We show an experimental procedure to certify the classical capacity for noisy qubit channels. The method makes use of a fixed bipartite entangled state, where the system qubit is sent to the channel input and the set of local measurements, ${\sigma }_x\otimes {\sigma }_x, {\sigma }_y\otimes {\sigma }_y$, and ${\sigma }_z\otimes {\sigma }_z$, is performed at the channel output and the ancilla qubit, thus without resorting to full quantum process tomography. The witness to the classical capacity is then achieved by reconstructing sets of conditional probabilities, noise deconvolution, and classical optimization of the pertaining mutual information. The performance of the method to provide lower bounds to the classical capacity is tested by a two-photon polarization entangled state in Pauli channels and amplitude damping channels. The measured lower bounds to the channels are in high agreement with the simulated data, which take into account both the experimental entanglement fidelity $F=0.979\pm 0.011$ of the input state and the systematic experimental imperfections.

中文翻译：

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量子通道经典容量的实验下限

我们展示了一个实验程序来证明嘈杂量子比特通道的经典容量。该方法利用固定的二分纠缠状态，其中系统量子位被发送到通道输入和本地测量集，${\sigma }_X\otimes {\sigma }_X, {\sigma }_{是}\otimes {\sigma }_{是}$， 和 ${\sigma }_z\otimes {\sigma }_z$, 是在通道输出和辅助量子位上执行的，因此无需采用全量子过程断层扫描。然后通过重建条件概率集、噪声解卷积和相关互信息的经典优化来实现经典容量的见证。通过泡利通道和振幅阻尼通道中的双光子极化纠缠态来测试为经典容量提供下限的方法的性能。通道的测量下限与模拟数据高度一致，同时考虑了实验纠缠保真度$F=0.979\pm 0.011$ 输入状态和系统实验缺陷。