Method for fabricating superconducting qubits with focused ion beam annealing

Abstract

The invention relates to the field of fabricating qubits and superconducting devices for quantum computers, and more particularly to systems based on thin-film Josephson junctions, and can be used for fine tuning, after fabrication, the resonance frequency of superconducting qubits containing thin-film Josephson junctions, for example adjustable-frequency or fixed-frequency qubits, as well as cryogenic Josephson parametric amplifiers. The essence of the invention is that in a method for fabricating superconducting qubits with focused ion beam annealing, which includes fabricating thin-film aluminium / aluminium-oxide / aluminium Josephson junctions (2) on a substrate (8), which are connected to two plates of a capacitor (3), and treating the superconducting qubits (1) by annealing the thin-film aluminium / aluminium-oxide / aluminium Josephson junctions (2), the superconducting qubits (1) are annealed with a Gaussian focused ion beam (13) by local changes in the properties of the thin-film aluminium / aluminium-oxide / aluminium Josephson junctions (2). The technical results of the invention consist in increasing the reproducibility of the resonance frequency tuning of any type of superconducting qubit and reducing the labour intensity and cost of the route for the fabrication of superconducting qubits and superconducting devices for quantum computers.

Description

[0001] METHOD FOR MANUFACTURING SUPERCONDUCTING QUBITS WITH ANNEALING BY A FOCUSED ION BEAM

[0002] The invention relates to the field of manufacturing qubits and superconducting devices for quantum computers, namely to systems based on thin-film Josephson junctions, and can be used for precise tuning of the resonant frequency of superconducting qubits containing thin-film Josephson junctions after their manufacture, for example, tunable or frequency-fixed qubits, as well as cryogenic Josephson parametric amplifiers.

[0003] A method for annealing superconducting qubits is known, which consists of positioning a radiating antenna directly above the first and second thin-film Josephson junctions in the superconducting qubits, thermally affecting the thin-film Josephson junction with an electromagnetic wave emanating from the radiating antenna, and then moving the antenna to the next thin-film Josephson junction [Patent US 11,050,009 B2, published on 06 / 29 / 2021].

[0004] Its disadvantages are that annealing of superconducting qubits requires the use of additional equipment containing radiating antennas. Due to the fixed size of the equipment, each new topology of superconducting qubits requires the manufacture of new equipment, which imposes restrictions on the flexibility of the technological process of manufacturing superconducting qubits and also leads to its increase in cost.

[0005] A method for annealing superconducting qubits is also known, which consists of forming multiple superconducting qubits on a chip, determining the initial frequency of each superconducting qubit, and annealing Josephson junctions as part of the superconducting qubits [Patent US 2019 / 0165244 A1, published 05 / 30 / 2019].

[0006] Its disadvantages are that due to the large contact spot, it is not possible to place superconducting qubits on the chip in close proximity to each other, which imposes restrictions on the scalability of superconducting qubit schemes. Another disadvantage is the low discreteness of the energy values ​​used in the annealing of superconducting qubits, which does not allow tuning the resonant frequency of superconducting qubits over a wide range.

[0007] A method for laser-thermal annealing of superconducting qubits by treating thin-film Josephson junctions with a 532 nm laser is also known, including the production of thin-film aluminum / aluminum oxide / aluminum Josephson junctions on a substrate connected to two capacitor plates, annealing the thin-film aluminum / aluminum oxide / aluminum Josephson junctions with a laser generating a Gaussian beam with a diameter of 20 μm [Patent US 10,424,713 B2, published 09.24.2019]. This method is chosen as a prototype of the proposed solution.

[0008] Its disadvantages are that during laser annealing of superconducting qubits by processing thin-film Josephson junctions, the laser Gaussian beam has a contact spot comparable to the size of the superconducting qubit, which does not allow affecting the thin-film Josephson junctions without affecting the substrate area. This leads to low reproducibility of tuning the resonant frequency of superconducting qubits. Another disadvantage is that laser annealing of thin-film Josephson junctions is only suitable for thin-film Josephson junctions located far from each other, since due to the temperature gradient caused by a large contact spot, it is not possible to process closely located thin-film Josephson junctions with the same energy.Therefore, this method does not allow tuning the resonant frequency of frequency-tunable qubits, and is suitable only for superconducting qubits with a fixed frequency. This leads to more stringent requirements at the stage of manufacturing superconducting qubits, an extension of the technological route caused by the need for additional purification stages and, as a consequence, an increase in the cost of their manufacturing process.

