JPWO2021029063A1 - Quantum circuit system - Google Patents

Abstract

Provided is a quantum circuit system 10 capable of preventing an unintended change in a quantum state. The quantum circuit system 10 includes a first quantum circuit 11a and a second quantum circuit 11b having at least two quantum states, respectively, and a first waveguide 12a and a second quantum circuit 11b electromagnetically connected to the first quantum circuit 11a. When the first high-frequency power is propagated to the second waveguide 12b and the first waveguide 12a electromagnetically connected to the first quantum circuit 11a to change the first quantum circuit 11a into a predetermined quantum state, the second quantum circuit 11b A high-frequency power source 13b for propagating the second high-frequency power to the second waveguide 12b, directly or indirectly, is provided so as to compensate for the change in the quantum state.

Description

The present invention relates to a quantum circuit system.

In recent years, research has been carried out toward the practical application of quantum computers. For example, in Non-Patent Document 1 below, a quantum circuit called Transmon was proposed. Transmon is highly resistant to electrical noise and has a relatively long relaxation time.

Further, Patent Document 1 below describes a quantum information processing system including a waveguide having an aperture, a nonlinear quantum circuit arranged in the waveguide, and an electromagnetic field source coupled to the aperture.

Further, Patent Document 2 below describes an uninterrupted elongated thin film due to Josephson junction and a superconducting quantum interference device (SQUID) in electrical contact with the proximal end of the elongated thin film, with less than three Josephsons. A superconducting quantum interference device (SQUID) with junctions and a ground plane that is coplanar with the elongated thin film and is in electrical contact with the distal end of the elongated thin film, the thin film, SQUID and ground plane are designed. Quantum bit devices are described that include materials that are superconducting at the given operating temperature.

Jens Koch, Terri M. Yu, Jay Gambetta, AA Houck, DI Schuster, J. Majer, Alexandre Blais, MH Devoret, SM Girvin, and RJ Schoelkopf, “Charge-insensitive qubit design derived from the Cooper pair box,” Phys. Rev. A 76, 042319, 2007

Japanese Unexamined Patent Publication No. 2016-510497 JP-A-2018-524795

The quantum state of a quantum circuit such as Transmon may be manipulated by propagating high frequency power through a waveguide connected to the quantum circuit. At this time, the electromagnetic field propagating in the waveguide may leak and power may propagate to other waveguides, and the quantum state of the quantum circuit connected to the other waveguide may change unintentionally. be.

In order to correct such unintended changes in the quantum state, it is being studied to use a quantum error correction technique. However, in order to implement quantum error correction, it is necessary to provide an extra quantum circuit, and it is necessary to increase the scale of the circuit.

Therefore, the present invention provides a quantum circuit system capable of preventing unintended changes in the quantum state.

The quantum circuit system according to one aspect of the present invention includes a first quantum circuit and a second quantum circuit having at least two quantum states, respectively, and a first waveguide and a second quantum electromagnetically connected to the first quantum circuit. The quantum state of the second quantum circuit when the first quantum circuit is changed to a predetermined quantum state by propagating the first high-frequency power to the second waveguide electromagnetically connected to the circuit and the first waveguide. It is provided with a high frequency power source that directly or indirectly propagates the second high frequency power to the second waveguide so as to compensate for the change.

According to this aspect, when the first quantum circuit is changed to a predetermined quantum state, the change in the quantum state of the second quantum circuit can be compensated, and the unintended change in the quantum state of the second quantum circuit can be prevented. can do.

In the above embodiment, the high frequency power supply directly or indirectly performs the second induction so as to compensate for the change in the quantum state of the second quantum circuit after the timing when the first high frequency power is propagated to the first waveguide. The second high frequency power may be propagated through the waveguide.

According to this aspect, it is possible to compensate for the change in the quantum state of the second quantum circuit at the same time as or after the timing of changing the first quantum circuit to a predetermined quantum state, and the unintended quantum state of the second quantum circuit can be compensated. Change can be prevented.

In the above embodiment, the high-frequency power supply changes the high-frequency power that compensates for the change in the quantum state of the second quantum circuit due to the propagation of the first high-frequency power through the first waveguide and the second quantum circuit to a predetermined quantum state. The second high-frequency power, which is a superposition with the high-frequency power to be caused, may be directly or indirectly propagated to the second waveguide.

According to this aspect, the quantum state of the second quantum circuit is changed to a predetermined quantum state while compensating for the change of the quantum state of the second quantum circuit caused by changing the first quantum circuit to a predetermined quantum state. Can be made to.

In the above embodiment, when an auxiliary waveguide extending along the second waveguide is further provided and the high frequency power source propagates the first high frequency power to the first waveguide to change the first quantum circuit into a predetermined quantum state. In addition, the third high-frequency power may be propagated to the auxiliary waveguide and indirectly propagate the second high-frequency power to the second waveguide so as to compensate for the change in the quantum state of the second quantum circuit.

According to this aspect, when the first quantum circuit is changed to a predetermined quantum state, the change in the quantum state of the second quantum circuit can be compensated without directly propagating the high frequency power to the second waveguide. can.

In the above aspect, the auxiliary waveguide may include a first portion and a second portion extending along the second waveguide, and a folded portion connecting the first portion and the second portion.

According to this aspect, when the third high frequency power is propagated to the auxiliary waveguide, the second high frequency power can be propagated to the second waveguide more accurately.

According to the present invention, it is possible to provide a quantum circuit system capable of preventing an unintended change in the quantum state.

