Pulse excitation microwave generation device for quantum limit amplifier

Abstract

The invention provides a pulse excitation microwave generation device for a quantum limit amplifier, and relates to the technical field of superconducting quantum calculation and other weak microwave signal measurement. The pulse excitation microwave generation device for the quantum limit amplifier comprises a microwave source used for generating continuous microwave signals; the microwave signal direct generation device is used for generating a pulse microwave signal; the frequency mixer is used for carrying out frequency mixing on the continuous microwave signal and the pulse microwave signal to generate a frequency mixing signal; the band-pass filter is used for filtering the frequency mixing signal; and the power amplifier is used for amplifying the filtered frequency mixing signal and generating pulse excitation microwaves for the quantum limit amplifier, so that the implementation cost is greatly reduced, the space occupied by equipment is reduced, and the space is saved.

Description

Technical Field

[0001] The present application relates to the technical field of superconducting quantum computing and other weak microwave signal measurement technologies. Specifically, it relates to a pulsed excitation microwave generation device for a quantum-limited amplifier, which can be used to excite the quantum-limited amplifier of a superconducting quantum computer, thereby amplifying the readout signal of the superconducting quantum computer. Background Art

[0002] With the rapid development of the superconducting quantum computing field and other weak microwave signal measurements, the need for ultra-high-quality readout of signals of several microwave photons is becoming increasingly urgent. To achieve this goal, a quantum-limited amplifier operating in an extremely low-temperature environment is the only option, such as the Josephson Parametric Amplifier (JPA) commonly used in the superconducting quantum computing field.

[0003] The JPA requires a strong external microwave pulse excitation to operate in the amplification region. According to the general low-temperature circuit structure of superconducting quantum computing, the power of this microwave pulse is approximately in the range of 0 dBm to 10 dBm, and the required excitation frequency is generally in the range of 12 GHz to 15 GHz.

[0004] Currently, the more popular and cost-acceptable JPA excitation scheme is generated by a continuous microwave source plus a microwave switch, as Figure 1 shown. However, this technology faces the following problems. Taking the 12-channel readout scheme based on JPA excitation as an example:

[0005] 1) The cost is getting higher and higher. In this scheme, 12 microwave sources (the cost of one qualified microwave source is 100,000, with a total exceeding 1.2 million), 12 arbitrary waveform generators (about 20,000 for 1 channel, with a total of about 240,000), 12 DC sources (with a total of about 10,000), and 12 microwave switches (about 5,000 for 1, with a total of about 60,000) are required. The total cost exceeds 1.5 million, and the microwave source is the main cost source.

[0006] 2) The volume is relatively large and it is difficult to integrate. Such 12 sets of systems approximately require the entire space of a standard 2-meter rack.

[0007] Therefore, as the scale of superconducting quantum computing becomes larger and larger, a JPA microwave excitation technology with lower cost and higher integration becomes increasingly urgent. Summary of the Invention

[0008] To solve at least one of the above problems, the present application proposes a pulsed excitation microwave generation device for a quantum-limited amplifier.

[0009] According to a first aspect of the present application, at least one embodiment of the present application provides a pulsed excitation microwave generation device for a quantum limit amplifier, comprising: a microwave source for generating a continuous microwave signal; a microwave signal direct generation device for generating a pulsed microwave signal; a mixer for mixing the continuous microwave signal and the pulsed microwave signal to generate a mixed signal; a band-pass filter for filtering the mixed signal; and a power amplifier for amplifying the filtered mixed signal to generate a pulsed excitation microwave for the quantum limit amplifier.

[0010] For example, in some embodiments of the present application, the microwave signal direct generation device comprises: N output channels for generating N pulsed microwave signals, where N is an integer greater than or equal to 5.

[0011] For example, in some embodiments of the present application, the frequency of the pulsed microwave signal is 2 - 5 GHz.

[0012] For example, in some embodiments of the present application, it further comprises: a power splitter connected to the microwave source for splitting the continuous microwave signal into N paths.

[0013] For example, in some embodiments of the present application, the mixer comprises: N mixers connected to the power splitter and the microwave signal direct generation device for correspondingly mixing N paths of the continuous microwave signals and N pulsed microwave signals to generate N mixed signals.

[0014] For example, in some embodiments of the present application, the band-pass filter comprises: N band-pass filters correspondingly connected to the N mixers for filtering N mixed signals.

