Quantum time crystals are systems characterized by spontaneously emerging periodic order in the time domain¹. While originally a phase of broken time translation symmetry was a mere speculation², a wide range of time crystals has been reported^3,4,5. 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 ³He-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 effect⁶—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.

量子时间晶体是指在时域^1中自发出现的周期性有序的系统。虽然最初打破时间平移对称性的阶段仅仅是一种推测²，但据报道^3,4,5的时间晶体种类繁多。但是，这种系统之间的动力学和相互作用尚未进行实验研究。在这里，我们研究了由超流体³ He-B中的两种强子冷凝物实现的两个相邻的量子时间晶体。我们观察到时间晶体之间会产生磁振子的交换，从而导致其种群中发生反相振荡，这是交流约瑟夫森效应的一个特征⁶-在整个实验过程中，定义的周期性运动保持相位一致。我们的结果表明，时间晶体遵循量子力学的一般动力学，并为进一步研究这些相的基本特性提供了基础，为在诸如量子信息处理等发展中领域的可能应用打开了途径。