Frequency division multiplexing module for quantum bits, and quantum chip

Abstract

The present disclosure provides a frequency division multiplexing module for quantum bits, and a quantum chip. The frequency division multiplexing module comprises: at least one control line, used for inputting a microwave pulse, wherein a plurality of sub-pulses of different frequencies are simultaneously superimposed on the microwave pulse; a plurality of bandpass filters, wherein each bandpass filter is connected to the control line, device parameters of different bandpass filters are different, and the bandpass filters only allow sub-pulses of one frequency to pass through; and a plurality of quantum couplers, wherein one quantum coupler is connected to one bandpass filter, and bandwidth parameters of different quantum couplers are different. The quantum couplers perform logical operation on two quantum bits on the basis of the sub-pulses outputted by the bandpass filters corresponding to the quantum couplers.

Description

Frequency division multiplexing modules and quantum chips for quantum bits Technical Field

[0001] The present disclosure relates to the field of quantum communication technology, and more specifically, to a frequency division multiplexing module and quantum chip for quantum bits. Background Art

[0002] With the rapid development of quantum computer technology, achieving precise control of quantum systems has become a key focus of quantum computing. Superconducting quantum chips, powered by superconducting qubits, are one of the most effective physical platforms for quantum computing. Achieving precise control of large-scale superconducting quantum chips is a core technology and challenge in improving the precision of quantum manipulation.

[0003] When dealing with large numbers of superconducting qubit processors, the signal fan-out of control lines will become a bottleneck limiting the growth of the number of qubits. Designing a suitable quantum chip control scheme and corresponding chip structure is an important way to reduce the number of control lines and ensure the control accuracy of each qubit.

[0004] Summary of the Invention

[0005] In view of this, the embodiments of the present disclosure provide a frequency division multiplexing module and a quantum chip for quantum bits.

[0006] One aspect of an embodiment of the present disclosure provides a frequency division multiplexing module for quantum bits, including:

[0007] At least one control line for inputting a microwave pulse, wherein the microwave pulse is simultaneously superimposed with a plurality of sub-pulses of different frequencies;

[0008] a plurality of bandpass filters, each of the bandpass filters being connected to the control line, wherein different bandpass filters have different device parameters and each bandpass filter only allows a sub-pulse of one frequency to pass through;

[0009] A plurality of quantum couplers, wherein one quantum coupler is connected to one bandpass filter, and bandwidth parameters of different quantum couplers are different;

[0010] The quantum coupler performs a logic operation on two quantum bits based on a sub-pulse output by a bandpass filter corresponding to the quantum coupler.

[0011] According to an embodiment of the present disclosure, the quantum coupler activates the interaction between two quantum bits associated with the quantum coupler under the action of a sub-pulse output by a bandpass filter corresponding to the quantum coupler, so as to realize a CZ gate or a CNOT gate.

[0012] According to an embodiment of the present disclosure, the number of the quantum couplers is determined according to the amplitude suppression ratio of the bandpass filter.

[0013] According to an embodiment of the present disclosure, the bandpass filter includes a superconducting bandpass filter, wherein the superconducting bandpass filter includes any one of a filter made of a superconducting resonant cavity formed by a coplanar waveguide, a filter of a slotline mode resonant cavity, and a filter of a lumped superconducting circuit resonant cavity.

[0014] According to an embodiment of the present disclosure, the filter made of the superconducting resonant cavity formed by the coplanar waveguide is generated by coupling multiple superconducting resonant cavities of the same frequency by the coplanar waveguide, wherein the device parameters include passband bandwidth, passband attenuation and rectangular coefficient.

[0015] According to an embodiment of the present disclosure, when the length of the superconducting resonant cavity is changed, the center frequency of the superconducting bandpass filter is changed;

[0016] When the distances between the different superconducting resonant cavities are changed, the coupling strengths between the different superconducting resonant cavities are changed.

[0017] According to an embodiment of the present disclosure, a plurality of the quantum couplers are connected to the control line in the form of an array through the bandpass filter.

[0018] Another aspect of the embodiments of the present disclosure provides a quantum chip including the frequency division multiplexing module as described above.

[0019] According to an embodiment of the present disclosure, multiple bandpass filters are provided on each control line so that the bandpass filters output only sub-pulses of one frequency to the quantum coupler, thereby enabling the quantum coupler to perform quantum gate operations on two quantum bits under the action of the sub-pulses of this frequency. This reduces the number of control lines while ensuring the fidelity of the quantum gate, thereby increasing the number of quantum bits in the quantum chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0021] FIG1 schematically shows a circuit diagram of a frequency division multiplexing module according to an embodiment of the present disclosure; and

[0022] FIG2 schematically shows a schematic diagram of the use of a frequency division multiplexing module according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In the detailed description below, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0024] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise," "include," etc. used herein indicate the presence of the features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0025] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0026] When expressions such as "at least one of A, B and C, etc." are used, they should generally be interpreted in accordance with the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0027] FIG1 schematically shows a circuit diagram of a frequency division multiplexing module according to an embodiment of the present disclosure.

