Synopsis: Reality, locality, and “free will”

By relaxing certain assumptions, it is possible to describe quantum correlations as both local and real.

In 1964, John Bell devised a testable prediction (now known as Bell’s inequality) based on two reasonable assumptions: that the measurement of one particle cannot instantaneously influence another, distant particle (locality) and that particles have properties before you measure them (reality).  Numerous experiments have since shown that Bell’s inequality is violated, forcing one to conclude that, contrary to the view held by Einstein, Podolsky, and Rosen, quantum mechanics cannot be both local and real.

But what of other assumptions built into Bell’s inequality?  In a paper appearing in Physical Review Letters, Michael Hall at the Australian National University in Canberra considers an assumption, called measurement independence, in the following experimental paradigm: A source emits two particles in an entangled state and sends them to two distant laboratories, where two experimenters randomly choose apparatus settings that measure a system property.  The measurement outcomes can be correlated in a way that violates Bell’s inequality, but measurement independence assumes that the experimenters freely choose apparatus settings, independent of any properties of the systems that they measure.  By relaxing this assumption, Michael Hall constructs a local and real model that describes the correlations of the experiment.  He shows that locality and reality can be retained with a 14% reduction of the experimenters’ “free will”—that is, the assumption of measurement independence need not be given up completely. – Sonja Grondalski


Announcements

More Announcements »

Subject Areas

Quantum Information

Previous Synopsis

Nuclear Physics

Unequal parts

Read More »

Next Synopsis

Astrophysics

Friction in a vacuum

Read More »

Related Articles

Synopsis: One-Way Quantumness
Quantum Physics

Synopsis: One-Way Quantumness

Experiments provide evidence for one-way quantum steering—an effect by which distant entangled systems can influence one another in a directional way. Read More »

Viewpoint: Quantum Hoverboards on Superconducting Circuits
Quantum Physics

Viewpoint: Quantum Hoverboards on Superconducting Circuits

A new quantum device uses a superconducting circuit to monitor a 2D gas of electrons floating on the surface of superfluid helium. Read More »

Synopsis: Even-Handed Control of Quantum Dot Qubits
Quantum Information

Synopsis: Even-Handed Control of Quantum Dot Qubits

A new way to control the coupling of spins between adjacent quantum dots produces qubits that are less susceptible to electronic noise. Read More »

More Articles