[0009] The technical results of the invention consist in increasing the reproducibility of tuning the resonant frequency of superconducting qubits of any type, reducing the labor intensity and cost of the technological route for manufacturing superconducting qubits and superconducting devices for quantum computers.

[0010] The essence of the invention is that in a method for producing superconducting qubits with annealing by a focused ion beam, including producing thin-film aluminum / aluminum oxide / aluminum Josephson junctions on a substrate connected to two capacitor plates, processing the superconducting qubits by annealing the thin-film aluminum / aluminum oxide / aluminum Josephson junctions, annealing the superconducting qubits is carried out by a Gaussian focused ion beam by locally changing the properties of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions.

[0011] There is an option in which either aluminum, niobium, tantalum, or molybdenum is used as the material for the capacitor plates.

[0012] There is a variant in which the Gaussian focused ion beam is formed by either helium ions, or neon ions, or gallium ions, or gold ions, or silicon ions.

[0013] There is a variant in which the processing of superconducting qubits by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions with a focused ion beam is carried out with a Gaussian focused ion beam with a diameter of 0.3 to 30 nm.

[0014] There is a variant in which the processing of superconducting qubits by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions with a focused ion beam is carried out by means of successive local changes in the properties of thin-film aluminum / aluminum oxide / aluminum Josephson junctions with a focused beam.

[0015] There is a variant in which, when processing superconducting qubits by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions with a focused ion beam, the penetration depth of charged particles in the volume of thin-film aluminum / aluminum oxide / aluminum Josephson junctions is controlled by changing the irradiation dose in the range from 1x10 п up to 5x10 14 ion / cm 2 .

[0016] There is a variant in which, during the processing of superconducting qubits by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions with a focused ion beam, the focused beam is applied directly to the region of thin-film aluminum / aluminum oxide / aluminum Josephson junctions without heating the substrate.

[0017] There is a variant in which, during the processing of superconducting qubits by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions with a focused ion beam, the focused beam is applied both to the region of thin-film aluminum / aluminum oxide / aluminum Josephson junctions and to the substrate.

[0018] There is a variant in which by processing superconducting qubits by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions with a focused ion beam, the area of ​​the processing region exactly matches the area of ​​the thin-film aluminum / aluminum oxide / aluminum Josephson junctions.

[0019] There is a variant in which, when processing superconducting qubits by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions with a focused ion beam, the area of ​​the processing region is set to be larger than the area of ​​the thin-film aluminum / aluminum oxide / aluminum Josephson junctions.

[0020] There is a variant in which, when processing superconducting qubits by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions with a focused ion beam, the shape of the processing region of thin-film aluminum / aluminum oxide / aluminum Josephson junctions is determined using polygons of both simple and complex shapes.

[0021] There is a variant in which, when processing superconducting qubits by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions with a focused ion beam, the energy of charged particles transferred into the volume of thin-film aluminum / aluminum oxide / aluminum Josephson junctions is set for each processing region.

[0022] There is a variant in which, when processing superconducting qubits, both fixed and frequency-tunable, each thin-film aluminum / aluminum oxide / aluminum Josephson junction within the superconducting qubit is processed independently, without cross-talk from neighboring thin-film aluminum / aluminum oxide / aluminum Josephson junctions.

[0023] Fig. 1 shows the electrical circuit of a superconducting qubit, fixed in frequency (a), tunable in frequency (b) and a fluxonium qubit (c). The presented versions of the superconducting qubit consist of one or more thin-film Josephson junctions and a parallel-connected capacitor. The Josephson junction and capacitor can be capacitively coupled both to the reading line and to the ground plane.

[0024] Fig. 2 shows the topology of a thin-film aluminum / aluminum oxide / aluminum Josephson junction connected to two capacitor plates and a ground plane. The variant is shown where the processing area is larger than the Josephson junction area. However, there is a variant where the processing area exactly matches the Josephson junction area.