It is a figure which shows the network configuration of the quantum computing system which concerns on embodiment of this invention. It is a figure which shows the structure of the quantum circuit system which concerns on this embodiment. It is a circuit diagram of the quantum circuit which concerns on this embodiment. It is a figure which shows 1st example of the waveform of the 1st waveguide, the waveform of the 2nd waveguide, and the quantum state of the 2nd quantum circuit of the quantum circuit system which concerns on this embodiment. It is a figure which shows the 2nd example of the waveform of the 1st waveguide, the waveform of the 2nd waveguide, and the quantum state of the 2nd quantum circuit of the quantum circuit system which concerns on this embodiment. It is a figure which shows the 3rd example of the waveform of the 1st waveguide, the waveform of the 2nd waveguide, and the quantum state of the 2nd quantum circuit of the quantum circuit system which concerns on this embodiment. It is a figure which shows the 4th example of the waveform of the 1st waveguide, the waveform of the 2nd waveguide, and the quantum state of the 2nd quantum circuit of the quantum circuit system which concerns on this embodiment. It is a figure which shows the structure of the quantum circuit system which concerns on the 1st modification of this embodiment. It is a figure which shows the waveform of the 1st waveguide, the waveform of the 2nd waveguide, and the 1st example of the quantum state of the 2nd quantum circuit of the quantum circuit system which concerns on the 1st modification of this embodiment. It is a figure which shows the waveform of the 1st waveguide, the waveform of the 2nd waveguide, and the 2nd example of the quantum state of the 2nd quantum circuit of the quantum circuit system which concerns on the 1st modification of this embodiment. It is a figure which shows the structure of the quantum circuit system which concerns on the 2nd modification of this embodiment. It is a figure which shows the structure of the quantum circuit system which concerns on the 3rd modification of this embodiment. It is a figure which shows the structure of the quantum circuit system which concerns on the 4th modification of this embodiment. It is a figure which shows the structure of the quantum circuit system which concerns on the 5th modification of this embodiment.

Embodiments of the present invention will be described with reference to the accompanying drawings. In each figure, those having the same reference numerals have the same or similar configurations.

FIG. 1 is a diagram showing a network configuration of a quantum computing system 100 according to an embodiment of the present invention. The quantum computing system 100 includes a quantum circuit system 10 and a user terminal 20. The quantum circuit system 10 and the user terminal 20 are connected to each other so as to be able to communicate with each other via a communication network N such as the Internet. The user of the quantum calculation system 100 inputs data to the quantum circuit system 10 by using the user terminal 20 composed of a general-purpose classical computer, and acquires the result of the quantum calculation performed by the quantum circuit system 10. ..

FIG. 2 is a diagram showing a configuration of a quantum circuit system 10 according to the present embodiment. The quantum circuit system 10 includes a first quantum circuit 11a and a second quantum circuit 11b having at least two quantum states, respectively, and a first waveguide 12a and a second quantum circuit 11b electromagnetically connected to the first quantum circuit 11a. A second waveguide 12b, which is electromagnetically connected to the circuit, is provided. Further, the quantum circuit system 10 compensates for the change in the quantum state of the second quantum circuit 11b when the first high frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state. As such, a second high-frequency power source 13b for propagating the second high-frequency power directly or indirectly to the second waveguide 12b is provided. The quantum circuit system 10 compensates for the change in the quantum state of the first quantum circuit 11a when the high frequency power is propagated to the second waveguide 12b to change the second quantum circuit 11b to a predetermined quantum state. A first high-frequency power source 13a for propagating high-frequency power directly or indirectly to the first waveguide 12a is provided.

Further, the quantum circuit system 10 includes a third quantum circuit 11c and a fourth quantum circuit 11d having at least two quantum states, respectively, and a third waveguide 12c and a fourth quantum electromagnetically connected to the third quantum circuit 11c. A fourth waveguide 12d, which is electromagnetically connected to the circuit 11d, is further provided. Further, the quantum circuit system 10 compensates for the change in the quantum state of the fourth quantum circuit 11d when the third high frequency power is propagated to the third waveguide 12c to change the third quantum circuit 11c to a predetermined quantum state. As such, a fourth high-frequency power source 13d for propagating the fourth high-frequency power directly or indirectly to the fourth waveguide 12d is provided. Further, the quantum circuit system 10 compensates for the change in the quantum state of the third quantum circuit 11c when the high frequency power is propagated to the fourth waveguide 12d to change the fourth quantum circuit 11d to a predetermined quantum state. In addition, a third high-frequency power source 13c for propagating high-frequency power directly or indirectly to the third waveguide 12c is provided.

The first quantum circuit 11a, the second quantum circuit 11b, the third quantum circuit 11c, and the fourth quantum circuit 11d may each have the same configuration, and may be, for example, a quantum circuit containing Transmon. The first waveguide 12a, the second waveguide 12b, the third waveguide 12c, and the fourth waveguide 12d may each have the same configuration, and are, for example, a waveguide including a coplanar line, a microstrip line, and the like. good. The first high-frequency power supply 13a, the second high-frequency power supply 13b, the third high-frequency power supply 13c, and the fourth high-frequency power supply 13d may each have the same configuration, and may include, for example, a power supply that outputs a high-frequency pulse of several GHz.

In the present specification, a plurality of quantum circuits including the first quantum circuit 11a, the second quantum circuit 11b, the third quantum circuit 11c, and the fourth quantum circuit 11d are simply referred to as quantum circuits 11. Further, a plurality of waveguides including the first waveguide 12a, the second waveguide 12b, the third waveguide 12c, and the fourth waveguide 12d are simply referred to as the waveguide 12, and the first high frequency power supply 13a and the second high frequency power supply 13b. A plurality of high-frequency power supplies including the third high-frequency power supply 13c and the fourth high-frequency power supply 13d are simply referred to as high-frequency power supplies 13.

FIG. 2 illustrates a quantum circuit system 10 including four quantum circuits 11, four waveguides 12, and four high-frequency power supplies 13, but the number of quantum circuits 11, waveguides 12, and high-frequency power supplies 13 is illustrated. Is optional. The number of high-frequency power supplies 13 may be smaller than the number of quantum circuits 11, and the structure may be connected to the quantum circuits 11 via a demultiplexer or the like.

