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arXiv 2007.12575quant-ph
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量子关联的条件熵计算

Computing conditional entropies for quantum correlations

Peter Brown, Hamza Fawzi, Omar Fawzi

摘要:

量子密码协议的速率通常表示为一组量子态上的条件熵最小化。特别地,在设备无关的设置中,最小化是在对手和各方共同持有的与各方看到的统计一致的所有量子态上。在这里,我们介绍一种方法来近似这样的熵量。将其应用于设备无关随机数生成和量子密钥分发的设置,得到了不同设置下协议速率的改善。特别是,我们找到了新的上限的最小全球检测效率所需的设备无关的量子密钥分发,而无需额外的预处理。此外,我们表明,我们的建设可以很容易地结合熵积累定理,以建立完整的有限密钥安全证明这些协议。为了实现这一点,我们引入了家庭的迭代平均量子雷尼发散参数$α_k = 1+\frac{1}{2^{k}-1}$的正整数$k$。然后,我们表明,相应的条件熵承认一个特别好的形式,在设备无关优化的背景下,可以放松到一个半定规划问题使用Navascués-Pironio-Acín层次结构。

英文摘要:

The rates of quantum cryptographic protocols are usually expressed in terms of a conditional entropy minimized over a certain set of quantum states. In particular, in the device-independent setting, the minimization is over all the quantum states jointly held by the adversary and the parties that are consistent with the statistics that are seen by the parties. Here, we introduce a method to approximate such entropic quantities. Applied to the setting of device-independent randomness generation and quantum key distribution, we obtain improvements on protocol rates in various settings. In particular, we find new upper bounds on the minimal global detection efficiency required to perform device-independent quantum key distribution without additional preprocessing. Furthermore, we show that our construction can be readily combined with the entropy accumulation theorem in order to establish full finite-key security proofs for these protocols. In order to achieve this we introduce the family of iterated mean quantum Rényi divergences with parameters $α_k = 1+\frac{1}{2^{k}-1}$ for positive integers $k$. We then show that the corresponding conditional entropies admit a particularly nice form which, in the context of device-independent optimization, can be relaxed to a semidefinite programming problem using the Navascués-Pironio-Acín hierarchy.

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