A master equation approach to the study of environmental effects in the adiabatic population transfer in three-state systems is presented. A systematic comparison with the non-Hermitian Hamiltonian approach [Vitanov and Stenholm, Phys. Rev. A 56, 1463 (1997)] shows that, in the weak-coupling limit, the two treatments lead to essentially the same results. In contrast, in the strong-damping limit the predictions are quite different: In particular, the counterintuitive sequences in the STIRAP scheme turn out to be much more efficient than expected before. This point is explained in terms of quantum Zeno dynamics.
A master equation approach to the study of environmental effects in the adiabatic population transfer in three-state systems is presented. A systematic comparison with the non-Hermitian Hamiltonian approach [Vitanov and Stenholm, Phys. Rev. A 56, 1463 (1997)] shows that, in the weak-coupling limit, the two treatments lead to essentially the same results. In contrast, in the strong-damping limit the predictions are quite different: In particular, the counterintuitive sequences in the STIRAP scheme turn out to be much more efficient than expected before. This point is explained in terms of quantum Zeno dynamics.
The prospect of employing the stimulated Raman adiabatic Passage (STIRAP) technique under the influence of pure dephasing is explored. A general analysis of how decoherence influences the performance of STIRAP is provided. Starting from a general and fully quantum-mechanical system–bath Hamiltonian, we derive a quantum master equation (QME) that describes the reduced dynamics of a dissipative STIRAP system. The derivation is based on the standard assumptions of (1) weak system–bath coupling; (2) Markovity, in the sense that the relaxation times are long in comparison to the bath correlation time, τc; and (3) weak field–matter interaction, in the sense that the Rabi period of the driving laser fields, Ω−1, is longer than τc. The dissipative term in this QME is the same as it would have been in the absence of the driving fields, because of the assumption of weak field–matter interaction. This type of uncontrollable dephasing is seen to diminish the efficiency of STIRAP, although the actual loss strongly depends on the specific dephasing mechanism. We also derive a more general QME, which is applicable to driving fields of arbitrary intensity. The dissipative term in the new QME is explicitly dependent on the driving fields, and therefore controllable. Intense fields are shown to effectively slow down the dephasing when Ωτc>1, which suggests that it may be possible to use STIRAP in order to transfer population between the quantum states of a solute molecule embedded in a solvent.
The Stimulated Raman Adiabatic Passage (STIRAP) on a three-state system interacting with a spin bath is considered, focusing on the efficiency of the population transfer. Our analysis is based on the perturbation treatment of the interaction term evaluated beyond the Rotating Wave Approximation, thus focusing on the limit of weak system–bath coupling. The analytical expression of the correction to the efficiency and the consequent numerical analysis show that, in most of the cases, the effects of the environment are negligible, confirming the robustness of the population transfer.
The Stimulated Raman Adiabatic Passage, a very efficient technique for manipulating a quantum system based on the adiabatic theorem, is analyzed in the case where the manipulated physical system is interacting with a spin bath. The exploitation of the rotating wave approximation allows for the identification of a constant of motion, which simplifies both the analytical and the numerical treatment, which allows for evaluating the total unitary evolution of the system and bath. The efficiency of the population transfer process is investigated in several regimes, including the weak and strong coupling with the environment and the off-resonance. The formation of appropriate Zeno subspaces explains the lowering of the efficiency in the strong damping regime.
We exploit a microscopically derived master equation for the study of stimulated Raman adiabatic passage in the presence of spontaneous decay from the intermediate state toward the initial and final states and compare our results with the predictions obtained from a phenomenological model used previously [P. A. Ivanov, N. V. Vitanov, and K. Bergmann, Phys. Rev. A 72, 053412 (2005)]. It is shown that our approach predicts a much higher efficiency for counterintuitively ordered pulses, while no significant difference between the two approaches is found for intuitively ordered pulses. These features are readily explained in the dressed-state picture.
We propose a method to improve the stimulated Raman adiabatic passage (STIRAP) via dissipative quantum dynamics, taking into account the dephasing effects. Fast and robust population transfer can be obtained with the scheme by the designed pulses and detuning, even though the initial state of the system is imperfect. With a concrete three-level system as an example, the influences of the imperfect initial state, variations in the control parameters, and various dissipation effects are discussed in detail. The numerical simulation shows that the scheme is insensitive to moderate fluctuations of experimental parameters and the relatively large dissipation effects of the excited state. Furthermore, the dominant dissipative factors, namely, the dephasing effects of the ground states and the imperfect initial state are no longer undesirable, in fact, they are the important resources to the scheme. Therefore, the scheme could provide more choices for the realization of the complete population transfer in the strong dissipative fields where the standard stimulated Raman adiabatic passage or shortcut schemes are invalid.
The problem of the coherent control of atomic states, preparation of atoms in a stable superposition state, and atomic population transfer has attracted much attention in the last decade. One of the main motivations is associated with the rapid development of the field of quantum computing. One of the key problems of quantum information processing is the construction of given coherent superposition atomic states in a macroscopic volume. Stimulated Raman adiabatic passage (STIRAP) [1] is considered to be the most common method for atomic population transfer in quantum systems. Being analyzed in detail on various quantum systems from both theoretical and experimental points of view, this method is widely adopted for the implementation of tools as optical devices for atomic beams, control of chemical reactions, high-precision magnetometry, atom cooling, etc. Meanwhile, an alternative method for population transfer, based on the intuitive pulse sequence with large one-photon detunings was demonstrated in [2]. In contrast with the STIRAP method, where the population transfer is realized via a dark state, the population transfer for the intuitive pulse sequence is obtained via a bright state. The authors of [2] called the atomic population transfer of this kind b-STIRAP. A detailed theoretical analysis of the b-STIRAP process in media with equal oscillator strength on adjacent transitions was performed in [3]. However, it is well-known that an oscillator strengths ratio different from unity can considerably impact on the coherent processes in Λ-media (see e.g. [4]). In the present work an analytical and numerical analysis of the b-STIRAP process in a medium with unequal oscillator strengths is performed. It is shown that the length of population transfer can be considerably increased by an appropriate choice of the dipole transitions. 1. N.V.Vitanov, B.W.Shore,K.Bergman, Adv. Atom.,Mol, Optical Physics, 46, 55-190, (2001). 2. J.Klein, F.Beil, Th.Halfmann, , Phys.Rev.Lett. 99,113003 (2007) 3. G.G. Grigoryan, G. Nikoghosyan, T. Halfmann, Y.T. Pashayan-Leroy, C. Leroy, S.Guerin, Phys.Rev. A 80, 033402 (2009) 4. G.G.Grigoryan, Y.Pashayan, Propagation of pulses in a three-level medium at exact two-photon resonance. Phys.Rev. A 64, 013816, 2001