A super-brief note on entanglement

Today, I am borrowing from a field of science other than what I usually do (biostatistics, bioinformatics, genetics): physics, more specifically the physics of subatomic particles.

Why this? Because this result seems paradoxical at first, and can be used later on by us -The Bioinformateachers!- to illustrate some of the (apparently) paradoxical phenomena that we encounter in our disciplines.

Let’s get started: we all know that, according to Einstein’s relativity theory and experiments, in the universe there’s nothing faster than light, right?

Entanglement refers to the peculiar property of some particles -atoms, but more specifically subatomic particles- to be “intertwined” in an almost magical way: such two particles can not be described independently from one another. What this means, is that if we know the status of one such particles, the status of the other is also indissolubly determined, even if the two particles are located in two different galaxies!

Hold on, does this mean that the two particles can communicate instantly, transmitting information faster than light? Was Albert Einstein wrong? No, Einstein was not wrong, and the two entangled particles can not communicate faster than light.

Here’s what happens (extreme simplification inside): we have two entangled particles, one on the Earth, the other in a galaxy far, far away. The two particles are entangled in reverse phase, so that if one particle is in state 0, the other will be in state 1, and vice versa. So let’s say that we want to measure the state of the particle here on the Earth: according to quantum mechanics, until we measure it, the particle can be in either state 0 or state 1, with probability 50% (Schroedinger’s cat: rings a bell?). When I measure it, I will know the particle on the earth is in state 0, and I also automatically know that the entangled particle in a far, far away galaxy is in state 1. But this does not imply any exchange of information between the two particles, nor the two places. Any observer in the far, far away galaxy will have to measure its particle of the entangled pair to be able to know it’s state, and this will be “1”.

It is true, we on the earth will know in advance that the entangled particle in the far, far away galaxy is in state 1, but the only way for us to communicate this is at speed lower than or at most equal to light.

After measuring, the entanglement is resolved and the two particles remain frozen in their disclosed state (0 and 1 in this case).

So Einstein was right, nothing can go faster than light. And entanglement remains one of the weirdest aspects of quantum mechanics, i.e. the physics of subatomic particles.

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