupling capacitance between the two is 1fF, and the direct coupling strength is 1.36MHz. For the frequency of the tunable coupler we set to a maximum of 5.5GHz, where the effective lateral coupling strength between bits can be calculated by:
calculated, wherein delta i Representing the difference between the frequency of the first qubit (or the second qubit) and the tunable coupler, Σ i Representing the sum of the first qubit (or the second qubit) and the frequency of the tunable coupler. So that proper parameters can be selected to obtain the result that the effective transverse coupling strength changes along with the frequency of the coupler, fig. 3 is a schematic diagram showing the effective transverse coupling strength changes along with the frequency of the coupler. The frequency point of the coupling off point and the fast two-bit gate operation can be obtained from fig. 3.
In another aspect of the embodiments of the present invention, a quantum computer is provided, as shown in fig. 4, the quantum computer including a waveguide tunable coupling assembly, the waveguide tunable coupling assembly including:
a first qubit, a second qubit, a tunable coupler, two waveguides coupled together, a first capacitor and a second capacitor,
the first qubit has one end grounded, the other end connected to the first ends of the first capacitor and the second capacitor respectively, the one end grounded of the second qubit, the other end connected to the second ends of the first capacitor and the second capacitor respectively, the dielectric layer of the second capacitor is the two waveguides coupled together, and the adjustable coupler is connected to the two waveguides coupled together.
In some embodiments, the first qubit and the second qubit are comprised of an inductance, a capacitance, and a nonlinear inductance in parallel.
In some embodiments, the first qubit and the second qubit are connected in series by a plurality of josephson junctions to provide inductance.
In some embodiments, the dielectric layer of the first capacitor is an air layer.
In some embodiments, the two waveguides coupled together comprise: a first waveguide, a first end of which is connected to a first end of the second capacitor; and the first end of the second waveguide is connected with the second end of the first waveguide, and the second end of the second waveguide is connected with the second end of the second capacitor.
In some embodiments, the quantum computer is configured to: and determining the Hamiltonian amount of the second capacitor according to the Hamiltonian amount of the first quantum bit, the Hamiltonian amount of the second quantum bit, the Hamiltonian amount of the adjustable coupler and the Hamiltonian amounts of the two waveguides coupled together.
In some embodiments, the quantum computer is configured to: limiting the first quantum bit and the second quantum bit to the lowest energy level to form a calculation base, determining parasitic coupling strength according to the calculation base, and determining Hamiltonian amount between the first quantum bit and the second quantum bit according to the parasitic coupling strength and the effective transverse coupling strength.
In some embodiments, the quantum computer is configured to: calculating a first difference and a first sum of the frequencies of the first qubit and the tunable coupler and a second difference and a second sum of the frequencies of the second qubit and the tunable coupler; calculating a first coupling strength between the first qubit and the tunable coupler, a second coupling strength between the tunable coupler and the second qubit, and a third coupling strength between the first qubit and the second qubit; and determining the effective lateral coupling strength based on the first difference, the first sum, the second difference, the second sum, the first coupling strength, the second coupling strength, and the third coupling strength.
In some embodiments, the quantum computer is configured to: the first coupling strength, the second coupling strength, and the third coupling strength are calculated from the capacitance of the first qubit, the capacitance of the second qubit, the capacitance between the first qubit and the tunable coupler, the capacitance between the second qubit and the tunable coupler, and the capacitance between the first qubit and the second qubit.
In some embodiments, the quantum computer is configured to: calculating a third sum of the reciprocal of the first difference and the reciprocal of the second difference, calculating a fourth sum of the reciprocal of the first sum and the reciprocal of the second sum, and calculating a difference of the third sum and the fourth sum; calculating a first product of the first coupling strength and the second coupling strength, calculating a second product of the first product and the difference value, and dividing the second product by two to obtain an intermediate result; and taking the sum of the intermediate result and the third coupling strength as the effective lateral coupling strength.
The first qubit 1 and the second qubit 2 are Fluxonium bits and the tunable coupler 3 is a transmon type coupler. The existing mainstream superconducting qubit is transmon. Wherein the transmon takes two states with/without electron shock excitation (plasmon) in the circuit as '0' and '1' of the quantum bit, has a simple structure that only one to two Josephson tunneling junctions are needed, and is insensitive to electric noise. While Fluxonium is a bit of "0" and "1" of the flux quanta in a superconducting ring circuit. In addition, fluxonium uses magnetic fields as a way of quantum information storage, is not only insensitive to electrical noise, but also has greatly reduced sensitivity to dielectric loss compared with tranmon, so that it is a qubit with stronger resistance to external noise interference. Meanwhile, fluxonium is a qubit more approaching two energy levels, between "0" and "1" realizing high speedDuring the control, the quantum operation with higher precision can be made because the quantum operation is less easy to transition to other energy levels except for 0 and 1. The Fluxonium bit is formed by connecting about 100 Josephson junctions in series to provide an inductance E L E in parallel with J Is smaller than the E of Josephson junction providing inductance J· . In the embodiment of the invention, the first qubit and the second qubit are simply indicated as parallel connection of an inductor, a capacitor and a nonlinear inductor.
The embodiment of the invention utilizes the waveguide as an intermediate medium to realize long-distance magnetic flux bit coupling, can provide space for high-fidelity bit reading (for example, reading a resonant cavity and a Purcell filter), and in addition, the physical distance between the bits can be increased to reduce the coupling strength between non-adjacent bits so as to realize lower crosstalk when a flip-chip technology is utilized to expand a circuit structure.
