What if we freed ourselves from space-time with quantum entanglements?

Yet this is what quantum entanglement implies, according to which two particles that have previously interacted with each other can share an intimate relationship, be interdependent, as if they formed a single and unique system. Enough to imagine harnessing this curiosity to transfer information beyond spacetime, an overview of telepathy and even, why not, dreams of teleportation…

But be careful! Quantum teleportation, as defined today, has nothing to do with a system on star trek, where you would go into one machine to come out of another. “This would require a complete analysis of a macroscopic system, in order to rematerialize it elsewhere while dematerializing it at first”, points out Nicolas Cerf, director of Center for Quantum Information and Communication and professor at the Free University of Brussels.

Such instantaneous transfer is unrealistic in practice given the number of particles involved. “Quantum teleportation has more modest ambitions, but they are no less amazing. Already it allows a transfer not of matter or energy, but of the state of a particle – the spin of an electron, the polarization of a photon – between two qubits, that is, the elementary device capable of carrying quantum information .In theory, any medium can be used to collect qubit: a photon, an atom, an ion, or even a mixture of different particles.

First of all, you need two entangled particles, e.g. two photons. One of the possibilities is to produce them at the same time, for example by sending a beam of light onto a crystal with certain specific properties. Two “twin” photons can then emerge from it before rapidly moving away from each other. Each of them will be considered a qubit, linked to the other by the trace of a common past.

Also read: Quantum communication in space could be possible! Researchers from the University of Edinburgh have just demonstrated in Physical Review D that interstellar space is so clean that it can allow the transmission of messages over hundreds of thousands of light years without the signal being subject to decoherence. They reached this conclusion using mathematical calculations.

MORSE IN ROOM

Two experimenters, let’s call them Alice and Bob, then only have to grab one of these photons. They separate in the room and begin the experiment. Alice comes into possession of a third qubit whose quantum state she wants to teleport to Bob: all she has to do is perform a special measurement involving the newcomer and its emitter photon. Then to send the result in a traditional way, via e-mail for example, to Bob, who applies the same measurement to his own receptor photon. By observing his entangled photon and knowing the measurement performed, Bob can deduce the quantum state of the qubit that Alice wanted to transmit to him. And which immediately dissolves into the latter, under an effect called “impossibility of quantum cloning”.

Good, but this communication required sending an email, so what interest? So let’s imagine that Alice has left all her devices connected and is patiently observing her entangled qubit. As soon as a usual measurement of his photon changes, it is a sign that Bob has changed his quantum state: information transmitted instantly! And if Alice and Bob agreed upstream on a code – when I act on my photon to induce a change in the measurement result in yours, that is to say “danger” or “at the table” – this information becomes communication!

Instantaneous teleportation is not realistic given the number of particles involved – NICHOLAS STAG, Director of the Center for Quantum Information and Communication

All that would then be left was to execute the protocol on quantities of particles at a time, for ever more complex communication, a kind of space Morse code! ” Nothing in the physical laws seems to forbid it. Some works focus on larger and larger objects, but the task remains heavy ”, comments Nicolas Cerf. In particular, this idea runs into a major problem, decoherence, ie. the collapse of quantum effects observed at the infinitesimal during the transition to the macroscopic world where classical physics rules. The future of quantum teleportation is hidden in a long-awaited theory: the one that will finally unite the two worlds.

Also read: Is it possible to warp space-time using the warp drive? What if man, instead of traveling across light years, simply brought his destination closer… by contracting space-time?

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