ceptimus
Does this thought experiment refute immaterialism?
Thought experiments never qualifies as proofs,there is no necessity that logical conclusions,even correctly derived from a set of premises considered true,experimetally derived,must also hold experimentally.Not even in the case when is proved that the conclusion is unique.Only if immaterialism were proved inconsistent internally or incompatible with observed facts would we have a more solid base,inductively derived,to consider it as refuted.Not the case I'm afraid.
But it would certainly represent a sufficient reason to consider that consciousness is entirely material and that relations between physical 'entities' (known or not) are enough to give rise to the consciousness
based on observed facts if such a robot will be built in practice.Moreover if the architecture of the brain is macroscopic and computational (using switches and logic gates,not depending on quantum effects) the argument would represent a sufficient reason to consider that the computational emergentist theory of consciousness is much more than a simple open conjecture.
Indeed since the observed facts are the basis of all 'objective knowledge' [not some possible 'hidden reality' acting behind the scene,potentially unknowable-even if it existed ontologically the burden of proof is upon those who make the positive claim that it exist] and given the lack of any serious scientific alternative this is the only rational conclusion which can be derived from the current variant of the scientific method.
Of course this does not imply certitudes since all we can do is to make the constatation that the external behaviour of the robot is indistinguishable from that of a human being,a fact exploited by the 'zombies' argument.Even if we constructed a perfect clone (experimentally indistinguishable at the level of 'architecture') of a human being from raw material.
Anyway even if such a robot will ever be built,giving us a high degree of confidence that consciousness is entirely physical certified by the best method of establishing the truth,it is far from giving sufficient arguments that we and our reality are not in the 'mind of God' as simple 'information'.Depends therefore of what you mean by 'immaterialism'.If immaterialism merely means that consciousness is,at least,not entirely physical (stuff we can potentially probe) then yes the construction of a robot whose behaviour is indistiguishable from that of a human being does represent a sufficient reason against (Berkeleyan type or matrix type, where minds belong to a higher-up level different from the world we observe around,included).If immaterialism is extended to mean the existence of transcedental entities such a Creator (we and our reality being mere information or existing in the 'mind of God') or the existence of 'substances' which cannot interact with the physical then the construction of such a robot cannot qualify as a sufficient reason against.