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arXiv:2503.08932

Simulation of STIRAP from the 1S to the 2S states of the Hydrogen/Antihydrogen atoms

Amer, AbdAlGhaffar K., A. Capra, Tim Friesen, M. C. Fujiwara, Takamasa Momose, Chukman So, F. Robicheaux

Published Mar 11, 2025• 0 citations
arXivHTMLPDF

Abstract

Achieving a high population of antihydrogen/hydrogen atoms in the 2S level is essential for spectroscopy measurements testing similarities between matter and antimatter. We propose and examine the efficiency of applying the STIRAP (Stimulated Raman Adiabatic Passage) process in achieving high population transfer from the 1S to the 2S levels. We utilized a circularly polarized Lyman alpha, Ly-$α$, pulse to couple the 1S state to the 2P state and a microwave pulse to couple the 2P state and the 2S state. We calculate the efficiency of the STIRAP process for transferring the population between the stretched states $(1S_d, 2S_d)$ as a function of experimental parameters such as Rabi frequencies and pulse durations. We find that a Ly-$α$ pulse with an energy of a few nanojoules could produce nearly perfect transfer at zero detunings for atoms on the laser beam axis. We extended the analysis to a thermal ensemble of atoms, where Doppler detuning affects the velocity distribution of the hydrogen atoms produced in the 2S level. We found that the width of such velocity distribution is controlled by the Rabi frequency. We show that the peak velocity of the hydrogen atoms in the 2S level after STIRAP can be controlled by the Ly-$α$ pulse detuning. The efficiency of STIRAP in transferring population increases at low temperature (T$\sim$1~mK). Finally, we show that a background magnetic field improves the transfer rates between the other trappable states $(1S_c, 2S_c)$.

DOI
10.48550/arxiv.2503.08932

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Achieving a high population of antihydrogen and hydrogen atoms in the $2S$ level is essential for spectroscopy measurements testing similarities between matter and antimatter. We propose and examine the efficiency of applying the STIRAP (stimulated Raman adiabatic passage) process in achieving high population transfer from the 1$S$ to the $2S$ levels. We utilized a circularly polarized Lyman alpha $(\mathrm{Ly}\text{\ensuremath{-}}\ensuremath{\alpha})$ pulse to couple the $1S$ state to the $2P$ state and a microwave pulse to couple the $2P$ state and the $2S$ state. We calculate the efficiency of the STIRAP process for transferring the population between the stretched states $(1{S}_{d},2{S}_{d})$ as a function of experimental parameters such as Rabi frequencies and pulse durations. We find that a $\mathrm{Ly}\text{\ensuremath{-}}\ensuremath{\alpha}$ pulse with an energy of a few nanojoules could produce nearly perfect transfer at zero detunings for atoms on the laser beam axis. We extended the analysis to a thermal ensemble of atoms, where Doppler detuning affects the velocity distribution of the hydrogen atoms produced in the $2S$ level. We found that the width of such velocity distribution is controlled by the Rabi frequency. We show that the peak velocity of the hydrogen atoms in the $2S$ level after STIRAP can be controlled by the $\mathrm{Ly}\text{\ensuremath{-}}\ensuremath{\alpha}$ pulse detuning. The efficiency of STIRAP in transferring population increases at low temperature $(T\ensuremath{\sim}1\phantom{\rule{0.16em}{0ex}}\mathrm{mK})$. Finally, we show that a background magnetic field improves the transfer rates between the other trappable states $(1{S}_{c},2{S}_{c})$.

