Quantum device

Abstract

A quantum device comprises a plurality of superconducting qubits, a plurality of resonators capacitively coupled to each of the plurality of the superconducting qubits, a filter coupled to the plurality of the resonators, and a port capacitively coupled to the filter, wherein the shortest distance between the port and the resonators is the same between the plurality of the resonators. The quantum device can be used in, for example, quantum computing.

Description

quantum devices

[0001] The present disclosure relates to quantum devices.

[0002] A quantum device has been proposed in which multiple quantum bits are coupled to one readout port via a resonator and a filter.

[0003] Japanese Patent Publication No. 2018-533253 Japanese Patent Publication No. 2019-530336 Japanese Patent Application Laid-Open No. 2022-172189 U.S. Patent Application No. 2016 / 0112031

[0004] In conventional quantum devices, the parasitic capacitances tend to differ among multiple resonators.

[0005] An object of the present disclosure is to provide a quantum device that can suppress variations in the parasitic capacitance of a resonator.

[0006] According to one aspect of the present disclosure, there is provided a quantum device comprising a plurality of superconducting quantum bits, a plurality of resonators capacitively coupled to each of the plurality of superconducting quantum bits, a filter coupled to the plurality of resonators, and a port capacitively coupled to the filter, wherein the shortest distance between the port and the resonator is equal among the plurality of resonators.

[0007] According to the present disclosure, it is possible to suppress variations in the parasitic capacitance of the resonator.

[0008] FIG. 1 is a plan view showing a quantum device according to a first embodiment. FIG. 2 is a plan view showing a quantum device according to a reference example. FIG. 3 is a diagram showing calculation results of resonant frequencies. FIG. 4 is a plan view showing a quantum device according to a second embodiment. FIG. 5 is a plan view showing a quantum device according to a third embodiment. FIG. 6 is a plan view showing a quantum device according to a fourth embodiment. FIG. 7 is a plan view showing a quantum device according to a fifth embodiment. FIG. 8 is a plan view showing a quantum device according to a sixth embodiment. FIG. 9 is a plan view showing a quantum device according to a seventh embodiment. FIG. 10 is a diagram showing simulation results for a quantum device according to a reference example. FIG. 11 is a diagram showing simulation results for a quantum device according to the fourth embodiment. FIG. 12 is a diagram showing simulation results for a quantum device according to the sixth embodiment.

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Note that in this specification and the drawings, components having substantially the same functional configuration may be designated by the same reference numerals to avoid redundant description. In the following description, an XYZ Cartesian coordinate system is used, but this coordinate system is defined for the purpose of explanation and does not limit the orientation of the quantum device. Furthermore, from an arbitrary point, the +Z side may be referred to as the upper side, top side, or top, and the -Z side may be referred to as the lower side, bottom side, or bottom. Furthermore, a planar view refers to viewing an object from the +Z side, and a planar shape refers to the shape of an object viewed from the +Z side.

[0010] First Embodiment First, a first embodiment will be described. The first embodiment relates to a quantum device. Fig. 1 is a plan view showing a quantum device according to the first embodiment.

[0011] As shown in FIG. 1 , quantum device 1 according to the first embodiment has quantum bits 11, 12, 13, and 14. Qubits 11 to 14 are superconducting quantum bits and include, for example, Josephson junctions. Qubits 11 to 14 are located at the vertices of square 10 in a plan view. The X coordinates of quantum bits 11 and 12 are the same, and the X coordinates of quantum bits 13 and 14 are the same. The Y coordinates of quantum bits 11 and 14 are the same, and the Y coordinates of quantum bits 12 and 13 are the same. Qubit 11 is on the +X side of quantum bit 14, and quantum bit 12 is on the +X side of quantum bit 13. Qubit 12 is on the +Y side of quantum bit 11, and quantum bit 13 is on the +Y side of quantum bit 14. Qubits 11 to 14 have a resonant frequency of, for example, 3-10 GHz.

[0012] The quantum device 1 has a readout port 30. The readout port 30 is located at the center of the square 10. The readout port 30 has, for example, a circular metal film.

[0013] The quantum device 1 has resonators 21, 22, 23, and 24. The resonator 21 has a base 21A and a resonant frequency adjustment portion 21B connected to the base 21A. The resonator 22 has a base 22A and a resonant frequency adjustment portion 22B connected to the base 22A. The resonator 23 has a base 23A and a resonant frequency adjustment portion 23B connected to the base 23A. The resonator 24 has a base 24A and a resonant frequency adjustment portion 24B connected to the base 24A.

