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We demonstrate the transfer of $^{23}\mathrm{Na}^{40}\mathrm{K}$ molecules from a closed-channel-dominated Feshbach-molecule state to the absolute ground state. The Feshbach molecules are initially created from a gas of sodium and potassium atoms via adiabatic ramping over a Feshbach resonance at 78.3 G. The molecules are then transferred to the absolute ground state using stimulated Raman adiabatic passage with an intermediate state in the spin-orbit-coupled complex $|{c}^{3}{\mathrm{\ensuremath{\Sigma}}}^{+},\phantom{\rule{0.16em}{0ex}}v=35,\phantom{\rule{0.16em}{0ex}}J=1\ensuremath{\rangle}\ensuremath{\sim}|{B}^{1}\mathrm{\ensuremath{\Pi}},\phantom{\rule{0.16em}{0ex}}v=12,\phantom{\rule{0.16em}{0ex}}J=1\ensuremath{\rangle}$. Our measurements show that the pump transition dipole moment linearly increases with the closed-channel fraction. Thus, the pump-beam intensity can be two orders of magnitude lower than is necessary with open-channel-dominated Feshbach molecules. We also demonstrate that the phase noise of the Raman lasers can be reduced by filter cavities, significantly improving the transfer efficiency.

In this paper we evaluate the performance of two superadiabatic stimulated Raman adiabatic passage (STIRAP) protocols derived from Gaussian and sin-cos pulses, under dissipation and Ornstein-Uhlenbeck noise in the energy levels. We find that, for small amplitudes of Stokes and pump pulses, the population transfer is mainly achieved directly through the counterdiabatic pulse, while for large amplitudes the conventional STIRAP path dominates. This kind of ``hedging'' leads to a remarkable robustness against dissipation in the lossy intermediate state. For small pulse amplitudes and increasing noise correlation time the performance is decreased, since the dominant counterdiabatic pulse is affected more, while for large pulse amplitudes, where the STIRAP path dominates, the efficiency is degraded more for intermediate correlation times (compared to the pulse duration). For the Gaussian superadiabatic STIRAP protocol we also investigate the effect of delay between pump and Stokes pulses and find that under the presence of noise the performance is improved for increasing delay. We conclude that the Gaussian protocol with suitably chosen delay and the sin-cos protocol perform quite well even under severe noise conditions. The present work is expected to have a broad spectrum of applications, since STIRAP has a crucial role in modern quantum technology.

Multistate stimulated Raman adiabatic passage (STIRAP) is a process which allows for adiabatic population transfer between the two ends of a chainwise-connected quantum system. The process requires large temporal areas of the driving pulsed fields (pump and Stokes) in order to suppress the nonadiabatic couplings and thereby to make adiabatic evolution possible. To this end, in the present paper a variation of multistate STIRAP, which accelerates and improves the population transfer, is presented. In addition to the usual pump and Stokes fields it uses shortcut fields applied between the states, which form the dark state of the system. The shortcuts cancel the couplings between the dark state and the other adiabatic states thereby resulting (in the ideal case) in a unit transition probability between the two end states of the chain. Specific examples of five-state systems formed of the magnetic sublevels of the transitions between two degenerate levels with angular momenta ${J}_{g}=2$ (of ground or lower level) and ${J}_{e}=1$ or ${J}_{e}=2$ (of excited or upper level) are considered in detail, for which the shortcut fields are derived analytically. The proposed method is simpler than the usual ``shortcuts to adiabaticity'' recipe, which prescribes shortcut fields between all states of the system, while the present proposal uses shortcut fields between the sublevels forming the dark state only. The results are of potential interest in applications where high-fidelity quantum control is essential, e.g., quantum information, atom optics, formation of ultracold molecules, cavity QED, etc.

