基于腔QED和相干态的无记忆量子中继器
Memoryless quantum repeaters based on cavity-QED and coherent states
AI总结：
提出一种基于腔QED和旋转对称玻色子码的无记忆量子中继方案，通过受控旋转门实现纠缠制备与纠错，数值模拟表明在低损耗和短基本距离下长距离通信保真度和成功率接近1，密钥率可超无中继界限。
摘要：
提出了一种基于腔QED和通过旋转对称玻色子码（RSBC）进行信道损耗量子纠错的量子中继方案，该方案无需存储器即可在长距离上以高时钟速率分发原子纠缠态。在该方案中，受控旋转门，即由置于腔内的原子状态决定的光传播模式的相位移动，既为纠缠态制备提供了机制，也为错误综合征识别提供了机制。分发得到的纠缠对随后可用于量子密钥分发（QKD）。为了评估该中继协议的性能，对RSBC的一个具体实例——多分量猫码进行了定量研究。数值模拟表明，在考虑足够小的站点间基本距离（小于0.1公里或0.01公里）和相当低的局部损耗（高达0.1%）的条件下，长距离（如1000公里）量子通信的总保真度和成功概率几乎都能接近1。每信道使用的密钥率可以相应变高，超过无中继界限，并且由于无记忆方案相对较高的时钟速率，每秒的密钥率也可以相应变高。这些结果预测，如果采用更高损耗的码，更大的基本距离也可能使保真度和成功概率保持在接近1的水平。基于腔QED设置，该方案可在室温下和光频范围内实现。
英文摘要：
A quantum repeater scheme based on cavity-QED and quantum error correction of channel loss via rotation-symmetric bosonic codes (RSBC) is proposed to distribute atomic entangled states over long distances without memories and at high clock rates. In this scheme, controlled rotation gates, i.e., phase shifts of the propagating light modes conditioned upon the state of an atom placed in a cavity, provide a mechanism both for the entangled-state preparations and for the error syndrome identifications. The distributed entangled pairs can then be used for quantum key distribution (QKD). In order to assess the performance of this repeater protocol, an explicit instance of RSBC--multi-component cat codes are studied quantitatively. A numerical simulation shows that the total fidelity and the success probability for quantum communication over a long distance (such as 1000km) both can almost approach unity provided a small enough elementary distance between stations (smaller than 0.1km or 0.01km) and rather low local losses (up to 0.1%) are considered. Secret key rates can become correspondingly high, both per channel use, beating the repeaterless bound, and per second thanks to the relatively high clock rates of the memoryless scheme. It is predicted from these results that a larger elementary distance might also keep both the fidelity and the success probability close to unity if higher-loss codes are employed. Based upon the cavity-QED setting, this scheme can be realized at room temperature and at optical frequencies.
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