Albert Einstein said quantum mechanics should allow two objects to interact over great distances. He had called this behavior “spooky action at a distance”. Experiments have confirmed this theory decades after his death.
In quantum mechanics, their states remain bound when particles connect with each other in a certain way, no matter how far apart they are. Every action on one of these particles affects the others. Einstein, Boris Podolsky, and Nathan Rosen published an article in the 1930s that examined how strongly correlated quantum states interact with one another.
A united state
The team found that when two subatomic particles are strongly correlated, they lose their individual quantum states. This creates a single, unified state. This uniform state is called quantum entanglement or quantum entanglement.
If two particles are entangled or entangled, i.e. their quantum states are strongly correlated and thus unified, then the observations of one automatically influence the other. As Live Science emphasizes, Erwin Schrödinger was one of the first physicists to use the term “entanglement”. In his opinion, this is one of the fundamental aspects of quantum mechanics.
“Perhaps the most famous example that explains the singularity of quantum mechanics is Schrödinger’s cat, a thought experiment designed by Erwin Schrödinger in 1935,” writes Scientific American magazine.
An instant phenomenon
Moreover, as Rosen, Einstein, and Podolsky noted, the entanglement is instantaneous. It is enough to know the properties of a particle to know the properties of all entangled particles, regardless of the distance separating them.
Abstract artist representation of a quantum computer. Image credit: Shutterstock / Plotplot
In this context, the concept of entanglement seems to violate the limit of the speed of light. In fact, it would be possible to place two entangled particles at opposite ends of the universe while still having this instant knowledge. Physicists call this behavior the “EPR paradox” (short for Einstein, Podolsky and Rosen) or “spooky action at a distance”.
Diverse fields of application
However, while it is possible to know the state of a distant particle, observers on both sides must be able to exchange information at a much faster rate than light to confirm entanglement. But since nothing can travel faster than the latter, this remains a mere theory.
Due to its special features, quantum entanglement offers interesting prospects for use in real life. This includes cryptography, in which a sender and a receiver set up a secure communication link. The system integrates pairs of entangled particles that generate secure keys. If an intruder intercepts the signal and tries to access it, both parties know that the communication has been compromised.
Quantum computing is also a common area of application for quantum entanglement. With this technology, particles are entangled, which enables complex computer calculations to be solved. For example, a few months ago China announced that it had built a quantum computer 100 trillion times faster than Google’s supercomputer.
Artist’s impression of a system for generating two entangled photons. Photo credits: From J-Wiki in English Wikipedia – Completely self-made with computer graphics applications., CC BY-SA 4.0