报告主题：Randomness and one-shot decoupling in quantum information science
报告人：Yoshifumi Nakata Project researcher（The University of Tokyo）
报告时间：2017年 12月22日（周五）10:00
报告地点：校本部G507
邀请人：Nakahara Mikio
主办部门：太阳集团tyc539数学系
报告摘要：Randomness is often very useful in information processing. This is true even in the quantum regime, where randomness is described by a random unitary uniformly distributed with respect to the Haar measure. In this talk, we begin with a brief review of the so-called one-shot decoupling, one of the most important applications of a Haar random unitary in quantum information theory. We then turn to one-shot decoupling with unitaries less random than the Haar ones. We especially consider decoupling with "unitary t-designs", random unitaries simulating Haar random ones up to the t-th order moments. It was known that good approximations of unitary 2-designs are sufficient for decoupling. Here, we show that rather bad approximations of unitary 2-designs suffice. Our result raises interesting questions: how much randomness is needed for decoupling, and more fundamentally, how can we define random unitaries which are less random than 2-designs?
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