[0028] As shown in Figure 1, the frequency division multiplexing module for quantum bits includes:

[0029] at least one control line for inputting a microwave pulse, wherein the microwave pulse is simultaneously superimposed with a plurality of sub-pulses of different frequencies;

[0030] a plurality of band-pass filters, each of which is connected to a control line, wherein different band-pass filters have different device parameters and the band-pass filters only allow a sub-pulse of one frequency to pass through;

[0031] Multiple quantum couplers, one quantum coupler is connected to a bandpass filter, and the bandwidth parameters of different quantum couplers are different;

[0032] The quantum coupler processes two quantum bits based on the sub-pulses output by the bandpass filter corresponding to the quantum coupler.

[0033] According to the embodiments of the present disclosure, the frequency of the microwave pulses can be specifically set according to actual needs. For example, the frequency range can be set to be selected from 50 MHz to 8 GHz, and the target frequency can be selected from a selectable frequency range of approximately 500 MHz. For example, different sub-pulses are arranged at a frequency interval of 30 MHz.

[0034] According to an embodiment of the present disclosure, after a microwave pulse is input into the control line, each bandpass filter only allows sub-pulses of one frequency to pass through. For example, the first bandpass filter allows sub-pulses of 100 MHz to pass through, the second bandpass filter allows sub-pulses of 200 MHz to pass through... and the nth bandpass filter allows sub-pulses of 100 nm to pass through.

[0035] According to an embodiment of the present disclosure, the quantum coupler connected to the first bandpass filter processes two quantum bits corresponding to the quantum coupler based on its own bandwidth parameters when receiving a 100 MHz sub-pulse, thereby realizing a quantum gate operation.

[0036] According to an embodiment of the present disclosure, multiple bandpass filters are provided on each control line so that the bandpass filters output only sub-pulses of one frequency to the quantum coupler, thereby enabling the quantum coupler to perform quantum gate operations on two quantum bits under the action of the sub-pulses of this frequency. This reduces the number of control lines while ensuring the fidelity of the quantum gate, thereby increasing the number of quantum bits in the quantum chip.

[0037] According to an embodiment of the present disclosure, under the action of a sub-pulse output by a bandpass filter corresponding to the quantum coupler, the quantum coupler activates the interaction between two quantum bits associated with the quantum coupler to implement a CZ gate or a CNOT gate.

[0038] According to an embodiment of the present disclosure, a CZ gate refers to performing a Z operation on a quantum bit when the control bit (ie, a sub-pulse) is 1.

[0039] According to an embodiment of the present disclosure, a CNOT gate refers to performing an X operation on a quantum bit when the control bit (ie, a sub-pulse) is 1.

[0040] According to an embodiment of the present disclosure, the frequency at which each quantum coupler realizes alternating current needs to be designed according to a bit frequency method, and the bandpass frequency of the bandpass filter is specifically designed according to the driving frequency required by each quantum coupler, wherein the input frequency bandwidth of each quantum coupler can be set to 5 MHz.

[0041] According to an embodiment of the present disclosure, the number of quantum couplers is determined according to the amplitude suppression ratio of the bandpass filter.

[0042] According to an embodiment of the present disclosure, the bandpass filter includes a superconducting bandpass filter, wherein the superconducting bandpass filter includes any one of a filter made of a superconducting resonant cavity formed by a coplanar waveguide, a filter of a slotline mode resonant cavity, and a filter of a lumped superconducting circuit resonant cavity.

[0043] According to an embodiment of the present disclosure, a filter made of a superconducting resonant cavity formed by a coplanar waveguide is generated by coupling multiple superconducting resonant cavities of the same frequency by the coplanar waveguide, wherein the device parameters include passband bandwidth, passband attenuation and rectangular coefficient.

[0044] According to an embodiment of the present disclosure, when the length of the superconducting resonant cavity is changed, the center frequency of the superconducting bandpass filter changes;

[0045] When the distances between different superconducting resonant cavities are changed, the coupling strengths between the different superconducting resonant cavities are changed.

[0046] According to the embodiments of the present disclosure, when the center frequency and the coupling strength are changed, the passband bandwidth, the passband attenuation and the rectangular coefficient can be changed.

[0047] According to an embodiment of the present disclosure, a plurality of quantum couplers are connected to a control line in the form of an array through a bandpass filter.

