  Efficacious quantum information processing relies on extended coherence and
precise control. Investigating the limitations surrounding quantum processors
is vital for their advancement. In their operation, one challenge is
inadvertent wave function collapse. Decoherence-free subspaces, theoretically
capable of mitigating specific non unitary dynamics, present a promising
avenue. However, our study unveils their inability to safeguard against
spontaneous wave function collapse. Thus, the spontaneous-collapse rate becomes
a critical limiting factor for quantum systems' physical coherence, restricting
the options for maintaining coherence to active error correction.
