We show how to absorb fermionic quantum simulation's expensive
fermion-to-qubit mapping overhead into the overhead already incurred by
surface-code-based fault-tolerant quantum computing. The key idea is to process
information in surface-code twist defects, which behave like logical Majorana
fermions. Our approach implements a universal set of fault-tolerant gates on
these logical Majorana fermions by effecting encoded measurement-based
topological quantum computing with them. A critical feature of our approach is
the use of code deformations between logical tetron and logical hexon
surface-code-patch encodings, which enables one to move beyond the limitations
of a wholly square-patch tetronic surface-code approach. To motivate near-term
implementations, we also show how one could realize each of a universal set of
logical Majorana gates on a small-scale testbed using noisy intermediate scale
quantum (NISQ) technology on as few as 13 qubits.Comment: 14 pages, 15 figure