[0015] For example, in some embodiments of the present application, the bandwidth of the band-pass filter is 12 - 15 GHz.

[0016] For example, in some embodiments of the present application, the power amplifier comprises: N amplifiers correspondingly connected to the N band-pass filters for amplifying N filtered mixed signals to generate the pulsed excitation microwave for the quantum limit amplifier.

[0017] According to a second aspect of the present application, at least one embodiment of the present application provides a superconducting quantum computer, comprising: a quantum limit amplifier; and a pulsed excitation microwave generation device as described in any one of the first aspect, connected to the quantum limit amplifier for generating a pulsed excitation microwave for the quantum limit amplifier so that the quantum limit amplifier amplifies the readout signal of the superconducting quantum computer.

[0018] For example, in some embodiments of the present application, the quantum limit amplifier is disposed in an extremely low temperature environment; the pulsed excitation microwave generating device is disposed in a room temperature environment.

[0019] Through the above exemplary embodiments, a pulsed excitation microwave generating device for a quantum limit amplifier provided by the present application only requires a microwave source, a microwave signal direct generating device, a power divider, corresponding numbers of mixers, band-pass filters and amplifiers, and can generate pulsed excitation microwaves for the quantum limit amplifier, greatly reducing the implementation cost, reducing the space occupied by the device, and saving space.

[0020] It should be understood that the above general description and the following detailed description are only exemplary and do not limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] By referring to the accompanying drawings and describing its exemplary embodiments in detail, the above and other objects, features and advantages of the present application will become more apparent. The following described drawings are only some embodiments of the present application and do not limit the present application.

[0022] Figure 1 Showing a schematic diagram of an existing JPA excitation device;

[0023] Figure 2 Showing a schematic diagram of a pulsed excitation microwave generating device for a quantum limit amplifier according to an exemplary embodiment;

[0024] Figure 3 Showing a schematic diagram of a quantum limit amplifier system according to an exemplary embodiment;

[0025] Figure 4 Showing the waveform spectrum effect diagram generated by the pulsed excitation microwave generating device of the present application;

[0026] Figure 5A Showing the reading effect diagram without applying a microwave excitation pulse to the Josephson amplifier;

[0027] Figure 5B Showing the reading effect diagram after applying the microwave excitation pulse generated by the present application to the Josephson amplifier. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, the exemplary embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. Like reference numerals in the figures denote like or similar parts, and thus their repetitive description will be omitted.

[0029] The described features, structures, or characteristics can be combined in one or more embodiments in any suitable manner. In the following description, numerous specific details are provided to give a thorough understanding of the embodiments of the present disclosure. However, those skilled in the art will realize that the technical solutions of the present disclosure can be practiced without one or more of these specific details, or other methods, components, materials, devices, etc. can be adopted. In these cases, well-known structures, methods, devices, implementations, materials, or operations will not be shown or described in detail.

[0030] The flowchart shown in the accompanying drawings is only an exemplary illustration, and does not necessarily include all the content and operations / steps, nor does it necessarily execute in the described order. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined, so the actual execution order may change according to the actual situation.

[0031] The terms "first", "second", etc. in the specification, claims, and the above-mentioned accompanying drawings of the present application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally further includes steps or units not listed, or optionally further includes other steps or units inherent to these processes, methods, products, or devices.

[0032] Those skilled in the art can understand that the accompanying drawings are only schematic diagrams of exemplary embodiments, and the modules or processes in the accompanying drawings are not necessarily essential for implementing the present application, so they cannot be used to limit the protection scope of the present application.

[0033] Figure 2 Schematic diagram of a pulse excitation microwave generation device for a quantum limit amplifier showing an exemplary embodiment.

[0034] As Figure 2 shown, the pulse excitation microwave generation device for a quantum limit amplifier includes: a microwave source 101, a microwave signal direct generation device 102, a mixer 104, a band-pass filter 105, and a power amplifier 106.

[0035] Among them, the microwave source 101 is used to generate a continuous microwave signal. The microwave signal direct generation device 102 is used to generate a pulsed microwave signal. The mixer 104 is used to mix the continuous microwave signal and the pulsed microwave signal to generate a mixed signal. The band-pass filter 105 is used to filter the mixed signal. The power amplifier 106 is used to amplify the filtered mixed signal to generate a pulsed excitation microwave for the quantum limit amplifier.

