JP6651213B1 - Quantum circuit system - Google Patents

Abstract

Provided is a quantum circuit system 10 that can prevent 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 quantum circuit 11a is changed to a predetermined quantum state by transmitting the first high-frequency power to the second waveguide 12b electromagnetically connected to the second quantum circuit 11b, A high-frequency power supply 13b for directly or indirectly transmitting the second high-frequency power to the second waveguide 12b so as to compensate for a change in the quantum state.

Description

  The present invention relates to a quantum circuit system.

  In recent years, research has been advanced toward the practical use of quantum computers. For example, in Non-Patent Document 1 below, a quantum circuit called a transmon is proposed. Transmons have high electrical noise immunity and have relatively long relaxation times.

  Further, Patent Document 1 described below discloses a quantum information processing system including a waveguide having an opening, a non-linear quantum circuit disposed in the waveguide, and an electromagnetic field source coupled to the opening.

  In addition, U.S. Patent No. 6,064,086 discloses a non-interrupted elongated thin film by a Josephson junction and a superconducting quantum interference device (SQUID) in electrical contact with the proximal end of the elongated thin film, wherein less than three Josephson A superconducting quantum interference device (SQUID) with a junction and a ground plane coplanar with the elongated membrane and in electrical contact with the distal end of the elongated membrane, wherein the membrane, SQUID and ground plane are designed A qubit device is described that includes a material that becomes superconducting at a specified 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

JP-A-2006-510497 JP 2018-524795 A

  The quantum state of a quantum circuit such as a transmon is sometimes manipulated by propagating high-frequency power through a waveguide connected to the quantum circuit. At this time, the electromagnetic field propagating in the waveguide leaks, and power may also propagate to other waveguides, and the quantum state of the quantum circuit connected to the other waveguide may change unintentionally. is there.

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

  Thus, the present invention provides a quantum circuit system that can prevent an unintended change in the quantum state.

  A quantum circuit system according to one embodiment of the present invention includes a first quantum circuit and a second quantum circuit each having at least two quantum states, a first waveguide and a second quantum circuit electromagnetically connected to the first quantum circuit. A second waveguide that is electromagnetically connected to the circuit, and a first high-frequency power that propagates through the first waveguide to change the first quantum circuit to a predetermined quantum state. 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 changing the first quantum circuit to the 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 aspect, the high-frequency power supply directly or indirectly compensates for a 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 in the wave path.

  According to this aspect, the change of the quantum state of the second quantum circuit can be compensated for at the same time as or after the timing of changing the first quantum circuit to the predetermined quantum state. Changes can be prevented.

  In the above aspect, the high-frequency power supply includes a high-frequency power for compensating a change in a quantum state of the second quantum circuit due to the propagation of the first high-frequency power through the first waveguide, and a change in the second quantum circuit to a predetermined quantum state. The second high-frequency power, which is superimposed on the high-frequency power to be made, 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 the 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 the predetermined quantum state. Can be done.

  In the above aspect, the semiconductor device may further include an auxiliary waveguide extending along the second waveguide, wherein the high-frequency power supply propagates the first high-frequency power to the first waveguide to change the first quantum circuit to a predetermined quantum state. Alternatively, the third high-frequency power may be propagated to the auxiliary waveguide and the second high-frequency power may be indirectly propagated to the second waveguide so as to compensate for a change in the quantum state of the second quantum circuit.

  According to this aspect, when changing the first quantum circuit to the predetermined quantum state, it is possible to compensate for the change in the quantum state of the second quantum circuit without directly transmitting the high-frequency power to the second waveguide. it 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 transmitting the third high-frequency power to the auxiliary waveguide, the second high-frequency power can be more accurately propagated to the second waveguide.