The foregoing is an exemplary embodiment of the present disclosure, but it should be noted that various changes and modifications could be made herein without departing from the scope of the disclosure as defined by the appended claims. The functions, steps and/or actions of the method claims in accordance with the disclosed embodiments described herein need not be performed in any particular order. Furthermore, although elements of the disclosed embodiments may be described or claimed in the singular, the plural is contemplated unless limitation to the singular is explicitly stated.
It should be understood that as used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly supports the exception. It should also be understood that "and/or" as used herein is meant to include any and all possible combinations of one or more of the associated listed items.
The foregoing embodiment of the present invention has been disclosed with reference to the number of embodiments for the purpose of description only, and does not represent the advantages or disadvantages of the embodiments.
It will be understood by those skilled in the art that all or part of the steps for implementing the above embodiments may be implemented by hardware, or may be implemented by a program for instructing relevant hardware, and the program may be stored in a computer readable storage medium, where the storage medium may be a read-only memory, a magnetic disk or an optical disk, etc.
Those of ordinary skill in the art will appreciate that: the above discussion of any embodiment is merely exemplary and is not intended to imply that the scope of the disclosure of embodiments of the invention, including the claims, is limited to such examples; combinations of features of the above embodiments or in different embodiments are also possible within the idea of an embodiment of the invention, and many other variations of the different aspects of the embodiments of the invention as described above exist, which are not provided in detail for the sake of brevity. Therefore, any omission, modification, equivalent replacement, improvement, etc. of the embodiments should be included in the protection scope of the embodiments of the present invention.
Claims (10)
1. A waveguide tunable coupling assembly comprising:
a first qubit, a second qubit, a tunable coupler, two waveguides coupled together, a first capacitor and a second capacitor,
the first quantum bit has one end grounded, the other end connected to the first ends of the first capacitor and the second capacitor respectively, the one end of the second quantum bit has one end grounded, the other end connected to the second ends of the first capacitor and the second capacitor respectively, the dielectric layer of the second capacitor is the two waveguides coupled together, and the adjustable coupler is connected to the two waveguides coupled together.
2. The waveguide tunable coupling assembly of claim 1, wherein the first qubit and the second qubit are comprised of an inductance, a capacitance, and a nonlinear inductance in parallel.
3. The waveguide tunable coupling assembly of claim 2, wherein the first qubit and the second qubit are coupled in series by a plurality of josephson junctions to provide an inductance.
4. The waveguide tunable coupling assembly of claim 1, wherein the dielectric layer of the first capacitor is an air layer.
5. The waveguide tunable coupling assembly of claim 1, wherein the two waveguides coupled together comprise:
a first waveguide, a first end of which is connected to a first end of the second capacitor;
and the first end of the second waveguide is connected with the second end of the first waveguide, and the second end of the second waveguide is connected with the second end of the second capacitor.
6. The waveguide tunable coupling assembly of claim 1, wherein the waveguide tunable coupling assembly is configured to:
and determining the Hamiltonian amount of the second capacitor according to the Hamiltonian amount of the first quantum bit, the Hamiltonian amount of the second quantum bit, the Hamiltonian amount of the adjustable coupler and the Hamiltonian amounts of the two waveguides coupled together.
7. The waveguide tunable coupling assembly of claim 1, wherein the waveguide tunable coupling assembly is configured to:
limiting the first quantum bit and the second quantum bit to the lowest energy level to form a calculation base, determining parasitic coupling strength according to the calculation base, and determining Hamiltonian amount between the first quantum bit and the second quantum bit according to the parasitic coupling strength and the effective transverse coupling strength.
8. The waveguide tunable coupling assembly of claim 7, wherein the waveguide tunable coupling assembly is configured to:
calculating a first difference and a first sum of the frequencies of the first qubit and the tunable coupler and a second difference and a second sum of the frequencies of the second qubit and the tunable coupler;
calculating a first coupling strength between the first qubit and the tunable coupler, a second coupling strength between the tunable coupler and the second qubit, and a third coupling strength between the first qubit and the second qubit; and
and determining the effective transverse coupling strength according to the first difference value, the first sum value, the second difference value, the second sum value, the first coupling strength, the second coupling strength and the third coupling strength.
9. The waveguide tunable coupling assembly of claim 8, wherein the waveguide tunable coupling assembly is configured to:
calculating the first coupling strength, the second coupling strength, and the third coupling strength from the capacitance of the first qubit, the capacitance of the second qubit, the capacitance between the first qubit and the tunable coupler, the capacitance between the second qubit and the tunable coupler, and the capacitance between the first qubit and the second qubit;
calculating a third sum of the reciprocal of the first difference and the reciprocal of the second difference, calculating a fourth sum of the reciprocal of the first sum and the reciprocal of the second sum, and calculating a difference of the third sum and the fourth sum;
calculating a first product of the first coupling strength and the second coupling strength, calculating a second product of the first product and the difference value, and dividing the second product by two to obtain an intermediate result; and
and taking the sum of the intermediate result and the third coupling strength as the effective transverse coupling strength.
10. A quantum computer comprising a waveguide tunable coupling assembly according to any one of the preceding claims 1-9.
Priority Applications (1)
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