The 2022 Nobel Prize for physics winners got their award for their pioneering work in quantum information and entanglement. But what is entanglement, and what does it mean for science and technology? Here we briefly examine what entanglement is and what it is not, and where you might come across it.
What on earth is entanglement?
One of the strangest phenomena which still has people confused. It appears to defy much of how we think about the world. Entanglement means that two entities (I call them entities), which could be photons or particles, are linked so that one can affect the other. For example, should we measure particle A, entangled with particle B, then if we go to measure particle B, it will have a state-dependent upon particle A. You might say, so what, but this can happen no matter the distance that these particles are apart from each other. And to make matters spooky, the states of particles A and B can be initially unknown. So that means when we measure particle A, particle B must take on an appropriate value, and here is the rub; it does this instantly. Such a phenomenon is therefore named entanglement.
Why is entanglement useful?
You might be forgiven for thinking that entanglement can make for instant communication. But whilst it is possible for the connection to be instant, it is not possible to transmit information faster than the speed of light. So whilst we have this fantastic process, you won’t be getting quantum super fast internet anytime soon.
That isn’t the end of the story. The fact that the speed of light remains a constant limiting factor doesn’t mean that entanglement isn’t useful. Being able to entangle particles can be used to make connections more secure, for the simple fact that man-in-the-middle attacks can be detected. So without going into the physics details (you can if you want to), there is a whole new field of quantum communication with applications such as QKD (Quantum Key Distribution) and quantum security which has opened up to exploit entanglement.
Many researchers around the planet are looking at the Quantum internet, which might mean that Quantum Computers can actively communicate at vast distances and might even provide the means to build larger and larger systems.
Here is an excellent video on Quantum Entanglement and spooky action at a distance.