Conceptual artwork of a pair of entangled quantum particles. Credit: Science Photo Library/Alamy Stock Photo
Topics: Modern Physics, Particle Physics, Quantum Mechanics, Theoretical Physics
Quantum entanglement is a complex phenomenon in physics that is usually poorly described as an invisible link between distant quantum objects that allows one to instantly affect the other. Albert Einstein famously dismissed this idea of entanglement as “spooky action at a distance.” In reality, entanglement is better understood as information, but that’s admittedly bland. So nowadays, every news article, explainer, opinion piece, and artistic interpretation of quantum entanglement equates the phenomenon with Einstein’s spookiness. The situation has only worsened with the 2022 Nobel Prize in Physics going to Alain Aspect, John F. Clauser, and Anton Zeilinger for quantum entanglement experiments. But it’s time to cut this adjective loose. Calling entanglement spooky completely misrepresents how it actually works and hinders our ability to make sense of it.
In 1935, physicist Erwin Schrödinger coined the term entanglement, emphasizing that it was “not one but rather the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought.” He was writing in response to a famous paper (known simply to physicists as the EPR argument) by Einstein, Boris Podolsky, and Nathan Rosen that claimed quantum physics was incomplete. The New York Times headline read, “Einstein attacks quantum theory,” which solidified the widespread perception that Einstein hated quantum physics.
The EPR argument concerns the everyday notion of reality as a collection of things in the world with physical properties waiting to be revealed through measurement. This is how most of us intuitively understand reality. Einstein’s theory of relativity fits into this understanding and says reality must be local, meaning nothing can influence anything else faster than the speed of light. But EPR showed that quantum physics isn’t compatible with these ideas—that it can’t account for a theory of local reality. In other words, quantum physics was missing something. To complete quantum physics, Einstein suggested scientists should look for a “deeper” theory of local reality. Many physicists responded in defense of quantum theory, but the matter remained unresolved until 1964 when physicist John S. Bell proposed an experiment that could rule out the existence of local reality. Clauser was the first to perform the test, which was later improved and perfected by Aspect and Zeilinger.
Quantum Entanglement Isn’t All That Spooky After All, Chris Ferrie, Scientific American