Cryogenic Controller for Electrostatically Controlled Quantum Dots in 22-nm Quantum SoC

Abstract

We present a fully integrated cryogenic controller for electrostatically controlled quantum dots (QDs) implemented in a commercial 22-nm FD-SOI CMOS process and operating in a quantum regime. The QDs are realized in local well areas of transistors separated by tunnel barriers controlled by voltages applied to gate terminals. The QD arrays (QDA) are co-located with the control circuitry inside each quantum experiment cell, with a total of 28 of such cells comprising this system-on-chip (SoC). The QDA structure is controlled by small capacitive digital-to-analog converters (CDACs) and its quantum state is measured by a single-electron detector.The SoC operates at a cryogenic temperature of 3.4 K. The occupied area of each QD array is 0.7×0.4 µm 2 , while each QD occupies only 20×80 nm 2 . The low power and miniaturized area of these circuits are an important step on the way for integration of a large quantum core with millions of QDs, required for practical quantum computers. The performance and functionality of the CDAC are validated in a loop-back mode with the detector sensing the CDAC-compelled electron tunneling from the quantum point contact (QPC) node into the quantum structure. Position of the injected charge inside the QD array is intended to be controlled through the CDAC codes and programmable pulse width. Quantum effects are shown by an experimental characterization of charge injection and quantization into the QD array consisting of three coupled QDs. The charge can be transferred to a QD and sensed at the QPC, and this process is controlled by the relevant voltages and CDACs.Index Terms-Capacitive DAC (CDAC), charge qubits, cryo-CMOS, fully depleted silicon-on-insulator (FD-SOI), imposer, positionbased qubits, quantum computer (QC), quantum dot (QD), single-electron detector, single-electron injector. I. INTRODUCTIONQ UANTUM computing is a new paradigm that utilizes the fundamental principles of quantum mechanics, such as superposition, interference and entanglement [1], [2]. The range of complex problems from mathematics, chemistry and material science that could be solved with quantum computing is far beyond the reach of today's most powerful supercomputers. The potential is thus immense. Quantum bits (qubits), basic units of quantum information, operate at a molecular/atomic level. They are extremely fragile and difficult to manipulate and read out. Some quantum computer technologies, such as based on trapped ions and photons, do not require the equipment to be cryogenically cooled [3], [4], but the majority of qubits must operate under extremely low Manuscript received