2000/07/09 by R. Englman, Robert Englman, Asher Yahalom +2
Physics and Astronomy · #Disordered Systems and Neural Networks (cond-mat.dis-nn) #FOS: Physical sciences #Laser-Matter Interactions and Applications #Quantum Mechanics and Applications #Quantum chaos and dynamical systems #cond-mat.dis-nn
paper · pdf · doi:10.48550/arxiv.cond-mat/0007142
15 pages, Latex, to appear in Foundations of Phys. Lett. (2000)
arxiv created 2000/07/09 · openalex publication_date 2000/07/09 · arxiv updated 2016/08/31 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Availability of short, femtosecond laser pulses has recently made feasible the probing of phases in an atomic or molecular wave-packet (superposition of energy eigenstates). With short duration excitations the initial form of the wave-packet is an essentially real "doorway state", and this develops phases for each of its component amplitudes as it evolves. It is suggested that these phases are hallmarks of a time arrow and irreversibility that are inherent in the quantum mechanical processes of preparation and evolution. To display the non-triviality of the result, we show under what conditions it would not hold; to discuss its truth, we consider some apparent contradictions. We propose that (in time-reversal invariant systems) the preparation of "initially" complex wave-packets needs finite times to complete, i.e., is not instantaneous.