Today we rely on electromagnetic field for communication. I'm a entrepreneur, I want to know why we can't transfer data with this technology to transfer data from one place to another place. It can reduce us to rely on emf. And quantum entanglement able to send data to everywhere.
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Quantum entanglement doesn't transmit information.
When you have two experimenters (usually called Alice and Bob, because real people aren't named A and B) doing widely-separated experiments on entangled particles, each of them does a separate experiment on each particle. For example if the entangled particles are photons with opposite polarizations, each experimenter must decide whether to analyze the polarization as horizontal/vertical, or one-or-the-other 45º diagonal, or left/right circularly polarized. What Alice and Bob get from these experiments in their own labs are completely random lists of orientations (horizontal, +45º, horizontal, right-circular, vertical, –45º, etc.).
It's only when Alice and Bob compare notes later — using a classical communication channel, like a telephone — that they can determine whether there was entanglement or not. Alice and Bob must compare notes to determine which measurements they made using the same basis. If Alice determined that her 47th photon was horizontally polarized, and Bob determined that his 47th photon was right-circular polarized, those two measurements are completely uncorrelated and carry zero information. However, if Alice determined that her 48th photon was horizontally polarized, and Bob measured his photon in a horizontal/vertical basis, then Alice knows (assuming a high-fidelity experiment, low noise, etc.) that Bob's 48th photon must have come out vertically polarized.
This is great for encryption! It lets Alice share innocuous information (her detector orientations) over an insecure communication channel, so that Bob suddenly knows secret information (a random subset of Alice's measurement results) about Alice's lab. Even better for encryption, if a third party (Eve, the eavesdropper) tries to "steal" the secret information by measuring Bob's photons en route, the entanglement is destroyed in a detectable way. But Alice can't control her measurement results to send information to Bob. Even if Alice and Bob agree in advance on the pattern of measurements they will make, e.g. "always horizontal/vertical" or "diagonal every third time," the polarization results in Alice's lab are still random. She can know what Bob is getting, but cannot send him a message.
The philosophically interesting part of quantum entanglement is even more subtle. If Alice and Bob measure their polarizations in different but not orthogonal bases — for example, Alice measures horizontal/vertical and Bob measures linear polarization at 22.5º rather than at 45º — then quantum mechanics predicts more correlation than any classical theory. But from your perspective I think just means that even more measurements are required to determine whether entanglement is present or not. In order to transmit information you must also have a classical communication channel.
rob
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rob's answer already touches on your misconception that quantum entanglement by itself could be used to send information.
From an engineering point of view, the problems are even more basic:
In order for Alice and Bob to create an entangled state, we must first choose a quantum system. For convenience, let's use the polarization of photons, i.e. an entangled state will be a system of two photons whose correlations show entanglement. In order to create such a pair of photons, they need to interact. It is simply not possible for Alice to create a photon and Bob to create another on the other side of the planet such that the state for the two photons is entangled. Alice and Bob need to meet with their photons and let them interact - or else: Alice creates an entangled pair and sends half of it to Bob. But this means that you cannot avoid sending quantum systems (e.g. particles with spins, which must be stored somewhere like a memory or photons, which means electromagnetic radiation).
Now, when you have done this, information can only be sent by a) quantum teleportation, which requires classical information to be sent between Alice and Bob or b) superdense coding, where Alice encodes the message she wants to send into her photon and then sends it to Bob - this is only interesting, because to send a two bit message, Alice only needs to send her one-bit photon (because Bob has already been sent a one-bit photon in advance). In any case, you cannot avoid transferring data by either transferring a memory (via postal service) or electromagnetic waves. Entanglement just doesn't let you save any physical resources for communication in the way you hope.
Martin
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