FIG. 3 is an example of a circuit diagram of the quantum circuit 11 according to the present embodiment. Quantum circuit 11 includes a Toranzumon 111 including Josephson junction JJ and capacitor _{C B,} a resonator 112 includes an inductor _{L r} and a capacitor _{C r.} The high-frequency power supply 13 is _{connected to one end of the input capacitor C in} , and the high-frequency pulse output from the high-frequency power supply 13 _{is input to the transmon 111 via the gate capacitor C g} to change the quantum state of the transmon 111. The number of Josephson junction JJs is not limited to one, and when two are connected in parallel to form a dc-SQUID configuration, or when Josephson junction JJs of different sizes are connected in parallel (Flux qubit, etc.), There may be cases where multiple Josephson junction JJs of different sizes are connected (Fluxonium, etc.). In this way, the energy potential of the system may be adjusted according to the purpose depending on the number and size of the Josephson junction JJ.

FIG. 4 is a diagram showing a first example of the waveform of the first waveguide 12a, the waveform of the second waveguide 12b, and the quantum state of the second quantum circuit 11b of the quantum circuit system 10 according to the present embodiment. In the figure, a waveform graph showing the relationship between the voltage and time of the first waveguide 12a, a waveform graph showing the relationship between the voltage and time of the second waveguide 12b, and a bloch sphere showing the quantum state of the second quantum circuit 11b. It shows that. In the figure, for the sake of simplicity, the voltage graph of the first waveguide 12a and the second waveguide 12b is shown, but the high frequency pulse propagates to the first waveguide 12a and the second waveguide 12b. Therefore, electric power that is not clearly separated into voltage and current is propagated.

In the following, when the first high frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, the change in the quantum state of the second quantum circuit 11b is compensated for. An example of propagating the second high-frequency power to the two waveguides 12b will be described, but the relationship may be reversed. That is, when high-frequency power is propagated to the second waveguide 12b to change the second quantum circuit 11b to a predetermined quantum state, the first waveguide is compensated for the change in the quantum state of the first quantum circuit 11a. High frequency power may be propagated to 12a. Further, the same processing may be performed between the second waveguide 12b and the third waveguide 12c, or the same processing may be performed between the third waveguide 12c and the fourth waveguide 12d. ..

When the first high-frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, a relatively large first high-frequency power is input to the first waveguide 12a, and the first waveguide A leaking electromagnetic field is generated around 12a. Then, due to the influence of the leaking electromagnetic field, unintended high-frequency power propagates to the second waveguide 12b adjacent to the first waveguide 12a, and the quantum state of the second quantum circuit 11b changes. FIG. 4 shows how the quantum state of the second quantum circuit 11b changes due to the influence of the leaking electromagnetic field by a Bloch sphere in which the direction of the qubit is tilted.

The second high-frequency power source 13b directly or indirectly propagates the second high-frequency power to the second waveguide 12b so as to compensate for the change in the quantum state of the second quantum circuit 11b. In the case of this example, the second high-frequency power supply 13b directly or indirectly compensates for the change in the quantum state of the second quantum circuit 11b after the timing when the first high-frequency power is propagated to the first waveguide 12a. Therefore, the second high frequency power is propagated through the second waveguide 12b. More specifically, in the case of this example, the second high-frequency power supply 13b compensates for the change in the quantum state of the second quantum circuit 11b after the timing at which the first high-frequency power is propagated to the first waveguide 12a. As described above, the second high frequency power is directly propagated to the second waveguide 12b. In FIG. 4, the quantum state of the second quantum circuit 11b after compensation is shown by a Bloch sphere in which the direction of the qubit is returned to the vertical upward direction.

The magnitude of the second high-frequency power propagated to the second waveguide 12b so as to compensate for the change in the quantum state of the second quantum circuit 11b depends on the physical characteristics of the plurality of materials constituting the quantum circuit system 10 and the first. It may be calculated theoretically based on the arrangement of the 1 waveguide 12a and the 2nd waveguide 12b, or it may be experimentally determined by actually operating the quantum circuit system 10.

In this way, when the first quantum circuit 11a is changed to a predetermined quantum state, the change in the quantum state of the second quantum circuit 11b can be compensated, and the unintended change in the quantum state of the second quantum circuit 11b can be caused. Can be prevented. As a matter of course, by performing the same processing with the high frequency power supply 13 other than the second high frequency power supply 13b, it is possible to prevent an unintended change in the quantum state of the arbitrary quantum circuit 11.

Further, it is possible to compensate for the change in the quantum state of the second quantum circuit 11b at the same time as or after the timing of changing the first quantum circuit 11a to a predetermined quantum state, and the unintended change in the quantum state of the second quantum circuit 11b can be compensated. Can be prevented.

FIG. 5 is a diagram showing a second example of the waveform of the first waveguide 12a, the waveform of the second waveguide 12b, and the quantum state of the second quantum circuit 11b of the quantum circuit system 10 according to the present embodiment. In the figure, a waveform graph showing the relationship between the voltage and time of the first waveguide 12a, a waveform graph showing the relationship between the voltage and time of the second waveguide 12b, and a bloch sphere showing the quantum state of the second quantum circuit 11b. It shows that. In the figure, for the sake of simplicity, the voltage graph of the first waveguide 12a and the second waveguide 12b is shown, but the high frequency pulse propagates to the first waveguide 12a and the second waveguide 12b. Therefore, electric power that is not clearly separated into voltage and current is propagated.

In the following, when the first high frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, the change in the quantum state of the second quantum circuit 11b is compensated for. An example of propagating the second high-frequency power to the two waveguides 12b will be described, but the relationship may be reversed. That is, when high-frequency power is propagated to the second waveguide 12b to change the second quantum circuit 11b to a predetermined quantum state, the first waveguide is compensated for the change in the quantum state of the first quantum circuit 11a. High frequency power may be propagated to 12a. Further, the same processing may be performed between the second waveguide 12b and the third waveguide 12c, or the same processing may be performed between the third waveguide 12c and the fourth waveguide 12d. ..

When the first high-frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, a relatively large first high-frequency power is input to the first waveguide 12a, and the first waveguide A leaking electromagnetic field is generated around 12a. Then, due to the influence of the leaking electromagnetic field, unintended high-frequency power propagates to the second waveguide 12b adjacent to the first waveguide 12a, and the quantum state of the second quantum circuit 11b changes.

