  We investigate a quantum key distribution (QKD) scheme which utilizes a
biased basis choice in order to increase the efficiency of the scheme. The
optimal bias between the two measurement bases, a more refined error analysis,
and finite key size effects are all studied in order to assure the security of
the final key generated with the system. We then implement the scheme in a
local entangled QKD system that uses polarization entangled photon pairs to
securely distribute the key. A 50/50 non-polarizing beamsplitter with different
optical attenuators is used to simulate a variable beamsplitter in order to
allow us to study the operation of the system for different biases. Over 6
hours of continuous operation with a total bias of 0.9837/0.0163 (Z/X), we were
able to generate 0.4567 secure key bits per raw key bit as compared to 0.2550
secure key bits per raw key bit for the unbiased case. This represents an
increase in the efficiency of the key generation rate by 79%.
