Autti S, Heikkinen P J, Mäkinen J T, Volovik G E, Zavjalov V V, Eltsov V B
Low Temperature Laboratory, Department of Applied Physics, Aalto University, Espoo, Finland.
Department of Physics, Lancaster University, Lancaster, UK.
Nat Mater. 2021 Feb;20(2):171-174. doi: 10.1038/s41563-020-0780-y. Epub 2020 Aug 17.
Quantum time crystals are systems characterized by spontaneously emerging periodic order in the time domain. While originally a phase of broken time translation symmetry was a mere speculation, a wide range of time crystals has been reported. However, the dynamics and interactions between such systems have not been investigated experimentally. Here we study two adjacent quantum time crystals realized by two magnon condensates in superfluid He-B. We observe an exchange of magnons between the time crystals leading to opposite-phase oscillations in their populations-a signature of the AC Josephson effect-while the defining periodic motion remains phase coherent throughout the experiment. Our results demonstrate that time crystals obey the general dynamics of quantum mechanics and offer a basis to further investigate the fundamental properties of these phases, opening pathways for possible applications in developing fields, such as quantum information processing.
量子时间晶体是在时域中具有自发出现的周期性秩序特征的系统。虽然最初关于时间平移对称性破缺相仅仅是一种推测，但现在已经报道了各种各样的时间晶体。然而，此类系统之间的动力学和相互作用尚未通过实验进行研究。在这里，我们研究了由超流He-B中的两个磁振子凝聚体实现的两个相邻量子时间晶体。我们观察到时间晶体之间磁振子的交换，导致它们的粒子数出现反相振荡——这是交流约瑟夫森效应的一个特征——而在整个实验过程中，定义性的周期性运动保持相位相干。我们的结果表明，时间晶体服从量子力学的一般动力学，并为进一步研究这些相的基本性质提供了基础，为量子信息处理等发展领域的可能应用开辟了途径。
