Superluminal signal velocity

The formal analogy between classical evanescent modes and particle tunneling in wave mechanics has recently initiated microwave experiments. Studies with microwaves and later with single photons have revealed superluminal group and energy velocities of evanescent modes (the classical analogy to tunneling solutions). Microwave experiments have even demonstrated superluminal propagation of frequency bandwidth limited signals. This result does allow a change of chronological order of events in an inertial system or between different inertial systems.