Week 6 QKD Protocols

Week 6 QKD Protocols

1. 6 states are the standard basis, the hadamard basis and the y basis (i.e. all orthogonal sates of the block sphere)

2. BB84 is basically the protocal that uses basis checks (equivalent to photons being polarsed in x or y, (but could potentially also use 6 BB84 states if take advantage of 3 orthogonal states.))

   • Need step 2, as otherwise eve could store all the quantum channel data in a huge memory, wait for alice to send her basis measurements, and then know perfectly which basis to measure in (as states held in their quantum states with eves memory). After the perfect measurements, they can send the states onto bob, who wouldn't be able to spot eve tampered with it. So its important for bob to say he recieved the quantum message before alice sends out her basis choices

3. can improve security with EPR states. When Alice measures her half, it collapses Bobs state immeadiatly

   • Another modification to make is give eve the ability to form the states sent to Alice and Bob (A lot of power)

4. if eve is able to decide the states sent to alce and bob and these states are epr states from each other.

   • look in lect notes for section 6.2.1 and 6.2.2

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