Non-abelian quasi-particles, topoconductors and Microsoft's Majorana-1 chip
Third installment of the series, covering Majorana fermions, topological qubits, and a critical analysis of Microsoft’s Majorana-1 chip announcement. Originally published in French.
Majorana fermions are emergent excitations in condensed matter systems, not elementary particles in the Standard Model sense. They satisfy the self-conjugation condition (ψ = ψc) and appear at interfaces of topological superconducting systems. Their fundamental property is the non-commutativity of braiding: exchanging two fermions produces a unitary transformation whose result depends on the operation order.
The article distinguishes Majorana fermions (particle physics), Majorana modes (condensed matter), and Majorana zero-mode states (MZMs). Topoconductors are semiconductor nanowires (InAs, InSb) coupled to superconducting layers (Al, NbTiN), under perpendicular magnetic field, with electrostatic gates for manipulation.
Topological computing robustness relies on exclusive dependence on the braiding path’s homotopy class, not geometric details. However, braiding alone is insufficient for computational universality: complementary techniques (parity measurements, auxiliary operations) are required.
The article analyzes Microsoft’s claims about the “new state of matter,” intrinsic robustness, and Majorana-1 chip scalability (8 qubits), highlighting the gap between theoretical promise and experimental reality, and the fundamental tension between stable-slow and fast-less-stable qubit architectures.