Frequency modulation device and method for superconducting quantum bit device, electronic device and storage medium

Abstract

The present application provides a frequency modulation device and method, electronic device and storage medium for superconducting quantum bit devices, and relates to the field of superconducting quantum computing technology. The frequency modulation device for superconducting quantum bit devices includes: a laser, an optical shutter, a first optical focusing lens, a beam splitter, a second optical focusing lens, a CMOS camera, and a host computer. The phase-locked amplifier is used to monitor the resistance value of the superconducting quantum bit device, and when the resistance value of the superconducting quantum bit device is less than a set value, the feedback signal is output to the host computer. The host computer outputs a first control signal to the laser based on the feedback signal to control the power and / or bandwidth of the mode-locked laser pulse output by the laser, and / or outputs a second control signal to the optical shutter to control the opening time and / or number of openings of the optical shutter, thereby changing the frequency of the superconducting quantum bit device and realizing an orderly arrangement of the resonant frequency of the superconducting quantum bit device in a highly integrated chip.

Description

Technical Field

[0001] The present application relates to the field of superconducting quantum computing technology, and more specifically, to a frequency modulation device and method, electronic equipment, and storage medium for superconducting quantum bit devices. Background Art

[0002] Josephson junction-based superconducting quantum computing, with its excellent Hamiltonian designability, ease of scalability, and ease of coupling and manipulation, has become one of the most sought-after physical implementations of quantum computing. Currently, superconducting quantum computing chips have reached the 100-bit scale and are rapidly expanding to larger scales.

[0003] During large-scale expansion, the parameters of each qubit in the chip must be reasonably distributed within a narrow frequency band, thus facing the problem of "frequency collision": two qubits with different frequencies, as designed, must operate at the same or very similar frequencies. However, the critical current of the Josephson junction varies exponentially with the thickness of the barrier layer, making it difficult to achieve very high consistency and uniformity in its preparation parameters from a process perspective. This problem is particularly serious for fixed-frequency qubits with single Josephson junctions, as in-situ frequency regulation is impossible at extremely low temperatures.

[0004] Laser annealing technology, through a focused laser beam, can locally adjust the parameters of a qubit's Josephson junction. This is primarily achieved through the thermal effect of laser irradiation, which alters the properties of the Josephson junction's tunneling barrier. This allows the qubit frequency to be preset to a desired level, mitigating frequency collision issues. Therefore, laser annealing has become a key technology for producing high-quality, fixed-frequency qubit chips.

[0005] The existing laser annealing technologies are all based on single crystal silicon substrates. Single crystal silicon is a commonly used substrate material for growing Josephson junctions. However, at low temperatures (20mK operating temperature), silicon has high dielectric loss in the radio frequency band (5-10GHz band). This will lead to a more serious decoherence process, resulting in the coherent quantum state of the quantum bit being maintained at only 10 microseconds. A shorter coherence time means that there is a greater probability of introducing errors in the process of quantum computing, which will lead to a higher probability of introducing errors.

[0006] This limits the improvement of quantum computing fidelity and the integration of quantum chips.

[0007] In order to overcome the disadvantages of silicon substrates, researchers used single-crystal sapphire as a substrate for preparing quantum bits. Single-crystal sapphire substrates are used instead of single-crystal silicon because the dielectric loss of sapphire in the radio frequency band is two orders of magnitude smaller than that of silicon at low temperatures (20mK). However, after replacing the substrate, the coherence time of the quantum bit can be increased by one order of magnitude. Although the coherence of the quantum bit has been significantly improved, due to the lack of processing methods when preparing highly integrated quantum chips, the "frequency collision" problem of the quantum bit on the sapphire substrate has not been effectively solved. Summary of the Invention

[0008] In order to solve at least one of the above problems, the present application proposes a frequency modulation device and method, an electronic device and a storage medium for a superconducting quantum bit device.