[0025] Fig. 3 shows a cross-section of a thin-film aluminum / aluminum oxide / aluminum Josephson junction at the moment of processing with a Gaussian focused ion beam. It is noted that the size of the contact spot is much smaller than the characteristic size of the thin-film Josephson junction. A variant is presented in which the penetration depth of charged particles is greater than the thickness of the metal of the upper electrode and the tunnel barrier. However, there is a variant in which the penetration depth of charged particles is less than or exactly corresponds to the thickness of the metal of the upper electrode and the tunnel barrier.

[0026] Fig. 4 shows a simplified diagram of a helium-ion microscope used for ion annealing of superconducting qubits, which allows obtaining a focused ion beam diameter of less than 30 nm. The method for producing superconducting qubits (Fig. 1) with annealing by a focused ion beam can be implemented by one of a number of known technological processes. Two examples of such processes can be: 1) a subtractive process for producing superconducting qubits based on three-layer thin-film Josephson junctions or 2) a process based on Dolan bridge technology. Below, as an example, a description of the process for producing superconducting qubits based on Dolan bridge technology is given.

[0027] On a wafer 8 (Fig. 2, Fig. 3) made of silicon, or sapphire, or magnesium oxide with a diameter of 25 mm to 300 mm and a thickness of 430 μm to 650 μm, superconducting qubits 1 are formed using electron-beam lithography and shadow deposition methods on thin-film aluminum / aluminum oxide / aluminum or niobium / aluminum-aluminum oxide / niobium Josephson junctions 2 with a lower thin-film electrode 9 thickness of 15 to 25 nm and an upper thin-film electrode 10 thickness of 35 to 60 nm, as well as a tunnel barrier made of aluminum oxide 12 thickness of 0.1 to 10 nm. In such processes, the thin-film Josephson junction 2 is located between the plates of the capacitor 3, which can be capacitively coupled to the line 7 through the capacitor 6 or with ground plane 4 through capacitor 5. The location and geometry of superconducting qubit 1 are selected based on modeling and design data.According to one of the possible embodiments, the capacitance of the capacitor 3 is in the range from 0.01 fF to 200 fF. According to one of the possible embodiments of the superconducting qubit 1, the critical current of the thin-film Josephson junctions 2 is in the range from 10 to 100 nA. The critical current is related to the room resistance of the thin-film Josephson junction 2 through the Ambegaokar-Baratov relation. In particular, the relation predicts that the resistance of the thin-film Josephson junction 2 before reaching the superconducting state is inversely proportional to the critical current after the transition to the superconducting state. Below, as an example, a description of the fabrication of a superconducting transmon qubit is given.

[0028] According to one of the possible variants of manufacturing the superconducting qubit 1, a two-layer resistive mask is formed on the surface of the substrate 8, the lower layer of which can be made of methyl methacrylate copolymer (MMA), and the upper, thinner layer can be made of polymethyl methacrylate (PMMA). Then, electron beam lithography is carried out in order to form the geometry of thin-film Josephson junctions 2 in the two-layer resistive mask. Then, the areas of the resistive mask exposed to the electron beam are removed in a solution of M1BK:1PA (methyl isobutyl ketone: isopropyl alcohol) at a concentration of 1:3. The MMA layer is more sensitive to the effect of the electron beam, which allows the formation of a suspension bridge from PMMA, also called a Dolan bridge.The sample is then placed in an electron beam evaporation setup where aluminum is evaporated through previously formed holes in the resist mask at two different angles with intermediate oxidation in an argon atmosphere between aluminum evaporation steps. As a result of evaporation, a thin-film Josephson junction 2 is formed in the Dolan suspension bridge region (Fig. 3). The remaining resist and unwanted metal are then removed by embedding the sample in N-methyl-2-pyrrolidone (NMP). This basic fabrication process can be used with other additional fabrication steps such as plasma-enhanced chemical vapor deposition (PECVD), optical lithography, and plasma-enhanced and wet etching to fabricate more complex devices. Next, the superconducting qubits 1 are annealed with a Gaussian focused ion beam 13 by locally changing the properties of thin-film Josephson junctions 2 (Fig. 3) in chamber 15 of a helium-ion microscope 16 (Fig. 4).

[0029] There is an option in which either aluminum, or niobium, or tantalum, or molybdenum, or niobium nitride is used as the material for the capacitor 3 plates with a film thickness of 80 nm to 130 nm and characteristic dimensions of the capacitor 3 plates from 1 μm to 500 μm.

