Fortescue Ben, Lo Hoi-Kwong
Center for Quantum Information and Quantum Control, Department of Electrical and Computer Engineering, University of Toronto, Toronto, Ontario, M5S 3G4, Canada.
Phys Rev Lett. 2007 Jun 29;98(26):260501. doi: 10.1103/PhysRevLett.98.260501. Epub 2007 Jun 28.
We describe a protocol for distilling maximally entangled bipartite states between random pairs of parties from those sharing a tripartite W state |W=(1/sqrt[3])(|100+|010+|001)(ABC), and show that the total distillation rate E(t)(infinity) [the total number of Einstein-Podolsky-Rosen (EPR) pairs distilled per W, irrespective of who shares them] may be done at a higher rate than EPR distillation between specified pairs of parties. Specifically, the optimal rate for distillation to specified parties has been previously shown to be 0.92 EPR pairs per W, while our protocol can asymptotically distill 1 EPR pair per W between random pairs of parties, which we conjecture to be optimal. We thus demonstrate a tradeoff between overall distillation rate and final distribution of EPR pairs. We further show that there exist states with fixed lower-bounded E(t)(infinity), but arbitrarily small distillable entanglement for specified parties.
我们描述了一种协议，用于从共享三方W态|W = (1/√3)(|100 + |010 + |001)(ABC)的各方的随机对中提取最大纠缠的二分态，并表明总提取率E(t)(∞) [每W态提取的爱因斯坦 - 波多尔斯基 - 罗森（EPR）对的总数，无论谁共享它们] 可以以比指定各方之间的EPR提取更高的速率完成。具体而言，先前已表明向指定各方提取的最佳速率为每W态0.92个EPR对，而我们的协议可以在各方的随机对之间渐近地每W态提取1个EPR对，我们推测这是最优的。因此，我们证明了在整体提取率和EPR对的最终分布之间存在权衡。我们进一步表明，存在具有固定下限E(t)(∞)的态，但对于指定各方而言，可提取的纠缠任意小。