[0009] According to the first aspect of the present application, at least one embodiment of the present application provides a frequency modulation device for a superconducting quantum bit device, comprising: a laser for emitting a mode-locked laser pulse; an optical shutter for controlling the passage of the mode-locked laser pulse; a first optical focusing lens for focusing and amplifying the mode-locked laser pulse to generate a laser spot; a beam splitter for transmitting the laser spot to the superconducting quantum bit device; a second optical focusing lens for collecting an optical signal reflected from the surface of the superconducting quantum bit device; a CMOS camera connected to the second optical focusing lens for receiving the optical signal; and a host computer connected to the CMOS camera for A signal is used to locate the relative position between the superconducting quantum bit device and the laser spot so that the laser spot can act on the superconducting quantum bit device; a phase-locked amplifier is used to monitor the resistance value of the superconducting quantum bit device, and when the resistance value of the superconducting quantum bit device is less than a set value, output a feedback signal to the host computer, and the host computer is further used to output a first control signal to the laser according to the feedback signal to control the power and / or bandwidth of the mode-locked laser pulse output by the laser, and / or output a second control signal to the optical shutter to control the opening time and / or number of openings of the optical shutter, thereby changing the frequency of the superconducting quantum bit device.

[0010] For example, in some embodiments of the present application, it also includes: a first ultrafast optical reflector, arranged between the laser and the optical shutter to reflect the mode-locked laser pulse to the optical shutter; a second ultrafast optical reflector, arranged between the optical shutter and the first optical focusing lens, for receiving the mode-locked laser pulse passing through the optical shutter and reflecting it to the first optical focusing lens.

[0011] For example, in some embodiments of the present application, the superconducting quantum bit device includes: a single crystal sapphire substrate; and a Josephson junction grown on the single crystal sapphire substrate.

[0012] For example, in some embodiments of the present application, the frequency of the superconducting quantum bit device is inversely proportional to the resistance of the Josephson junction:

[0013]

[0014] Wherein, f is the frequency of the superconducting quantum bit, h is the Planck constant, e is the natural constant, Δ is the superconducting energy gap of the Josephson junction material, and E c is the design parameter of the superconducting quantum bit, and R is the resistance of the Josephson junction.

[0015] For example, in some embodiments of the present application, the laser is a Ti:Sapphire mode-locked laser.

[0016] For example, in some embodiments of the present application, the magnification of the first optical focusing lens and the second optical focusing lens is 5-15 times.

[0017] For example, in some embodiments of the present application, the reflectivity and transmittance of the beam splitter are 3:1-18:1.

[0018] According to the second aspect of the present application, at least one embodiment of the present application provides a frequency modulation method for a superconducting quantum bit device, which is executed by a host computer of a frequency modulation device as described in any one of the first aspects, and the frequency modulation method includes: receiving a feedback signal output by the phase-locked amplifier; outputting a first control signal to the laser to control the power and / or bandwidth of the mode-locked laser pulse output by the laser; outputting a second control signal to the optical shutter to control the opening time and / or number of openings of the optical shutter; by changing the power and / or bandwidth of the mode-locked laser pulse, the opening time and / or number of openings of the optical shutter, so as to achieve the heating of the superconducting quantum bit device by the mode-locked laser pulse, thereby changing the resistance value of the superconducting quantum bit device, and achieving frequency modulation of the superconducting quantum bit device.

[0019] According to the third aspect of the present application, at least one embodiment of the present application provides an electronic device, comprising: one or more processors; a memory for storing one or more programs; when the one or more programs are executed by the one or more processors, the one or more processors execute the method described in the second aspect.

[0020] According to a fourth aspect of the present application, at least one embodiment of the present application provides a computer-readable storage medium having a computer program stored thereon, characterized in that when the program is executed by a processor, the method described in the second aspect is implemented.

[0021] Through the above-mentioned example embodiments, the present application provides a frequency modulation device and method for superconducting quantum bit devices, which replaces the single crystal silicon substrate with a single crystal sapphire substrate, and replaces the 532nm continuous laser with a mode-locked pulse laser. The sapphire substrate is selectively and locally heated by means of a pulsed laser, thereby adjusting the tunneling resistance of the superconducting quantum bit devices one by one, and finally realizing the orderly arrangement of the resonant frequencies of the superconducting quantum bit devices in a highly integrated chip.