[0014] The shapes and sizes of bases 21A, 22A, 23A, and 24A are identical to one another. That is, bases 21A, 22A, 23A, and 24A are congruent in a planar view. Bases 21A, 22A, 23A, and 24A include lines having a meandering shape. Base 21A has a portion that extends perpendicular to the line segment connecting readout port 30 and quantum bit 11. Base 22A has a portion that extends perpendicular to the line segment connecting readout port 30 and quantum bit 12. Base 23A has a portion that extends perpendicular to the line segment connecting readout port 30 and quantum bit 13. Base 24A has a portion that extends perpendicular to the line segment connecting readout port 30 and quantum bit 14. Base 21A is capacitively coupled to quantum bit 11. Base 22A is capacitively coupled to quantum bit 12. Base 23A is capacitively coupled to quantum bit 13. Base 24A is capacitively coupled to quantum bit 14. Bases 21A, 22A, 23A, and 24A are arranged to have four-fold rotational symmetry around readout port 30. The shortest distances between readout port 30 and each of bases 21A, 22A, 23A, and 24A are equal among resonators 21 to 24.

[0015] The resonant frequency adjusting units 21B, 22B, 23B, and 24B have lines with slightly different path lengths. These lines are short-circuited to a ground line. The resonant frequencies of the resonators 21 to 24 are slightly different. For example, the resonant frequency of the resonator 21 is 10.1 GHz, the resonant frequency of the resonator 22 is 10.2 GHz, the resonant frequency of the resonator 23 is 10.3 GHz, and the resonant frequency of the resonator 24 is 10.4 GHz. Each of the resonant frequency adjusting units 21B, 22B, 23B, and 24B is spaced apart from the portion of each of the bases 21A, 22A, 23A, and 24A that is closest to the readout port 30. The shortest distance between the readout port 30 and each of the resonators 21 to 24 is equal among the resonators 21 to 24.

[0016] The quantum device 1 includes a filter 100. The filter 100 is coupled to the resonators 21 to 24. For example, the filter 100 is capacitively coupled to the resonators 21 to 24. The readout port 30 is also capacitively coupled to the filter 100. The filter 100 includes lines 110, 120, 130, 140, 150, 121, 122, 123, 124, 131, and 132.

[0017] The line 131 is provided near the readout port 30 and has a planar shape that follows the outer edge of the readout port 30. The planar shape of the line 131 is, for example, an arc. The line 131 is on the -Y side of the readout port 30. The line 132 is connected to the line 131 and extends from the line 131 to the -Y side along the Y axis.

[0018] Line 121 is connected to line 132 and extends from the −Y side end of line 132 to the +X side along the X axis. Line 110 is connected to line 121 and extends from the +X side end of line 121 to the +X and +Y sides, perpendicular to the line segment connecting readout port 30 and quantum bit 11, and intersects with the line segment connecting readout port 30 and quantum bit 11. Line 122 is connected to line 110 and extends from the +X and +Y side end of line 110 to the +Y side along the Y axis. Line 120 is connected to line 122 and extends from the +Y side end of line 122 to the −X and +Y sides, perpendicular to the line segment connecting readout port 30 and quantum bit 12, and intersects with the line segment connecting readout port 30 and quantum bit 12. Line 123 is connected to line 120 and extends from the −X side and +Y side end of line 120 toward the −X side along the X axis. Line 130 is connected to line 123 and extends from the −X side end of line 123 toward the −X side and −Y side, perpendicular to the line segment connecting readout port 30 and quantum bit 13, and intersects with the line segment connecting readout port 30 and quantum bit 13. Line 124 is connected to line 130 and extends from the −X side and −Y side end of line 130 toward the −Y side along the Y axis. Line 140 is connected to line 124 and extends from the −Y side end of line 124 toward the +X side and −Y side, perpendicular to the line segment connecting readout port 30 and quantum bit 14, and intersects with the line segment connecting readout port 30 and quantum bit 14. The line 150 is connected to the line 140 and has a meandering shape that snakes from the ends of the line 140 on the +X side and the −Y side toward the read port 30 .

[0019] The path length of filter 100 may be approximately 1 time the wavelength λ. For example, it may be approximately 1 / 2 the wavelength λ in order to prevent the propagation of photons emitted from the quantum bit at the resonant frequency of 6 GHz. On the other hand, this filter does not prevent the propagation of signals at the resonant frequency of resonators 21-24, for example, 10 GHz. When the path length of filter 100 is approximately 1 time or 1 / 2 the wavelength λ, the end of filter 100 opposite to readout port 30 is open.

[0020] The lines 110, 120, 130, and 140 are arranged to have four-fold rotational symmetry around the readout port 30. The shortest distances between the readout port 30 and each of the lines 110, 120, 130, and 140 are equal to each other. In addition, the shortest distances between the line 110 and the base 21A, the shortest distance between the line 120 and the base 22A, the shortest distance between the line 130 and the base 23A, and the shortest distance between the line 140 and the base 24A are also equal to each other.

[0021] In quantum device 1, the states of quantum bits 11 to 14 can be read out simultaneously by inputting a 10 GHz signal to readout port 30. That is, because the resonant frequencies of resonators 21 to 24 are different, the states of quantum bits 11 to 14 can be read out simultaneously by frequency-separating the readout signal.

