13.3 A Cryo-BiCMOS Controller for 9Be+-Trapped-Ion-Based Quantum Computers

Trapped ions (TI) are one of the leading platforms for the realization of a universal quantum computer (QC). They feature several advantages compared to competing technologies. Key benefits of TI qubits utilizing hyperfine transitions are the long achievable coherence time T2 of up to hours and the almost infinite excited state lifetime T1 [1]. The error rate of single-qubit operations is already in the 10^–6 range [2], while the error rate of entangled two-qubit gates approaches the fault tolerance error-correction threshold of 10^–4 [3], [4]. The combined state preparation and measurement fidelity depends on the ion species and is usually above 99.5%. Ion traps can comfortably work at moderate cryogenic temperatures around 4 K, and even room temperature (RT) operation has been demonstrated [4]. The quantum-charge-coupled-device (QCCD) [5], [6] architecture allows scalable ion trapping and shuttling, thus enabling all-to-all qubit interconnection.