[0030] There is also a variant in which the Gaussian focused ion beam13 is formed by either helium ions, or neon ions, or gallium ions, or gold ions, or silicon ions with a focused ion beam energy 13 from 10 keV to 30 keV.

[0031] There is also a variant in which the processing of superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam is carried out with a Gaussian focused ion beam 13 with a diameter from 0.3 to 30 nm, wherein the diameter of the Gaussian focused beam 13 is changed by varying the diameter of the aperture installed in the electron-optical column of the helium-ion microscope 16.

[0032] Thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2, for example, can be processed with focused ion beams 13 of helium and neon with a beam energy from 10 keV to 30 keV, and a beam diameter from 3 nm to 15 nm. A change in the diameter of the focused ion beam 13 can be indicated by a change in the focused ion beam current for a given aperture of the helium-ion microscope 16. For example, an aperture diameter of 70 μm corresponds to a focused ion beam current of 1.5 pA and a beam diameter of 15 nm, and an aperture diameter of 5 μm corresponds to a beam current of 0.2 pA and a beam diameter of 3 nm. The area of ​​processing with the focused ion beam 11 can be specified by compiling the processing topology in electronic format.The area of ​​the processing region 11, for example, for each thin-film aluminum / aluminum oxide / aluminum Josephson junction 2 can be 5x5 μm, and the focused ion beam 13 will act both on the region of the Josephson junction 2 and on the silicon substrate 8.

[0033] When treating thin-film Josephson junctions with 2focused ion beams 13 of high energies, an increase in room resistance (R N ) Josephson junctions 2, which can be caused by a local change in the structure of the thin-film Josephson junction 2 due to its heating by a focused ion beam 13. The range of scattering of R values N can be reduced by reducing the diameter (current) of the focused ion beam 13. Thus, for a focused ion beam 13 with a diameter of 8 nm (current 0.6 pA), the range of dispersion of the values ​​of R Ncan correspond to 8.3%, and for a beam with a diameter of 3 nm (current of 0.2 pA) - 3.5%. Also, the scattering range can be reduced by reducing the energy of the focused ion beam, which can be explained by the reduction in the degree of substrate damage due to the reduction in the number of back-reflected ions. For a beam with an energy of 30 keV, the scattering range can be 15%, and for a beam with an energy of 10 keV - 10%. Based on the selection of the design option, energy, and diameter of the focused ion beam, the room resistance shift values ​​​​for a given set of conditions with high processing accuracy can be tested and determined.

[0034] There is also a variant in which the processing of superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13 is carried out by means of a sequential local change in the properties of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused beam 13, for example, by means of local sequential heating of the structure of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with phonons formed as a result of inelastic collisions of the ions of the primary beam with the atoms of the structure of the thin-film Josephson junction, or by sequential formation of vacancies in the structure of the tunnel barrier of the Josephson junction made of aluminum oxide 12.

[0035] There is also a variant in which, when processing superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13, the penetration depth of charged particles 14 in the volume of thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 is controlled in the range from 20 nm to 70 nm by changing the irradiation dose in the range from lxio 11 ion / cm 2 up to 5x10 14 ion / cm 2 by increasing the scanning time per point in the range from 0.5 μs to 50 μs and changing the scanning step in the range from 20 nm to 0.5 nm.

[0036] Thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 can be processed, for example, with focused ion beams 13 of helium and neon with varying irradiation doses in the range from lxlO 11 ion / cm 2 up to 5x10 14 ion / cm 2at a fixed area of ​​the processing area I. The processing area of ​​the focused ion beam 11 can be specified by composing the processing topology in electronic format. The area of ​​the processing area 11 for each thin-film aluminum / aluminum oxide / aluminum Josephson junction 2 can exactly correspond to its area. As an example, the processing of thin-film Josephson junctions 2 can be performed in the chamber 15 of the OrionNanoFab helium-ion microscope 16 with a beam energy of 10 keV and an ion beam current of 0.2 pA. However, other ion-optical systems with other parameters of the focused ion beam can be used to achieve optimal parameters of the frequency shift of superconducting qubits.

