This is a concept so strange that Albert Einstein called it “Spukhafte Fernwirkung” in a letter to Max Born, one of the founders of Quantum Mechanics. This is roughly translated to “spooky action at a distance.” He wasn’t sure if he really believed it, but all his calculations said that he should. There was no proof of its existence, until now. Einstein felt that this observation was evidence that the theory of Quantum Mechanics was incomplete. If you don’t understand it don’t feel bad, Einstein didn’t either.
So, what is entanglement, and why is it important? Much modern technology depends on entanglement’s reality and existence. It allows for ultra-precise measurements. Sensors of various items such as chemicals or time intervals utilize entanglement technology, as does GPS, Television, atomic clocks, quantum computers, more accurate MRI machines, detectors of stealth aircraft, and many more technologies. Quantum computers use qubits as a unit of information instead of bits. A bit is either a 1 or a 0. It is either on or off, while a qubit is not 1 or 0; it is anywhere between those two numbers, in other words, an infinite number. Secure communications, and thwarting hackers, will be another one of entanglement’s benefits, as an attempt to interfere with systems that use entanglement disrupts it immediately.
Entanglement on its surface seems impossible. Two particles that are entangled can exchange information even though they are separated by a distance, even if they are at opposite ends of the universe! If that seems impossible, wait until I tell you that this happens instantly. This exchange of information happens faster than the speed of light, which, according to Einstein is the fastest anything can travel in the universe. It breaks the speed limit of light! Another impossibility.
The simplest explanation I have found that helps in partially understanding entanglement, is the spinning wheel that has two colors, for example, red and yellow. As it spins, you do not know what color it will land on (Heisenberg’s uncertainty principle 1). When it stops it is either red or yellow without a doubt (Schrödinger’s dead cat 2). Now you happen to have another identical wheel on the moon that is entangled with your wheel on earth, which is also spinning. If your wheel on earth comes up yellow the one on the moon will always come up red and vice versa. There are no wires or radio waves or any connection between the wheels. The potential uses of this method of instant transmission of information are enormous. If we should find other intelligent life millions of light-years away, and we had entangled communicators, we could talk.
The trick is to get two particles to entangle. That, as it turns out, is not all that difficult. There are four ways:
- Find particles that are already entangled.
- Take two photons that are already entangled and shoot them into two separate atoms. Now the atoms are also entangled.
- Take atoms that emit photons and have beam splitters that separate them into two beams, horizontal and vertical polarized light. If one is horizontal the other is vertical (anti-correlated), and that makes them entangled.
- By exciting atoms into higher energy state (Rydberg state), you can create two atoms that are anti-correlated with each other, i.e. they are entangled.
The researchers have shown that they can shoot a particle by laser beam into outer space and keep a paired entangled particle in the lab. The two particles exchange information with each other instantly. As if that were not enough, the same experiment was done with two quasars 600 light-years away, and they were able to demonstrate communication between entangled particles from each quasar billions of miles apart. Things are more connected than we realize. Spukhaft indeed! And at quite a distance!
- Werner Heisenberg was a German theoretical physicist and Nobel Laureate, one of the pioneers of Quantum Mechanics. His uncertainty principle states that it is not possible to know both pairs of complementary properties of an object at the same time.
- Erwin Schrödinger, also a Nobel Laureate, was an Austrian physicist who developed a thought experiment in which a cat is theoretically both dead and alive inside a box, but it requires an actual measurement to determine the outcome. In this case, the measurement is looking inside the box to see if the cat is dead or alive.