A 2x2 Quantum Processor in ²⁸Si/SiGe

Some of the largest semiconductor-based quantum processors are constrained to a linear arrangement of qubits. Executing an algorithm in such one-dimensional arrays demands an excessive overhead and requires higher fidelities to meet error correction thresholds. Thus, it is crucial to expand these linear arrays in the second dimension and increase the connectivity of each qubit. While in other platforms such as GaAs or Ge/SiGe 2D arrays were successfully implemented, such a demonstration has not yet been realized in Si/SiGe.

We present control over a 4-qubit device in a square 2x2 configuration. The device is based on a ²⁸Si/SiGe heterostructure, with each quantum dot tuned to the single electron regime. Utilizing an on-chip micro magnet we selectively drive single-qubit rotations using resonant microwave bursts. Dedicated barrier gates between neighboring quantum dots allow us to implement two-qubit gates between qubits while staying at the noise-resilient symmetry point. Finally, we will present the latest experimental results on crosstalk effects and small-scale algorithms realized in this device.