Twin paradox with macroscopic clocks in superconducting circuits
  We propose an implementation of a twin paradox scenario in superconducting circuits, with velocities as large as a few percent of the speed of light. Ultrafast modulation of the boundary conditions for the electromagnetic field in a microwave cavity simulates a clock moving at relativistic speeds. Since our cavity has a finite length, the setup allows us to investigate the role of clock size as well as interesting quantum effects on time dilation. In particular, our theoretical results show that the time dilation increases for larger cavity lengths and is shifted due to quantum particle creation. 
Joel Lindkvist, Carlos Sab\'in, Ivette Fuentes, Andrzej Dragan,   Ida-Maria Svensson, Per Delsing and G\"oran Johansson
quant-ph cond-mat.mes-hall gr-qc