Scalability of of semiconductor quantum dot architectures: shared control, qubit addressability, and connectivity

The efficient control of a large number of qubits is one of the most challenging aspects for practical quantum computing. Current approaches in solid-state quantum technology are based on brute-force methods, where each and every qubit requires at least one unique control line, an approach that will become unsustainable when scaling to the required millions of qubits [1].

In this talk, I will present our progress in this direction and detail our ambitions to advance the state-of-the-art of semiconductor qubits toward fault-tolerant quantum computing. In our path, we adopt concepts from random access architectures in classical electronics and introduce the shared control of semiconductor quantum dots to efficiently operate a two-dimensional crossbar array in planar germanium [2].  We demonstrate the tune-up and the identification of each of the 16 quantum dots of the array in the few-hole regime and establish a method for the selective control of the quantum dot interdot coupling.

Finally, we consider a minimal 2x2 qubit array and investigate both experimentally and theoretically the bichromatic electric dipole spin resonance technique as a method for spatially selective qubit rotations in larger crossbar arrays [3]. We demonstrate coherent bichromatic rotations with Rabi frequencies exceeding 1 MHz, and observe resonance anticrossings originating from the ac Stark shift. I will conclude by presenting our efforts in tuning and controlling a 10-quantum dot qubit system as the basis for the next generation of experiments based on low-power, low magnetic field and high-fidelity quantum gates [4].

1. Franke et al., Microprocess. Microsyst. (2018)

2. Borsoi et al., Nature Nano. 1-7 (2023)

3. John, Borsoi, Gyorgy et al., arXiv:2308.01720 (2023)

4. Wang et al., in preparation (2023)