Starting from an ultracold ensemble of ${}^{6}{\mathrm{Li}}_{2}$ Feshbach molecules, we produce deeply bound triplet $a(1{\phantom{\rule{0.16em}{0ex}}}^{3}{\mathrm{\ensuremath{\Sigma}}}_{u}{}^{+})$ molecules in a single quantum state by stimulated Raman adiabatic passage. The ensemble lifetime is found to be limited by two-body molecule-molecule collisions that depend on both the vibrational and rotational states. The loss rate observed is near the universal rate for the $|v=0,5,8;N=0,2\ensuremath{\rangle}$ states and, remarkably, below universality for the $|v=9,N=0\ensuremath{\rangle}$ state. We also observe a strong rotational state dependence of the $v=9$ reaction rate. Consistent with theoretical predictions, we observe that molecules in the absolute lowest triplet level are unstable and likely decay due to trimer formation.

International audience; A concept for the realization of waveguide-based polarization beam splitters working over a wide spectral range is presented. The adiabatically evolving three-waveguide system is inspired by the quantum-mechanical stimulated Raman adiabatic passage process and involves waveguides with an anisotropic refractive index contrast. It is shown that an index contrast ratio of 5 is sufficient to obtain excellent efficiency and output polarization purity over a spectral range approximately equal to 350 nm centered at a wavelength of 1550 nm. The center wavelength can be easily modified by tuning the parameters of the waveguides.

We present a method for the creation and control of cold molecules that involves coherently combining Feshbach resonances and stimulated Raman adiabatic passage. We present analytical and numerical results showing how to optimize this process that can be implemented using techniques readily available in standard experimental setups. This will provide a link in the chain from atoms to ground-state molecules and can serve as a building block towards more complex processes in coherent ultracold chemistry.

We study the many-body dynamics of stimulated Raman adiabatic passage in the presence of on-site interactions. In the classical mean-field limit, explored in Phys. Rev. Lett. {\bf 121}, 250405 (2018), interaction-induced chaos leads to the breakdown of adiabaticity under the quasi-static variation of the parameters, thus producing {\em low} sweep rate boundaries on efficient population transfer. We show that for the corresponding many-body system, alternative quantum pathways from the initial to the target state, open up at even slower sweep rates. These quantum detours avoid the chaotic classical path and hence allow a robust and efficient population transfer., 11 pages, 17 figures

Schemes for creation of N particle entangled Greenberger-Horne-Zeilinger (GHZ) states are important for understanding multi-particle non-classical correlations. Here, a theoretical scheme for creation of a multi-particle GHZ state implemented on a target ensemble of N, $\Lambda$ three-level Rydberg atoms and a single Rydberg atom as a control using Stimulated Raman Adiabatic Passage (STIRAP) is presented. We work in the Rydberg blockade regime for the ensemble atoms induced due to excitation of the control atom to a high lying Rydberg level. It is shown that using STIRAP, atoms from one ground state of the ensemble can be adiabatically transferred to the other ground state, depending on the state of the control atom with high fidelity. Measurement of the control atom in a specific basis after this conditional transfer facilitates one-step creation of a N particle GHZ state. A thorough analysis of adiabatic conditions for this scheme and the influence of radiative decay from the excited Rydberg levels is presented. We show that this scheme is immune to the decay rate of the excited level in ensemble atoms and provides a robust way of creating GHZ states.

The detuning-induced stimulated Raman adiabatic passage (D-STIRAP) in two-level systems with permanent dipole moments (PDMs) is investigated. Based on a transformed Schr\"odinger equation, we discuss the coherence generation under the one- and two-photon excitations, respectively. In the one-photon excitation, our analysis shows that the envelope of the pump pulse gets modulated in presence of the PDMs. The modulation becomes stronger while the difference between the PDMs of the two levels becomes larger. Gradually, the adiabatic process of the D-STIRAP fails to complete and the robustness of the technique disappears. Therefore, parameters have to be chosen with care if maximum coherence is desired in systems with large or giant difference between the PDMs. Similar results can also be found in the two-photon excitation, although the influence of the PDMs on the D-STIRAP seems weaker compared with that in the one-photon excitation case. Finally, we point out that the negative role of the PDMs can be effectively avoided by simply choosing longer pulses instead and the D-STIRAP can be safely applied in two-level systems with PDMs.