[0022] It should be understood that the foregoing general description and the following detailed description are merely illustrative and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] By describing in detail exemplary embodiments thereof with reference to the accompanying drawings, the above and other objects, features and advantages of the present application will become more apparent. The drawings described below are only some embodiments of the present application, and are not intended to limit the present application.

[0024] Figure 1 A schematic diagram showing a frequency modulation device for a superconducting quantum bit device according to an exemplary embodiment;

[0025] Figure 2 A schematic diagram illustrating a frequency modulation method for a superconducting quantum bit device according to an exemplary embodiment is shown;

[0026] Figure 3 A diagram showing the effect of changing the resistance value of a superconducting quantum bit device by changing the number of times the optical shutter is opened according to an exemplary embodiment;

[0027] Figure 4 A comparison diagram showing a scheme without laser annealing and a scheme with laser annealing according to an exemplary embodiment;

[0028] Figure 5 The figure shows a structural diagram of an electronic device provided by the present application. DETAILED DESCRIPTION

[0029] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many 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 concepts of the example embodiments.

[0030] The same reference numerals in the drawings denote the same or similar parts, and thus their repeated description will be omitted.

[0031] The described features, structures or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of these specific details, or other methods, components, materials, devices, etc. may be employed. In these cases, well-known structures, methods, devices, implementations, materials or operations will not be shown or described in detail.

[0032] The flowcharts shown in the accompanying drawings are for illustrative purposes only and do not necessarily include all contents and operations / steps, nor must they be executed in the order described. For example, some operations / steps may be decomposed, while others may be combined or partially combined. Therefore, the actual execution order may vary depending on the actual situation.

[0033] The terms "first," "second," and the like in the specification and claims of this application and the accompanying drawings are used to distinguish between different objects, not to describe a particular order. Furthermore, the terms "including," "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0034] Those skilled in the art will understand that the drawings are merely schematic diagrams of example embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing the present application, and therefore cannot be used to limit the scope of protection of the present application.

[0035] Figure 1 A schematic diagram of a frequency modulation apparatus for a superconducting quantum bit device according to an exemplary embodiment is shown.

[0036] like Figure 1 As shown, the frequency modulation device for superconducting quantum bit devices includes: a laser 1, an optical shutter 3, a first optical focusing lens 4, a beam splitter 5, a second optical focusing lens 6, a CMOS camera 7, a host computer 9 and a lock-in amplifier 8.

[0037] Among them, the laser 1 is used to emit the mode-locked laser pulse. The optical shutter 3 is used to control the passage of the mode-locked laser pulse. The first optical focusing lens 4 is used to focus and amplify the mode-locked laser pulse to generate a laser spot. The beam splitter 5 is used to transmit the laser spot to the superconducting quantum bit device.

[0038] The second optical focusing lens 6 is used to collect light signals reflected from the surface of the superconducting qubit device. A CMOS camera 7 is connected to the second optical focusing lens 6 for receiving the light signal. A host computer 9 is connected to the CMOS camera 7 for locating the relative position between the superconducting qubit device and the laser spot based on the light signal, so that the laser spot can act on the superconducting qubit device. The lock-in amplifier 8 is used to monitor the resistance value of the superconducting qubit device and output a feedback signal to the host computer 9 when the resistance value of the superconducting qubit device is less than a set value. The host computer 9 is also used to output a first control signal to the laser 1 based on the feedback signal to control the power and / or bandwidth of the mode-locked laser pulse output by the laser 1, and / or output a second control signal to the optical shutter 3 to control the opening time and / or number of openings of the optical shutter 3, so that when the laser spot generated by the mode-locked pulse laser is focused on the superconducting qubit device, it will heat the surface of the superconducting qubit device, thereby increasing the resistance value of the superconducting qubit device and changing the frequency of the superconducting qubit device.