[0022] Furthermore, the shortest distance between the readout port 30 and each of the resonators 21 to 24 is the same for all of the resonators 21 to 24. This reduces the difference in parasitic capacitance between the resonators 21 to 24. If the difference in parasitic capacitance is large, the resonant frequencies of the resonators 21 to 24 may easily deviate from their design values. Furthermore, the amount of deviation in the resonant frequencies may differ between the resonators 21 to 24, making frequency separation difficult. This embodiment reduces these problems.

[0023] Furthermore, the resonators 21 to 24 include, for example, superconducting thin films, and even if the thickness of the superconducting thin films varies, the uniformity of the degree of thickness variation is high because the shortest distances are equal among the resonators 21 to 24. Therefore, the amount of shift in resonant frequency due to thickness variation is also highly uniform, and frequency separation can be reliably performed even if the thickness of the superconducting thin films varies.

[0024] Furthermore, via holes may be formed in the quantum device 1 to suppress chip modes or unwanted modes. The via holes may be formed before or after the resonators 21-24. If the via holes are formed before the resonators 21-24, the thickness of the resist used to form the resonators 21-24 may be affected by the via holes. However, since the shortest distances are equal among the resonators 21-24, it is easy to achieve high uniformity in the thickness of the resist around the areas where the resonators 21-24 are formed. Furthermore, if the via holes are formed after the resonators 21-24, the thickness of the resist used to form the via holes and interference during exposure may be affected by the resonators 21-24. However, since the shortest distances are equal among the resonators 21-24, it is easy to achieve high uniformity in the thickness of the resist around the areas where the resonators 21-24 are formed and interference during exposure.

[0025] The filter 100 may be magnetically coupled to the resonators 21 to 24 .

[0026] The effects of the first embodiment will now be further described in comparison with a reference example. Fig. 2 is a plan view showing a quantum device according to the reference example.

[0027] 2, a quantum device 1X according to the reference example has a filter 100X instead of the filter 100, and a resonator 24X instead of the resonator 24. Other configurations of the quantum device 1X are similar to those of the quantum device 1.

[0028] Filter 100X has line 124X instead of line 124, and line 140X instead of line 140. The other configurations of filter 100X are similar to those of filter 100. Line 124X is shorter than line 124. Line 140X extends slightly from the -Y side end of line 124X toward the -X and -Y sides, and then, like line 140, extends from there toward the +X and -Y sides, perpendicular to the line segment connecting readout port 30 and quantum bit 14, and intersects with the line segment connecting readout port 30 and quantum bit 14. Line 150 is connected to line 140X, and has a meandering shape that snakes from the +X and -Y side ends of line 140X toward readout port 30.

[0029] In quantum device 1X, the shortest distance between readout port 30 and line 140X is longer than the shortest distance between readout port 30 and each of lines 110, 120, and 130. Also, the shortest distance between readout port 30 and line 150 is equal to the shortest distance between readout port 30 and each of lines 110, 120, and 130.

[0030] The resonator 24X has a base 24AX and a resonant frequency adjusting portion 24B connected to the base 24A. The base 24AX includes a line having a meandering shape with a shorter period than the base 24A. The shortest distance between the readout port 30 and the resonator 24X is longer than the shortest distance between the readout port 30 and each of the resonators 21, 22, and 23. Other configurations of the resonator 24X are similar to those of the resonator 24.

[0031] The inventors of the present application performed simulations to calculate the resonant frequencies of quantum devices manufactured according to the first embodiment and the reference example. In the first embodiment, the resonant frequencies of the resonators 21 and 24 were calculated, and in the reference example, the resonant frequencies of the resonators 21 and 24X were calculated. The designed resonant frequency F1 of the resonator 21 was set to 10.18 GHz, and the resonant frequencies of the resonators 24 and 24X were set to 10.27 GHz. The results of the resonant frequency calculations are shown in FIG. 3 . FIG. 3 is a diagram showing the results of the resonant frequency calculations. As shown in FIG. 3 , in the quantum device manufactured according to the first embodiment, the resonant frequencies of the resonators 21 and 24 were nearly identical to the design values. On the other hand, in the quantum device manufactured according to the reference example, the resonant frequencies of the resonators 21 and 24X were higher than the design values.

[0032] This result supports the fact that the first embodiment has the effect of suppressing fluctuations in the resonant frequency.

[0033] Second Embodiment Next, a second embodiment will be described. The second embodiment differs from the first embodiment mainly in the configuration of the filter. Fig. 4 is a plan view showing a quantum device according to the second embodiment.

[0034] 4 , the quantum device 2 according to the second embodiment has a filter 200 instead of the filter 100. The filter 200 has lines 222A, 222B, 222C, 222D, and 222E instead of the line 122, lines 223A, 223B, 223C, 223D, and 223E instead of the line 123, and lines 224A, 224B, 224C, 224D, and 224E instead of the line 124.

