A Fully Integrated DAC for CMOS Position-Based Charge Qubits with Single-Electron Detector Loopback Testing

This letter presents a fully integrated interface circuitry with a position-based charge qubit structure implemented in 22-nm FDSOI CMOS. The quantum structure is controlled by a tiny capacitive DAC (CDAC) that occupies 3.5×45 μm
²
and consumes 0.27mW running at a 2-GHz system clock. The state of the quantum structure is measured by a single-electron detector that consumes 1 mW (including its output driver) with an area of 40×25 μm
²
. The low power and miniaturized layout of these circuits pave the way for integration in a large quantum core with thousands of qubits, which is a necessity for practical quantum computers. The CDAC output noise of 12 μV-rms is estimated through mathematical analysis while the ≤ 0.225 mV-rms input referred noise of the detector is verified by measurements at 3.4K. The functionality of the system and performance of the CDAC are verified in a loopback mode with the detector sensing the CDAC-induced electron tunneling from the floating diffusion node into the quantum structure.