[0039] According to some embodiments, the superconducting quantum bit device requiring frequency adjustment in the present application includes: a single crystal sapphire substrate and a Josephson junction, wherein the Josephson junction is grown on the single crystal sapphire substrate.

[0040] Moreover, the frequency of the superconducting quantum bit device is inversely proportional to the resistance of the Josephson junction:

[0041]

[0042] Where f is the frequency of the superconducting quantum bit, h is the Planck constant, e is the natural constant, Δ is the superconducting energy gap of the Josephson junction material, and E c is the design parameter of the superconducting quantum bit, and R is the resistance of the Josephson junction.

[0043] According to an example embodiment, the frequency modulation device further includes a first ultrafast optical mirror 201 and a second ultrafast optical mirror 202 .

[0044] like Figure 1 As shown, the first ultrafast optical reflector 201 is disposed between the laser 1 and the optical shutter 3 to reflect the mode-locked laser pulse to the optical shutter 3. The second ultrafast optical reflector 202 is disposed between the optical shutter 3 and the first optical focusing lens 4 to receive the mode-locked laser pulse passing through the optical shutter 3 and reflect it to the first optical focusing lens 202.

[0045] According to some embodiments, the laser 1 is a Ti:Sapphire mode-locked laser. Mode-locking is a technique in optics for generating extremely short laser pulses, with pulse lengths typically in the order of picoseconds or even

[0046] To femtoseconds.

[0047] According to some embodiments, sapphire is an insulator with a band gap of about 6eV, while silicon is a semiconductor with a band gap of about 1eV. The band structures of the two are completely different, and therefore their responses to lasers are also different. On the one hand, the 532nm continuous laser suitable for silicon will pass through sapphire without absorption and will not be able to effectively heat the superconducting quantum bit material. On the other hand, the mode-locked pulse laser can output ultrafast laser pulses with a pulse width on the order of femtoseconds. These laser pulses have very high instantaneous power (on the order of hundreds of kilowatts), and such instantaneous power can excite thermal effects through nonlinear optical processes in the sapphire material, thereby achieving heating of the material.

[0048] According to some embodiments, the magnification of the first optical focusing lens 4 and the second optical focusing lens 5 is 5-15 times, and the reflectivity and transmittance ratio of the beam splitter is 3:1-18:1. Preferably, the magnification of the first optical focusing lens 4 and the second optical focusing lens 5 is 10 times, and the reflectivity and transmittance ratio of the beam splitter is 9:1. This application only uses this as an example, but the magnification of the optical focusing lens and the reflectivity and transmittance ratio of the beam splitter are not limited to this.

[0049] The present application provides a frequency modulation device for superconducting qubit devices, which replaces a single-crystal silicon substrate with a single-crystal sapphire substrate and replaces a 532nm continuous laser with a mode-locked pulse laser. The sapphire substrate is selectively and locally heated by means of a pulsed laser, thereby adjusting the tunneling resistance (i.e., the resistance of the Josephson junction) of the superconducting qubit devices one by one, and ultimately achieving an orderly arrangement of the resonant frequencies of the superconducting qubit devices in a highly integrated chip (the number of superconducting qubit devices is greater than 100).

[0050] Figure 2 A schematic diagram illustrating a frequency modulation method for a superconducting quantum bit device according to an exemplary embodiment is shown.

[0051] like Figure 2 As shown, the frequency modulation method for a superconducting quantum bit device is executed by the host computer of the frequency modulation device described above, and the frequency modulation method includes steps S201-S203:

[0052] In step S201 , a feedback signal output by a lock-in amplifier is received.

[0053] According to an exemplary embodiment, a lock-in amplifier monitors the resistance of a superconducting qubit device and outputs a feedback signal to a host computer when the resistance of the superconducting qubit is less than a set target value. The host computer receives the feedback signal from the lock-in amplifier and uses it to output a control signal.

[0054] In step S202 , a first control signal is output to the laser to control the power and / or bandwidth of the mode-locked laser pulse output by the laser.

