Quantizing Billiards with Arbitrary Trajectories
  The structure of the semiclassical trace formula can be used to construct a quasi-classical evolution operator whose spectrum has a one-to-one correspondence with the semiclassical quantum spectrum. We illustrate this for marginally unstable integrable and non-integrable billiards and demonstrate its utility by quantizing them using arbitrary non-periodic trajectories. 
Debabrata Biswas (Niels Bohr Institute, Copenhagen & B.A.R.C., Mumbai)