[0037] When changing the dose of irradiation with a focused ion beam, for example, in the range from 0.02x10 13 ion / cm 2 up to 7.90x10 13 ion / cm 2, it is possible to smoothly increase the room resistance of thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 in the range from 1% to 40% for a focused beam formed by neon ions, and in the range from 1% to 25% for a helium focused ion beam 13. For example, when treating thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13 with a irradiation dose of less than 4x10 13 ion / cm 2 , it is possible to controllably change the resonant frequency of superconducting qubits! in the range from 50 MHz to 100 MHz, and at a radiation dose greater than 4x10 13 ion / cm 2 The range of change of the resonant frequency of superconducting qubits 1 can be from 100 to 400 MHz.

[0038] There is also a variant in which, during the processing of superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13, the focused beam 13 is applied directly to the region of thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 without heating the substrate 8.

[0039] There is also a variant in which, during the processing of superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13, the focused beam 13 acts both on the region of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 and on the substrate 8.

[0040] There is also a variant in which, when processing superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13, the area of ​​the processing region 11 exactly corresponds to the area of ​​the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 and lies in the range from 0.01 μm 2 up to 1 micron 2 .

[0041] There is also a variant in which, when processing superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13, the area of ​​the processing region 11 is set to be greater than the area of ​​the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 in the range from 1 μm 2 up to 100 microns 2 .

[0042] There is also a variant in which, when processing superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13, the shape of the processing region 11 of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 is set using polygons of both simple and complex shapes, for example, in the form of a rectangle, circle, ellipse or a polygon, the shape of which exactly repeats the shape of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2.

[0043] There is also a variant in which, when processing superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13, for each processing region 11 the energy of charged particles transferred to the volume of thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 is set in the range from OTIXIO 11 ion / cm 2UP TO 5X10 14 ion / cm 2 , due to the formation of a polygon in the region of each thin-film aluminum / aluminum oxide / aluminum Josephson junction 2.

[0044] There is also a variant in which, when processing superconducting qubits 1, both fixed and frequency-tunable, each thin-film aluminum / aluminum oxide / aluminum Josephson junction 2 in the superconducting qubit 1 is processed independently, without cross-influence from neighboring thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2, by setting the processing region 11 and the energy of charged particles for each thin-film Josephson junction.

[0045] As an example, both fixed and frequency-tunable superconducting transmon qubits can be processed by a focused ion beam of neon with an energy of 10 keV and a beam current of 0.2 pA. For example, a fixed-frequency transmon qubit with a resonant frequency of 4.2 GHz and a relaxation time of 370 μs can be processed. This qubit can be processed by a focused ion beam, recharacterized, and as a result, its resonant frequency can be equal to 4.1 GHz and a relaxation time of 340 μs. The second frequency-fixed transmon qubit with a resonant frequency of 4.52 GHz and a relaxation time of 159 μs could, for example, be treated with a higher dose of FIB, resulting in its frequency being 4.38 GHz and a relaxation time of 320 μs. The increase in relaxation time could be due to the distance of the qubit resonant frequency from the frequency of the two-level TLS defect.Also, as an example, frequency-tunable transmon qubits can be processed by a focused ion beam of neon. For example, their resonant frequencies before processing can be 4.85 and 4.66 GHz. Thin-film Josephson junctions in each of the superconducting frequency-tunable qubits can be processed by a focused ion beam independently, without cross-talk. As a result of the processing, the resonant frequencies of these qubits can be equal to 4.74 GHz and 4.57 GHz. The resulting frequency of the superconducting qubit can be determined as applicable to the current quantum application, as a result of which the qubit can be fixed at this frequency.

[0046] The fact that in the method for producing superconducting qubits with annealing by a focused ion beam, including the production of thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 on a substrate 8 connected to two plates of a capacitor 3, the processing of superconducting qubits 1 by annealing the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2, the annealing is carried out by a Gaussian focused ion beam 13 by locally changing the properties of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 leads to an increase in the reproducibility of tuning the resonant frequency for any type of superconducting qubits 1 and to a decrease in the labor intensity and cost of the technological route for producing superconducting qubits 1.This is achieved by limiting the processing area 11 directly to the area of ​​thin-film aluminum / aluminum oxide / aluminum-Josephson junctions 2, which leads to the fact that closely located thin-film aluminum / aluminum oxide / aluminum-Josephson junctions 2 can be processed each separately, both with the same and with different energies, which allows for group processing of closely located thin-film aluminum / aluminum oxide / aluminum-Josephson junctions 2 and reduces the requirements for the quality of manufacturing superconducting qubits 1.

