Thwarting the photon-number-splitting attack with entanglement-enhanced BB84 quantum key distribution

We develop an improvement to the weak laser pulse BB84 scheme for quantum key distribution, which utilizes entanglement to improve the security of the scheme and enhance its resilience to the photon-number-splitting attack. This protocol relies on the non-commutation of phase and number to detect an eavesdropper performing quantum non-demolition measurement on photon number. The potential advantages and disadvantages of this scheme are compared to the coherent decoy state protocol. (paper)