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

FIG. 1 is a diagram illustrating a network configuration of a quantum computation system according to an embodiment of the present invention. FIG. 1 is a diagram illustrating a configuration of a quantum circuit system according to an embodiment. FIG. 2 is a circuit diagram of the quantum circuit according to the embodiment. It is a figure showing the 1st example of the waveform of the 1st waveguide of the quantum circuit system concerning this embodiment, the waveform of the 2nd waveguide, and the quantum state of the 2nd quantum circuit. It is a figure showing the 2nd example of the waveform of the 1st waveguide of the quantum circuit system concerning this embodiment, the waveform of the 2nd waveguide, and the quantum state of the 2nd quantum circuit. It is a figure showing the 3rd example of the waveform of the 1st waveguide of the quantum circuit system concerning this embodiment, the waveform of the 2nd waveguide, and the quantum state of the 2nd quantum circuit. It is a figure showing the 4th example of the waveform of the 1st waveguide of the quantum circuit system concerning this embodiment, the waveform of the 2nd waveguide, and the quantum state of the 2nd quantum circuit. FIG. 9 is a diagram illustrating a configuration of a quantum circuit system according to a first modification of the present embodiment. It is a figure showing the 1st example of the waveform of the 1st waveguide of the quantum circuit system concerning the 1st modification of this embodiment, the waveform of the 2nd waveguide, and the quantum state of the 2nd quantum circuit. FIG. 11 is a diagram illustrating a second example of the waveform of the first waveguide, the waveform of the second waveguide, and the quantum state of the second quantum circuit in the quantum circuit system according to the first modification of the embodiment. FIG. 11 is a diagram illustrating a configuration of a quantum circuit system according to a second modification of the present embodiment. FIG. 11 is a diagram illustrating a configuration of a quantum circuit system according to a third modification of the present embodiment. FIG. 14 is a diagram illustrating a configuration of a quantum circuit system according to a fourth modification of the present embodiment. It is a figure showing the composition of the quantum circuit system concerning the 5th modification of this embodiment.

  An embodiment of the present invention will be described with reference to the accompanying drawings. In each of the drawings, the components denoted by the same reference numerals have the same or similar configurations.

  FIG. 1 is a diagram illustrating a network configuration of a quantum computation system 100 according to an embodiment of the present invention. The quantum computation system 100 includes a quantum circuit system 10 and a user terminal 20. The quantum circuit system 10 and the user terminal 20 are communicably connected to each other via a communication network N such as the Internet. A user of the quantum computation system 100 inputs data to the quantum circuit system 10 using a user terminal 20 configured by a general-purpose classical computer, or acquires a result of quantum computation performed by the quantum circuit system 10. .

  FIG. 2 is a diagram illustrating a configuration of the 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. And a second waveguide 12b electromagnetically connected to the second waveguide 12b. The quantum circuit system 10 compensates for a change in the quantum state of the second quantum circuit 11b when the first high-frequency power is propagated through the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state. The second high-frequency power supply 13b for directly or indirectly transmitting the second high-frequency power to the second waveguide 12b is provided. The quantum circuit system 10 compensates for 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 high-frequency power supply 13a for directly or indirectly transmitting high-frequency power 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 circuit electromagnetically connected to the third quantum circuit 11c. A fourth waveguide 12d electromagnetically connected to the circuit 11d. The quantum circuit system 10 compensates for a change in the quantum state of the fourth quantum circuit 11d when the third high-frequency power is propagated through the third waveguide 12c to change the third quantum circuit 11c to a predetermined quantum state. As a result, a fourth high-frequency power supply 13d for directly or indirectly transmitting the fourth high-frequency power to the fourth waveguide 12d is provided. The quantum circuit system 10 also compensates for a change in the quantum state of the third quantum circuit 11c when the high-frequency power is transmitted to the fourth waveguide 12d to change the fourth quantum circuit 11d to a predetermined quantum state. And a third high-frequency power supply 13c for directly or indirectly transmitting high-frequency power to the third waveguide 12c.

  Each of the first quantum circuit 11a, the second quantum circuit 11b, the third quantum circuit 11c, and the fourth quantum circuit 11d may have the same configuration, and may be, for example, a quantum circuit including tranmon. The first waveguide 12a, the second waveguide 12b, the third waveguide 12c, and the fourth waveguide 12d may have the same configuration, 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 have the same configuration, and may include a power supply that outputs a high-frequency pulse of several GHz, for example.

  In this 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 the quantum circuit 11. 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 a waveguide 12, and include a first high-frequency power supply 13a and a 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 a high-frequency power supply 13.

