量子转子与约瑟夫森结：紧致相位与扩展相位及耗散量子相变
Quantum rotator and Josephson junction: compact vs. extended phase and dissipative quantum phase transition
AI总结：
本文重新探讨量子转子与约瑟夫森结中相位态的可区分性问题，提出相位差2π的态不可区分，但不改变传统理论对小型约瑟夫森结超导-绝缘相变的结论。
摘要：
本文重新评估了量子转子与约瑟夫森结量子理论中“紧致相位与扩展相位”这一长期存在的两难问题，以及这两个系统与周期势中运动粒子的类比关系。该两难问题的核心是相位为$φ$和$φ+2π$的量子态是否可区分。过去学界普遍认为，在约瑟夫森结中这些态是可区分的，就像周期势中运动的粒子一样。本文提出，这些相位差为$2π$的态是不可区分的，与单摆（量子转子的一个特例）的情况一致。不过，这一结论并不会推翻传统理论关于小型约瑟夫森结中存在超导态到绝缘态转变的预测。
英文摘要：
The paper reassesses the old dilemma "compact vs. extended phase" in the quantum theory of the rotator and the Josephson junction and the analogy of these two systems with the a particle moving in a periodic potential. This dilemma is in fact the dilemma whether the states with the phases $φ$ and $φ+2π$ are distinguishable, or not. In the past it was widely accepted that in the Josephson junction these states are distinguishable like for a particle moving in a periodic potential. This paper argues that the states with the phases $φ$ and $φ+2π$ are indistinguishable as in a pendulum (a particular example of the quantum rotator). However, this does not lead to revision of the conclusions of the conventional theory predicting the transition from the superconducting to the insulating state in the small Josephson junction.
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。