[0048] In one embodiment, a superconducting AC CZ gate can be implemented using microwave pulses in the 50MHz to 8GHz frequency range. To account for potential frequency conflicts in AC CZ gates, the available frequencies for a given chip are divided into selectable frequency intervals of approximately 500MHz, from which the target frequency can be selected. By arranging the frequency intervals of different AC CZ gates at 30MHz intervals and achieving a 30dB amplitude suppression ratio at 15dB for each filter, the errors caused by mutual interference between the signals of different AC CZ gates can be made negligible in experiments. Under this control scheme, a single control line can control m quantum couplers and independently achieve the CZ gate target, reducing the number of required quantum coupler control lines to 1 / m of the original number.

[0049] In a specific embodiment, each control line connection independently controls 15 quantum couplers to realize the ability of AC CZ gate with almost no impact on the fidelity of the AC CZ gate. This can significantly reduce the number of control lines required for the superconducting quantum chip and reduce the control line scale of the quantum coupler to 1 / 15 of the original.

[0050] FIG2 schematically shows a schematic diagram of the use of a frequency division multiplexing module according to an embodiment of the present disclosure.

[0051] According to an embodiment of the present disclosure, as shown in Figure 2, the digital number is a quantum bit, and the horizontal bar is a coupler connecting two quantum bits. Each quantum coupler needs to apply a specific frequency to activate the interaction between the two connected quantum bits, thereby realizing a CZ gate. In the traditional control scheme, each quantum coupler needs to have a dedicated control line to realize the input of a microwave signal of the target frequency. In the present disclosure, N quantum couplers can be connected to a control line through a bandpass filter. In actual control, a microwave pulse of the corresponding frequency that needs to be used for the CZ gate can be input through the control line. Due to the isolation of the bandpass filter corresponding to the quantum coupler, the quantum coupler will only respond to microwave sub-pulses of the target frequency.

[0052] Another aspect of the embodiments of the present disclosure provides a quantum chip, including multiple frequency division multiplexing modules and other necessary functional modules to realize complete quantum chip functions.

[0053] According to an embodiment of the present disclosure, multiple bandpass filters are provided on each control line so that the bandpass filters output only sub-pulses of one frequency to the quantum coupler, thereby enabling the quantum coupler to perform quantum gate operations on two quantum bits under the action of the sub-pulses of this frequency. This reduces the number of control lines while ensuring the fidelity of the quantum gate, thereby increasing the number of quantum bits in the quantum chip.

[0054] The embodiments of the present disclosure are described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be used in combination to advantage. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A frequency division multiplexing module for qubits, comprising: At least one control line for inputting microwave pulses, wherein the microwave pulses are simultaneously superimposed with multiple sub-pulses of different frequencies; Multiple band-pass filters, each of the band-pass filters being connected to the control line, wherein the device parameters of different band-pass filters are different, and the band-pass filter only allows a sub-pulse of one frequency to pass through; Multiple quantum couplers, one quantum coupler being connected to one of the band-pass filters, and the bandwidth parameters of different quantum couplers being different; Wherein, the quantum coupler performs a logical operation on two qubits based on the sub-pulse output by the band-pass filter corresponding to the quantum coupler.

2. The frequency division multiplexing module according to claim 1, wherein Under the action of the sub-pulse output by the band-pass filter corresponding to the quantum coupler, the quantum coupler activates the interaction between two qubits associated with the quantum coupler to implement a CZ gate or a CNOT gate.

3. The frequency division multiplexing module according to claim 1, wherein, The number of the quantum couplers is determined according to the amplitude suppression ratio of the band-pass filter.

4. The frequency division multiplexing module according to claim 1, wherein The band-pass filter includes a superconducting band-pass filter, wherein the superconducting band-pass filter includes any one of a filter made of a superconducting resonator formed by a coplanar waveguide, a filter of a slot-line mode resonator, and a filter of a lumped superconducting circuit resonator.

5. The frequency division multiplexing module according to claim 4, wherein The filter made of a superconducting resonator formed by a coplanar waveguide is generated by coupling multiple superconducting resonators of the same frequency through a coplanar waveguide, wherein the device parameters include a passband bandwidth, a passband attenuation, and a rectangularity coefficient.

6. The frequency division multiplexing module according to claim 4, wherein, When the length of the superconducting resonator is changed, the center frequency of the superconducting band-pass filter is changed; When the distance between different superconducting resonators is changed, the coupling strength between different superconducting resonators is changed.

7. The frequency division multiplexing module according to claim 1, wherein Multiple of the quantum couplers are connected to the control line through the band-pass filter in an array form.

8. A quantum chip, comprising: The frequency division multiplexing module according to any one of claims 1 to 7.

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