中文摘要：

为了提高Ping-Pong协议的传输效率,对其加以改进。改进的协议增加了随机数序列。相对于原协议,将传输的经典消息与控制信息从1∶1的比例改变为N∶（M-N）。按照量子通信效率评价公式,相对于原协议0.333的通信效率,改进协议的Matlab仿真和数值推导结果均显示,只需满足条件N1,极限通信效率可达N/（N＋2）,故改进后的效率均大于原协议。

英文摘要：

An improved ping-pong protocol is put forward to increase transmission efficiency. In the improved version, a sequence of random number is added. The ratio of control mode to message mode is N ： （M-N） compared with 1 ： 1 in the initial protocol. According to the quantum communication efficiency formula, it is 0. 333 for the initial protocol while N/（2M-N） for the improved protocol by Matlab simulation and numerical calculation under the only condition of N〈M〈2N. The deduced limitation of efficiency is N/（N＋ 2） with the least control mode. The efficiency will be increased only if N〉1.