The second high-frequency power source 13b directly or indirectly propagates the second high-frequency power to the second waveguide 12b so as to compensate for the change in the quantum state of the second quantum circuit 11b. In the case of this example, the second high-frequency power supply 13b directly compensates for the change in the quantum state of the second quantum circuit 11b at the same time as the timing at which the first high-frequency power is propagated to the first waveguide 12a. The second high frequency power is propagated in the second waveguide 12b. FIG. 5 shows that the quantum state of the second quantum circuit 11b does not change before and after the first high-frequency power is input by the Bloch sphere in which the direction of the qubit remains vertically upward and does not change. ..

In this way, when the first quantum circuit 11a is changed to a predetermined quantum state, the change in the quantum state of the second quantum circuit 11b can be compensated, and the unintended change in the quantum state of the second quantum circuit 11b can be caused. Can be prevented. As a matter of course, by performing the same processing with the high frequency power supply 13 other than the second high frequency power supply 13b, it is possible to prevent an unintended change in the quantum state of the arbitrary quantum circuit 11.

Further, it is possible to compensate for the change in the quantum state of the second quantum circuit 11b at the same time as or after the timing of changing the first quantum circuit 11a to a predetermined quantum state, and the unintended change in the quantum state of the second quantum circuit 11b can be compensated. Can be prevented.

FIG. 6 is a diagram showing a third example of the waveform of the first waveguide 12a, the waveform of the second waveguide 12b, and the quantum state of the second quantum circuit 11b of the quantum circuit system 10 according to the present embodiment. In the figure, a waveform graph showing the relationship between the voltage and time of the first waveguide 12a, a waveform graph showing the relationship between the voltage and time of the second waveguide 12b, and a bloch sphere showing the quantum state of the second quantum circuit 11b. It shows that. In the figure, for the sake of simplicity, the voltage graph of the first waveguide 12a and the second waveguide 12b is shown, but the high frequency pulse propagates to the first waveguide 12a and the second waveguide 12b. Therefore, electric power that is not clearly separated into voltage and current is propagated.

In the following, when the first high frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, the change in the quantum state of the second quantum circuit 11b is compensated for. An example of propagating the second high-frequency power to the two waveguides 12b will be described, but the relationship may be reversed. That is, when high-frequency power is propagated to the second waveguide 12b to change the second quantum circuit 11b to a predetermined quantum state, the first waveguide is compensated for the change in the quantum state of the first quantum circuit 11a. High frequency power may be propagated to 12a. Further, the same processing may be performed between the second waveguide 12b and the third waveguide 12c, or the same processing may be performed between the third waveguide 12c and the fourth waveguide 12d. ..

When the first high-frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, a relatively large first high-frequency power is input to the first waveguide 12a, and the first waveguide A leaking electromagnetic field is generated around 12a. Then, due to the influence of the leaking electromagnetic field, unintended high-frequency power propagates to the second waveguide 12b adjacent to the first waveguide 12a, and the quantum state of the second quantum circuit 11b changes. In FIG. 6, a state in which the quantum state of the second quantum circuit 11b changes due to the influence of the leaking electromagnetic field is shown by a Bloch sphere in which the direction of the qubit is tilted.

The second high-frequency power supply 13b has a high-frequency power that compensates for a change in the quantum state of the second quantum circuit 11b due to propagation of the first high-frequency power through the first waveguide 12a, and a predetermined quantum state of the second quantum circuit 11b. The second high-frequency power, which is a superposition with the high-frequency power that is changed to, is directly or indirectly propagated to the second waveguide 12b. In the case of this example, the second high-frequency power supply 13b propagates the first high-frequency power to the first waveguide 12a after the timing at which the first high-frequency power is propagated to the first waveguide 12a, so that the second quantum The second high-frequency power, which is the superposition of the high-frequency power that compensates for the change in the quantum state of the circuit 11b and the high-frequency power that changes the second quantum circuit 11b to a predetermined quantum state, is directly applied to the second waveguide 12b. It is propagated to. In FIG. 6, the second high-frequency power whose pulse height is lowered by δ due to compensation is illustrated, and the quantum state of the second quantum circuit 11b is changed to a predetermined quantum state horizontally to the right by the second high-frequency power including compensation. It is shown by the Bloch sphere that changed to. It should be noted that such a transform corresponds to a transform in which the Hadamard gate acts to change to a predetermined quantum state of (| 0> + | 1>) / √2 when the initial quantum state is | 0>. do.

The magnitude δ of the compensation may be theoretically calculated based on the physical characteristics of the plurality of materials constituting the quantum circuit system 10 and the arrangement of the first waveguide 12a and the second waveguide 12b. The quantum circuit system 10 may be put into operation and determined experimentally.

In this way, while compensating for the change in the quantum state of the second quantum circuit 11b caused by changing the first quantum circuit 11a to a predetermined quantum state, the quantum state of the second quantum circuit 11b is changed to a predetermined quantum state. Can be changed.

FIG. 7 is a diagram showing a fourth example of the waveform of the first waveguide 12a, the waveform of the second waveguide 12b, and the quantum state of the second quantum circuit 11b of the quantum circuit system 10 according to the present embodiment. In the figure, a waveform graph showing the relationship between the voltage and time of the first waveguide 12a, a waveform graph showing the relationship between the voltage and time of the second waveguide 12b, and a bloch sphere showing the quantum state of the second quantum circuit 11b. It shows that. In the figure, for the sake of simplicity, the voltage graph of the first waveguide 12a and the second waveguide 12b is shown, but the high frequency pulse propagates to the first waveguide 12a and the second waveguide 12b. Therefore, electric power that is not clearly separated into voltage and current is propagated.

When the first high-frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, a relatively large first high-frequency power is input to the first waveguide 12a, and the first waveguide A leaking electromagnetic field is generated around 12a. Then, due to the influence of the leaking electromagnetic field, unintended high-frequency power propagates to the second waveguide 12b adjacent to the first waveguide 12a, and the quantum state of the second quantum circuit 11b changes. In FIG. 7, a state in which the quantum state of the second quantum circuit 11b changes due to the influence of the leaking electromagnetic field is shown by a Bloch sphere in which the direction of the qubit is tilted.

