Distinguishing decoherence from alternative quantum theories by dynamical decoupling

A long standing challenge in the foundations of quantum mechanics is the verification of alternative collapse theories despite their mathematical similarity to decoherence. To this end, we suggest a novel method based on dynamical decoupling. Experimental observation of non-zero saturation of the decoupling error in the limit of fast decoupling operations can provide evidence for alternative quantum theories. The low decay rates predicted by collapse models are challenging, but high fidelity measurements as well as recent advances in decoupling schemes for qubits let us explore a similar parameter regime to experiments based on macroscopic superpositions. As part of the analysis we prove that unbounded Hamiltonians can be perfectly decoupled. We demonstrate this on a novel dilation of a Lindbladian to a fully Hamiltonian model that induces exponential decay.