
A thought experiment illustrating quantum superposition, here applied to a mechanical resonator.Schrödinger's cat is a thought experiment proposed by Erwin Schrödinger in 1935 to illustrate the counterintuitive nature of quantum superposition. In the original scenario, a cat in a sealed box is coupled to a radioactive atom that may or may not trigger a poison release. Until the box is opened, quantum mechanics describes the atom as being in a superposition of decayed and not decayed states, which would imply the cat is simultaneously alive and dead. The thought experiment was designed to highlight the absurdity of applying quantum superposition to macroscopic objects.
Erwin Schrödinger introduced the thought experiment in 1935 in a paper discussing the Einstein-Podolsky-Rosen paradox. The first experimental realization of a 'mechanical Schrödinger's cat' was achieved in 2010 by Andrew Cleland and colleagues at UCSB, using a microscopic mechanical resonator.
In modern experiments, the 'cat' is not a real animal but a macroscopic mechanical resonator—a tiny vibrating drum or cantilever—that is placed in a superposition of two distinct vibrational states. By coupling the resonator to a superconducting qubit or a photon, researchers can prepare and verify the superposition. The resonator's large mass (compared to atoms) makes it a testbed for exploring how quantum effects fade at macroscopic scales, a question central to understanding the boundary between quantum and classical physics.
Mechanical Schrödinger's cat states are used in quantum computing and quantum sensing, where superposition of macroscopic mechanical modes can enhance sensitivity to forces and enable quantum information processing with sound waves.
In 2010, researchers at UCSB created a mechanical resonator in a superposition of two states, each involving the motion of about 10 trillion atoms—the largest object to exhibit quantum superposition at that time.











