Superheterodyne control scheme of quantum bits
By adopting a three-tiered superheterodyne control scheme for qubits, the problem of spurious frequency accumulation in the traditional IQ mixing architecture is solved, achieving low-cost and high-stability qubit control, which is suitable for large-scale quantum computing systems.
Patent Information
- Application Number
- CN202511110380.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-08
- Publication Date
- 2025-11-11
AI Technical Summary
Traditional IQ mixing architectures cannot effectively suppress spurious frequencies in multi-qubit systems, leading to frequency congestion and inter-qubit crosstalk, which limits system scalability and stability, and also requires frequent and costly hardware calibration.
A three-tiered superheterodyne control scheme for qubits is adopted, including pre-selection filtering, mixing, and post-filtering. The frequency range is limited by the pre-selection filter, the signal is mixed by a three-port mixer, and the spurious component is filtered by the post-filter, thereby reducing spurious sources and retaining the pure target frequency signal.
It effectively eliminates spurious frequencies, reduces the number of channels, lowers hardware requirements and operation and maintenance difficulty, improves system stability and compatibility, and is suitable for large-scale quantum computing systems.
Smart Images
Figure CN120930816A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of superconducting quantum bit control, superheterodyne technology and quantum electrodynamics, and particularly to a superheterodyne control scheme for quantum bits. This scheme is based on an XY controller with a superheterodyne architecture to eliminate the problems of frequency leakage, harmonic interference and frequency congestion in multi-qubit control. Background Technology
[0002] Superconducting quantum circuits are one of the most promising candidate platforms for realizing quantum computing. As an artificial atom, superconducting qubits have a large degree of parameter freedom. Because of their unique advantages in scalability, qubits can be encoded through circuit structures. Therefore, qubits can be integrated using mature microelectronic manufacturing processes and controlled using standard microwave electronics.
[0003] In superconducting qubit systems, quantum control mainly relies on the precise generation and manipulation of microwave signals, and the traditional IQ mixing architecture plays an important role in this process. However, the IQ mixing XY control architecture, which is widely used in traditional quantum electrodynamics (cQED), faces significant challenges when expanding to multiple qubits and is unable to adapt.
[0004] Quantum computing requires a large number of qubits to maintain its leading position, and a large number of qubits requires a massive control system. Traditional architectures use IQ mixers to upconvert baseband signals to the target microwave frequency to drive qubits, but spurious frequencies generated during the mixing process (such as local oscillator leakage, upper sidebands, and higher harmonics) are difficult to completely suppress. If the traditional IQ mixing architecture is still used when controlling a large number of qubits, these spurious components will undoubtedly accumulate rapidly in the 4GHz to 8GHz frequency band, leading to frequency congestion and inter-qubit crosstalk, severely limiting the fidelity and scalability of multi-qubit systems. Summary of the Invention
[0005] To address the shortcomings of the existing technologies, this invention proposes a superheterodyne control scheme and system for qubits. Through a three-tiered design of pre-selection filtering, mixing, and post-filtering, it can effectively eliminate spurious frequencies while halving the number of control channels required and eliminating the need for frequent calibration. This provides a highly stable and low-cost solution for large-scale quantum computing systems.
[0006] The technical solution adopted in this invention is a superheterodyne control scheme for qubits. The control scheme includes: limiting the input signal to a specific frequency range to obtain a preselected signal; mixing the preselected signal with a pre-set reference signal to generate a sideband signal; and filtering the sideband signal to remove signals outside the target frequency range to obtain the target signal.
[0007] Preferably, the reference signal is a local oscillator signal.
[0008] Preferably, limiting the input signal to a specific frequency range to obtain a preselected signal means limiting the input signal to the first Nyquist zone or the second Nyquist zone.
[0009] Preferably, the step of filtering the sideband signal to remove signals outside the target frequency range and obtain the target signal means setting a filtering frequency range according to the frequency range of the target signal, removing high-frequency / low-frequency signals from the sideband signal to obtain the lower sideband signal / upper sideband signal, which is the target signal.
