  We study the lifetime of topological qubits based on Majorana bound states
hosted in a one-dimensional Rashba nanowire (NW) with proximity-induced
superconductivity and non-uniform chemical potential needed for manipulation
and read-out. If nearby gates tune the chemical potential locally so that part
of the NW is in the trivial phase, Andreev bound states (ABSs) can emerge which
are localized at the interface between topological and trivial phases with
energies significantly less than the gap. The emergence of such subgap states
strongly decreases the Majorana qubit lifetime at finite temperatures due to
local perturbations that can excite the system into these ABSs. Using Keldysh
formalism, we study such excitations caused by fluctuating charges in
capacitively coupled gates and calculate the corresponding Majorana lifetimes
due to thermal noise, which are shown to be much shorter than those in NWs with
uniform chemical potential.