[0035] Line 222A is connected to line 110 and extends from the +X and +Y ends of line 110 to the +Y side along the Y axis. Line 222B is connected to line 222A and extends from the +Y end of line 222A to the +X side along the X axis. Line 222C is connected to line 222B and extends from the +X end of line 222B to the +Y side along the Y axis. Line 222D is connected to line 222C and extends from the +Y end of line 222C to the -X side along the X axis. Line 222E is connected to lines 222D and 120 and extends from the -X end of line 222D to the +Y side along the Y axis. With a line passing through the center of the square 10 and parallel to the X-axis as the axis of symmetry, the lines 222A and 222E are arranged symmetrically with each other, and the lines 222B and 222D are arranged symmetrically with each other.

[0036] Line 223A is connected to line 120 and extends from the -X and +Y end of line 120 to the -X side along the X axis. Line 223B is connected to line 223A and extends from the -X side end of line 223A to the +Y side along the Y axis. Line 223C is connected to line 223B and extends from the +Y side end of line 223B to the -X side along the X axis. Line 223D is connected to line 223C and extends from the -X side end of line 223C to the -Y side along the Y axis. Line 223E is connected to lines 223D and 130 and extends from the -Y side end of line 223D to the -X side along the X axis. With a line passing through the center of square 10 and parallel to the Y axis as the axis of symmetry, lines 223A and 223E are arranged symmetrically with each other, and lines 223B and 223D are arranged symmetrically with each other.

[0037] Line 224A is connected to line 130 and extends from the -X and -Y ends of line 130 to the -Y side along the Y axis. Line 224B is connected to line 224A and extends from the -Y side end of line 224A to the -X side along the X axis. Line 224C is connected to line 224B and extends from the -X side end of line 224B to the -Y side along the Y axis. Line 224D is connected to line 224C and extends from the -Y side end of line 224C to the +X side along the X axis. Line 224E is connected to lines 224D and 140 and extends from the +X side end of line 224D to the -Y side along the Y axis. With a line passing through the center of the square 10 and parallel to the X-axis as the axis of symmetry, the lines 224A and 224E are arranged symmetrically with each other, and the lines 224B and 224D are arranged symmetrically with each other.

[0038] The path length of filter 200 may be approximately 1 / 2 or 1 times the wavelength λ. For example, if the resonant frequency of the quantum bit is 6 GHz, the path length is approximately 1 / 2 or 1 time the wavelength λ in order to prevent the propagation of photons emitted from the quantum bit. On the other hand, this filter does not prevent the propagation of signals at the resonant frequency of resonators 21-24, for example, 10 GHz. Filter 200 may also be magnetically coupled to resonators 21-24.

[0039] Other configurations of the quantum device 2 are the same as those of the quantum device 1. The quantum device 2 according to the second embodiment can also achieve the same effects as those of the first embodiment.

[0040] Third Embodiment Next, a third embodiment will be described. The third embodiment differs from the first embodiment mainly in the configuration of the filter. Fig. 5 is a plan view showing a quantum device according to the third embodiment.

[0041] 5 , the quantum device 3 according to the third embodiment has a filter 300 instead of the filter 100. The filter 300 has lines 321A, 321B, and 321C instead of the line 121, lines 322A and 322B instead of the line 122, lines 323A and 323B instead of the line 123, and lines 324A and 324B instead of the line 124.

[0042] Line 321B is connected to line 132 and extends from the -Y side end of line 132 to the +X and -X sides along the X axis. Line 321A is connected to line 140 and extends from the +X and -Y side ends of line 140 to the +X side along the X axis. Line 321C is connected to line 110 and extends from the -X and -Y side ends of line 110 to the -X side along the X axis. Lines 321A and 321C are separated from line 321B. Lines 321A, 321B, and 321C have the same Y coordinate. Line 321A and line 321B are capacitively coupled to each other, and line 321C and line 321B are capacitively coupled to each other. The +X side end of line 321A, the −X side end of line 321B, the +X side end of line 321B, and the −X side end of line 321C are open ends. Lines 321A and 321C are arranged symmetrically with respect to a line parallel to the Y axis that passes through the center of square 10.

[0043] Line 322A is connected to line 110 and extends from the end of line 110 on the +X side and +Y side to the +Y side along the Y axis. Line 322B is connected to line 120 and extends from the end of line 120 on the +X side and -Y side to the -Y side along the Y axis. Lines 322A and 322B have the same X coordinate. Lines 322A and 322B are capacitively coupled to each other. The +Y side end of line 322A and the -Y side end of line 322B are open ends. Lines 322A and 322B are arranged symmetrically with respect to each other, with a line parallel to the X axis that passes through the center of square 10 as the axis of symmetry.

[0044] Line 323A is connected to line 120 and extends from the end of line 120 on the -X side and +Y side toward the -X side along the X axis. Line 323B is connected to line 130 and extends from the end of line 130 on the +X side and +Y side toward the +X side along the X axis. The Y coordinates of lines 323A and 323B are the same. Lines 323A and 323B are capacitively coupled to each other. The -X side end of line 323A and the +X side end of line 323B are open ends. Lines 323A and 323B are arranged symmetrically with respect to a line parallel to the Y axis that passes through the center of square 10.

