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arXiv 0802.0870quant-ph
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用旋转不变的Hamilton算子构造所有时间演化

Building all Time Evolutions with Rotationally Invariant Hamiltonians

I. Marvian, R. B. Mann

摘要:

自然界中所有的基本哈密顿量都是旋转不变的。尽管有这样的限制,我们通常假设任何任意的测量或幺正时间演化都可以在一个物理系统上实现,这个假设的有效性并不明显。我们介绍了两种不同的计划,任何任意的酉时间演化和测量可以实现所需的精度,通过使用旋转不变的哈密顿量,作用于给定的系统和两个辅助系统作为参考系。这些帧指定z和x方向,并且与期望的时间演化无关。我们还研究了由于使用有限系统作为参考系而不可避免地产生的量子涨落的影响,并估计了当参考系的大小趋于无穷大时,这些涨落趋于零的速度。此外,我们还证明了对于一般对称性,任何对称量子操作都可以仅利用对称态中的对称相互作用和辅助作用来实现。

英文摘要:

All elementary Hamiltonians in nature are expected to be invariant under rotation. Despite this restriction, we usually assume that any arbitrary measurement or unitary time evolution can be implemented on a physical system, an assumption whose validity is not obvious. We introduce two different schemes by which any arbitrary unitary time evolution and measurement can be implemented with desired accuracy by using rotationally invariant Hamiltonians that act on the given system and two ancillary systems serving as reference frames. These frames specify the z and x directions and are independent of the desired time evolution. We also investigate the effects of quantum fluctuations that inevitably arise due to usage of a finite system as a reference frame and estimate how fast these fluctuations tend to zero when the size of the reference frame tends to infinity. Moreover we prove that for a general symmetry any symmetric quantum operations can be implemented just by using symmetric interactions and ancillas in the symmetric states.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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