[0047] The fact that either aluminum, or niobium, or tantalum, or molybdenum is used as the material for the capacitor 3 plates leads to the fact that ion annealing of thin-film aluminum / aluminum oxide / aluminum-Josephson junctions 2 can be carried out for any route technological process for the manufacture of superconducting qubits 1, which leads to an increase in the flexibility of the technological process for the manufacture of superconducting qubits 1 and, as a consequence, to an increase in the quality of the manufacture of superconducting qubits 1.

[0048] The fact that the Gaussian focused ion beam 13 is formed either by helium ions, or neon ions, or gallium ions, or gold ions, or silicon ions leads to the fact that during the ion annealing of thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 it is possible to change the diameter of the focused beam 13 in the range from 30 nm to 0.3 nm, which leads to regulation of the diameter of the contact spot of the focused beam 13, as well as regulation of the degree of amorphization of the structure of the thin-film aluminum / aluminum oxide / aluminum Josephson junction 2, and, as a consequence, to an increase in the reproducibility of tuning the resonant frequency for any type of superconducting qubits 1.

[0049] The fact that the processing of superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam is carried out with a Gaussian focused ion beam 13 with a diameter of 0.3 to 30 nm leads to the fact that the contact spot of the focused beam 13 during the ion annealing of thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 can be reduced to 1 nm, which leads to the addressed transfer of energy from the focused beam of charged particles 13 to the atoms of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 and, as a consequence, to an increase in the reproducibility of tuning the resonant frequency for any type of superconducting qubits 1

[0050] The fact that the processing of superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13 is carried out by means of a sequential local change in the properties of thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused beam 13 leads to an increase or decrease in the room resistance of thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2, which leads to a decrease or increase in the resonant frequency of superconducting qubits 1 and, as a consequence, to a decrease in the requirements for the quality of manufacturing of superconducting qubits 1.

[0051] That when processing superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13, the penetration depth of charged particles 14 in the volume of thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 is controlled by changing the irradiation dose in the range from lxio 11 up to 5x10 14 ion / cm 2 leads to the fact that it is possible to change the room resistance of thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 in the range from 1% to 40%, which leads to a change in the resonant frequency of superconducting qubits 1 in the range from 50 MHz to 600 MHz and, as a consequence, to a reduction in the requirements for the quality of manufacturing of superconducting qubits 1.

[0052] The fact that during the processing of superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13, the focused beam 13 is applied directly to the region of thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 without heating the substrate 8 leads to the fact that during the ion annealing, the structure of the substrate 8 does not change, which leads to minimization of defects at the interface of the substrate 8 - capacitor 3 and, as a consequence, to an increase in the quality of manufacturing superconducting qubits 1.

[0053] The fact that during the processing of superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13, the focused beam 13 acts both on the region of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 and on the substrate 8 leads to the region of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 being heated both directly due to the interaction with the focused ion beam 13 and as a result of cross-heating from the substrate 8, which leads to an increase in the thermal effect on the region of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 and, as a consequence, to an expansion of the range of tuning the resonant frequency of the superconducting qubits 1.

[0054] The fact that, when processing superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13, the area of ​​the processing region 11 exactly corresponds to the area of ​​the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 leads to the fact that the ion annealing of each of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 can be carried out separately, with individually specified parameters, which leads to the fact that, by means of ion annealing, it is possible to eliminate the irreproducibility of the electrical parameters of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 in the composition of the superconducting qubit 1, tunable in frequency, and, as a consequence, to a reduction in the requirements for the quality of the manufacture of superconducting qubits 1.

[0055] The fact that, when processing superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13, the area of ​​the processing region 11 is set to be greater than the area of ​​the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 leads to the fact that the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 in the composition of the frequency-tunable superconducting qubit 1 can be processed together with the same energy of the focused beam 13, which leads to a minimization of the positioning error when moving between adjacent thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 and, as a consequence, to an increase in the accuracy of tuning the resonant frequency for any type of superconducting qubits 1.

[0056] The fact that during the processing of superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13, the shape of the processing region 11 of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 is determined using polygons of both simple and complex shapes, leads to a limitation of the region of interaction of the focused beam 13 with the interfaces of the superconducting qubit 1, which leads to a minimization of the number of defects in the volume of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 caused by thermal action, and, as a consequence, to an increase in the quality of the production of superconducting qubits 1.

