Quantum computers are one of the most exciting developments of today’s physics. There are a lot of open questions in this field: on which technical platform they should be built, how should they work, which algorithms should they use, just to name a few.
Michelle Simmons is a Professor at the University of New South Wales in Sydney and the Director of the Centre of Excellence for Quantum Computation and Communication Technology. Her work is making a strong case for atomic-scale qubits. Prof. Simmons and her team have developed Scanning Tunnelling Microscope (STM) Hydrogen resist lithography. With an STM tip, hydrogen atoms that cover an atomically flat silicon substrate, are locally desorbed from the surface. The remaining hydrogen then acts as a lithographic mask for phosphine molecules. After the mask is removed, epitaxial silicon grown via molecular beam epitaxy encapsulates the device. The whole device circuitry is written this way, and protected from any dangling bonds, interfaces, or defects. Such devices are atomically precise while being incredibly robust and allow for 3-dimensional many-qubits architecture, which the team is exploring now.
Michelle Simmons shared with The Lithographer how the idea of such devices emerged, why she is making qubits this way, and what challenges her team had to overcome so far. “Every time humans figure out how to control the world at smaller length scales, good things happen” – says Prof. Simmons. Read the full interview in the Quantum issue of The Lithographer, p.26.