[0010] Preferably, the process of limiting the input signal to a specific frequency range to obtain a preselected signal is achieved through a preselection filter; the process of mixing the preselected signal with a pre-set reference signal to generate a sideband signal is achieved through a mixer; and the process of filtering the sideband signal to remove signals outside the target frequency range to obtain the target signal is achieved through a post-filter.
[0011] The present invention also proposes a superheterodyne control system for qubits, which uses the control scheme described above to control the qubits. The system includes a signal generator, a preselection filter, a mixer and a post-filter connected in sequence, and a microwave signal generator connected to the mixer. The microwave signal generator emits a local oscillator signal source to the mixer.
[0012] Preferably, it also includes a microwave transmission link, one end of which is connected to the post-filter signal and the other end is connected to the control port signal of the quantum bit.
[0013] Compared with the prior art, the present invention has the following beneficial effects:
[0014] 1. Traditional IQ mixing architectures require multiple channels to control a single qubit, and spurious frequencies accumulate as the number of qubits increases, leading to frequency congestion and crosstalk, which limits scalability. The proposed solution achieves this through a three-tiered design: ① A pre-selection filter limits the frequency range entering the mixer, reducing spurious sources; ② A three-port mixer mixes the signal with the local oscillator signal to generate a sideband signal; ③ A post-filter removes spurious components such as local oscillator leakage, upper sideband, and higher harmonics generated after mixing, ultimately retaining the pure target frequency signal. This solves the spurious frequency problem, reduces crosstalk, and is more suitable for the expansion needs of large-scale qubit systems.
[0015] 2. The proposed solution requires only one arbitrary waveform generator (AWG) channel to control one quantum bit, halving the number of channels, reducing hardware requirements, and greatly reducing costs and operational and maintenance difficulties;
[0016] 3. The proposed solution does not require frequent calibration, which avoids the frequent calibration caused by tolerance and environmental changes in traditional architectures, improves the stability and reliability of the system, and is conducive to the long-term stable operation of the quantum system.
[0017] 4. This invention is applicable to most DAC chips and AWGs used in cQED, without requiring large-scale modifications to existing hardware devices. It is easy to integrate into existing quantum computing control systems, has good compatibility and versatility, and is suitable for widespread application. Attached Figure Description
[0018] The present invention will now be described in detail with reference to the embodiments and accompanying drawings, wherein:
[0019] Figure 1 This is a flowchart of method steps in one embodiment;
[0020] Figure 2 This is a system diagram of the superheterodyne control system for a quantum bit in one embodiment, as well as signal spectrum diagrams at different locations.
[0021] 1. Signal generator; 2. Pre-selection filter; 3. Mixer; 4. Microwave signal generator; 5. Post-filter. Detailed Implementation
[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.
[0023] This invention discloses a superheterodyne control scheme for qubits, specifically for controlling Transmon qubits, and is particularly applicable to scenarios involving the control of large numbers of qubits. Large numbers of qubits require large control systems. Traditional architectures use IQ mixers to upconvert baseband signals to the target microwave frequency to drive the qubits. However, spurious frequencies generated during the mixing process, such as local oscillator leakage, upper sidebands, and higher harmonics, are difficult to completely suppress. These spurious components accumulate in the 4GHz to 8GHz frequency band, leading to frequency congestion and inter-qubit crosstalk, severely limiting the fidelity and scalability of multi-qubit systems. Even using the same IQ mixer, the IQ modulation parameters vary with different LO frequencies and powers; therefore, using a traditional IQ mixer for control inevitably results in the aforementioned problems.
[0024] Meanwhile, the parameters of the IQ mixer are easily affected by factors such as ambient temperature and component aging, which can exacerbate the imbalance in amplitude and phase of the DAC, cables, mixer IQ channels, and phase splitter channels, resulting in a "mirror image" in the mixer output. Additionally, DC components, primarily from the LO feedthrough and the IQ channels, can cause the local oscillator frequency component to leak into the mixer output, forming local oscillator leakage. Since the gain and phase of the hardware circuit cannot be adjusted, we need to frequently perform error correction and compensation for the IQ channels in the AWG (Automatic Gain Control) system. This frequent calibration to maintain performance significantly increases system complexity and maintenance costs.