  FIG. 2 illustrates a quantum circuit system 10 including four quantum circuits 11, four waveguides 12, and four high-frequency power sources 13. Is optional. The number of the high-frequency power supplies 13 may be smaller than the number of the quantum circuits 11, and may be connected to the quantum circuit 11 via a duplexer 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.} High frequency power source 13 is connected to one end of the input capacitor C _in, the high-frequency pulse output from the high frequency power source 13 is input to the Toranzumon 111 via the gate capacitor C _g, changing the quantum state of Toranzumon 111. The number of Josephson junctions JJ is not limited to one, and two are connected in parallel to form a dc-SQUID configuration. There may be a case where a plurality of Josephson junctions JJ having different sizes are connected (such as Fluxonium). As described above, the energy potential of the system may be adjusted depending on the purpose depending on the number and size of the Josephson junctions JJ.

  FIG. 4 is a diagram illustrating 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 representing the quantum state of the second quantum circuit 11b. Are shown. In FIG. 1, for simplicity of description, a graph of the voltage of the first waveguide 12a and the voltage of the second waveguide 12b is shown, but the high-frequency pulse propagates to the first waveguide 12a and the second waveguide 12b. Therefore, power that is not clearly separated into voltage and current propagates.

  Hereinafter, when the first high frequency power is propagated through the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, the first quantum circuit 11a is compensated for a change in the quantum state of the second quantum circuit 11b. An example in which the second high frequency power is propagated through the two waveguides 12b will be described, but this relationship may be reversed. That is, when the 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 leakage electromagnetic field is generated around 12a. Then, due to the effect of the leakage 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. 4, a state in which the quantum state of the second quantum circuit 11b changes due to the influence of the leakage electromagnetic field is indicated by a Bloch sphere in which the direction of the qubit is inclined.

  The second high-frequency power supply 13b directly or indirectly propagates the second high-frequency power to the second waveguide 12b so as to compensate for a change in the quantum state of the second quantum circuit 11b. In the case of this example, the second high-frequency power supply 13b is directly or indirectly controlled so as to compensate for a 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. Specifically, 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 a 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. 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 the compensation is indicated by a Bloch sphere in which the direction of the qubit has returned to a vertical upward direction.

  The magnitude of the second high-frequency power transmitted 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 a plurality of materials constituting the quantum circuit system 10 and the second high-frequency power. It may be calculated theoretically based on the arrangement of the first waveguide 12a and the second waveguide 12b, or may be determined experimentally by actually operating the quantum circuit system 10.

  As described above, when the first quantum circuit 11a is changed to a predetermined quantum state, the change of the quantum state of the second quantum circuit 11b can be compensated, and the unintended change of the quantum state of the second quantum circuit 11b can be prevented. Can be prevented. Naturally, by performing the same processing using 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 an arbitrary quantum circuit 11.

  In addition, the change in the quantum state of the second quantum circuit 11b can be compensated for at the same time as or after the timing of changing the first quantum circuit 11a to the predetermined quantum state. Can be prevented.

  FIG. 5 is a diagram illustrating 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 representing the quantum state of the second quantum circuit 11b. Are shown. In FIG. 1, for simplicity of description, a graph of the voltage of the first waveguide 12a and the voltage of the second waveguide 12b is shown, but the high-frequency pulse propagates to the first waveguide 12a and the second waveguide 12b. Therefore, power that is not clearly separated into voltage and current propagates.

  Hereinafter, when the first high frequency power is propagated through the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, the first quantum circuit 11a is compensated for a change in the quantum state of the second quantum circuit 11b. An example in which the second high frequency power is propagated through the two waveguides 12b will be described, but this relationship may be reversed. That is, when the 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 leakage electromagnetic field is generated around 12a. Then, due to the effect of the leakage 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 supply 13b directly or indirectly propagates the second high-frequency power to the second waveguide 12b so as to compensate for a change in the quantum state of the second quantum circuit 11b. In the case of the present example, the second high-frequency power supply 13b directly transmits the first high-frequency power to the first waveguide 12a at the same time as compensating for a change in the quantum state of the second quantum circuit 11b. The second high frequency power is propagated through the second waveguide 12b. In FIG. 5, before and after the input of the first high-frequency power, the fact that the quantum state of the second quantum circuit 11 b has not changed is indicated by a Bloch sphere in which the direction of the qubit remains unchanged vertically upward. .

  As described above, when the first quantum circuit 11a is changed to a predetermined quantum state, the change of the quantum state of the second quantum circuit 11b can be compensated, and the unintended change of the quantum state of the second quantum circuit 11b can be prevented. Can be prevented. Naturally, by performing the same processing using 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 an arbitrary quantum circuit 11.