The first high-frequency power source 13a indirectly propagates the second high-frequency power to the second waveguide 12b so as to compensate for the change in the quantum state of the second quantum circuit 11b. In the case of this example, the first high-frequency power supply 13a indirectly compensates for the change in the quantum state of the second quantum circuit 11b after the timing at which the first high-frequency power is propagated to the first waveguide 12a. , The second high frequency power is propagated to the second waveguide 12b. More specifically, the first high-frequency power supply 13a compensates for the change in the quantum state of the second quantum circuit 11b after the timing when the first high-frequency power is propagated to the first waveguide 12a. High-frequency power having a phase opposite to that of high-frequency power is propagated to the first waveguide 12a, and the second high-frequency power is indirectly propagated to the second waveguide 12b by the leakage electromagnetic field. In FIG. 7, the quantum state of the second quantum circuit 11b after compensation is shown by a Bloch sphere in which the direction of the qubit is returned to the vertical upward direction.

The magnitude of the high-frequency power having a phase opposite to that of the first high-frequency power propagated in the first waveguide 12a so as to compensate for the change in the quantum state of the second quantum circuit 11b is determined by the plurality of materials constituting the quantum circuit system 10. It may be calculated theoretically based on the physical characteristics and the arrangement of the first waveguide 12a and the second waveguide 12b, or it may be experimentally determined by actually operating the quantum circuit system 10.

In this way, when the first quantum circuit 11a is changed to a predetermined quantum state, the change in the quantum state of the second quantum circuit 11b can be compensated, and the unintended change in the quantum state of the second quantum circuit 11b can be caused. Can be prevented.

FIG. 8 is a diagram showing a configuration of a quantum circuit system 10a according to a first modification of the present embodiment. The quantum circuit system 10a according to the first modification is the first quantum circuit 11a and the second quantum circuit 11b having at least two quantum states, respectively, and the first waveguide 12a electromagnetically connected to the first quantum circuit 11a. And a second waveguide 12b electromagnetically connected to the second quantum circuit 11b. Further, the quantum circuit system 10a according to the first modification includes a second auxiliary waveguide 15b extending along the second waveguide 12b. Further, in the quantum circuit system 10a according to the first modification, when the first high frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a into a predetermined quantum state, the second quantum circuit 11b A second auxiliary high frequency power supply 16b that propagates the third high frequency power to the second auxiliary waveguide 15b and indirectly propagates the second high frequency power to the second auxiliary waveguide 12b so as to compensate for the change in the quantum state. Be prepared.

The quantum circuit system 10a according to the first modification is a change in the quantum state of the first quantum circuit 11a when the high frequency power is propagated to the second waveguide 12b to change the second quantum circuit 11b to a predetermined quantum state. A first auxiliary high-frequency power source 16a that propagates high-frequency power to the first auxiliary waveguide 15a and indirectly propagates high-frequency power to the first auxiliary waveguide 12a is provided so as to compensate for the above.

In the present specification, a plurality of auxiliary waveguides including the first auxiliary waveguide 15a and the second auxiliary waveguide 15b are simply referred to as auxiliary waveguides 15. Further, a plurality of auxiliary high frequency power supplies including the first auxiliary high frequency power supply 16a and the second auxiliary high frequency power supply 16b are simply referred to as auxiliary high frequency power supplies 16.

Note that FIG. 8 relates to a first variation example including two quantum circuits 11, two waveguides 12, two high frequency power supplies 13, two auxiliary waveguides 15, and two auxiliary high frequency power supplies 16. Although the quantum circuit system 10a is illustrated, the number of the quantum circuit 11, the waveguide 12, the high frequency power supply 13, the auxiliary waveguide 15, and the auxiliary high frequency power supply 16 is arbitrary.

FIG. 9 is a diagram showing a first example of the waveform of the first waveguide 12a, the waveform of the second waveguide 12b, and the quantum state of the second quantum circuit 11b of the quantum circuit system 10a according to the first modification of the present embodiment. Is. In the figure, a waveform graph showing the relationship between the voltage and time of the first waveguide 12a, a waveform graph showing the relationship between the voltage and time of the second waveguide 12b, and an auxiliary waveguide (second auxiliary waveguide 15b). A waveform graph showing the relationship between voltage and time and a Bloch sphere showing the quantum state of the second quantum circuit 11b are shown. In the figure, for the sake of simplicity, the voltage graphs of the first waveguide 12a, the second waveguide 12b, and the second auxiliary waveguide 15b are shown, but the first waveguide 12a and the second waveguide 12b are shown. And it is the high frequency pulse that propagates in the second auxiliary waveguide 15b, and the electric power that is not clearly separated into the voltage and the current propagates.

In the following, when the first high frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, the change in the quantum state of the second quantum circuit 11b is compensated for. An example of propagating the third high-frequency power to the auxiliary waveguide 15b will be described, but this relationship may be reversed. That is, when high-frequency power is propagated through the second waveguide 12b to change the second quantum circuit 11b to a predetermined quantum state, the first auxiliary guide is compensated for the change in the quantum state of the first quantum circuit 11a. High frequency power may be propagated through the waveguide 15a.

When the first high-frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, a relatively large first high-frequency power is input to the first waveguide 12a, and the first waveguide A leaking electromagnetic field is generated around 12a. Then, due to the influence of the leaking electromagnetic field, unintended high-frequency power propagates to the second waveguide 12b adjacent to the first waveguide 12a, and the quantum state of the second quantum circuit 11b changes. In FIG. 9, a state in which the quantum state of the second quantum circuit 11b changes due to the influence of the leaking electromagnetic field is shown by a Bloch sphere in which the direction of the qubit is tilted.