[0025] Current solutions, such as high-frequency direct digital synthesis (DDS), can theoretically address the aforementioned issues to some extent. However, the implementation of this solution relies on high-cost DAC chips and customized hardware, making it difficult to achieve cost-effective and large-scale deployment. Therefore, other alternative solutions are still needed.
[0026] Based on the above, the control scheme of this application includes: limiting the input signal to a specific frequency range to obtain a preselected signal; mixing the preselected signal with a pre-set reference signal to generate a sideband signal; and filtering the sideband signal to remove signals outside the target frequency range to obtain the target signal.
[0027] In a specific embodiment of the present invention, a superheterodyne controller is used to control a Transmon qubit. For example, when implementing single-qubit gate operations, the rotation operations of different qubit gates can be achieved by adjusting the amplitude, frequency and duration of the pulse.
[0028] In one embodiment, the reference signal is a local oscillator signal. Limiting the input signal to a specific frequency range to obtain a pre-selected signal means limiting the input signal to the first or second Nyquist zone. Filtering the sideband signal to remove signals outside the target frequency range to obtain the target signal means setting a filtering frequency range based on the target signal's frequency range, removing high-frequency / low-frequency signals from the sideband signal to obtain a lower / upper sideband signal, which is the target signal.
[0029] For example, in a specific embodiment, such as Figure 2 As shown, the pre-selection filter filters the input signal, limiting the frequency range entering the mixer to reduce the generation of spurious frequencies. The mixer mixes the pre-selected signal with the frequency generated by the local oscillator (LO) signal to generate upper (lower) sideband signals. The post-filter filters the mixed signal, removing unwanted high-frequency signals, such as LO leakage, upper sidebands, and higher harmonics, while retaining the target signal.
[0030] Taking a 2.5 Gsa / s DAC and a 6 GHz quantum bit frequency as an example, the pre-selection filter is a bandpass filter from 1.6 GHz to 2 GHz, the post-filter is a low-pass filter (or bandpass filter) at 6.4 GHz, and the local oscillator frequency is set to 7.8 GHz. The DAC output signal is limited to the second Nyquist zone to ensure sufficient signal amplitude. The pre-selection filter selects an input signal of 1.8 GHz, which is mixed to generate upper and lower sideband signals. The post-filter removes unwanted high-frequency signals to obtain the target frequency signal, which can then be output and used to control a large number of quantum bits.
[0031] In the field of superconducting quantum computing, with the increase in the number of qubits, the traditional XY control architecture based on IQ mixing faces key problems such as frequency congestion, unstable spurious frequency suppression, and crosstalk in multi-qubit control. Existing solutions are either too costly or require custom hardware, making them difficult to widely apply to large-scale qubit control systems. The solution described above, however, is different. It achieves this through a three-tiered design: ① A pre-selection filter limits the frequency range entering the mixer, reducing spurious sources; ② A three-port mixer mixes the signal with the local oscillator signal to generate a sideband signal; ③ A post-filter removes spurious components such as local oscillator leakage, upper sidebands, and higher harmonics generated after mixing, ultimately retaining the pure target frequency signal. This solves the spurious frequency problem, reduces crosstalk, and is more adaptable to the expansion needs of large-scale qubit systems.
[0032] Moreover, only one channel is needed to control one qubit, halving the number of channels, reducing hardware requirements, and greatly reducing costs and operational and maintenance difficulties. Due to the single-channel design, there is no need for frequent calibration, avoiding the frequent asynchrony between the two channels caused by tolerance and environmental changes in the traditional architecture, improving the stability and reliability of the system, and facilitating the long-term stable operation of the quantum system.