A scheme is presented to perform an entangling gate between two atomic ensembles or Bose-Einstein condensates in a optical cavity with a common optical mode. The method involves using a generalized Stimulated Raman Adiabatic Passage (STIRAP) to adiabatically evolve the ground state. We show that dark states exist for any atom number within the cavities, and find that the operation produces an unusual type of evolution where the minimum of the number of atoms between two levels transitions to another state. This produces a unconventional type of entangling Hamiltonian which creates a phase depending on the minimum operation. We analyze its reliability under a variety of conditions ranging from the ideal decoherence-free case to that including photon loss and spontaneous emission. Ways of combating decoherence are analyzed and the amount of entanglement that is generated is calculated.

International audience; We propose an adiabatic method for the robust transfer of light between the two outer waveguides in a three-waveguide directional coupler. Unlike the established technique inherited from stimulated Raman adiabatic passage (STIRAP), the method proposed here is symmetric with respect to an exchange of the left and right waveguides in the structure and permits the transfer in both directions. The technique uses the adiabatic elimination of the middle waveguide together with level crossing and adiabatic passage in an effective two-state system involving only the external waveguides. It requires a strong detuning between the outer and the middle waveguide and does not rely on the adiabatic transfer state (dark state) underlying the STIRAP process. The suggested technique is generalized to an array of N waveguides and verified by numerical beam propagation calculations.

Ultracold fermionic ${}^{23}$Na${}^{40}$K polar molecules are produced in their ground rovibrational state. A multilevel stimulated Raman adiabatic passage (STIRAP) state-transfer process is employed with an intermediate state having an unresolved hyperfine structure, which can be a situation commonly encountered in performing the state transfer.

We theoretically study the transparency in the generalized two-level system with hyperfine structure by utilizing double detuning-induced stimulated Raman adiabatic passage (double D-STIRAP). The double D-STIRAP is carried out by sequentially applying the three pulses, one near-resonant pump pulse and two far-off resonant Stark pulses before and after the pump pulse. From the study of single-atom response we can roughly learn the transparency conditions, since the full recovery of the system to the initial state is associated with the perfect transparency. After the numerical calculations we find that, for the perfect transparency, the pulse intensities of double D-STIRAP for the generalized two-level systems with hyperfine structure has to be stronger than that for the ideal two-level system. More precisely, we find that the ratio of amplitude to time for the Rabi frequency of the pump pulse and the detuning induced by the Stark pulse have to be close to each other to satisfy the adiabatic conditions. The above conditions, however, are necessary conditions we can learn from the single-atom response, and to ensure that they are indeed sufficient for perfect transparency, we perform the propagation calculations to obtain the temporal profile of the pump pulse at arbitrary propagation depths to find that double D-STIRAP, when applied to the generalized two-level system with hyperfine structure, is indeed robust for perfect transparency.

Realization of the highly efficient $\ensuremath{\pi}$ and $\ensuremath{\pi}/2$ pulses is crucial in an atom interferometry. Here we propose a scheme to realize these operations based on an intrinsically fault-tolerant geometric phase and stimulated Raman shortcuts to the adiabatic passage. The scheme is fast due to the shortcuts to adiabaticity and is robust based on the geometric phase. In the presence of various noises, we show that the fringe contrast of the proposed interferometer is higher than that of the resonant Raman pulse and the stimulated Raman adiabatic passage. Furthermore, the scheme is demonstrated to be especially suitable for applications that require a large space-time area enclosed by interfering wave packets.

We report the binding energy of $^{87}\mathrm{Rb}^{133}\mathrm{Cs}$ molecules in their rovibrational ground state measured using an offset-free optical frequency comb based on difference frequency generation technology. We create molecules in the absolute ground state using stimulated Raman adiabatic passage (STIRAP) with a transfer efficiency of 88%. By measuring the absolute frequencies of our STIRAP lasers, we find the energy-level difference from an initial weakly bound Feshbach state to the rovibrational ground state with a resolution of $\ensuremath{\sim}5$ kHz over an energy-level difference of more than $114\phantom{\rule{0.28em}{0ex}}\mathrm{T}\mathrm{Hz}$; this lets us discern the hyperfine splitting of the ground state. Combined with theoretical models of the Feshbach-state binding energies and ground-state hyperfine structure, we determine a zero-field binding energy of $h\ifmmode\times\else\texttimes\fi{}114\phantom{\rule{0.16em}{0ex}}268\phantom{\rule{0.16em}{0ex}}135.24(4)(3)\phantom{\rule{0.28em}{0ex}}\mathrm{M}\mathrm{Hz}$. To our knowledge, this is the most accurate determination to date of the dissociation energy of a molecule.