The second auxiliary high frequency power supply 16b propagates the third high frequency power to the second auxiliary waveguide 15b so as to compensate for the change in the quantum state of the second quantum circuit 11b, and indirectly to the second waveguide 12b. 2 Propagate high frequency power. More specifically, in the case of this example, the second auxiliary high-frequency power supply 16b compensates for the change in the quantum state of the second quantum circuit 11b after the timing at which the first high-frequency power is propagated to the first waveguide 12a. As such, the third high-frequency power is propagated to the second auxiliary waveguide 15b, and the second high-frequency power is indirectly propagated to the second waveguide 12b. In FIG. 9, the quantum state of the second quantum circuit 11b after compensation is shown by a Bloch sphere in which the direction of the qubit is returned vertically upward.

The magnitude of the third high-frequency power propagated to the second auxiliary waveguide 15b so as to compensate for the change in the quantum state of the second quantum circuit 11b depends on the physical characteristics of the plurality of materials constituting the quantum circuit system 10 and the physical characteristics of the plurality of materials. It may be calculated theoretically based on the arrangement of the first waveguide 12a, the second waveguide 12b, and the second auxiliary waveguide 15b, or the quantum circuit system 10a according to the first modification may be put into operation experimentally. It may be set to.

In this way, when the first quantum circuit 11a is changed to a predetermined quantum state, the change in the quantum state of the second quantum circuit 11b is compensated without directly propagating the high frequency power to the second waveguide 12b. Can be done.

FIG. 10 is a diagram showing a second example of the waveform of the first waveguide 12a, the waveform of the second waveguide 12b, and the quantum state of the second quantum circuit 11b of the quantum circuit system 10a according to the first modification of the present embodiment. Is. In the figure, a waveform graph showing the relationship between the voltage and time of the first waveguide 12a, a waveform graph showing the relationship between the voltage and time of the second waveguide 12b, and an auxiliary waveguide (second auxiliary waveguide 15b). A waveform graph showing the relationship between voltage and time and a Bloch sphere showing the quantum state of the second quantum circuit 11b are shown. In the figure, for the sake of simplicity, the voltage graphs of the first waveguide 12a, the second waveguide 12b, and the second auxiliary waveguide 15b are shown, but the first waveguide 12a and the second waveguide 12b are shown. And it is the high frequency pulse that propagates in the second auxiliary waveguide 15b, and the electric power that is not clearly separated into the voltage and the current propagates.

In the following, when the first high frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, the change in the quantum state of the second quantum circuit 11b is compensated for. An example of propagating the third high-frequency power to the auxiliary waveguide 15b will be described, but this relationship may be reversed. That is, when high-frequency power is propagated through the second waveguide 12b to change the second quantum circuit 11b to a predetermined quantum state, the first auxiliary guide is compensated for the change in the quantum state of the first quantum circuit 11a. High frequency power may be propagated through the waveguide 15a.

When the first high-frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, a relatively large first high-frequency power is input to the first waveguide 12a, and the first waveguide A leaking electromagnetic field is generated around 12a. Then, due to the influence of the leaking electromagnetic field, unintended high-frequency power propagates to the second waveguide 12b adjacent to the first waveguide 12a, and the quantum state of the second quantum circuit 11b changes. In FIG. 10, a state in which the quantum state of the second quantum circuit 11b changes due to the influence of the leaking electromagnetic field is shown by a Bloch sphere in which the direction of the qubit is tilted.

The second auxiliary high frequency power supply 16b propagates the third high frequency power to the second auxiliary waveguide 15b so as to compensate for the change in the quantum state of the second quantum circuit 11b, and indirectly to the second waveguide 12b. 2 Propagate high frequency power. More specifically, in the case of this example, the second auxiliary high frequency power supply 16b compensates for the change in the quantum state of the second quantum circuit 11b at the same time as the timing when the first high frequency power is propagated to the first waveguide 12a. As described above, the third high-frequency power is propagated to the second auxiliary waveguide 15b, and the second high-frequency power is indirectly propagated to the second waveguide 12b. In FIG. 10, the fact that the quantum state of the second quantum circuit 11b does not change before and after the first high-frequency power is input is shown by the Bloch sphere in which the direction of the qubit remains vertically upward and does not change. ..

The magnitude of the third high-frequency power propagated to the second auxiliary waveguide 15b so as to compensate for the change in the quantum state of the second quantum circuit 11b depends on the physical characteristics of the plurality of materials constituting the quantum circuit system 10 and the physical characteristics of the plurality of materials. It may be calculated theoretically based on the arrangement of the first waveguide 12a, the second waveguide 12b, and the second auxiliary waveguide 15b, or the quantum circuit system 10a according to the first modification may be put into operation experimentally. It may be set to.

In this way, when the first quantum circuit 11a is changed to a predetermined quantum state, the change in the quantum state of the second quantum circuit 11b is compensated without directly propagating the high frequency power to the second waveguide 12b. Can be done.

FIG. 11 is a diagram showing a configuration of a quantum circuit system 10b according to a second modification of the present embodiment. The quantum circuit system 10b according to the second modification is the first quantum circuit 11a and the second quantum circuit 11b having at least two quantum states, respectively, and the first waveguide 12a electromagnetically connected to the first quantum circuit 11a. And a second waveguide 12b electromagnetically connected to the second quantum circuit 11b. Further, the quantum circuit system 10b according to the second modification includes a second auxiliary waveguide 15b extending along the second waveguide 12b. Further, in the quantum circuit system 10b according to the second modification, when the first high frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a into a predetermined quantum state, the second quantum circuit 11b A second auxiliary high frequency power supply 16b that propagates the third high frequency power to the second auxiliary waveguide 15b and indirectly propagates the second high frequency power to the second auxiliary waveguide 12b so as to compensate for the change in the quantum state. Be prepared.

The quantum circuit system 10b according to the second modification is a change in the quantum state of the first quantum circuit 11a when the high frequency power is propagated to the second waveguide 12b to change the second quantum circuit 11b to a predetermined quantum state. A first auxiliary high-frequency power source 16a that propagates high-frequency power to the first auxiliary waveguide 15a and indirectly propagates high-frequency power to the first auxiliary waveguide 12a is provided so as to compensate for the above.

