Largest quantum state created

Physicists have created the largest ever quantum state, allowing an object large enough to be seen by the naked eye to be in two states at once.

They started by cooling a mechanical resonator to the quantum ground state – the lowest level of vibration allowed by quantum mechanics.

With the mechanical resonator as close as possible to being perfectly still, they added a single quantum of energy to the resonator using a quantum bit (qubit). The resonator responded precisely as predicted by the theory of quantum mechanics.

“This is an important validation of quantum theory, as well as a significant step forward for nanomechanics research,” said University of California professor Andrew Cleland.

The researchers were able to create a single phonon – the smallest unit of vibrational energy – and watch as this quantum of energy exchanged between the mechanical resonator and the qubit.


While exchanging this energy, the qubit and resonator become ‘quantum entangled,’ meaning that measuring the qubit actually forces the mechanical resonator to ‘choose’ the vibrational state in which it should remain.

In a related experiment, the team placed the mechanical resonator in a quantum superposition – a state in which it simultaneously had zero and one quantum of excitation, and the equivalent of an object being in two places at the same time.