[0036] Among them, the microwave source is used to generate a continuous microwave signal of about 10 GHz. The frequency of the pulsed microwave signal is 2 - 5 GHz. This application only takes the continuous microwave signal generated by the microwave source with a frequency of 10 GHz and the pulsed microwave signal with a frequency of 2 - 5 GHz as an example, but this application is not limited thereto, and both can also generate microwave signals of other frequencies. The specific value can be adjusted according to the required frequency of the excitation microwave of the quantum limit amplifier (such as 12 GHz to 15 GHz in this exemplary embodiment).

[0037] According to the exemplary embodiment, the pulsed excitation microwave generating device further includes: a power splitter 103. The power splitter 103 is connected to the microwave source 101 and is used to divide the continuous microwave signal into N paths. Among them, N is an integer greater than or equal to 5.

[0038] The microwave signal direct generating device 102 includes: N output channels for generating N pulsed microwave signals. N mixers 104 are connected to the power splitter 103 and the microwave signal direct generating device 102, and are used to mix the N paths of continuous microwave signals and the N pulsed microwave signals correspondingly to generate N mixed signals. N band-pass filters 105 are correspondingly connected to the N mixers 104 and are used to perform filtering processing on the N mixed signals. N power amplifiers 106 are correspondingly connected to the N band-pass filters 105 and are used to perform amplification processing on the N filtered mixed signals to generate pulsed excitation microwaves for the quantum limit amplifier.

[0039] According to some embodiments, the signal power generated by the microwave signal direct generating device 102 is relatively weak, about -10 dBm. The bandwidth of the band-pass filter is 12 - 15 GHz. However, after the pulsed microwave signal and the microwave signal of this application are mixed by the mixer and amplified by the amplifier, the highest power of the generated pulsed excitation microwave can reach 8.18 dBm, and its center frequency is 14.0687 GHz, as Figure 4 shown, meeting the microwave pulse excitation requirements of the quantum limit amplifier. Among them, the bandwidth range of the band-pass filter can be changed according to the needs of the quantum limit amplifier. This application only takes the bandwidth of the band-pass filter as 12 - 15 GHz as an example, but is not limited thereto. The gain of the power amplifier is generally 30 dB to 50 dB.

[0040] This application also provides a superconducting quantum computer, including a quantum limit amplifier and the pulsed excitation microwave generating device as described above. As Figure 3 shown, taking the 12-channel Josephson amplifier as an example of the quantum limit amplifier, the pulsed excitation microwave generating device is connected to the quantum limit amplifier, and the pulsed excitation microwave generated by the pulsed excitation microwave generating device can be used to excite the quantum limit amplifier so that the quantum limit amplifier completes the amplification of the readout signal of the superconducting quantum computer.

[0041] According to some embodiments, the quantum-limited amplifier of the present application can also be other amplifiers that require pulsed excitation microwave.

[0042] Among them, the pulsed excitation microwave generating device includes: 1 microwave source; 1 microwave signal direct generating device including 12 output channels; 1 power splitter for splitting the continuous microwave signal of the microwave source into 12 paths; 12 mixers for mixing the 12 paths of continuous microwave signals and 12 pulsed microwave signals to generate 12 mixed signals; 12 band-pass filters for filtering the 12 mixed signals; 12 amplifiers for amplifying the 12 filtered mixed signals to generate 12 pulsed excitation microwaves for 12 Josephson amplifiers.

[0043] Among them, the quantum-limited amplifier is arranged in an extremely low temperature environment, and the pulsed excitation microwave generating device is arranged in a room temperature environment.

[0044] According to some embodiments, the extremely low temperature environment is about 10 mK.

[0045] Taking the above example as an example, a microwave signal direct generating device that generates 12 lower-frequency (below 5 GHz) pulsed microwave signals (about 30,000 per path, about 360,000 in total), 1 lower-frequency microwave source (about 100,000 in total) generates a continuous microwave signal of about 10 GHz. After being split into 12 paths by a power splitter (about 10,000 in total), the two frequencies are mixed by 12 mixers (about 5,000 per path, about 60,000 in total), and then passed through 12-channel band-pass filters (bandwidth is 12 - 15 GHz, about 5,000 each, about 60,000 in total). Finally, it is amplified by 12-channel amplifiers (about 5,000 each, and this amplifier requires DC power supply, about 70,000 in total). The cost estimate of this scheme is 660,000, and the cost is greatly reduced. Moreover, as the number of paths of the microwave signal direct generating device increases, the cost savings of this scheme are more obvious.