[0045] Line 324A is connected to line 130 and extends from the end of line 130 on the -X and -Y sides toward the -Y side along the Y axis. Line 324B is connected to line 140 and extends from the end of line 140 on the -X and +Y sides toward the +Y side along the Y axis. Lines 324A and 324B have the same X coordinate. Lines 324A and 324B are capacitively coupled to each other. The -Y side end of line 324A and the +Y side end of line 324B are open ends. Lines 324A and 324B are arranged symmetrically with respect to a line parallel to the X axis that passes through the center of square 10.

[0046] The path length of filter 300 may be approximately 1 / 2 or 1 times the wavelength λ. For example, if the resonant frequency of the quantum bit is 6 GHz, the path length is approximately 1 / 2 or 1 time the wavelength λ in order to prevent the propagation of photons emitted from the quantum bit. On the other hand, this filter does not prevent the propagation of signals at the resonant frequency of resonators 21 to 24, for example, 10 GHz. Furthermore, filter 300 may be magnetically coupled to resonators 21 to 24.

[0047] Other configurations of the quantum device 3 are the same as those of the quantum device 1. The quantum device 3 according to the third embodiment can also achieve the same effects as those of the first embodiment.

[0048] Furthermore, in the quantum device 3, the filter 300 has a plurality of lines that are capacitively coupled to each other, which improves isolation and reduces unwanted modes.

[0049] Fourth Embodiment Next, a fourth embodiment will be described. The fourth embodiment differs from the first embodiment mainly in the configuration of the filter. Fig. 6 is a plan view showing a quantum device according to the fourth embodiment.

[0050] 6 , the quantum device 4 according to the fourth embodiment has a filter 400 instead of the filter 100. The filter 400 has lines 421A, 421B, and 421C instead of the line 121, lines 422A and 422B instead of the line 122, lines 423A and 423B instead of the line 123, and lines 424A and 424B instead of the line 124.

[0051] The line 421B is connected to the line 132 and extends from the -Y side end of the line 132 to the +X side along the X axis. The line 421A is connected to the line 140 and extends from the +X side and -Y side end of the line 140 to the +X side along the X axis. The line 421C is connected to the line 110 and extends from the -X side and -Y side end of the line 110 to the -X side along the X axis. The lines 421A and 421C are spaced apart from the line 421B. The Y coordinates of the lines 421A and 421C are the same. The Y coordinate of the line 421B is greater than the Y coordinates of the lines 421A and 421C. When viewed from the Y axis direction, a portion of the line 421B and a portion of the line 421C overlap, and the lines 421C and 421B are capacitively coupled to each other. The magnitude of the capacitive coupling between line 421A and line 421B is smaller than the magnitude of the capacitive coupling between line 421B and line 421C. The +X side end of line 421A, the +X side end of line 421B, and the -X side end of line 421C are open ends. Lines 421A and 421C are arranged symmetrically with respect to a line parallel to the Y axis that passes through the center of square 10.

[0052] The line 422A is connected to the line 110 and extends from the end of the line 110 on the +X side and the +Y side toward the +Y side along the Y axis. The line 422B is connected to the line 120 and extends from the end of the line 120 on the +X side and the -Y side toward the -Y side along the Y axis. The X coordinates of the end of the line 110 on the +X side and the +Y side and the line 422A are smaller than the X coordinates of the end of the line 120 on the +X side and the -Y side and the line 422B. When viewed from the X-axis direction, a portion of the line 422A and a portion of the line 422B overlap, and the line 422A and the line 422B are capacitively coupled to each other. The end of the line 422A on the +Y side and the end of the line 422B on the -Y side are open ends.

[0053] The line 423A is connected to the line 120 and extends from the -X and +Y end of the line 120 to the -X side along the X axis. The line 423B is connected to the line 130 and extends from the +X and +Y end of the line 130 to the +X side along the X axis. The Y coordinates of the -X and +Y end of the line 120 and the line 423A are smaller than the Y coordinates of the +X and +Y end of the line 130 and the line 423B. When viewed from the Y axis direction, a portion of the line 423A and a portion of the line 423B overlap, and the line 423A and the line 423B are capacitively coupled to each other. The -X side end of the line 423A and the +X side end of the line 423B are open ends.

[0054] The line 424A is connected to the line 130 and extends from the -X and -Y end of the line 130 to the -Y side along the Y axis. The line 424B is connected to the line 140 and extends from the -X and +Y end of the line 140 to the +Y side along the Y axis. The X coordinates of the -X and -Y end of the line 130 and the line 424A are larger than the X coordinates of the -X and +Y end of the line 140 and the line 424B. When viewed from the X axis direction, a portion of the line 424A and a portion of the line 424B overlap, and the line 424A and the line 424B are capacitively coupled to each other. The -Y end of the line 424A and the +Y end of the line 424B are open ends.

