Research On Electronics For Manipulation And Measurement Of Superconducting Quantum Computing

In quantum computing,both data storage and data processing are completed in qubits.For superconducting quantum computing,when performing quantum gate operations,a series of control pulses need to be generated and applied to the qubits in turn.Due to this characteristic that superconducting quantum computing relies on classical electronics to complete the manipulation and measurement of qubits.At present,commercial measurement instruments are widely used in superconducting quantum laboratories in academia.But with the rapid development of the field of superconducting quantum computing,the development of fault-tolerant quantum computing based on quantum error correction and noisy medium-scale quantum computing have brought new challenges to electronic systems for qubit manipulation and measurement:1)The continuous expansion of the number of qubits not only greatly increases the number of electronic channels,but also puts forward higher requirements for the scalability,integration,and synchronization of the system;2)The Quantum error correction algorithm requires quantum feedback to be completed within hundreds of nanoseconds,which means that electronic systems need to have real-time signal processing capabilities;3)Due to the complex low-level constraints of the current quantum underlying circuits,it is difficult for the high-level quantum languages that have been developed to be implemented on real qubits.Electronic systems need to improve the abstraction ability of the underlying circuits and solve the contradiction between abstract quantum algorithms and precise quantum control.In response to these new challenges,this dissertation investigates customized control and measurement electronics systems,focusing on the electronics system architecture,quantum feedback implementation methods,and system control modes.After full investigation,this paper studies the key methods of electronic scheme design.1)Considering that with the increase in the size of qubits,the control and measurement system presents the characteristics of large-scale distributed data conversion,the modular design idea is more suitable for electronic architecture design.As the size of qubits increases,we only need to focus on the combination relationship between modules.In order to further improve the integration level,this paper proposes a qubit manipulation signal generation architecture of "digital I/Q mixing+analog I/Q mixing",in which the radio frequency signal generation architecture based on digital mixing realizes the direct transmission of microwave manipulation signals.This results in half the number of Digital to Analog Converter(DAC)channels compared to traditional analog mixing methods,while removing analog mixing circuitry.Based on FPGA,this system realizes the functions of real-time analysis of qubit state,rapid generation of arbitrary waveforms,and feedback arbitration.The IFAWG and DAQ modules in the quantum feedback loop are specially designed for low latency,the feedback transmission link is optimized in hardware,and the gate sequence generation function and fast demodulation algorithm are implemented in the FPGA firmware,which further reduces the digital signal processing.The delay reduces the feedback delay of the electronic system to 125 ns,reaching the advanced level in this field.2)Drawing on the design ideas of classical processor architecture,a microcontrol architecture based on a quantum instruction set is constructed in the electronic system to improve the abstraction ability of the underlying circuit.The micro-control architecture solution can be designed based on the working platform of the open standard instruction architecture RISC-V.RISC-V CORE and quantum instruction decoder can execute assembly language mixed with classical instructions and quantum instructions.At the same time,the microcontrol architecture is easy to implement operations such as "conditional selection","branch jump" and "loop",which makes the electronic system the potential to realize complex active control algorithms.3)For the low-latency quantum feedback requirement,this paper completes the real-time measurement of the qubit state based on the Field Programmable Gate Array(FPGA).method,processing time,and data transfer volume have been reduced by orders of magnitude.After determining the key methods in the electronic design,this paper designs the electronic system architecture based on the modular design idea.In order to ensure that the electronic system scheme can be fully verified,a prototype system prototype is designed in this paper.The system prototype consists of a System Timing Control Module(STCM),two intermediate frequency arbitrary waveform generator modules(IFAWG),a Radio Frequency Arbitrary Waveform Generator(RFAWG),a High Precision Bias Voltage Generator(BVG)and a Data Acquisition(DAQ)Manipulation and measurement of three superconducting qubits.Finally,this paper conducts electronic testing and qubit characterization experiments for the prototype system prototype.The electronic test results show that the performance of the system prototype meets the requirements of the system design indicators,among which the electronic feedback delay of 125 ns and the system synchronization performance of 5 ps have reached the leading level in this field.In addition,the system prototype successfully realized the manipulation and measurement of the Fluxonium superconducting qubit and completed the qubit characterization experiment.The experimental results of energy relaxation time T1≈90.18 μs and dephasing time T2*≈19.7 μs have reached the advanced level in this field,verifying the feasibility of the electronic system scheme.