We propose a quantum rotation diversity (QRD) scheme for optical quantum communication using binary phase-shift-keying displaced squeezed states and homodyne detection over Gamma-Gamma turbulence channels. Consecutive temporal modes are coupled by a passive orthogonal rotation that redistributes the displacement amplitude between slots, yielding a diversity order of two under independent fading and joint maximum-likelihood detection. Analytical expressions for the symbol-error rate performance, along with asymptotic results for the diversity and coding gains, are derived. The optimal rotation angle and energy allocation between displacement and squeezing are obtained in closed form. Furthermore, we show that when both the displacement amplitude and the squeezing strength scale with the total photon number, an effective diversity order of four is achieved. Numerical results validate the analysis and demonstrate the super-diversity behaviour of the proposed QRD scheme.

翻译：本文提出了一种用于光量子通信的量子旋转分集方案，该方案在Gamma-Gamma湍流信道上采用二进制相移键控位移压缩态和零差探测。通过一个无源正交旋转耦合连续的时间模式，该旋转在时隙间重新分配位移幅度，在独立衰落和联合最大似然检测下实现了二阶分集。推导了符号错误率性能的解析表达式，以及分集增益和编码增益的渐近结果。以闭合形式获得了最优旋转角度以及位移与压缩之间的能量分配。此外，我们证明，当位移幅度和压缩强度均随总光子数缩放时，可实现四阶有效分集。数值结果验证了分析，并证明了所提QRD方案的超分集特性。