[0055] The path length of filter 400 may be approximately 1 / 2 or 1 times the wavelength λ. For example, if the resonant frequency of the quantum bit is 6 GHz, the path length is approximately 1 / 2 or 1 time the wavelength λ in order to prevent the propagation of photons emitted from the quantum bit. On the other hand, this filter does not prevent the propagation of signals at the resonant frequency of resonators 21 to 24, for example, 10 GHz. Furthermore, filter 400 may be magnetically coupled to resonators 21 to 24.

[0056] Other configurations of the quantum device 4 are the same as those of the quantum device 1. The quantum device 4 according to the fourth embodiment can also achieve the same effects as those of the third embodiment.

[0057] Furthermore, in the quantum device 4 according to the fourth embodiment, the capacitively coupled lines within the filter 400 have overlapping portions when viewed from the X-axis direction or the Y-axis direction, which makes it easy to control the direction in which a signal propagates within the filter 400.

[0058] Fifth Embodiment Next, a fifth embodiment will be described. The fifth embodiment differs from the fourth embodiment mainly in the configuration of the filter. Fig. 7 is a plan view showing a quantum device according to the fifth embodiment.

[0059] As shown in FIG. 7 , the quantum device 5 according to the fifth embodiment includes a filter 500 instead of the filter 400. The filter 500 differs from the filter 400 in that the path length from the line 131 to the line 421A is shorter than that of the fourth embodiment and further includes a line 521D. The line 521D is capacitively coupled to the line 421A. Both ends of the line 521D are open. The path length of the filter 500 may be approximately 1 / 2 or 1 times the wavelength λ. For example, if the resonant frequency of the quantum bit is 6 GHz, the filter length is approximately 1 / 2 or 1 time the wavelength λ to prevent the propagation of photons emitted from the quantum bit. On the other hand, this filter does not impede the propagation of signals at the resonant frequency of the resonators 21 to 24, for example, 10 GHz.

[0060] Other configurations of the quantum device 5 are the same as those of the quantum device 4. The quantum device 5 according to the fifth embodiment can also achieve the same effects as those of the fourth embodiment.

[0061] Sixth Embodiment Next, a sixth embodiment will be described. The sixth embodiment differs from the first embodiment mainly in the configuration of the filter. Fig. 8 is a plan view showing a quantum device according to the sixth embodiment.

[0062] 8 , the quantum device 6 according to the sixth embodiment includes a filter 600 instead of the filter 100. The filter 600 includes lines 621A, 621B, 621C, and 621D instead of the line 621, lines 622A, 622B, 622C, and 622D instead of the line 122, lines 623A, 623B, 623C, and 623D instead of the line 123, and lines 624A, 624B, 624C, and 624D instead of the line 124. The filter 600 further includes lines 633 and 644.

[0063] The line 633 is provided near the readout port 30 and has a planar shape that follows the outer edge of the readout port 30. The planar shape of the line 633 is, for example, an arc shape. The line 633 is on the +Y side of the readout port 30. The line 634 is connected to the line 633 and extends from the line 633 to the +Y side along the Y axis.

[0064] The line 621A is connected to the line 140 and extends from the end of the line 140 on the +X side and the -Y side toward the +X side along the X axis. The line 621B is connected to the line 621A and extends from the end of the line 621A on the +X side toward the +Y side along the Y axis. The line 621D is connected to the line 110 and extends from the end of the line 110 on the -X side and the -Y side toward the -X side along the X axis. The line 621C is connected to the line 621D and extends from the end of the line 621D on the -X side toward the +Y side along the Y axis. The Y coordinates of the lines 621A and 621D are the same. The X coordinate of the line 621B is smaller than the X coordinate of the line 132. When viewed from the X axis direction, the line 621B and the line 132 partially overlap, and the line 621B and the line 132 are capacitively coupled to each other. The X coordinate of line 621C is larger than the X coordinate of line 132. When viewed from the X-axis direction, line 621C and part of line 132 overlap, and line 621C and line 132 are capacitively coupled to each other. The +Y side end of line 621B and the +Y side end of line 621C are open ends. With a line parallel to the Y axis passing through the center of square 10 as the axis of symmetry, lines 621A and 621D are arranged line-symmetrically with each other, and lines 621B and 621C are arranged line-symmetrically with each other.

[0065] Line 622A is connected to line 110 and extends from the end of line 110 on the +X and +Y sides toward the +Y side along the Y axis. Line 622B is connected to line 622A and extends from the end of line 622A on the +Y side toward the -X side along the X axis. Line 622D is connected to line 120 and extends from the end of line 120 on the +X and -Y sides toward the -Y side along the Y axis. Line 622C is connected to line 622D and extends from the end of line 622D on the -Y side toward the -X side along the X axis. Lines 622A and 622D have the same X coordinate. The Y coordinate of line 622B is smaller than the X coordinate of line 622C. When viewed from the Y axis direction, lines 622B and 622C overlap, and lines 622B and 622C are capacitively coupled to each other. The −X side end of line 622B and the −X side end of line 622C are open ends. With a line parallel to the X axis passing through the center of square 10 as the axis of symmetry, lines 622A and 622D are arranged symmetrically with each other, and lines 622B and 622C are arranged symmetrically with each other.