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Achieving a high population of antihydrogen/hydrogen atoms in the 2S level is essential for spectroscopy measurements testing similarities between matter and antimatter. We propose and examine the efficiency of applying the STIRAP (Stimulated Raman Adiabatic Passage) process in achieving high population transfer from the 1S to the 2S levels. We utilized a circularly polarized Lyman alpha, Ly-ααα, pulse to couple the 1S state to the 2P state and a microwave pulse to couple the 2P state and the 2S state. We calculate the efficiency of the STIRAP process for transferring the population between the stretched states (1Sd,2Sd)(1S_d, 2S_d)(1Sd​,2Sd​) as a function of experimental parameters such as Rabi frequencies and pulse durations. We find that a Ly-ααα pulse with an energy of a few nanojoules could produce nearly perfect transfer at zero detunings for atoms on the laser beam axis. We extended the analysis to a thermal ensemble of atoms, where Doppler detuning affects the velocity distribution of the hydrogen atoms produced in the 2S level. We found that the width of such velocity distribution is controlled by the Rabi frequency. We show that the peak velocity of the hydrogen atoms in the 2S level after STIRAP can be controlled by the Ly-ααα pulse detuning. The efficiency of STIRAP in transferring population increases at low temperature (T∼\sim∼1~mK). Finally, we show that a background magnetic field improves the transfer rates between the other trappable states (1Sc,2Sc)(1S_c, 2S_c)(1Sc​,2Sc​).
Achieving a high population of antihydrogen and hydrogen atoms in the 2S2S2S level is essential for spectroscopy measurements testing similarities between matter and antimatter. We propose and examine the efficiency of applying the STIRAP (stimulated Raman adiabatic passage) process in achieving high population transfer from the 1SSS to the 2S2S2S levels. We utilized a circularly polarized Lyman alpha $(\mathrm{Ly}\text{\ensuremath{-}}\ensuremath{\alpha})$ pulse to couple the 1S1S1S state to the 2P2P2P state and a microwave pulse to couple the 2P2P2P state and the 2S2S2S state. We calculate the efficiency of the STIRAP process for transferring the population between the stretched states (1Sd,2Sd)(1{S}_{d},2{S}_{d})(1Sd​,2Sd​) as a function of experimental parameters such as Rabi frequencies and pulse durations. We find that a $\mathrm{Ly}\text{\ensuremath{-}}\ensuremath{\alpha}$ pulse with an energy of a few nanojoules could produce nearly perfect transfer at zero detunings for atoms on the laser beam axis. We extended the analysis to a thermal ensemble of atoms, where Doppler detuning affects the velocity distribution of the hydrogen atoms produced in the 2S2S2S level. We found that the width of such velocity distribution is controlled by the Rabi frequency. We show that the peak velocity of the hydrogen atoms in the 2S2S2S level after STIRAP can be controlled by the $\mathrm{Ly}\text{\ensuremath{-}}\ensuremath{\alpha}$ pulse detuning. The efficiency of STIRAP in transferring population increases at low temperature $(T\ensuremath{\sim}1\phantom{\rule{0.16em}{0ex}}\mathrm{mK})$. Finally, we show that a background magnetic field improves the transfer rates between the other trappable states (1Sc,2Sc)(1{S}_{c},2{S}_{c})(1Sc​,2Sc​).
We investigate the coherent population transfer and associated effects for a three level atomic system, with the third level being a Rydberg state. The scheme adopted here is the stimulated Raman adiabatic passage (STIRAP). An atomic beam of metastable helium is orthogonally crossing two laser beams in a tunable dc electric field. The ir laser of 790 - 830 nm connects the triplet 3P state to the Rydberg states (n = 12 - 50) and the uv laser of 389 nm connects the metastable triplet 2S state to the triplet 3P state. A third laser of 1083 nm driving 2S-2P transition is applied downstream, providing a strong bichromatic force on the atoms remaining in the 2S state to deflect them, establishing the absolute count of Rydberg atoms. Rydberg atoms can be ionized by background thermal radiations at room temperature and it is observed in this experiment. This fact actually enables precise measurement, especially spectroscopy, of Rydberg atoms by simply looking at the ions, which are easy to detect. It is also confirmed that background thermal radiation could significantly redistribute the population between neighboring Rydberg states. The 2S, 3P and the final Rydberg states all have magnetic sub-levels, hence the linkage pattern of the excitation has non-trivial crossings, if the polarizations of the two lasers are not parallel to each other. Those phase differences in different excitation paths induced by the laser polarizations can lead to interference which would determine the excitation probability and the polarization of the excited atom. Theoretical calculations predict interesting interference patterns as a function of laser polarizations and Rabi frequencies. Those interference structures have been experimentally observed. Transverse velocity distribution in the atomic beam turns out to be a limiting factor in the efficiency of production of Rydberg atoms. The transverse velocity of an atom can not only induce one-photon detuning but also two-photon detuning, which could effectively reduce the STIRAP process efficiency. By adding a laser to make Doppler molasses in the transverse direction, we can heat or cool the atomic beam transversely and verify this effect. | 190 pages
