Interferometric single-shot parity measurement in InAs-Al hybrid devices.

The fusion of non-Abelian anyons is a fundamental operation in measurement-only topological quantum computation ¹ . In one-dimensional topological superconductors (1DTSs) ^2-4 , fusion amounts to a determination of the shared fermion parity of Majorana zero modes (MZMs). Here we introduce a device architecture ⁵ that is compatible with future tests of fusion rules. We implement a single-shot interferometric measurement of fermion parity ^6-11 in indium arsenide-aluminium heterostructures with a gate-defined superconducting nanowire ^12-14 . The interferometer is formed by tunnel-coupling the proximitized nanowire to quantum dots. The nanowire causes a state-dependent shift of the quantum capacitance of these quantum dots of up to 1 fF. Our quantum-capacitance measurements show flux h/2e-periodic bimodality with a signal-to-noise ratio (SNR) of 1 in 3.6 μs at optimal flux values. From the time traces of the quantum-capacitance measurements, we extract a dwell time in the two associated states that is longer than 1 ms at in-plane magnetic fields of approximately 2 T. We discuss the interpretation of our measurements in terms of both topologically trivial and non-trivial origins. The large capacitance shift and long poisoning time enable a parity measurement with an assignment error probability of 1%.
Competing Interests: Competing interests: The authors declare no competing interests.
(© 2025. The Author(s).)