  In this paper, we present the first experimental demonstration on continuous
variable quantum key distribution using determinant Einstein-Podolsky-Rosen
entangled states of optical field. By means of the instantaneous measurements
of the quantum fluctuations of optical modes respectively distributed at sender
and receiver, the random bits of secret key are obtained without the need for
signal modulation. The post-selection boundaries for the presented
entanglement-based scheme against both Gaussian collective and individual
attacks are theoretically concluded. The final secret key rates of 84 kbits/s
and 3 kbits/s are completed under the collective attack for the transmission
efficiency of 80% and 40%, respectively.
