- #1

- 59

- 9

## Main Question or Discussion Point

So, I am doing my undergraduate research project in Quantum Cryptography, and I have some confusion in a few areas, especially in the topic of continuous variable quantum key distribution.

From what I understand,

I understand that is Bob measures in the right quadrature in the BB-84 protocol, then he'll get the right corresponding bit. However, if he chooses the wrong quadrature, he'll get the right bit 50% of the time.

But in CV-QKD, if Bob chooses the right quadrature either X or P, then he'll get the right information, but what happens if he chooses the wrong quadrature?

One more question, in continuous-variable QKD, what is the difference between coherent states and squeeze states. I understand that squeeze states either increase or decrease the certainty in the quadrature X and P because of the uncertainty principle. Is coherent states still used in DV-QKD (similar to weak pulses)?

Thanks for your help!

From what I understand,

**Discrete Variable**- Single photon. That is, for example, the BB84 protocol. Bob is measuring 1 photon at a time.**Continuous Variable-**Alice encodes key bits (is it more than 1 bit of the key?) in the quadrature X and P.I understand that is Bob measures in the right quadrature in the BB-84 protocol, then he'll get the right corresponding bit. However, if he chooses the wrong quadrature, he'll get the right bit 50% of the time.

But in CV-QKD, if Bob chooses the right quadrature either X or P, then he'll get the right information, but what happens if he chooses the wrong quadrature?

One more question, in continuous-variable QKD, what is the difference between coherent states and squeeze states. I understand that squeeze states either increase or decrease the certainty in the quadrature X and P because of the uncertainty principle. Is coherent states still used in DV-QKD (similar to weak pulses)?

Thanks for your help!