In the quantum circuit system 10b according to the second modification, the second auxiliary waveguide 15b has a first portion 151b and a second portion 152b extending along the second waveguide 12b, and a first portion 151b and a second portion 152b. Includes a folded portion 153b and a folded portion for connecting the above. Further, the first auxiliary waveguide 15a includes a first portion 151a and a second portion 152a extending along the first waveguide 12a, and a folded-back portion 153a connecting the first portion 151a and the second portion 152a.

In this way, by configuring the auxiliary waveguide 15 with the first portion 151, the second portion 152, and the folded portion 153, the first portion 151 in which a relatively uniform electromagnetic field is generated can be adjacent to the waveguide 12. Therefore, when the third high-frequency power is propagated to the auxiliary waveguide 15, the second high-frequency power can be propagated to the second waveguide more accurately.

Note that FIG. 11 relates to a second modification including two quantum circuits 11, two waveguides 12, two high frequency power supplies 13, two auxiliary waveguides 15, and two auxiliary high frequency power supplies 16. Although the quantum circuit system 10b is illustrated, the number of the quantum circuit 11, the waveguide 12, the high frequency power supply 13, the auxiliary waveguide 15, and the auxiliary high frequency power supply 16 is arbitrary.

FIG. 12 is a diagram showing a configuration of a quantum circuit system 10c according to a third modification of the present embodiment. The quantum circuit system 10c according to the third modification is the first quantum circuit 11a and the second quantum circuit 11b having at least two quantum states, respectively, and the first waveguide 12a electromagnetically connected to the first quantum circuit 11a. And a second waveguide 12b electromagnetically connected to the second quantum circuit 11b. Further, the quantum circuit system 10c according to the third modification includes a second auxiliary waveguide 15b extending along the second waveguide 12b. Further, in the quantum circuit system 10c according to the third modification, when the first high frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a into a predetermined quantum state, the second quantum circuit 11b A second auxiliary high frequency power supply 16b that propagates the third high frequency power to the second auxiliary waveguide 15b and indirectly propagates the second high frequency power to the second auxiliary waveguide 12b so as to compensate for the change in the quantum state. Be prepared.

The quantum circuit system 10c according to the third modification is a change in the quantum state of the first quantum circuit 11a when the high frequency power is propagated to the second waveguide 12b to change the second quantum circuit 11b to a predetermined quantum state. A first auxiliary high-frequency power source 16a that propagates high-frequency power to the first auxiliary waveguide 15a and indirectly propagates high-frequency power to the first auxiliary waveguide 12a is provided so as to compensate for the above.

In the quantum circuit system 10c according to the third modification, the first quantum circuit 11a, the second quantum circuit 11b, the first waveguide 12a, the second waveguide 12b, the first high frequency power supply 13a, the second high frequency power supply 13b, and the first A plurality of configurations having the auxiliary waveguide 15a, the second auxiliary waveguide 15b, the first auxiliary high frequency power supply 16a, and the second auxiliary high frequency power supply 16b as one unit are arranged side by side.

More specifically, in the quantum circuit system 10c according to the third modification, the waveguide 12 has the above-mentioned one-unit configuration so that the positions where the high-frequency power supply 13 is provided are opposite to each other with the quantum circuit 11 in between. Are arranged adjacent to each other in a direction orthogonal to the extending direction. With such an arrangement, the area of the substrate on which the plurality of quantum circuits 11 are provided can be efficiently used, and the auxiliary waveguide 15 can compensate for unintended changes in the quantum state of the quantum circuits 11.

Note that FIG. 12 relates to a third modification including eight quantum circuits 11, eight waveguides 12, eight high frequency power supplies 13, eight auxiliary waveguides 15, and eight auxiliary high frequency power supplies 16. Although the quantum circuit system 10c is illustrated, the number of the quantum circuit 11, the waveguide 12, the high frequency power supply 13, the auxiliary waveguide 15, and the auxiliary high frequency power supply 16 is arbitrary.

FIG. 13 is a diagram showing a configuration of a quantum circuit system 10d according to a fourth modification of the present embodiment. The quantum circuit system 10d according to the fourth modification has a first quantum circuit 11a and a second quantum circuit 11b having at least two quantum states, respectively, and a first waveguide 12a electromagnetically connected to the first quantum circuit 11a. And a second waveguide 12b electromagnetically connected to the second quantum circuit 11b. Further, the quantum circuit system 10d according to the fourth modification includes a second auxiliary waveguide 15b extending along the second waveguide 12b. Further, in the quantum circuit system 10d according to the fourth modification, when the first high frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, the second quantum circuit 11b A second auxiliary high frequency power supply 16b that propagates the third high frequency power to the second auxiliary waveguide 15b and indirectly propagates the second high frequency power to the second auxiliary waveguide 12b so as to compensate for the change in the quantum state. Be prepared.

The quantum circuit system 10d according to the fourth modification is a change in the quantum state of the first quantum circuit 11a when the high frequency power is propagated to the second waveguide 12b to change the second quantum circuit 11b to a predetermined quantum state. A first auxiliary high-frequency power source 16a that propagates high-frequency power to the first auxiliary waveguide 15a and indirectly propagates high-frequency power to the first auxiliary waveguide 12a is provided so as to compensate for the above.

In the quantum circuit system 10d according to the fourth modification, the first quantum circuit 11a, the second quantum circuit 11b, the first waveguide 12a, the second waveguide 12b, the first high frequency power supply 13a, the second high frequency power supply 13b, and the first A plurality of configurations having the auxiliary waveguide 15a, the second auxiliary waveguide 15b, the first auxiliary high frequency power supply 16a, and the second auxiliary high frequency power supply 16b as one unit are arranged side by side.