[0066] Line 623A is connected to line 120 and extends from the -X and +Y end of line 120 to the -X side along the X axis. Line 623B is connected to line 623A and extends from the -X end of line 623A to the -Y side along the Y axis. Line 623D is connected to line 130 and extends from the +X and +Y end of line 130 to the +X side along the X axis. Line 623C is connected to line 623D and extends from the +X end of line 623D to the -Y side along the Y axis. Lines 623A and 623D have the same Y coordinate. The X coordinate of line 623B is greater than the X coordinate of line 634. When viewed from the X axis direction, line 623B and line 634 partially overlap, and line 623B and line 634 are capacitively coupled to each other. The X coordinate of line 623C is smaller than the X coordinate of line 634. When viewed from the X-axis direction, line 623C and part of line 634 overlap, and line 623C and line 634 are capacitively coupled to each other. The -Y side end of line 623B and the -Y side end of line 623C are open ends. With a line parallel to the Y axis passing through the center of square 10 as the axis of symmetry, lines 623A and 623D are arranged line-symmetrically with each other, and lines 623B and 623C are arranged line-symmetrically with each other.

[0067] Line 624A is connected to line 130 and extends from the -X and -Y end of line 130 to the -Y side along the Y axis. Line 624B is connected to line 624A and extends from the -Y end of line 624A to the +X side along the X axis. Line 624D is connected to line 140 and extends from the -X and +Y end of line 140 to the +Y side along the Y axis. Line 624C is connected to line 624D and extends from the +Y end of line 624D to the +X side along the X axis. Lines 624A and 624D have the same X coordinate. The Y coordinate of line 624B is larger than the X coordinate of line 624C. When viewed from the Y axis direction, lines 624B and 624C overlap, and lines 624B and 624C are capacitively coupled to each other. The +X side end of line 624B and the +X side end of line 624C are open ends. With a line parallel to the X axis passing through the center of square 10 as the axis of symmetry, lines 624A and 624D are arranged symmetrically with each other, and lines 624B and 624C are arranged symmetrically with each other.

[0068] Other configurations of the quantum device 6 are the same as those of the quantum device 1. The quantum device 6 according to the sixth embodiment can also achieve the same effects as those of the third embodiment. Furthermore, in the quantum device 6, the filter 600 has a higher symmetry in a planar view, which can improve the uniformity of the parasitic capacitances of the resonators 21 to 24.

[0069] Seventh Embodiment Next, a seventh embodiment will be described. The seventh embodiment differs from the sixth embodiment mainly in the configuration of the filter. Fig. 9 is a plan view showing a quantum device according to the seventh embodiment.

[0070] 9, the quantum device 7 according to the seventh embodiment includes a filter 700 instead of the filter 600. The filter 700 differs from the filter 600 in that it further includes lines 735, 736, 737, and 738.

[0071] The line 735 is provided near the readout port 30 and has a planar shape that follows the outer edge of the readout port 30. The planar shape of the line 735 is, for example, an arc shape. The line 735 is on the +X side of the readout port 30. The line 736 is connected to the line 735 and extends from the line 735 to the +X side along the X axis. When viewed from the Y axis direction, the lines 622B and 622C partially overlap with the line 736, and the lines 622B and 622C are capacitively coupled to the line 736.

[0072] The line 737 is provided near the readout port 30 and has a planar shape that follows the outer edge of the readout port 30. The planar shape of the line 737 is, for example, an arc shape. The line 737 is on the −X side of the readout port 30. The line 738 is connected to the line 737 and extends from the line 737 to the −X side along the X axis. When viewed from the Y axis direction, the lines 624B and 624C partially overlap with the line 738, and the lines 624B and 624C and the line 738 are capacitively coupled to each other.

[0073] Other configurations of the quantum device 7 are the same as those of the quantum device 6. The quantum device 7 according to the seventh embodiment can also achieve the same effects as those of the sixth embodiment. Furthermore, in the quantum device 7, the filter 700 has a higher symmetry in a planar view, which can further improve the uniformity of the parasitic capacitances of the resonators 21 to 24.

