Decoherence of Majorana qubits by 1/f noise

Abstract: Qubits based on Majorana Zero Modes (MZMs) in superconductor-semiconductor nanowires have attracted intense interest as a platform for utility-scale quantum computing. These qubits have been predicted to show extremely low error rates due to topological protection of the MZMs, where decoherence processes have been thought to be exponentially suppressed by either the nanowire length or the temperature. However, here we show that 1/f noise, which is ubiquitous in semiconductors, gives rise to a previously unexplored mechanism for Majorana qubit decoherence. The high frequency components of this noise causes quasiparticle excitations in the bulk of the topological superconductor, which in turn result in qubit errors that increase with the length of the nanowire. We calculate the probability of quasiparticle excitation for disorder-free nanowires in the presence of 1/f noise and show that this mechanism limits the decoherence times of the MZM qubits currently being developed to less than a microsecond even for perfectly uniform nanowires with no disorder. This decoherence time is significantly shorter than the time to implement quantum gates using this technology and is also shorter than the decoherence times of qubits in other leading solid-state architectures.