A quantum-state preparation scheme is demonstrated for the next generation ACME experiment searching for the electron electric dipole moment in ThO molecules, where the stimulated Raman adiabatic passage technique, together with other experimental improvements, brings in at least a 75 times increase in combined preparation and detection efficiency of the molecules in the target state.

We propose an experimental scheme of generating entangled states between two spinor Bose-Einstein condensates (BECs) using Rydberg excitations. Due to the strong interaction between Rydberg atoms, the Rydberg excitation creates an interaction between two closely located BECs. The method is suitable particularly for atom chip and permanent magnetic trap systems, which can create many BECs with an arbitrary two-dimensional geometry. We show two schemes of entangled state generation, based on stimulated Raman adiabatic passage (STIRAP) methods. The first method produces a symmetric state with total Sx spin zero between ground and excited states of the atoms using a single STIRAP pair, while the second produces a NOON state between hyperfine ground states using two STIRAP pairs. We show that despite the additional complexity of the BECs, it is possible to identify the initial and final adiabatic states exactly. We verify our theoretical predictions using numerical simulations on small boson number systems.

We combine multichannel electronic structure theory with quantum optimal control to derive femtosecond-time-scale Raman pulse sequences that coherently populate a valence excited state. For a neon atom, Raman target populations of up to 13% are obtained. Superpositions of the ground and valence Raman states with a controllable relative phase are found to be reachable with up to 4.5% population and arbitrary phase control facilitated by the pump pulse carrier-envelope phase. Analysis of the optimized pulse structure reveals a sequential mechanism in which the valence excitation is reached via a fast (femtosecond) population transfer through an intermediate resonance state in the continuum rather than avoiding intermediate-state population with simultaneous or counterintuitive (stimulated Raman adiabatic passage) pulse sequences. Our results open a route to coupling valence excitations and core-hole excitations in molecules and aggregates that locally address specific atoms and represent an initial step towards realization of multidimensional spectroscopy in the xuv and x-ray regimes.

We propose a potentially practical scheme for quantum state transfer between a Cooper-pair box circuit and an electron spin ensemble of diamond nitrogen-vacancy (NV) centers. Both subsystems are placed into a common circuit QED and can be modeled as effective three-level subsystems under the appropriate external biases. Due to significant suppression of the photon decay, the robust state transfer between the two subsystems can be accomplished by using the technique of stimulated Raman adiabatic passage by individual microwave pulses, where a superconducting coplanar resonator serves as the quantum data bus. Numerical simulations show that the present scheme could offer a viable route towards robust quantum state transfer in hybrid solid-state systems.

We consider systems of two and three qubits, mutually coupled by Heisenberg-type exchange interaction and interacting with external laser fields. We show that these systems allow one to create maximally entangled Bell states, as well as three qubit Greenberger-Horne-Zeilinger and W states. In particular, we point out that some of the target states are the eigenstates of the initial bare system. Due to this, one can create entangled states by means of pulse area and adiabatic techniques, when starting from a separable (non-entangled) ground state. On the other hand, for target states, not present initially in the eigensystem of the model, we apply the robust stimulated Raman adiabatic passage and $\pi$ pulse techniques, that create desired coherent superpositions of non-entangled eigenstates., Comment: 9 pages, 7 figures. Updated version for publication

Efficient laser scheme to create ultracold KRb molecules into their rovibronic ground state using stimulated Raman adiabatic passage was presented and state-of-the-art molecular potentials, spin-orbit couplings, and transition strengths are used to perform the involved calculations.

