Research On Key Technologies Of Electronic Control Systems In Error-correctable Superconducting Quantum Processors

With the vigorous development of the information industry in modern society,people’s demands for the ability and speed of computing are almost everlasting.However,as the size of classical transistor approaches the atomic level where quantum effect governs the role of behavior,the classical computing gradually approaches its limit.In this case,new more powerful computing paradigms are urgently required.Fortunately,quantum computing provides such a new computing paradigm that makes use of the principles of quantum mechanics,such as quantum superposition and entanglement,to parallelly execute computing tasks.Therefore,quantum computers can efficiently solve some specific computing problems while they are intractable for classical computers,resulting in an exponential quantum advantage.Among all candidates,superconducting qubit has received extensive attention and development recently,owing to its extremely high compatibility with existing semiconductor technologies in the design,fabrication and measurement,and its excellent performance in fidelity,decoherence time,etc.Very recently,Google and University of Science and Technology of China have successively used superconducting quantum computing to achieve "quantum computational advantage",nevertheless,there is still a long way to go before error-corrected universal quantum computing.To this end,multiple physical qubits should be encoded into one logical qubit to tolerant depolarization errors.Meanwhile,fast measurement,feedback and control of qubits are needed to correct the errors of logical bits.This requires that the electronic control system of superconducting quantum computing can support large-scale qubit control,and can realize fast feedback for error correction processing.During my Ph.D.,my research focused on large-scale control and fast feedback error correction in error-correctable superconducting quantum processors.The research contents of this thesis mainly include:1.From the point of view of the electronic control system,in order to improve the physical integration of the control system,this thesis designs a set of integrated electronic control system,including the chassis structure,the control electronics,and the clock and synchronization structure.Compared with the Zuchongzhi quantum processor electronic measurement and control system of the University of Science and Technology of China,which has achieved the "quantum advantage"[3-4],the physical integration has increased by about 1.3 times.2.In order to improve the efficiency of complex experimental systems in largescale quantum processors,two high-efficiency measurement and control technologies are studied in this paper:1)The high-efficiency layered communication mechanism,which divides the communication links between devices and within devices in the control system into 3 communication layers,for which,the communication protocols are designed separately.Finally,a set of communication architecture that is easy to expand and transplant is constructed.2)The efficient experimental scheduling scheme.By optimizing the experimental processing flow,each experimental task is scheduled in parallel.Verify the scheme on a 62-bit electronic system and a 24-bit quantum processor.Compared with Zuchongzhi,the experimental efficiency is improved by about 62%when running complex Xeb experiments.3.Focusing on the requirement of fast dynamic feedback,this thesis designs a dynamic arbitrary waveform generator by studying the feedback control logic of the control system,which can realize the low-latency real-time modulation output of the qubit control waveform.It also supports non-real-time modulation output.In this mode,the qubit control waveform is pre-generated in the host computer,and the control electronics directly control the output waveform.In the two modes of direct output and modulated output,the loop delay of quantum error correction closed-loop feedback control is 101.5 ns and 133.5 ns,respectively,and the loop delay in direct output is lower than the feedback delay in all public schemes at home and abroad.The main innovations of this thesis are as follows:1.A high-efficiency layered communication protocol is customized to improve communication efficiency on the entire link.In large-scale quantum processors,this communication mechanism can efficiently transmit,distribute and process large amounts of data.And a high-efficiency experimental scheduling scheme for quantum circuits is proposed and implemented,which has the ability to support high-speed and high-precision control of more than 500 qubits.2.A low-latency dynamic arbitrary waveform generator is developed,which can modulate and generate qubit regulation waveforms in real time according to the feedback state information of qubits,laying a foundation for fast dynamic feedback in quantum error correction.