[0055] According to an example embodiment, the host computer outputs a first control signal to the laser to control the power and / or bandwidth of the mode-locked laser pulse output by the laser, so that when the laser spot generated by the mode-locked pulse laser is focused on the superconducting qubit device, it will heat the surface of the superconducting qubit device, thereby increasing the resistance value of the superconducting qubit device and further changing the frequency of the superconducting qubit device.

[0056] In step S203 , a second control signal is output to the optical shutter to control the opening time and / or opening times of the optical shutter.

[0057] According to an example embodiment, the host computer outputs a second control signal to the optical shutter to control the opening time and / or the number of openings of the optical shutter, so that after the mode-locked pulse laser passes through the optical shutter, the laser spot generated by the second ultrafast optical reflector is focused on the superconducting qubit device, which heats the surface of the superconducting qubit device, thereby increasing the resistance value of the superconducting qubit device and further changing the frequency of the superconducting qubit device.

[0058] like Figure 3 As shown in the figure, the horizontal axis is the number of times the optical shutter is opened, and the vertical axis is the rate of change of the resistance value of the superconducting qubit device. It can be seen that by increasing the number of times the optical shutter is opened, the resistance value of the superconducting qubit device can be changed.

[0059] Figure 4 Schematic diagrams show the effect of reducing the resistance fluctuation variance of a superconducting qubit device on a sapphire substrate, using laser annealing and without laser annealing. The left side shows the solution without laser annealing, while the right side shows the solution with laser annealing. As can be seen, using laser annealing on a sapphire test chip can reduce the statistical variance of the superconducting qubit device's resistance from 3% to 1%. Furthermore, when the resistance fluctuation variance is within 1%, the frequency fluctuation variance of the qubit device can be kept below 0.5%, achieving the same performance as previous silicon-based chips.

[0060] Figure 5 The figure shows a structural diagram of an electronic device provided by the present application.

[0061] See Figure 5 , Figure 5 An electronic device is provided, comprising a processor and a memory. The memory stores computer instructions, and when the computer instructions are executed by the processor, the processor executes the computer instructions to achieve the following Figure 2The method and refinement scheme shown.

[0062] It should be understood that the above device embodiments are only illustrative, and the device disclosed in this application can also be implemented in other ways. For example, the division of units / modules in the above embodiments is only a logical function division, and there may be other division methods in actual implementation. For example, multiple units / modules

[0063] Elements, modules or components may be combined or integrated into another system, or some features may be omitted or not performed.

[0064] In addition, unless otherwise specified, the functional units / modules in the various embodiments of the present application may be integrated into a single unit / module, each unit / module may exist physically separately, or two or more units / modules may be integrated together. The aforementioned integrated units / modules may be implemented in the form of hardware or software program modules.

[0065] If the integrated unit / module is implemented in hardware, the hardware may be digital circuits, analog circuits, etc. The physical implementation of the hardware structure includes, but is not limited to, transistors, memristors, etc. Unless otherwise specified, the processor or chip may be any appropriate hardware processor, such as a CPU, GPU, FPGA, DSP, and ASIC. Unless otherwise specified, on-chip cache, off-chip memory, and storage may be any appropriate magnetic storage medium or magneto-optical storage medium, such as resistive random access memory (RRAM), dynamic random access memory (DRAM), static random access memory (SRAM), enhanced dynamic random access memory (EDRAM), high-bandwidth memory (HBM), hybrid memory cube (HMC), etc.

[0066] If the integrated unit / module is implemented in the form of a software program module and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of the present application is essentially or the part that contributes to the prior art or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a memory, including a number of instructions for enabling a computer device (which can be a personal computer, server or network device, etc.) to execute all or part of the steps of the various embodiments of the present disclosure. The aforementioned memory includes: various media that can store program codes, such as a USB flash drive, a read-only memory (ROM), a random access memory (RAM), a mobile hard disk, a magnetic disk or an optical disk.

[0067] The embodiment of the present application also provides a non-transitory computer storage medium storing a computer program, which, when executed by multiple processors, causes the processors to execute the following Figure 2 The method and refinement scheme shown.