[0057] The fact that during the processing of superconducting qubits 1 by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 with a focused ion beam 13 for each processing region 11 the energy of charged particles transferred to the volume of thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 is set leads to the fact that for each thin-film aluminum / aluminum oxide / aluminum Josephson junction 2 the number of charged particles is controlled, both reaching the tunnel barrier of the Josephson junction 12 and slowing down in the volume of the upper thin-film electrode made of aluminum 10, which leads to the fact that in the process of ion annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 it is possible to control the number of vacancy-type defects arising in the volume of thin-film aluminum / aluminum oxide aluminum / aluminum-Josephson junctions 2 and, as a consequence, improving the quality of manufacturing superconducting qubits 1.

[0058] The fact that, when processing superconducting qubits 1, both fixed and frequency-tunable, each thin-film aluminum / aluminum oxide / aluminum Josephson junction 2 in the superconducting qubit 1 is processed independently, without cross-influence from the neighboring thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2, leads to the fact that the thin-film aluminum / aluminum oxide / aluminum Josephson junctions 2 in the superconducting qubits 1, frequency-tunable, can be processed with both the same and different energies, which leads to the fact that, during ion annealing, it is possible to take into account the asymmetry of the superconducting qubits 1 and, as a consequence, to increase the reproducibility of the resonant frequency tuning for any type of superconducting qubits 1.

Claims

Invention formula 1. A method for producing superconducting qubits with annealing by a focused ion beam, comprising producing thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) on a substrate (8) connected to two plates of a capacitor (3), processing the superconducting qubits (1) by annealing the thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2), characterized in that the annealing is carried out with a Gaussian focused ion beam (13) by locally changing the properties of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2).

2. The method according to item 1, characterized in that either aluminum, or niobium, or tantalum, or molybdenum is used as the material for the capacitor plates (3).

3. The method according to claim 1, characterized in that the Gaussian focused ion beam (13) is formed either by helium ions, or neon ions, or gallium ions, or gold ions, or silicon ions.

4. The method according to paragraph 2, 3, characterized in that the processing of superconducting qubits (1) by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) with a focused ion beam is carried out with a Gaussian focused ion beam (13) with a diameter of 0.3 to 30 nm.

5. The method according to paragraphs 2, 3, 4, characterized in that the processing of superconducting qubits (1) by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) with a focused ion beam (13) is carried out by means of successive local changes in the properties of thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) with a focused beam (13).

6. The method according to paragraphs 3, 4, 5, characterized in that when processing superconducting qubits (1) by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) with a focused ion beam (13), the penetration depth of charged particles (14) in the volume of thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) is controlled by changing the irradiation dose in the range from 1x1011 to 5x1014 ion / cm2.

7. The method according to paragraphs 3, 4, 5, 6, characterized in that during the processing of superconducting qubits (1) by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) with a focused ion beam (13), the focused beam (13) is applied directly to the region of thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) without heating the substrate (8).

8. The method according to paragraphs 3, 4, 5, 6, characterized in that during the processing of superconducting qubits (1) by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) with a focused ion beam (13), the focused beam (13) acts both on the region of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) and on the substrate (8).

9. The method according to claim 7, 8, characterized in that when processing superconducting qubits (1) by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) with a focused ion beam (13), the area of ​​the processing region (11) exactly corresponds to the area of ​​the thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2).

10. The method according to paragraph 7, 8, characterized in that when processing superconducting qubits (1) by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) with a focused ion beam (13) set the area of ​​the processing region (11) to be larger than the area of ​​the thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2).

11. The method according to paragraph 9, 10, characterized in that when processing superconducting qubits (1) by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) with a focused ion beam (13), the shape of the processing region (11) of the thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) is set using polygons of both simple and complex shape.

12. The method according to paragraph 9, 10, 11, characterized in that when processing superconducting qubits (1) by annealing thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) with a focused ion beam (13), the energy of charged particles transferred into the volume of thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) is set for each processing region (11).

13. The method according to claim 12, characterized in that when processing superconducting qubits (1), both fixed and frequency-tunable, each thin-film aluminum / aluminum oxide / aluminum Josephson junction (2) in the superconducting qubit (1) is processed independently, without cross-influence from the thin-film aluminum / aluminum oxide / aluminum Josephson junctions (2) adjacent to it.

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