  In addition, the change in the quantum state of the second quantum circuit 11b can be compensated for at the same time as or after the timing of changing the first quantum circuit 11a to the predetermined quantum state. Can be prevented.

  FIG. 6 is a diagram illustrating 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 representing the quantum state of the second quantum circuit 11b. Are shown. In FIG. 1, for simplicity of description, a graph of the voltage of the first waveguide 12a and the voltage of the second waveguide 12b is shown, but the high-frequency pulse propagates to the first waveguide 12a and the second waveguide 12b. Therefore, power that is not clearly separated into voltage and current propagates.

  Hereinafter, when the first high frequency power is propagated through the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, the first quantum circuit 11a is compensated for a change in the quantum state of the second quantum circuit 11b. An example in which the second high frequency power is propagated through the two waveguides 12b will be described, but this relationship may be reversed. That is, when the 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 leakage electromagnetic field is generated around 12a. Then, due to the effect of the leakage 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, how the quantum state of the second quantum circuit 11b changes due to the influence of the leakage electromagnetic field is shown by a Bloch sphere in which the direction of the qubit is inclined.

  The second high-frequency power supply 13b includes a high-frequency power for compensating a change in the quantum state of the second quantum circuit 11b due to the propagation of the first high-frequency power to the first waveguide 12a, and a second quantum circuit 11b having a predetermined quantum state. The second high-frequency power, which is a superposition with the high-frequency power to be changed to the above, is directly or indirectly propagated to the second waveguide 12b. In the case of this example, the second high-frequency power supply 13b is configured to transmit the second high-frequency power to the first waveguide 12a after the timing of transmitting the first high-frequency power to the first waveguide 12a. The second high frequency power, which is a superposition of the high frequency power for compensating the change in the quantum state of the circuit 11b and the high frequency power for changing the second quantum circuit 11b to a predetermined quantum state, is directly applied to the second waveguide 12b. Is propagated to. FIG. 6 illustrates the second high-frequency power in which the pulse height is reduced by δ due to the compensation, and the second high-frequency power including the compensation causes the quantum state of the second quantum circuit 11b to move in the horizontal right direction, which is the predetermined quantum state. Is shown by the Bloch sphere that has changed to. Note that such a conversion corresponds to a conversion in which, when the initial quantum state is | 0>, a Hadamard gate is operated to change to a predetermined quantum state of (| 0> + | 1>) / √2. I do.

  The magnitude of compensation δ may be theoretically calculated based on the physical characteristics of a 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 experimentally determined by actual operation.

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

  FIG. 7 is a diagram illustrating 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 representing the quantum state of the second quantum circuit 11b. Are shown. In FIG. 1, for simplicity of description, a graph of the voltage of the first waveguide 12a and the voltage of the second waveguide 12b is shown, but the high-frequency pulse propagates to the first waveguide 12a and the second waveguide 12b. Therefore, power that is not clearly separated into voltage and current propagates.

  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 leakage electromagnetic field is generated around 12a. Then, due to the effect of the leakage 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 leakage electromagnetic field is shown by a Bloch sphere in which the direction of the qubit is inclined.

  The first high-frequency power supply 13a indirectly propagates the second high-frequency power to the second waveguide 12b so as to compensate for a 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 a 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. The second high frequency power is propagated through the second waveguide 12b. More specifically, the first high-frequency power supply 13a compensates for a 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 high-frequency power having a phase opposite to that of the 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 the compensation is indicated by a Bloch sphere in which the direction of the qubit has returned vertically upward.

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

  As described above, when the first quantum circuit 11a is changed to a predetermined quantum state, the change of the quantum state of the second quantum circuit 11b can be compensated, and the unintended change of the quantum state of the second quantum circuit 11b can be prevented. Can be prevented.

  FIG. 8 is a diagram illustrating 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 includes 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. In addition, the quantum circuit system 10a according to the first modification includes a second auxiliary waveguide 15b extending along the second waveguide 12b. Furthermore, the quantum circuit system 10a according to the first modified example has a configuration in which the first quantum circuit 11a is changed to a predetermined quantum state by transmitting the first high-frequency power to the first waveguide 12a. A second auxiliary high-frequency power supply 16b for transmitting the third high-frequency power to the second auxiliary waveguide 15b and indirectly transmitting the second high-frequency power to the second waveguide 12b so as to compensate for the change in the quantum state. Prepare.

