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upstart writes in with an IRC submission:

Qubits comprised of holes could be the trick to build faster, larger quantum computers:

[...] [According to A/Prof Dimi Culcer (UNSW/FLEET), who led the theoretical roadmap study,] "Our theoretical studies show that a solution is reached by using holes, which can be thought of as the absence of an electron, behaving like positively-charged electrons."

In this way, a quantum bit can be made robust against charge fluctuations stemming from the solid background.

Moreover, the 'sweet spot' at which the qubit is least sensitive to such noise is also the point at which it can be operated the fastest.

"Our study predicts such a point exists in every quantum bit made of holes and provides a set of guidelines for experimentalists to reach these points in their labs," says Dimi.

Reaching these points will facilitate experimental efforts to preserve quantum information for as long as possible. This will also provide strategies for 'scaling up' quantum bits – ie, building an 'array' of bits that would work as a mini-quantum computer.

"This theoretical prediction is of key importance for scaling up quantum processors and first experiments have already been carried out," says Prof Sven Rogge of the Centre for Quantum Computing and Communication Technology (CQC2T)."

"Our recent experiments on hole qubits using acceptors in silicon already demonstrated longer coherence times than we expected," says A/Prof Joe Salfi of the University of British Columbia. "It is encouraging to see that these observations rest on a firm theoretical footing. The prospects for hole qubits are bright indeed."

Journal Reference:
Zhanning Wang, Elizabeth Marcellina, Alex. R. Hamilton, et al. Optimal operation points for ultrafast, highly coherent Ge hole spin-orbit qubits [open], npj Quantum Information (DOI: 10.1038/s41534-021-00386-2)

Original Submission