低温熵源用于片上真随机数生成：超越器件质量的普适鲁棒性
A low-temperature entropy source for on-chip true random number generation: universal robustness beyond device quality
- School of Information Science and Technology, Southwest Jiaotong University（西南交通大学信息科学与技术学院）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究证明单个电流偏置约瑟夫森结，无论器件参数质量如何，均可在毫开尔文温度下作为密码学级真随机数生成器，通过极端偏差器件测试，熵值接近理论极限，并经过SHA-256后处理通过全部NIST测试，实现普适鲁棒性。
AI中文摘要：
真随机数生成是毫开尔文温度下容错量子计算的关键能力。然而，现有的基于约瑟夫森结的真随机数生成器都依赖于一个被广泛接受但未经检验的假设：可靠的熵提取需要精确控制的器件参数。在这里，我们证明这一假设并非总是成立。我们展示了一个反直觉的发现：单个电流偏置的约瑟夫森结，无论其参数质量如何，都可以作为密码学级的真随机数生成器。为了确立这一结论的普适性，我们特意从制造中挑选了偏差最极端的器件，其临界电流偏离理论预测三个数量级，$I_cR$乘积比常规值高一个数量级，作为终极压力测试。即使在这些极端条件下，原始香农熵达到0.9981比特（理论最大值的99.8%），最小熵为0.9271比特。采用方波脉冲偏置方案，我们将开关概率调至$P\approx0.5$。经过SHA-256后处理后，比特流在比标准建议更严格的保守$m=3$准则下通过了所有15项NIST SP 800-22测试，且该认证在稀释制冷机的整个100-700毫开尔文工作窗口内均有效。
英文摘要：
True random number generation is a critical capability for fault-tolerant quantum computing at millikelvin temperatures. Yet existing Josephson-junction-based TRNGs all rest on a widely accepted but untested assumption: that reliable entropy extraction requires precisely controlled device parameters. Here we show that this assumption does not always hold. We demonstrate a counterintuitive finding: a single current-biased Josephson junction, regardless of its parameter quality, can serve as a cryptographic-grade true random number generator. To establish the universality of this conclusion, we deliberately selected the most extremely deviated devices from fabrication, with critical currents three orders of magnitude away from theoretical predictions and $I_cR$ products an order of magnitude above conventional values, as the ultimate stress test. Even under these extreme conditions, the raw Shannon entropy reaches 0.9981~bit (99.8\% of the theoretical maximum), with a min-entropy of 0.9271~bit. Using a square-wave pulsed-bias scheme, we tune the switching probability to $P\approx0.5$. After SHA-256 post-processing, the bitstreams pass all 15 NIST SP 800-22 tests under a conservative $m=3$ criterion that is more demanding than the standard recommendation, and this certification holds across the entire 100-700~mK operating window of a dilution refrigerator.
