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foodini
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Quantum cryptography depends upon the notion that a sender transmits photons of known polarity, then the receiver choses random polarizations to filter the incoming transmission through. As each photon is either accepted, therefore telling the receiver that he correctly guess the sent polarity, or rejected, the receiver takes note. At the end of the first stage, the receiver tells the sender which photons he received and, with both of them knowing the polarity of those photons, they have successfully communicated n bits of information, encoded as the polarities...
Here's my problem: the whole thing depends upon the assumption that a listener who attempts to determine the polarities of photons en route is destroying information - he has to send photons through a polarizer to determine their orientation. He cannot observe the communication and ensure that the intended receiver gets everything he was sent.
What if the listener sends the transmission through a stimulated emmission medium? Stimulated emmission evidently gives you two exit photons - each with the same qualities as the input photon - direction and polarity included. As a listener, I could copy the photons in transit, giving me plenty of spares to determine the exact orientation of the origional, then send off a copy to the intended receiver. Voilla - I snoop on the backchannel where the receiver tells the sender what he received and I know exactly what their shared secret is.
The only problem I see with this is if a pair of (stimulated) emmitted photons are either entangled or their polarity is not related to the stimulating photon's polarity, which is contrary to what I've been able to discern. Where am I (or the QC guys) wrong on this?
This is right at the bleeding edge of my understanding of quantum. Please keep the replies at the appropriate level of pedantics. Thanks...
rOn
Here's my problem: the whole thing depends upon the assumption that a listener who attempts to determine the polarities of photons en route is destroying information - he has to send photons through a polarizer to determine their orientation. He cannot observe the communication and ensure that the intended receiver gets everything he was sent.
What if the listener sends the transmission through a stimulated emmission medium? Stimulated emmission evidently gives you two exit photons - each with the same qualities as the input photon - direction and polarity included. As a listener, I could copy the photons in transit, giving me plenty of spares to determine the exact orientation of the origional, then send off a copy to the intended receiver. Voilla - I snoop on the backchannel where the receiver tells the sender what he received and I know exactly what their shared secret is.
The only problem I see with this is if a pair of (stimulated) emmitted photons are either entangled or their polarity is not related to the stimulating photon's polarity, which is contrary to what I've been able to discern. Where am I (or the QC guys) wrong on this?
This is right at the bleeding edge of my understanding of quantum. Please keep the replies at the appropriate level of pedantics. Thanks...
rOn