This paper begins with the premise that stimulated Raman adiabatic passage (STIRAP) from one state to another by coupling to an intermediate state necessarily requires some population of that intermediate state. The usual view of the process depends on having no population in the intermediate state, but a simple argument from the time-dependent Schr\"odinger equation shows that such adiabatic transfer cannot occur. From another perspective, removing the time dependence of the Hamiltonian by making the rotating frame transformation cancels the optical frequency oscillations but does not account for the envelopes of the pulses commonly used for STIRAP. By assuming a small but finite intermediate state amplitude ${\ensuremath{\varepsilon}}_{1}$ in the wave function, the propagator for the evolution between initial and final states is derived. Applying the propagator to the initial state produces a single compact formula for the final intermediate-state population that is readily evaluated for an arbitrary choice of laser pulse parameters. Several plots for various experimental conditions show that under the conditions normally used for STIRAP experiments the effects are typically a few percent or less, but in the end this effect puts an ultimate limit on total efficiency.

Population transfer between two valence states of the Li atom with a Raman process via intermediate autoionizing states well above the ionization threshold is investigated using a recently developed implementation of the muticonfiguration time-dependent Hartree Fock method. It is found that a properly chosen sequence of pump and Stokes $\ensuremath{\pi}$ pulses can yield a population transfer efficiency of $53%$ at relatively low intensities, while the extension of the stimulated Raman adiabatic passage (STIRAP) approach to the XUV in this case is far less efficient and loses its characteristic robustness at high intensities. A rule of thumb for when STIRAP is practical is given, suggesting that at still shorter wavelengths STIRAP may be possible.

We theoretically study the generation of coherence in generalized two-level atoms with hyperfine structure by utilizing the detuning-induced stimulated Raman adiabatic passage (D-STIRAP). As expected, the degree of attainable coherence between the ground and excited states cannot be as large as that for the ideal two-level atoms without hyperfine structure. However, we find that the substantial degree of coherence can still be produced with small modulations, and the modulation period is essentially determined by the hyperfine splittings in the ground and excited states. The D-STIRAP scheme in generalized two-level atoms is sufficiently robust against the various parameters such as intensities of lasers, initial detuning, time delay between the laser pulses, and Doppler broadening. As a specific example, we show realistic results for the ${D}_{1}$ transition of Na.

We discuss the detrimental effect of small rapid random fluctuations of laser-field amplitude and phase upon the efficiency of stimulated Raman adiabatic passage (STIRAP). Such fluctuations typically accompany the laser stabilization procedures that produce nearly monochromatic light on top of a much broader bandwidth Lorentz-profile pedestal which may carry only a few percent or less of the total power. As we will show, their effects differ qualitatively from the fluctuations that have hitherto been considered (for example, phase diffusion). We present analytic expressions for the population transfer efficiency of STIRAP when limited by stochastic fluctuations of this type. These expressions show, in contrast to situations discussed in the past in which population transfer improves with increasing peak Rabi frequencies, that for the weak broadband noise that accompanies a strong narrow-spectral component, there is an optimum value for the peak Rabi frequency and that the effect of fluctuations, although small, cannot be entirely eliminated in practice. The mission of the current work is to point out that, under the given circumstances, efforts in experiments trying to overcome the detrimental consequences of fluctuations by increasing the intensity, which is the intuitively proper approach, will not be successful.

We study different mechanisms of adiabatic population transfer in N-level systems by means of optimal control algorithms. Using two-dimensional topographic maps of the yield of population transfer as a function of time delay and intensity of the pulses we analyze the global properties of the schemes and the conditions that lead to optimization. For three-level systems it is shown that the optimal pulse sequence is the well-known STIRAP (stimulated Raman adiabatic passage) scheme. For five-level systems a family of solutions ranging from the alternating STIRAP scheme to the new straddling STIRAP (S-STIRAP) scheme is obtained and the behavior of the solutions is compared. For four-level systems we obtain as optimal a S-STIRAP type sequence that behaves as an effective two-level system. For both odd and even numbers of N-level systems, the crucial role of the straddling pulse in reducing the population of all intermediate levels is demonstrated.