More specifically, in the quantum circuit system 10d according to the fourth modification, the waveguide 12 extends radially, and the position where the high frequency power supply 13 is provided is arranged by rotating 90 ° around the position of the quantum circuit 11. A plurality of the above-mentioned one-unit configurations are arranged so as to be performed. With such an arrangement, the area of the substrate on which the plurality of quantum circuits 11 are provided can be efficiently used, and the auxiliary waveguide 15 can compensate for unintended changes in the quantum state of the quantum circuits 11.

Note that FIG. 13 relates to a fourth modification including eight quantum circuits 11, eight waveguides 12, eight high frequency power supplies 13, eight auxiliary waveguides 15, and eight auxiliary high frequency power supplies 16. Although the quantum circuit system 10d is illustrated, the number of the quantum circuit 11, the waveguide 12, the high frequency power supply 13, the auxiliary waveguide 15, and the auxiliary high frequency power supply 16 is arbitrary.

FIG. 14 is a diagram showing a configuration of a quantum circuit system 10e according to a fifth modification of the present embodiment. The quantum circuit system 10e according to the fifth modification is the first quantum circuit 11a and the second quantum circuit 11b having at least two quantum states, respectively, and the first waveguide 12a electromagnetically connected to the first quantum circuit 11a. And a second waveguide 12b electromagnetically connected to the second quantum circuit 11b. Further, the quantum circuit system 10e according to the fifth modification includes a second auxiliary waveguide 15b extending along the second waveguide 12b. Further, in the quantum circuit system 10e according to the fifth modification, when the first high frequency power is propagated to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, the second quantum circuit 11b A second auxiliary high frequency power supply 16b that propagates the third high frequency power to the second auxiliary waveguide 15b and indirectly propagates the second high frequency power to the second auxiliary waveguide 12b so as to compensate for the change in the quantum state. Be prepared.

The quantum circuit system 10e according to the fifth modification is a change in the quantum state of the first quantum circuit 11a when the high frequency power is propagated to the second waveguide 12b to change the second quantum circuit 11b to a predetermined quantum state. A first auxiliary high-frequency power source 16a that propagates high-frequency power to the first auxiliary waveguide 15a and indirectly propagates high-frequency power to the first auxiliary waveguide 12a is provided so as to compensate for the above.

Further, the quantum circuit system 10e according to the fifth modification has a first read line 14a for reading the quantum state of the first quantum circuit 11a and a second read line 14b for reading the quantum state of the second quantum circuit 11b. And. The first read-out line 14a may be connected between the _{input capacitor C in} and the gate capacitor C _g included in the first quantum circuit 11a via the output capacitor. Similarly, the second readout line 14b may be connected between the _{input capacitor C in} and the gate capacitor C _g included in the second quantum circuit 11b via the output capacitor. The output capacitor may also serve as the _{input capacitor C in.}

In the quantum circuit system 10e according to the fifth modification, the first quantum circuit 11a, the second quantum circuit 11b, the first waveguide 12a, the second waveguide 12b, the first high frequency power supply 13a, the second high frequency power supply 13b, and the first A plurality of configurations having the auxiliary waveguide 15a, the second auxiliary waveguide 15b, the first auxiliary high frequency power supply 16a, and the second auxiliary high frequency power supply 16b as one unit are arranged side by side.

More specifically, in the quantum circuit system 10e according to the fifth modification, the waveguide 12 has the above-mentioned one-unit configuration so that the positions where the high-frequency power supply 13 is provided are opposite to each other with the quantum circuit 11 in between. Are arranged adjacent to each other in a direction orthogonal to the extending direction. With such an arrangement, the area of the substrate on which the plurality of quantum circuits 11 are provided can be efficiently used, and the auxiliary waveguide 15 can compensate for unintended changes in the quantum state of the quantum circuits 11.

In FIG. 14, four quantum circuits 11, four waveguides 12, four high-frequency power supplies 13, four auxiliary waveguides 15, four auxiliary high-frequency power supplies 16, and four readout lines 14 are shown. Although the quantum circuit system 10e according to the fifth modification is illustrated, the number of the quantum circuit 11, the waveguide 12, the high frequency power supply 13, the auxiliary waveguide 15, the auxiliary high frequency power supply 16, and the four readout lines 14 is arbitrary. be.

The embodiments described above are for facilitating the understanding of the present invention, and are not for limiting and interpreting the present invention. Each element included in the embodiment and its arrangement, material, condition, shape, size, and the like are not limited to those exemplified, and can be changed as appropriate. In addition, the configurations shown in different embodiments can be partially replaced or combined.

Claims (5)

A first quantum circuit and a second quantum circuit having at least two quantum states, respectively,
A first waveguide electromagnetically connected to the first quantum circuit and a second waveguide electromagnetically connected to the second quantum circuit.
Directly or indirectly so as to compensate for the change in the quantum state of the second quantum circuit when the first high-frequency power is propagated through the first waveguide to change the first quantum circuit to a predetermined quantum state. A high-frequency power supply that propagates the second high-frequency power to the second waveguide,
Quantum circuit system with. The high-frequency power supply directly or indirectly compensates for the change in the quantum state of the second quantum circuit after the timing at which the first high-frequency power is propagated to the first waveguide. Propagating the second high frequency power through the waveguide,
The quantum circuit system according to claim 1. The high-frequency power supply has high-frequency power that compensates for a change in the quantum state of the second quantum circuit due to propagation of the first high-frequency power to the first waveguide, and brings the second quantum circuit into a predetermined quantum state. The second high-frequency power, which is a superposition with the high-frequency power to be changed, is directly or indirectly propagated to the second waveguide.
The quantum circuit system according to claim 1 or 2. An auxiliary waveguide extending along the second waveguide is further provided.
The high-frequency power supply compensates for the change in the quantum state of the second quantum circuit when the first high-frequency power is propagated to the first waveguide to change the first quantum circuit to a predetermined quantum state. In addition, the third high-frequency power is propagated to the auxiliary waveguide, and indirectly, the second high-frequency power is propagated to the second waveguide.
The quantum circuit system according to claim 1 or 2. The auxiliary waveguide includes a first portion and a second portion extending along the second waveguide, and a folded portion connecting the first portion and the second portion.
The quantum circuit system according to claim 4.

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