[0074] Here, a simulation of quantum devices 1X, 4, and 6 conducted by the present inventors will be described. In this simulation, the transmittance of a superconducting circuit simulating quantum devices 1X, 4, and 6 was calculated as an S-parameter when readout port 30 was the first port, quantum bit 11 was the second port, quantum bit 12 was the third port, quantum bit 13 was the fourth port, and quantum bit 14 was the fifth port. In this simulation, the coupling capacitance between readout port 30 and each filter was set to 5.5 fF, and the coupling capacitance between the lines in filters 400 and 600 was set to 50 fF. The characteristic impedance of resonators 21-24 was set to 50 Ω, the path lengths of resonators 21-24 were all set to 1 / 4 of the wavelength λ, and the path length of each filter was set to 1 / 2 of the wavelength λ. The coupling capacitance between quantum bits 11-14 and resonators 21-24 was set to 1.2 fF. The results are shown in FIGS. 10-12. FIG. 10 is a diagram showing the results of a simulation for quantum device 1X according to a reference example. FIG. 11 is a diagram showing the results of a simulation for quantum device 4 according to the fourth embodiment. FIG. 12 is a diagram showing the results of a simulation for quantum device 6 according to the sixth embodiment. "dB(S(A,1))" in FIGS. 10 to 12 indicates the transmittance at port A when a signal is input from port 1.

[0075] 10, unwanted modes are generated in the simulation of quantum device 1X. This is thought to be because coupling also occurs between resonators 21 to 24.

[0076] 11, no unwanted modes were generated in the simulation of quantum device 4. This is thought to be because filter 400 has multiple lines that are capacitively coupled to each other, thereby improving the isolation between resonators 21 to 24.

[0077] 12, in the simulation of quantum device 6, the characteristics of the second, third, fourth, and fifth ports are consistent. This is thought to be because filter 600 has high symmetry in a plan view and the signal transmission characteristics are highly uniform among resonators 21 to 24.

[0078] In this calculation, in order to clearly explain the effect of obtaining uniformity in characteristics, the eigenmode frequencies of the quantum bits 11 to 14 are aligned with the eigenmode frequencies of the resonators 21 to 24. In practice, the eigenmode frequencies of the resonators are multiplexed to read out the state, so the eigenmode frequencies may be detuned between quantum bits and between resonators. In this case, the same effect can be expected.

[0079] In the present disclosure, the path length of the filter is not particularly limited. For example, the path length of the filter may be approximately ¼ of the wavelength corresponding to the frequency at which the multiple resonators resonate, and the filter may be a coplanar waveguide filter. In this case, the tip of the filter is shorted to the ground line. That is, the end of the filter opposite to the port side is shorted. The filter may be a bandpass filter or a filter that attenuates signals in a specific frequency band. Furthermore, the filter is not limited to a coplanar waveguide filter, and a microstrip waveguide filter or the like may also be used.

[0080] Furthermore, the number of quantum bits coupled to one port is not particularly limited, and the quantum bits coupled to one port are preferably located at the vertices of a regular polygon with the port as its center.

[0081] In the present disclosure, "equal" does not necessarily mean a perfect match. For example, manufacturing variations are acceptable. Furthermore, as long as the shortest distance between the base of the resonator and the port is equal and an effect such as reduction in parasitic capacitance is obtained, the shortest distance between the resonator and the port may differ slightly depending on the arrangement of the resonant frequency adjuster, etc.

[0082] Quantum devices according to the present disclosure can be used, for example, in quantum computing.

[0083] Although the preferred embodiments have been described in detail above, the present disclosure is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0084] 1, 2, 3, 4, 5, 6, 7: Quantum device 10: Square 11, 12, 13, 14: Quantum bit 21, 22, 23, 24: Resonator 21A, 22A, 23A, 24A: Base 21B, 22B, 23B, 24B: Resonant frequency adjustment section 100, 200, 300, 400, 500, 600, 700: Filter

Claims

1. A quantum device comprising: a plurality of superconducting quantum bits; a plurality of resonators capacitively coupled to each of the plurality of superconducting quantum bits; a filter coupled to the plurality of resonators; and a port capacitively coupled to the filter, wherein the shortest distance between the port and the resonator is equal among the plurality of resonators.

2. The quantum device according to claim 1, characterized in that the path length of the filter is 1 or 1 / 2 the wavelength corresponding to the frequency at which the multiple resonators resonate, and the end of the filter opposite the port side is open.

3. The quantum device according to claim 2, wherein the filter is a coplanar waveguide filter.

4. The quantum device according to claim 1, characterized in that the path length of the filter is 1 / 4 of the wavelength corresponding to the frequency at which the multiple resonators resonate, and the end of the filter opposite the port side is short-circuited.

5. The quantum device according to any one of claims 1 to 4, wherein the filter has a plurality of lines capacitively coupled to each other.

6. The quantum device according to claim 5, wherein at least some of the multiple lines are arranged symmetrically between each of the multiple resonators and the port.

7. A quantum device as claimed in any one of claims 1 to 4, characterized in that the number of superconducting quantum bits and resonators is three or more, in a planar view, the three or more superconducting quantum bits are located at the vertices of a regular polygon, and the port is located at the center of the regular polygon.

8. The quantum device according to claim 7, characterized in that each of the three or more resonators has a base and a resonant frequency adjustment portion connected to the base, and the planar shape of the base is congruent among the three or more resonators.

9. The quantum device according to any one of claims 1 to 4, wherein the filter is capacitively coupled to the plurality of resonators.

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