State preparation of a fluxonium qubit with feedback from a custom FPGA-based platform

Abstract

We developed a versatile integrated control and readout instrument for experiments with superconducting quantum bits (qubits), based on a field-programmable gate array (FPGA) platform. Using this platform, we perform measurement-based, closed-loop feedback operations with $428\mathrm{ns}$ platform latency. The feedback capability is instrumental in realizing active reset initialization of the qubit into the ground state in a time much shorter than its energy relaxation time $T_1$. We show experimental results demonstrating reset of a fluxonium qubit with $99.4\%$ fidelity, using a readout-and-drive pulse sequence approximately $1.5\mu \mathrm{s}$ long. Compared to passive ground state initialization through thermalization, with the time constant given by $T_1=80\mu \mathrm{s}$, the use of the FPGA-based platform allows us to improve both the fidelity and the time of the qubit initialization by an order of magnitude.

arXiv comment3 pages, 2 figures. The following article has been submitted to the AIP Conference Proceedings of the Fifth International Conference on Quantum Technologies (ICQT-2019)

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• Quantum non-demolition dispersive readout of a superconducting artificial atom using large photon numbers
• Amplitude and frequency sensing of microwave fields with a superconducting transmon qudit
• FPGA-based electronic system for the control and readout of superconducting quantum processors
• ICARUS-Q: Integrated Control and Readout Unit for Scalable Quantum Processors
• Versatile Configuration and Control Framework for Real Time Data Acquisition Systems
• Efficient initialization of fluxonium qubits based on auxiliary energy levels
• High coherence fluxonium manufactured with a wafer-scale uniformity process
• Tunable coupling scheme for implementing two-qubit gates on fluxonium qubits
• Measurement and control of a superconducting quantum processor with a fully-integrated radio-frequency system on a chip
• The Virtual Quantum Device (VQD): A tool for detailed emulation of quantum computers