  The quantum circuit system 10a according to the first modified example changes the quantum state of the first quantum circuit 11a when the second quantum circuit 11b is changed to a predetermined quantum state by transmitting high-frequency power to the second waveguide 12b. And a first auxiliary high-frequency power supply 16a for transmitting high-frequency power to the first auxiliary waveguide 15a and indirectly transmitting high-frequency power to the first waveguide 12a so as to compensate for

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

  Note that FIG. 8 relates to a first modification 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 illustrating 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. It 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 the waveform graph of the auxiliary waveguide (second auxiliary waveguide 15b) are shown. A waveform graph showing the relationship between voltage and time and a Bloch sphere representing a quantum state of the second quantum circuit 11b are shown. In FIG. 3, for simplification of the description, the voltage of the first waveguide 12a, the second waveguide 12b, and the voltage of the second auxiliary waveguide 15b are graphs. However, the first waveguide 12a, the second waveguide 12b High-frequency pulses propagate to the second auxiliary waveguide 15b, and power that is not clearly separated into voltage and current propagates.

  Hereinafter, when the first high frequency power is propagated through the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, the first quantum circuit 11a is compensated for a change in the quantum state of the second quantum circuit 11b. An example in which the third high-frequency power is propagated through the second 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 waveguide is compensated for to compensate for the change in the quantum state of the first quantum circuit 11a. High-frequency power may be propagated through the wave path 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 leakage electromagnetic field is generated around 12a. Then, due to the effect of the leakage 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 leakage electromagnetic field is shown by a Bloch sphere in which the direction of the qubit is inclined.

  The second auxiliary high-frequency power supply 16b transmits the third high-frequency power to the second auxiliary waveguide 15b so as to compensate for a change in the quantum state of the second quantum circuit 11b, and indirectly transmits the third high-frequency power 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 a 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. As a result, the third high-frequency power is transmitted to the second auxiliary waveguide 15b, and the second high-frequency power is indirectly transmitted to the second waveguide 12b. In FIG. 9, the quantum state of the second quantum circuit 11b after the compensation is indicated by a Bloch sphere in which the direction of the qubit has returned vertically upward.

  The magnitude of the third high-frequency power transmitted 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 a plurality of materials constituting the quantum circuit system 10, 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 may be experimentally performed by actually operating the quantum circuit system 10a according to the first modification. May be determined.

  As described above, 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 transmitting the high-frequency power to the second waveguide 12b. Can be.

  FIG. 10 is a diagram illustrating 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. It 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 the waveform graph of the auxiliary waveguide (second auxiliary waveguide 15b) are shown. A waveform graph showing the relationship between voltage and time and a Bloch sphere representing a quantum state of the second quantum circuit 11b are shown. In FIG. 3, for simplification of the description, the voltage of the first waveguide 12a, the second waveguide 12b, and the voltage of the second auxiliary waveguide 15b are plotted, but the first waveguide 12a, the second waveguide 12b High-frequency pulses propagate to the second auxiliary waveguide 15b, and power that is not clearly separated into voltage and current propagates.

  Hereinafter, when the first high frequency power is propagated through the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state, the first quantum circuit 11a is compensated for a change in the quantum state of the second quantum circuit 11b. An example in which the third high-frequency power is propagated through the second 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 waveguide is compensated for to compensate for the change in the quantum state of the first quantum circuit 11a. High-frequency power may be propagated through the wave path 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 leakage electromagnetic field is generated around 12a. Then, due to the effect of the leakage 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 leakage electromagnetic field is shown by a Bloch sphere in which the direction of the qubit is inclined.

  The second auxiliary high-frequency power supply 16b transmits the third high-frequency power to the second auxiliary waveguide 15b so as to compensate for a change in the quantum state of the second quantum circuit 11b, and indirectly transmits the third high-frequency power to the second waveguide 12b. 2 Propagate high frequency power. More specifically, in the case of the present example, the second auxiliary high-frequency power supply 16b compensates for a 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 transmitted 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, before and after the input of the first high-frequency power, the fact that the quantum state of the second quantum circuit 11b has not changed is indicated by a Bloch sphere in which the direction of the qubit does not change while maintaining the vertical upward direction. .

