Difference between revisions of "TFNR - Entanglement"
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Latest revision as of 17:30, 26 June 2024
Let's try to explain in a few words what entanglement is according to current (conventional) physics and why it seems to violate the locality principle.
Quantum entanglement is considered a bizarre and counterintuitive phenomenon in which two subatomic particles, such as a pair of photons or electrons, are believed to be intimately linked to each other, even if separated by immense space. All the evidence collected experimentally has led the scientific community to believe that, despite their great separation, a change induced in one of the entangled particles instantly affects the other. A (spooky) action at a distance, as the particles seemed to communicate faster than light. The entangled particles appear to act not as individual particles but as an inseparable whole. They appear to remain connected even when separated by large distances, and their quantum states cannot be factored as a product of the states of its local constituents. If the state of one particle is measured, the other immediately assumes a correlated state. This profoundly challenges classical notions of space and time.
Even if scientists still debate how this strange phenomenon arises, what its intimate nature is, they consider it a real principle, corroborated by infinite tests, a completely natural phenomenon, not at all spooky. All composite ordinary / visible matter, molecules for example, con be seen as organized nets of subsystems, atoms of electrons and nuclei. Molecules appear to be entangled states of the electrons and nuclei that compose them (mutual positions, quantum states, etc.).
The incessant mutual push and attraction of the particles produces a sort of "tuning" (correlation, entanglement) of their quantum states and their dynamics. Placing them close enough together, their quantum states can overlap, share, making it impossible to distinguish the quantum state of one particle from that of the other.
If nothing disturbs those particles, this "tuning" is preserved even at relevant distances (maintenance of coherence). Entangled particles stop existing as independent, separate particles, but begin to act as a system, a quantum system. If collisions with other particles, forces, interactions with their surrounding environment disturb this "tuning", it is lost (de-coherence) and the quantum states or their dynamics become dis-entangled. Pre-entangled particles return to exist as independent, separate particles, with independent quantum states. Entanglement is lost.
Quantum states, which appear to be indeterminate until their measurement, both for non-entangled particles, as is natural, and for the entangled ones, which is surprising when coupled with the predictability of entangled states (for example, spin up for a particle and spin down for the other one). Nothing about the quantum states of the two individual entangled particles can be stated with certainty, but the global state of the two particles whose quantum states are correlated can be stated with certainty. Really strange!
Some problems, which actually seem like headaches!
The entangled particles appear to communicate instantaneously, but this communication does not allow information to be transferred at superluminal speeds. It seems really strange. Remote action on quantum states at infinite speed is hypothesized (which would imply a sort of instantaneous quantum causality), but at the same time it does not seem possible to cause or inform the other entangled particle (to act causally or transfer information at infinite speed betwwen the entangled particles). Quantum entanglement can cause particles to collapse at zero time over long distances, but we can't transport information instantaneously. A real mystery.
Communication / Action between entangled particles even if separated by a huge distance: an event (an interaction, a measurement, ...) on one quantum particle in an entanglement system impacts all other entangled particles. The most accredited interpretations have solved this problem "simply" by renouncing a truly important principle, that of locality. I definitely disagree with this approach!
Links to the tables of contents of TFNR Paper
