History of Quantum Entanglement

Abstract

Quantum entanglement, first described by Einstein and colleagues in 1935, puzzled scientists for decades. Schrödinger named it, Bell proved it, and Aspect confirmed it experimentally, leading to today's quantum revolution.

Have you ever heard of two particles being connected across space, no matter how far apart they are? This strange phenomenon is known as quantum entanglement, and it's one of the most perplexing concepts in all of science. But who conceived this mind-bending concept, and who has helped us understand it better over the years?

The Beginning: Einstein's "Spooky Action"

The story starts in 1935 with Albert Einstein and two other physicists, Boris Podolsky and Nathan Rosen. They wrote a famous paper that described an odd phenomenon in quantum mechanics—the science of tiny particles. They demonstrated that, according to quantum theory, two particles can be connected in a way that measuring one particle instantly affects the other, even if they are on opposite sides of the universe.

Einstein didn't like this idea at all. He called it "spooky action at a distance" and thought it proved that quantum mechanics was incomplete. He believed there must be hidden information that we couldn't see, which explained these connections.

Schrödinger Names the Phenomenon

That same year, physicist Erwin Schrödinger (famous for his thought experiment about a cat) read Einstein's paper. He was fascinated and wrote his own papers on the subject. Schrödinger actually gave this strange connection its name: "entanglement." He used the German word "Verschränkung," which means entanglement or interweaving. This name stuck, and we still use it today.

Bell Makes It Testable

For about 30 years, entanglement remained a peculiar theoretical concept. In 1964, John Bell formulated what is now known as "Bell's theorem" or "Bell's inequality." This was a mathematical test that could prove whether entanglement was genuine or if Einstein was right about hidden information.

Bell showed that if you measured entangled particles in specific ways, you could get results that would be impossible if hidden information existed. His work was revolutionary because it turned a philosophical debate into something scientists could actually test in a lab.

Aspect Proves It's Real

In the early 1980s, French physicist Alain Aspect conducted groundbreaking experiments that tested Bell's theorem. Using special equipment to measure entangled photons (particles of light), Aspect proved that entanglement was genuine. The particles were indeed connected in that "spooky" way Einstein had doubted. There were no hidden variables—quantum mechanics was correct, and the universe was stranger than Einstein had wanted to believe.

Recent Heroes and New Discoveries

The story didn't end with Aspect. In 2022, the Nobel Prize in Physics was awarded to Alain Aspect, John Clauser, and Anton Zeilinger for their work on quantum entanglement. Clauser had also conducted important early experiments in the 1970s. At the same time, Zeilinger pioneered new techniques, such as quantum teleportation, which transfers quantum information (not actual objects, as in science fiction).

Other scientists have also made significant contributions. Jian-Wei Pan in China has created entanglement with an increasing number of particles and over longer distances. Many researchers worldwide are now using entanglement to develop quantum computers and ultra-secure communication systems.

Why It Matters Today

Quantum entanglement has gone from a philosophical puzzle to the foundation of new technologies. Scientists are working on quantum computers that may solve problems today that computers have never been able to solve. They're creating unhackable communication networks. Some researchers even believe that entanglement may help us understand the nature of space and time itself.

Einstein was trying to prove that quantum mechanics was flawed. But the very thing he questioned in 1935 has become a cornerstone of today's quantum technology.

Credit where due:

https://www.fortanix.com/faq/post-quantum-cryptography/pqc

https://prongo.com/quantum-mechanics-simplified-making-sense-of-complex-physics/

© 2025 Tim Jackson. All Rights Reserved.