تقرير
Generic nonadditivity of quantum capacity in simple channels
| العنوان: | Generic nonadditivity of quantum capacity in simple channels |
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| المؤلفون: | Leditzky, Felix, Leung, Debbie, Siddhu, Vikesh, Smith, Graeme, Smolin, John A. |
| المصدر: | Physical Review Letters 130, 200801 (2023) |
| سنة النشر: | 2022 |
| المجموعة: | Computer Science Mathematics Quantum Physics |
| مصطلحات موضوعية: | Quantum Physics, Computer Science - Information Theory |
| الوصف: | Determining capacities of quantum channels is a fundamental question in quantum information theory. Despite having rigorous coding theorems quantifying the flow of information across quantum channels, their capacities are poorly understood due to super-additivity effects. Studying these phenomena is important for deepening our understanding of quantum information, yet simple and clean examples of super-additive channels are scarce. Here we study a family of channels called platypus channels. Its simplest member, a qutrit channel, is shown to display super-additivity of coherent information when used jointly with a variety of qubit channels. Higher-dimensional family members display super-additivity of quantum capacity together with an erasure channel. Subject to the "spin-alignment conjecture" introduced in the companion paper [IEEE Trans. Inf. Theory 69(6), pp. 3825-3849, 2023; arXiv:2202.08380], our results on super-additivity of quantum capacity extend to lower-dimensional channels as well as larger parameter ranges. In particular, super-additivity occurs between two weakly additive channels each with large capacity on their own, in stark contrast to previous results. Remarkably, a single, novel transmission strategy achieves super-additivity in all examples. Our results show that super-additivity is much more prevalent than previously thought. It can occur across a wide variety of channels, even when both participating channels have large quantum capacity. Comment: Comments: 25 pages, 9 figures. v2: matches published version. See also the companion paper arXiv:2202.08380 |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.1103/PhysRevLett.130.200801 |
| URL الوصول: | http://arxiv.org/abs/2202.08377 |
| رقم الأكسشن: | edsarx.2202.08377 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.1103/PhysRevLett.130.200801 |
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