[0033] Meanwhile, the inventors also discovered through market research that this solution is applicable to most DAC chips and AWGs used in cQED, requires no large-scale modification of existing hardware, is easy to integrate into existing quantum computing control systems, has good compatibility and versatility, and is suitable for promotion.
[0034] This application also discloses a superheterodyne control system for qubits. The system includes a signal generator 1, a preselection filter 2, a mixer 3, and a post-filter 5 connected in sequence. It also includes a microwave signal generator 4 connected to the mixer 3, which sends a local oscillator signal to the mixer 3. A microwave transmission link is also included, with one end connected to the post-filter 5 and the other end connected to the control port of the qubit. The signal generator 1 is used to generate and control pulse parameters; for example, it can be a DAC chip or AWG used in most cQEDs.
[0035] The system is implemented using the superheterodyne control scheme for qubits in any of the above embodiments.
[0036] In the description of this specification, the use of terms such as "Embodiment 1," "this embodiment," or "in one embodiment" indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example; moreover, the specific features, structures, materials, or characteristics described may be combined in any appropriate manner in one or more embodiments or examples.
[0037] In the description of this specification, the terms "connection," "installation," "fixing," "setting," and "having" are interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0038] In the description of this specification, relational terms such as “first” and “second” are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0039] The above description of the embodiments is intended to enable those skilled in the art to understand and apply the technology of this invention. Those skilled in the art can easily make various modifications to these examples and apply the general principles described herein to other embodiments without creative effort. Therefore, this invention is not limited to the above embodiments. Modifications in the following situations should be within the scope of protection of this invention: ① New technical solutions implemented based on the technical solution of this invention and combined with existing common knowledge, where the technical effects of the new technical solution do not exceed the technical effects of this invention; ② Equivalent substitutions of some features of the technical solution of this invention using known technology, resulting in the same technical effects as those of this invention; ③ Extendable technical solutions based on the technical solution of this invention, where the substantive content of the extended technical solution does not exceed the technical solution of this invention; ④ Equivalent transformations made using the content of this specification and drawings, directly or indirectly applied to other related technical fields.
Claims
1. A superheterodyne control scheme for qubits, characterized in that, The control scheme includes: limiting the input signal to a specific frequency range to obtain a preselected signal; mixing the preselected signal with a pre-set reference signal to generate a sideband signal; and filtering the sideband signal to remove signals outside the target frequency range to obtain the target signal.
2. The superheterodyne control scheme for a quantum bit according to claim 1, characterized in that, The reference signal is the local oscillator signal.
3. The superheterodyne control scheme for a quantum bit according to claim 1, characterized in that, The phrase "limiting the input signal to a specific frequency range to obtain a preselected signal" refers to limiting the input signal to the first Nyquist zone or the second Nyquist zone.
4. The superheterodyne control scheme for a quantum bit according to claim 1, characterized in that, The process of filtering the sideband signal to remove signals outside the target frequency range and obtain the target signal refers to setting a filtering frequency range according to the frequency range of the target signal, removing high-frequency / low-frequency signals from the sideband signal to obtain the lower sideband signal / upper sideband signal, which is the target signal.
5. The superheterodyne control scheme for a quantum bit according to claim 4, characterized in that, The process of limiting the input signal to a specific frequency range to obtain a preselected signal is achieved through a preselection filter; the process of mixing the preselected signal with a pre-set reference signal to generate a sideband signal is achieved through a mixer; and the process of filtering the sideband signal to remove signals outside the target frequency range to obtain the target signal is achieved through a post-filter.
6. A superheterodyne control system for qubits, wherein the qubits are controlled using a control scheme as described in any one of claims 1-5, characterized in that, The system includes a signal generator, a pre-selection filter, a mixer, and a post-filter connected in sequence, and also includes a microwave signal generator connected to the mixer, which sends a local oscillator signal to the mixer.
7. A superheterodyne control system for qubits according to claim 6, characterized in that, It also includes a microwave transmission link, one end of which is connected to the post-filter signal and the other end is connected to the control port signal of the quantum bit.