Testing spontaneous wavefunction collapse with quantum electromechanics

Theories of spontaneous wavefunction collapse offer an explanation of the possible breakdown of quantum mechanics for macroscopic systems. However, the challenge of resolving predicted collapse signatures above background noise has precluded conclusive tests. Here, we propose to overcome this challenge using quantum control and measurement of a superconducting qubit coupled to a macroscopic mechanical resonator. We show that this can amplify the weak signals from collapse-induced heating and simultaneously suppress qubit noise, initializing the qubit close to its ground state. Combined, this could enable a conclusive test of collapse models. The ability to quantum control macroscopic mechanical resonators and resolve extremely small signals from them could further other fundamental research beyond collapse models, such as laboratory-based dark matter searches and the reconciliation of quantum mechanics with gravity.