  The magnitude of the third high-frequency power transmitted 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 a plurality of materials constituting the quantum circuit system 10, 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 may be experimentally performed by actually operating the quantum circuit system 10a according to the first modification. May be determined.

  As described above, 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 transmitting the high-frequency power to the second waveguide 12b. Can be.

  FIG. 11 is a diagram illustrating 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 includes 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 10b according to the second modified example includes a second auxiliary waveguide 15b extending along the second waveguide 12b. Further, the quantum circuit system 10b according to the second modified example is configured to transmit the first high-frequency power to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state. A second auxiliary high-frequency power supply 16b for transmitting the third high-frequency power to the second auxiliary waveguide 15b and indirectly transmitting the second high-frequency power to the second waveguide 12b so as to compensate for the change in the quantum state. Prepare.

  The quantum circuit system 10b according to the second modified example changes the quantum state of the first quantum circuit 11a when the second quantum circuit 11b is changed to a predetermined quantum state by transmitting high-frequency power to the second waveguide 12b. And a first auxiliary high-frequency power supply 16a for transmitting high-frequency power to the first auxiliary waveguide 15a and indirectly transmitting high-frequency power to the first waveguide 12a so as to compensate for

  In the quantum circuit system 10b according to the second modification, the second auxiliary waveguide 15b includes 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. And a folded portion 153b for connecting 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 portion 153a connecting the first portion 151a and the second portion 152a.

  Thus, by forming the auxiliary waveguide 15 by the first portion 151, the second portion 152, and the folded portion 153, the first portion 151 where a relatively uniform electromagnetic field is generated around the first portion 151 can be adjacent to the waveguide 12. Thus, when the third high-frequency power is propagated to the auxiliary waveguide 15, the second high-frequency power can be more accurately propagated to the second waveguide.

  Note that FIG. 11 relates to a second modified 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 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 illustrating 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 includes 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 10c according to the third modification includes a second auxiliary waveguide 15b extending along the second waveguide 12b. Further, the quantum circuit system 10c according to the third modified example is configured to transmit the first high-frequency power to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state. A second auxiliary high-frequency power supply 16b for transmitting the third high-frequency power to the second auxiliary waveguide 15b and indirectly transmitting the second high-frequency power to the second waveguide 12b so as to compensate for the change in the quantum state. Prepare.

  The quantum circuit system 10c according to the third modification changes the quantum state of the first quantum circuit 11a when the second quantum circuit 11b is changed to a predetermined quantum state by transmitting high-frequency power to the second waveguide 12b. And a first auxiliary high-frequency power supply 16a for transmitting high-frequency power to the first auxiliary waveguide 15a and indirectly transmitting high-frequency power to the first waveguide 12a so as to compensate for

  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, the first A plurality of configurations each including 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 are arranged side by side.

  More specifically, in the quantum circuit system 10c according to the third modification, the configuration of one unit is such that the waveguides 12 are arranged such that the position where the high-frequency power supply 13 is provided is on the opposite side of the quantum circuit 11 therebetween. Are arranged adjacent to each other in a direction perpendicular to the direction in which the film is stretched. With such an arrangement, the substrate area on which the plurality of quantum circuits 11 are provided can be efficiently used, and the auxiliary waveguide 15 can compensate for an unintended change in the quantum state occurring in the quantum circuit 11.

  FIG. 12 relates to a third modified example 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 illustrating a configuration of a quantum circuit system 10d according to a fourth modification of the present embodiment. A quantum circuit system 10d according to a fourth modification includes 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. The quantum circuit system 10d according to the fourth modification includes a second auxiliary waveguide 15b extending along the second waveguide 12b. Further, the quantum circuit system 10d according to the fourth modified example is configured to transmit the first high-frequency power to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state. A second auxiliary high-frequency power supply 16b for transmitting the third high-frequency power to the second auxiliary waveguide 15b and indirectly transmitting the second high-frequency power to the second waveguide 12b so as to compensate for the change in the quantum state. Prepare.

  The quantum circuit system 10d according to the fourth modified example changes the quantum state of the first quantum circuit 11a when transmitting the high-frequency power to the second waveguide 12b to change the second quantum circuit 11b to a predetermined quantum state. And a first auxiliary high-frequency power supply 16a that propagates high-frequency power to the first auxiliary waveguide 15a and indirectly propagates high-frequency power to the first waveguide 12a so as to compensate for this.

