  A new scheme of quantum key distribution (QKD) using frequency and time
coding is proposed, in which the security is based on the frequency-time
uncertainty relation. In this scheme, the binary information sequence is
encoded randomly on either the central frequency or the time delay at the
sender. The central frequency of the single photon pulse is set as omega1 for
bit "0" and set as omega2 for bit "1" when frequency coding is selected. While,
the single photon pulse is not delayed for bit "0" and is delayed in tao for
"1" when time coding is selected. At the receiver, either the frequency or the
time delay of the pulse is measured randomly, and the final key is obtained
after basis comparison, data reconciliation and privacy amplification. With the
proposed method the photon splitting attack can also be detected, and the
effect of the noise in the fiber channel and environment on QKD system can be
reduced effectively.
