Description of Quantum Beams Using a Stationary Incoherent Superposition   of Wave Packets
  An original entity is defined to study quantum beams of conserved particles. The beam is described as a Stationary Incoherent Superposition of Wave packets (SISOW). Mean values are time-independent confirming that the SISOW describes a stationary flux of particles. The SISOW is a general entity that contains the Hamiltonian eigenstates as a particular limit. The decomposition of the SISOW into wave packets provides intrinsic dynamic information which is not accessible from Hamiltonian eigenstates. The SISOW provides and adequate framework to study mesoscopic systems 
Xavier Oriols and Jordi Sune