  Ballistic electron transport is a key requirement for existence of a
topological phase transition in proximitized InSb nanowires. However,
measurements of quantized conductance as direct evidence of ballistic transport
have so far been obscured due to the increased chance of backscattering in one
dimensional nanowires. We show that by improving the nanowire-metal interface
as well as the dielectric environment we can consistently achieve conductance
quantization at zero magnetic field. Additionally, studying the sub-band
evolution in a rotating magnetic field reveals an orbital degeneracy between
the second and third sub-bands for perpendicular fields above 1T.
