研究目的
Investigating the coherence of electron spin qubits in semiconductor quantum dots and the role of environmental noise during spin manipulation to determine the control fidelity.
研究成果
The study demonstrates a significant enhancement in the coherence time of a GaAs single-electron spin qubit through feedback control, achieving a high π-flip gate fidelity. It identifies high-frequency charge noise as the main limitation for qubit control fidelity, with the noise spectrum resembling 1=f noise observed in isotopically purified silicon qubits.
研究不足
The feedback control's effectiveness is limited by the precision of the Bayesian estimation and the hardware's capability to adjust the microwave frequency rapidly. The study also identifies high-frequency charge noise as a limiting factor for qubit control fidelity.
1：Experimental Design and Method Selection:
The study employs a feedback-control technique to actively suppress quasistatic noise and uses a triple quantum dot (TQD) device fabricated on a GaAs/AlGaAs heterostructure wafer for electron spin qubit manipulation.
2：Sample Selection and Data Sources:
The experiment uses a single-electron spin qubit located in the middle quantum dot of the TQD device, with an ancilla electron spin in the right quantum dot for readout.
3：List of Experimental Equipment and Materials:
The setup includes a dilution refrigerator, Ti/Au gate electrodes, a Co micromagnet, and a digital signal processing (DSP) hardware with programmable logic (FPGA) for feedback control.
4：Experimental Procedures and Operational Workflow:
The experiment involves initializing the qubit, applying microwave bursts for manipulation, and using a feedback loop to adjust the microwave frequency based on the qubit's estimated frequency.
5：Data Analysis Methods:
The study analyzes the coherence and fidelity of the qubit through Ramsey and Rabi oscillation measurements, using Bayesian estimation for frequency detuning and randomized benchmarking for gate fidelity assessment.
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