“A sapphire crystal weighing 16 micrograms is the largest object ever to exist in a quantum-mechanical superposition of two vibrational states.”
ETH Zurich put a 16 microgram sapphire into two vibrational states at once by coupling it to a superconducting qubit. The gap between the two states is about two billionths of a nanometer. The record holder for “macroscopic” quantum behaviour is still too small to see. The cat is a crumb, and nobody knows yet why the real cat stays classical.