Quantum entanglement allows us to ‘entangle’ photons so that a change in one may be detected at a distance by a change in the other. Now, scientists are working on entangled electrons, for quanutm computing.
How do we know that all the photons, protons, neutrons, electrons, muons, gluons, kaons, klaxons, and maxi-pads etc etc etc aren’t already entangled with each other?
What I’m asking is, is it possible that the big bang entangled every atomic and subatomic particle, and so every manipulation we (or the Universe) makes can be detected from a distance? Is there any way to prove that a particle is not entangled to a second particle we cannot detect? Is it possible that the ‘random chance’ of quantum physics is simply the results of interactions with particles entangled to the ones we are viewing? The particles of earth could, conceivably, be entangled to particles across the entire Universe. The interactions of these particles entangled with our own would be across such varying distances and circumstances they would be unidentifiable from random chance.
Tim
PS please no primers on how “detecting one will destroy any information stored in it,” I already know all that, and the tricks physicists use to get around it.
If you are given a large number of particles, identically prepared, which are either entangled with other particles (which you don’t have access to) or in an unknown “pure state”, you can tell whether the particles are entangled or not. (In the language of quantum mechanics, the “density matrices” for these two cases are different.)
But if you don’t get the luxury of having large numbers of identically-prepared particles to measure–a situation more like the one you’re considering–you can’t tell the difference between one entangled with another particle and one in an unknown but unentangled state.
It is indeed possible that
In the standard formulation of quantum mechanics, all of the randomness appears in the so-called “measurement postulate,” which explains how to calculate the possible measurement results, and their probabilities, for any measurement you can make of a state; apart from measurements, the evolution of a closed system is completely predictable. A measurement, the usual explanation goes, collapses the wavefunction of the system into one of the “eigenstates” of the measurement. But an equivalent formalism is to view the measurement as entangling the system and the measuring device. In this view, there’s never any probabilistic collapse, merely more and more entanglements.
This is a useful theoretical picture, but it is often more intuitive to think of measurements collapsing the state into one of a number of known states. And even though this picture seems deterministic, all it really does is hide the randomness. It says that if I make a quantum measurement which has two possible outcomes, each with probability 1/2, then I become entangled with that quantum system. But my conscious mind doesn’t “feel” entanglement, or see two outcomes; somehow my consciousness becomes associated (apparently randomly) with a single outcome. This is basically Everett’s “many-worlds” interpretation of quantum mechanics.