The entanglement tango and teleportation

Beam me up Scotty, but not yet

Peter Hamilton’s recent novel “Salvation” paints a science fiction view of our future where you can walk through a door (portal) in your living room in New York and enter into your dining room in San Francisco. Any place in the universe is only a step away if you have two portal doors that align with each other. The science behind this miracle of future travel is quantum entanglement.

So what is science, and what is fiction with entanglement? If you are a newbie to entanglement, it is a concept that is integral to quantum physics. This branch of physics deals with the very, very small (subatomic size) and the weird way these little guys behave. Einstein had reservations about the whole concept of entanglement and called it “spooky action at a distance.”

Quantum Particles

The first thing to know about the quantum world is that particles (like electrons or photons) don’t exist at a specific location like the earth orbiting the sun. The location of a photon can only be described by a probability wave function. This means that we don’t know where the photon is, we just know the probability that it could be at specific locations.

The “quantum state” of a particle is simply the totality of all the probability functions describing the particle’s measurable qualities. When two particles smack into each other, that interaction can cause them to become entangled, meaning that the state of one particle is linked to the state of the other particle. If you know the state of one particle, then you also know the state of the other. If you know one is red; then you know the other is blue. If the state of one changes, then the state of the other changes instantly. This is true even if one particle in on earth, and the other is 4.4 light-years away on Alpha Centauri.

The spooky part is that the information seems to travel between the two particles faster than the speed of light. A feat that physics deems to be impossible. This phenomenon leads to the crazy idea that an object (a person in the case of the Salvation novel) could instantaneously teleport from one location to another by taking advantage of the entangled state of the particles in each portal. A teleportation trick like this would require that you have enough entangled particles so that every subatomic particle in the person being teleported had a corresponding entangled pair of particles at the two portal locations.

Teleportation

Teleportation is not as mad and crazy as it seems, and small versions of it have already been accomplished, albeit only with single particles, not with people. But there is a catch. If I have two entangled particles A and B along with a third particle C, I can teleport particle C from A’s location to B’s location. I do this by entangling particles A and C. The catch is that A and C are destroyed in the process. Additionally, you need some instructions at B’s location to know how to reconstruct particle C. That information must be transmitted by conventional means at light speed or lower.

The implications for Hamilton’s science fiction world are that when I leave my living room in New York and step into my kitchen on Alpha Centauri, some information is needed at my new location to allow me to materialize. This information transmits at the speed of light, and I wouldn’t materialize on Alpha Centauri until 4.4 years later. In the intervening time between leaving and arriving, I wouldn’t exist since the original me was destroyed in New York when I entered the portal door, and the new me is still waiting for reassembly. I suppose the good news is that when I finally arrive at Alpha Centauri, I am 4.4 years younger than if I had stayed in my New York living room. Assuming I had a snack before I left, I wouldn’t be hungry since my food would still be digesting when I re-materialized.

Beam me up

I suppose that if I was on a planet and the Starship Enterprise was orbiting above, the delay would be manageable, and the command to “beam me up Scotty” would be more efficient than sending a shuttle to the surface. The only thing I need is about a quadrillion entangled particles that Scotty whips up from somewhere. So far, teleportation has only managed to send a single particle, so don’t call Scotty quite yet.