The primary quantum tool at work in ID Quantique's quantum communication scheme is known as "entanglement," a phenomena in which two particles — in this case individual photons — are placed in a correlated state. Under the rules of quantum mechanics, these two entangled photons are inextricably linked; a change to the state of one photon will affect the state of the other. Any tampering with the photon in transit would change the state of the entangled photon still in the sender's possession, raising a red flag. The sender could then simply discard the intercepted key and generate another.
Will this technique work ? Has quantum physics gone from abstract theory to everyday use ?
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