| In the past few decades,circuit quantum electrodynamics(c QED)has attracted widespread attention as a possible solution for quantum information processing(QIP).By coupling the qubit with the resonant cavity,non-destructive measurement of the qubit can be achieved.Since the qubit is not directly coupled to the environment,the decoherence time and the fidelity of gate operations have been greatly improved com-pared to previous superconducting qubits.In recent years,people have used supercon-ducting quantum computers to surpass classical computers in solving specific problems(random chromatic sampling)and achieve quantum supremacy.Large companies such as Google,IBM,and Huawei,as well as governments and research institutions of vari-ous countries have invested a lot of wealth in quantum computing and have made a lot of progress.It is expected to realize large-scale quantum computing in the future.This thesis reports on my related work in quantum computing measurement and active reset.Superconducting qubits have a central position in quantum computing research.After people’s unremitting efforts,the fidelity of single-bit logic gates has already reached 99.9%.In the past two years,multiple groups have proposed different schemes to achieve a two-bit logic gate operation fidelity greater than 99.6%.At this time,the fidelity of the qubit gate is mainly limited by the decoherence time,which lays the foun-dation for the realization of quantum error correction.The error correction algorithm represented by the surface code is based on auxiliary qubits for parity measurement.When an error occurs in the quantum circuit,the parity changes and is detected by people.This algorithm requires that the auxiliary qubits can be initialized frequently,which puts forward requirements for active reset.Existing active reset schemes,in-cluding feedback,microwave drive,frequency detuning,etc.,require the introduction of additional electronic equipment(FPGA)or quantum circuit(resonant cavity),which brings challenges to experimental operation and sample preparation.We propose a new active reset method,which uses auxiliary qubits to achieve fast initialization.At present,the efficiency of initialization is mainly limited by the fi-delity of SWAP gate operation,and there is still a gap compared with other solutions.However,this scheme is completely based on the existing experimental methods,and with the further improvement of the fidelity of gate operation,there is a lot of room for improvement.In addition,since there is no additional dissipation channel,the deco-herence performance of the qubit will not be reduced by the influence of low-quality cavities.Our solution can reset the qubit to the ground state faster,and at the same time achieve quantum cooling,which is of great significance for maintaining the coherence of qubits and high-fidelity control.We have verified this scheme experimentally and proved its ability to initialize qubits quickly.This solution is simple and fast,does not require demanding experimental equipment,and is easy to expand on a large scale.It will definitely be useful in future quantum computers. |
