Quantum Theorists State That Wavefunctions Are Real, States Not Just Statistical Tools

The mathematics behind the claims of a group of quantum theorists state that the wavefunction, a probability amplitude used to in quantum mechanics to describe a particle’s state, isn’t just a statistical tool but rather a real, objective state of a quantum system. The researchers published their findings in the journal Nature Physics.

This view was shared by Erwin Schrödinger, Austrian physicist, and quantum-mechanics pioneer. Others, like Albert Einstein, favored the opposing view that the wavefunction reflects the partial knowledge of that an experimenter has about a system.

Jonathan Barrett and his colleagues follow John Bell’s counterintuitive implication that he developed in 1964: that measurements on one particle can influence the state of another, distant particle, faster than the speed of light should allow. The theorem proposed by Barrett shows that theories that treat the wavefunction in terms of lack of knowledge of a system’s physical state will also fail to reproduce those predictions.

If wavefunctions simply reflect the experimenter’s uncertainty, then different wavefunctions could represent the same underlying reality. The authors show that the same reality cannot underpin different quantum states. The theorem depends on a controversial assumption, that quantum systems have an objective underlying physical state.

This theorem could have applications in quantum information theory and cryptography. The theorem is incompatible with the standard model of quantum mechanics, possibly showcasing some faults in it.

Reference: “On the reality of the quantum state” by Matthew F. Pusey, Jonathan Barrett and Terry Rudolph, 6 May 2012, Nature Physics.
DOI: 10.1038/nphys2309

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