[0046] At the same time, in this scheme, the largest devices are 1 microwave source and 1 microwave signal direct generating device. After adding various microwave devices and circuits, it occupies a maximum height of 50 cm in a standard instrument rack, so the space is also greatly saved.

[0047] By applying the microwave excitation pulse provided by the present application to the quantum-limited amplifier, the noise of the Josephson amplifier can reach the quantum noise limit, fully meeting the requirements of quantum computing. As shown in Figure 5A 、 5B shown, Figure 5A is without the microwave excitation pulse, Figure 5B is with the microwave excitation pulse. Compared with Figure 5A , Figure 5B the average distance between the two circles in it significantly increases, that is, there is a gain effect on the signal of the Josephson amplifier.

[0048] A pulse excitation microwave generation device for a quantum limit amplifier provided by the present application only requires a microwave source, a microwave signal direct generation device, a power divider, corresponding numbers of mixers, band-pass filters and amplifiers, and can generate pulse excitation microwaves for a quantum limit amplifier, greatly reducing the implementation cost, reducing the space occupied by the equipment, and saving space.

[0049] It should be clearly understood that the present application describes how to form and use specific examples, but the present application is not limited to any details of these examples. On the contrary, based on the teachings of the content disclosed in the present application, these principles can be applied to many other embodiments.

[0050] In addition, it should be noted that the above-mentioned drawings are only schematic illustrations of the processes included in the method according to the exemplary embodiments of the present application, rather than for limiting purposes. It is easy to understand that the processes shown in the above-mentioned drawings do not indicate or limit the chronological order of these processes. Additionally, it is also easy to understand that these processes can be executed, for example, synchronously or asynchronously in multiple modules.

[0051] The above specifically shows and describes the exemplary embodiments of the present application. It should be understood that the present application is not limited to the detailed structures, settings or implementation methods described herein; on the contrary, the present application is intended to cover various modifications and equivalent settings included within the spirit and scope of the appended claims.

Claims

1. A pulse excitation microwave generating device for a quantum limit amplifier, characterized in that, Comprising: A microwave source for generating a continuous microwave signal; A microwave signal direct generation device for generating a pulsed microwave signal; A mixer for mixing the continuous microwave signal and the pulsed microwave signal to generate a mixed signal; A band-pass filter for filtering the mixed signal; A power amplifier for amplifying the filtered mixed signal to generate a pulsed excitation microwave for the quantum limit amplifier.

2. The pulse excitation microwave generating device according to claim 1, characterized in that, The microwave signal direct generation device includes: N output channels for generating N pulsed microwave signals, where N is an integer greater than or equal to 5.

3. The pulse excitation microwave generating device according to claim 2, wherein The frequency of the pulsed microwave signal is 2 - 5 GHz.

4. The pulse excitation microwave generating device according to claim 2, wherein, Further comprising: A power splitter connected to the microwave source for splitting the continuous microwave signal into N paths.

5. The pulse-excited microwave generating device according to claim 4, characterized in that, The mixer includes: N mixers connected to the power splitter and the microwave signal direct generation device for correspondingly mixing N paths of the continuous microwave signals and N pulsed microwave signals to generate N mixed signals.

6. The pulse excitation microwave generating device according to claim 5, characterized in that, The band-pass filter includes: N band-pass filters correspondingly connected to the N mixers for filtering N mixed signals.

7. The pulse excitation microwave generating device according to claim 6, characterized in that, The bandwidth of the band-pass filter is 12 - 15 GHz.

8. The pulse excitation microwave generating device according to claim 6, wherein, The power amplifier includes: N amplifiers correspondingly connected to the N band-pass filters for amplifying N filtered mixed signals to generate the pulsed excitation microwave for the quantum limit amplifier.

9. A superconducting quantum computer, characterized in that, Comprising: A quantum limit amplifier; A pulsed excitation microwave generation device as described in any one of claims 1 - 8, connected to the quantum limit amplifier for generating a pulsed excitation microwave for the quantum limit amplifier to enable the quantum limit amplifier to amplify the readout signal of the superconducting quantum computer.

10. The superconducting quantum computer as claimed in claim 9, wherein The quantum limit amplifier is disposed in an extremely low temperature environment; The pulsed excitation microwave generation device is disposed in a room temperature environment.

Images