A Cryo-BiCMOS Controller for Quantum Computers based on Trapped Beryllium Ions

This article presents a cryo-BiCMOS system on chip (SoC) designed for single and two-qubit gate operations for quantum computers (QCs) based on beryllium trapped-ions (TIs). Signal generation from 0.7 to 1.6 GHz is supported, covering all microwave transitions in a ⁹Be⁺ QC realization. An integrated 48-kbit waveform memory is implemented for improved two-qubit gate fidelity. The fabricated IC is verified in a 4 K environment with up to 4 qubits, thus enabling quantum processor unit (QPU) cointegration. IC operation up to RT ensures compatibility with future system realizations. Measurements demonstrate qubit state control with an oscillation amplitude of 94% before SPAM correction and Rabi oscillation rate of 172 kHz. Evaluations of long sequences of σ_x gates indicate control of the quantum state with high quality. Interaction with one computational zone is possible at a total power consumption of 86 mW translating to 21.5 mW/qubit in the presented measurements. Comparison with the state-of-the-art controller reveals drastic power and form-factor reduction at comparable performance, thus paving the way for a scalable TI platform. The chip is fabricated in a 0.13-µm SiGe BiCMOS technology. To the best of our knowledge, this is the first reported from-scratch system design for TI-based QC concluding with a qubit state manipulation demonstration.