GaAs (and other III-V) would likely be an essential material for some kind of photonic or hybrid compute system.
The response below addressed the quantum sensors, but I would be careful of calling "everything" quantum such as image sensors. Sure they rely on the photoelectric effect which is quantum, but not really in the sense of what we would consider a 'quantum sensor' today.
I suspect what could be more relevant are III-V based SQUID Qubits. These are highly sensitive systems that multiple nations are exploring for submarine detection. More near term, quantum communication via quantum light sources also can leverage a III-V platform.