The Nobel Prize in physics this year has been awarded “for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science.”
October 7, 2022
The Nobel Prize in physics this year has been awarded “for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science.”
To understand what this means, and why this work is important, we need to understand how these experiments settled a long-running debate among physicists. And a key player in that debate was an Irish physicist named John Bell.
In the 1960s, Bell figured out how to translate a philosophical question about the nature of reality into a physical question that could be answered by science—and along the way broke down the distinction between what we know about the world and how the world really is.
Quantum entanglement
We know that quantum objects have properties we don’t usually ascribe to the objects of our ordinary lives. Sometimes light is a wave, sometimes it’s a particle. Our fridge never does this.
When attempting to explain this sort of unusual behavior, there are two broad types of explanation we can imagine. One possibility is that we perceive the quantum world clearly, just as it is, and it just so happens to be unusual. Another possibility is that the quantum world is just like the ordinary world we know and love, but our view of it is distorted, so we can’t see quantum reality clearly, as it is.
In the early decades of the 20th century, physicists were divided about which explanation was right. Among those who thought the quantum world just is unusual were figures such as Werner Heisenberg and Niels Bohr. Among those who thought the quantum world must be just like the ordinary world, and our view of it is simply foggy, were Albert Einstein and Erwin Schrödinger.
At the heart of this division is an unusual prediction of quantum theory. According to the theory, the properties of certain quantum systems that interact remain dependent on each other—even when the systems have been moved a great distance apart.
