Quantum key distribution without a single-photon source using a strong reference

We present a single-sideband scheme that uses an enhanced BB84 protocol with a strong reference. A matrix method allows us to prove that this reference makes the system secure against the photon number splitting attack when using an imperfect laser source. The performance of a stable experimental setup with a fainted laser source is tested using an optimum average energy μ=1 photon per pulse to maximize the final key rate.