Figure 3: Time-reversal operation.

The time-reversal operation is performed at the mid-point (t=4) of the evolution of a Majorana particle. The initial state is a moving Gaussian wave packet in momentum space and in position space, respectively, with initial average momentum P₀=1. (a) Time-dependent probability distribution in the momentum space. The solid curve represents the theoretical results of the average momentum , whereas the red dots with error bars are experimental results. The same conventions are used for c, and a and c of Fig. 4. Right after the time-reversal operation at t=4, the momentum p of the Majorana particle is reversed to −p, which makes the discontinuity at the evolution of the picture. It is clearly shown that the momentum-space Zitterbewegung is revived after the time-reversal operation. (b) Probability distributions in the momentum space at various times t=0, 3, 5 and 8 from bottom to top. The solid curves are obtained from theoretical calculation whereas the shades are from experiment. The same conventions are used for d, and b and d of Fig. 4. (c) Time-dependent probability distribution in the position space. The average position is not affected right after the time-reversal operation, but the trajectory is reversed. (d) The same as b in the position space. The error bars in a and c are estimated by the standard error propagation method of the measured observables with mainly the standard deviation (1σ) of quantum projection noise (see Supplementary Note 3).