Semiconductor qubits on the move

In recent years, planar germanium qubits in Ge/SiGe heterostructures emerged as a compelling platform for quantum computation[1]. Their favourable properties enabled to demonstrate a four-qubit quantum processor [2] and the implementation of scalable control strategies [3]. However, to demonstrate a quantum advantage with semiconductor qubits, larger quantum dot systems need to be developed meeting stringent requirements in device quality and performance.

To this end, we develop an extended system comprising 10 quantum dot qubits, where we have control over the interdot tunnel coupling and the detuning of each of the individual quantum dots. We operate the array at low magnetic fields of tens of mT. We develop a method that can statistically characterize the full system, by shuttling coherently through the array and only requiring to establish readout of a single spin. [4]. Variations in the spin quantization axes give rise to spin rotations, which allow to implement low-power single-qubit gates and to rapidly assess the 10 g-factors and dephasing times. By characterising multiple devices, we can interpret our results in terms of shape and quantum dot confinement, paving the way towards g-factor engineering for better qubit addressability in large architectures.

References:

1. G. Scappucci et al., Nature Rev. Mat. (2021).

2. N.W. Hendrickx et al., Nature 591, 580–585 (2021)

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

4. F. van Riggelen-Doelman, arXiv:2308.02406 (2023)