25th anniversary of the first publication of the STIRAP method

In 1990, STIRAP (= stimulated Raman adiabatic passage) was presented as a new laser method in a highly cited publication (Population transfer between molecular vibrational levels by stimulated Raman scattering with partially overlapping laser fields. A new concept and experimental results, J. Chem. Phys. 92, 5363, 1990) by Kaiserslautern physicist Klaas Bergmann and his research group. Since then, STIRAP has emerged as an important general tool in quantum optics and beyond. Exactly to the day 25 years later, the very same journal now published an invited review and perspective article by Bergmann and international colleagues of him, Bruce Shore from Livermore and Nikolay Vitanov from Sofia. (Stimulated Raman adiabatic passage: The status after 25 years, J. Chem.Phys. 142, 170901, 2015). To celebrate 25 years of STIRAP research and applications, this important laser method is especially highlighted through placing the STIRAP logo the cover page of the issue of the scientific journal. Many applications of STIRAP will also be in the focus of an international symposium “Stimulated Raman adiabatic passage in physics, chemistry and technology”, to be held at the University of Kaiserslautern September 22- 25, 2015 (www.stirap.com). Thirty speakers from 15 countries and 3 continents will come to Kaiserslautern and discuss with participants from around the world most recent developments in STIRAP related theory and experiments.

Scientific background: STIRAP is a laser method that induces lossless transfer of population between quantum states. Quantum physics describes this as complete transfer of population from state 1 to state 3 by coupling those quantum states  through the coherent radiation fields P and S via a decaying state 2, see the Figure. From the perspective of population transfer, it is surprising at first glance that the S field, which couples unpopulated states, needs to interact first with the quantum system. The intensity of the P-field rises only after the intensity of the S-field has reached its maximum. The timing of the radiative interaction is either done by controlling the time delay between laser pulses or by sending a stream of particles through spatially suitably displaced laser beams. Although the fields P and S are on resonance with the respective transitions, level 2 is never populated. Lossless transfer of population from state 1 to state 3 occurs. It is the destructive interference of the two transition amplitude which make this process happen. The STIRAP scheme can be applied to any object with a quantum structure with any suitable kind of coupling between the states. STIRAP has also been applied to the coupling of wave guides and has inspired similar process in classical systems.

Further reading:

K. Bergmann, H. Theuer, and B.W. Shore, „Coherent Population Transfer Among Quantum States of Atoms and Molecules“, Review of Modern Physics 70, 1003-1026 (1998)

N.V. Vitanov, M. Fleischhauer, B.W. Shore, and K. Bergmann, "Coherent Manipulation of Atoms and Molecules by Sequential Pulses" in:  Advances of Atomic, Molecular, and Optical Physics, 46, 55 - 190 (2001)
(eds. B. Bederson, H. Walther, Academic Press)