[0068] It should be clearly understood that this application describes how to form and use specific examples, but this application is not limited to any details of these examples. On the contrary, based on the teaching of the content disclosed in this application, these principles can be applied to many other embodiments.

[0069] Furthermore, it should be noted that the aforementioned figures are merely illustrative of the processes included in the methods according to exemplary embodiments of the present application and are not intended to be limiting. It is readily understood that the processes illustrated in the aforementioned figures do not indicate or limit the temporal order of these processes. Furthermore, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0070] While the exemplary embodiments of the present application have been specifically illustrated and described above, it should be understood that the present application is not limited to the detailed structures, configurations, or implementations described herein; rather, the present application is intended to encompass various modifications and equivalent configurations within the spirit and scope of the appended claims.

Claims

1. A frequency modulation device for a superconducting quantum bit device, characterized in that: include: A laser for emitting a mode-locked laser pulse; an optical shutter for controlling the passage of the mode-locked laser pulse; a first optical focusing lens, used for focusing and amplifying the mode-locked laser pulse to generate a laser spot; A beam splitter, used to transmit the laser spot to the superconducting quantum bit device; A second optical focusing lens is used to collect light signals reflected from the surface of the superconducting quantum bit device; a CMOS camera, connected to the second optical focusing lens, and configured to receive the optical signal; a host computer, connected to the CMOS camera, for locating the relative position between the superconducting quantum bit device and the laser spot according to the optical signal, so that the laser spot can act on the superconducting quantum bit device; A lock-in amplifier is used to monitor the resistance value of the superconducting qubit device and output a feedback signal to the host computer when the resistance value of the superconducting qubit device is less than a set value. The host computer is also used to output a first control signal to the laser based on the feedback signal to control the power and / or bandwidth of the mode-locked laser pulse output by the laser, and / or output a second control signal to the optical shutter to control the opening time and / or number of openings of the optical shutter, thereby changing the frequency of the superconducting qubit device.

2. The frequency modulation device according to claim 1, wherein Also includes: a first ultrafast optical reflector, disposed between the laser and the optical shutter, to reflect the mode-locked laser pulse to the optical shutter; The second ultrafast optical reflector is arranged between the optical shutter and the first optical focusing lens, and is used for receiving the mode-locked laser pulse passing through the optical shutter and reflecting it to the first optical focusing lens.

3. The frequency modulation device according to claim 1, wherein The superconducting quantum bit device comprises: Single crystal sapphire substrate; A Josephson junction is grown on the single crystal sapphire substrate.

4. The frequency modulation device according to claim 3, wherein The frequency of the superconducting qubit device is inversely proportional to the resistance of the Josephson junction: Wherein, f is the frequency of the superconducting quantum bit, h is the Planck constant, e is the natural constant, Δ is the superconducting energy gap of the Josephson junction material, and E c is the design parameter of the superconducting quantum bit, and R is the resistance of the Josephson junction.

5. The frequency modulation device according to claim 1, wherein The laser is a titanium sapphire mode-locked laser.

6. The frequency modulation device according to claim 1, wherein The magnification of the first optical focusing lens and the second optical focusing lens is 5-15 times.

7. The frequency modulation device according to claim 1, wherein The reflectivity and transmittance of the beam splitter are 3:1-18:

1.

8. A frequency modulation method for a superconducting quantum bit device, characterized in that: Executed by a host computer of the frequency modulation device according to any one of claims 1 to 7, the frequency modulation method includes: receiving a feedback signal output by the lock-in amplifier; Outputting a first control signal to the laser to control the power and / or bandwidth of the mode-locked laser pulse output by the laser; Outputting a second control signal to the optical shutter to control the opening time and / or opening times of the optical shutter; By changing the power and / or bandwidth of the mode-locked laser pulse, the opening time and / or the number of openings of the optical shutter, the mode-locked laser pulse heats the superconducting qubit device, thereby changing the resistance value of the superconducting qubit device and achieving frequency modulation of the superconducting qubit device.

9. An electronic device, characterized in that: include: one or more processors; a memory for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors are caused to perform the method according to claim 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to claim 8 is implemented.

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