  In a quantum circuit system 10d according to a fourth modification, a first quantum circuit 11a, a second quantum circuit 11b, a first waveguide 12a, a second waveguide 12b, a first high-frequency power supply 13a, a second high-frequency power supply 13b, a first A plurality of configurations each including 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 are arranged side by side.

  More specifically, in the quantum circuit system 10d according to the fourth modified example, the waveguide 12 extends radially, and the position where the high-frequency power supply 13 is provided is rotated by 90 ° around the position of the quantum circuit 11 and arranged. As shown in FIG. With such an arrangement, the substrate area on which the plurality of quantum circuits 11 are provided can be efficiently used, and the auxiliary waveguide 15 can compensate for an unintended change in the quantum state occurring in the quantum circuit 11.

  Note that FIG. 13 relates to a fourth modified example 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 illustrating 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 includes 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 10e according to the fifth modification includes a second auxiliary waveguide 15b extending along the second waveguide 12b. Furthermore, the quantum circuit system 10e according to the fifth modified example is configured to transmit the first high-frequency power to the first waveguide 12a to change the first quantum circuit 11a to a predetermined quantum state. A second auxiliary high-frequency power supply 16b for transmitting the third high-frequency power to the second auxiliary waveguide 15b and indirectly transmitting the second high-frequency power to the second waveguide 12b so as to compensate for the change in the quantum state. Prepare.

  The quantum circuit system 10e according to the fifth modified example changes the quantum state of the first quantum circuit 11a when the high frequency power is propagated through the second waveguide 12b to change the second quantum circuit 11b to a predetermined quantum state. And a first auxiliary high-frequency power supply 16a for transmitting high-frequency power to the first auxiliary waveguide 15a and indirectly transmitting high-frequency power to the first waveguide 12a so as to compensate for

The quantum circuit system 10e according to the fifth modification includes 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 line 14a through the output capacitor may be connected between the input capacitor C _in the gate capacitor C _g included in the first quantum circuit 11a. Similarly, the second read line 14b through the output capacitor may be connected between the input capacitor C _in the gate capacitor C _g in the second quantum circuit 11b. 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, the first A plurality of configurations each including 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 are arranged side by side.

  More specifically, in the quantum circuit system 10e according to the fifth modified example, the configuration of one unit is such that the waveguide 12 is arranged such that the position where the high-frequency power supply 13 is provided is on the opposite side of the quantum circuit 11 therebetween. Are arranged adjacent to each other in a direction perpendicular to the direction in which the film is stretched. With such an arrangement, the substrate area on which the plurality of quantum circuits 11 are provided can be efficiently used, and the auxiliary waveguide 15 can compensate for an unintended change in the quantum state occurring in the quantum circuit 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 connected. Although the quantum circuit system 10e according to the fifth modified example is illustrated, the numbers 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 are arbitrary. is there.

  The embodiments described above are intended to facilitate understanding of the present invention, and are not intended to limit and interpret the present invention. Each element included in the embodiment and the arrangement, material, condition, shape, size, and the like of the embodiment are not limited to those illustrated but can be appropriately changed. It is also possible to partially replace or combine the configurations shown in different embodiments.

Claims (5)

A first quantum circuit and a second quantum circuit each having at least two quantum states;
A first waveguide electromagnetically connected to the first quantum circuit and a second waveguide electromagnetically connected to 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 direct or indirect method is used to compensate for the change in the quantum state of the second quantum circuit. A high-frequency power source for transmitting a second high-frequency power to the second waveguide;
A quantum circuit system comprising: The high-frequency power supply directly or indirectly compensates for a 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 a waveguide;
The quantum circuit system according to claim 1. The high-frequency power supply includes a high-frequency power for compensating for a change in a quantum state of the second quantum circuit due to the propagation of the first high-frequency power to the first waveguide, and sets 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 changed, is directly or indirectly propagated to the second waveguide.
The quantum circuit system according to claim 1. An auxiliary waveguide extending along the second waveguide;
The high-frequency power supply compensates for a change in 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 first waveguide. Transmitting the third high-frequency power to the auxiliary waveguide and indirectly transmitting the second high-frequency power to the second waveguide;
The quantum circuit system according to claim 1. 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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