  We present measurements and simulations of semiconductor-superconductor
heterostructure devices that are consistent with the observation of topological
superconductivity and Majorana zero modes. The devices are fabricated from
high-mobility two-dimensional electron gases in which quasi-one-dimensional
wires are defined by electrostatic gates. These devices enable measurements of
local and non-local transport properties and have been optimized via extensive
simulations to ensure robustness against non-uniformity and disorder. Our main
result is that several devices, fabricated according to the design's
engineering specifications, have passed the topological gap protocol defined in
Pikulin et al. [arXiv:2103.12217]. This protocol is a stringent test composed
of a sequence of three-terminal local and non-local transport measurements
performed while varying the magnetic field, semiconductor electron density, and
junction transparencies. Passing the protocol indicates a high probability of
detection of a topological phase hosting Majorana zero modes as determined by
large-scale disorder simulations. Our experimental results are consistent with
a quantum phase transition into a topological superconducting phase that
extends over several hundred millitesla in magnetic field and several
millivolts in gate voltage, corresponding to approximately one hundred
micro-electron-volts in Zeeman energy and chemical potential in the
semiconducting wire. These regions feature a closing and re-opening of the bulk
gap, with simultaneous zero-bias conductance peaks at both ends of the devices
that withstand changes in the junction transparencies. The extracted maximum
topological gaps in our devices are 20-60 $\mu$eV. This demonstration is a
prerequisite for experiments involving fusion and braiding of Majorana zero
modes.