We report studies of state-to-state vibrational energy transfer in an isolated polyatomic molecule driven by combined stimulated Raman adiabatic passage (STIRAP) and counter-diabatic fields (CDFs). The goal of these studies is development of a method for improving the efficiency of level-to-level population transfer under conditions that degrade the efficiency of conventional STIRAP-generated population transfer. The vehicles for our studies are selective population of one of a pair of near-degenerate states in nonrotating SCCl 2 and enhancing the yield of nonrotating HNC in the HCN → HNC isomerization reaction. The efficiency of the population transfer within a subset of states embedded in a manifold of states is examined for the cases in which the transition dipole moments between the initial and target states are much smaller than and comparable to the transition dipole moments between background states and for the case in which the subset states have large transition dipole moments with the background states. We show that, in a subset of states that is coupled to background states, a combination of STIRAP fields and CDFs that do not individually generate processes that are competitive with the desired population transfer can generate population transfer efficiency greater than can ordinary STIRAP with field strength and/or pulse duration similarly restricted and that the exact CDF for an isolated three-level system is a useful approximation to the exact CDF for three- and five-state systems embedded in background states. We report a study of the stability of the STIRAP and approximate CDF control protocol to variation of the CDF intensity, the relative phase between the STIRAP and CDFs, and the pulse duration.
Previous studies have demonstrated that when experimental conditions generate non-adiabatic dynamics that prevents highly efficient population transfer between states of an isolated system by stimulated Raman adiabatic passage (STIRAP), the addition of an auxiliary counter-diabatic field (CDF) can restore most or all of that efficiency. This paper examines whether that strategy is also successful in a non-isolated system in which the energies of the states fluctuate, e.g., when a solute is subject to collisions with solvent. We study population transfer in two model systems: (i) the three-state system used by Demirplak and Rice [J. Chem. Phys. 116, 8028 (2002)] and (ii) a four-state system, derived from the simulation studies of Demirplak and Rice [J. Chem. Phys. 125, 194517 (2006)], that mimics HCl in liquid Ar. Simulation studies of the vibrational manifold of HCl in dense fluid Ar show that the collision induced vibrational energy level fluctuations have asymmetric distributions. Representations of these asymmetric energy level fluctuation distributions are used in both models (i) and (ii). We identify three sources of degradation of the efficiency of STIRAP generated selective population transfer in model (ii): too small pulse areas of the laser fields, unwanted interference arising from use of strong fields, and the vibrational detuning. For both models (i) and (ii), our examination of the efficiency of STIRAP + CDF population transfer under the influence of the asymmetric distribution of the vibrational energy fluctuations shows that there is a range of field strengths and pulse durations under which STIRAP + CDF control of population transfer has greater efficiency than does STIRAP generated population transfer.
We propose a pulse-shaping method for improving population transfer in multistate stimulated Raman adiabatic passage (STIRAP) with nearest-neighbour couplings only. The method extends the quasiparallel-eigenenergy approach, previously used for two- and three-state systems, to multistate chains without introducing additional shortcut fields. The pump and Stokes fields are shaped so that the eigenenergies closest to the dark state remain nearly parallel to it during the central part of the interaction, where nonadiabatic transitions are most likely to occur. We derive analytic prescriptions for the required pulse shapes and apply them to five-, seven-, and nine-state chains formed by magnetic sublevels of degenerate manifolds with angular momenta Jg→Je=JgJ_g\rightarrow J_e=J_gJg​→Je​=Jg​ and Jg→Je=Jg−1J_g\rightarrow J_e=J_g-1Jg​→Je​=Jg​−1 driven by a pair of right- and left-circularly polarized pulses. Numerical simulations show that the optimized pulses can reduce the population transfer error by several orders of magnitude compared to standard Gaussian pulses. The same shapes also improve robustness against variations of the peak Rabi frequency, the single-photon detuning, and the multiphoton detuning. The comparison between the two angular-momentum families shows that the Jg→JgJ_g\rightarrow J_gJg​→Jg​ chains are generally more favourable, because their Clebsch-Gordan coefficients keep the relevant bright-state gap larger in the region where the dark state changes most rapidly. Finally, simulations with spontaneous emission show that the optimized resonant pulses remain advantageous in the lossy regime as well.
The population transfer of stimulated Raman adiabatic passage (STIRAP) is investigated using a time-dependent quantum wave packet method. The population is transferred from an initial state to a target state through the interaction of the external laser field with the permanent dipole moment and the transition dipole moment. The laser field is composed of an infrared pulse and a near ultraviolet pulse. The two pulses with small detunings are more efficient to achieve the STIRAP transition. The process of STIRAP is sensitive to the detunings of the two pulses. When the two detunings are the same in a Λ transition or the positive detuning of the pump pulse is equal to the negative detuning of the Stokes pulse in a ladder transition, the final population in the intermediate state can be eliminated and the target population is increased.