We analyze the influence of three pulsed laser fields interacting with a four-state atomic system for which there occur two degenerate population-trapping dressed states. We present a simple expression for the geometrical phase acquired by such an atom during a stimulated Raman adiabatic passage (STIRAP) process using a delay between Stokes and pump pulses, during which the two Rabi frequencies adiabatically traverse a closed path in the parameter space. We describe techniques that can produce (geometrical) state-vector phases that are independent of the longitudial velocity with which atoms move across a laser beam, and that are insensitive to radiative decay from the intermediate excited state. The geometrical phase can be changed by changing the relative delay of the pulses. The geometrical phase can be measured by observing the population in atomic states. We show that when the pump and Stokes pulses are properly timed, high population transfer from the initial state to the target state is achieved. In the adiabatic limit the robustness of the population transfer is equivalent to that of STIRAP.

We investigate several configurations for complete population transfer on the basis of the dressed state picture in a three-level system. This picture allows us not only to confirm an atom staying in the only dark state all the time under the well-known stimulated Raman adiabatic passage but also to find the considerably different dynamics from the conventional adiabatic process in cases where the pulses are significantly overlapped or concurrent (optimal detuning method). We expand the concept of the adiabatic process in order to explain all these cases.

When one extends the conventional stimulated Raman adiabatic passage method of population transfer; involving a pump pulse preceded by a Stokes pulse, to situations in which the pump ~or pump and Stokes! interaction involves a two-photon transition, there occur unavoidable dynamic Stark shifts which prevent maintenance of the relevant resonance conditions. Such shifts can prevent the desired population transfer. We show, through numerical modeling and analytic considerations, that the detrimental effects of dynamic shifts can be compensated by a suitable choice of ~static! detunings of the carrier frequencies of the two pulses, so that population transfer can be achieved. We present simple analytic expressions for bounding the range of detunings for which population transfer can occur, and we present numerical results supporting the simple picture of the two-step linewidth. We illustrate these remarks by considering specific examples. @S1050-2947~98!09311-1#

We discuss various theoretical issues that arise when one extends the conventional stimulated Raman adiabatic passage, involving a pump pulse preceded by a Stokes pulse, to situations in which the pump interaction involves a two-photon transition. As in the simpler cases, it is possible to obtain complete population transfer between an initial state and a targeted final state, if certain general conditions on the pulses are met. We point out important considerations, associated with dynamic Stark shifts and multiphoton ionization, which make successful population transfer more difficult in the multiphoton extension. We illustrate these problems and requirements by considering specific examples of excitation in metastable helium.

Stimulated Raman adiabatic passage ~STIRAP @1‐3#, and references therein! is a well established and efficient technique for population transfer between two discrete atomic or molecular states via an intermediate state ui& @Fig. 1~a!#. This process requires three conditions: two-photon resonancebetween the initial ~ground! state ug& and the final ~excited! state ue&, counterintuitive pulse order, in which the Stokes pulse, driving the transition between states ui& and ue&, precedes the pump pulse, driving the transition between states ug& and ui&, though they must overlap partly, and adiabatic time evolution. STIRAP exploits the existence of an eigenstate of the Hamiltonian, which involves the bare states ug& and ue& only. In the adiabatic limit, the population is completely transferred to the final state ug& and no population resides in the intermediate state ui& at any time. It has recently been suggested by Carroll and Hioe @4# that population transfer by a counterintuitive pulse sequence may be realized even if the discrete intermediate state @Fig. 1~a!# is replaced by a continuum @Fig. 1~b!#. An attractive feature of such a scheme is its flexibility and generality. The CarrollHioe analytic model, which involves a quasicontinuum, suggests that complete population transfer is possible, the ionization being suppressed. Later, it was demonstrated by Nakajima et al. @5# that this result derives from the very stringent restrictions of the model, which are unlikely to be met in a realistic physical system. These latter authors considered in particular the role of the nonzero Fano parameter q in deteriorating the transfer efficiency. They have also suggested that other loss mechanisms, such as incoherent ionization channels, dynamic Stark shifts, and continuumcontinuum transitions, may reduce the transfer efficiency by orders of magnitude; however, this has been disputed recently @6‐8#. In the present paper, we study the effect of the incoherent ionization channels, the Stark shifts, and the Fano parameter on the transfer efficiency. We ignore continuum-continuum transitions that are significant for very high laser intensities only. This paper is organized as follows. In Sec. II, we introduce the basic equations and definitions. In Sec. III, we make an analogy between the scheme with a continuum and the standard STIRAP, which provides a better insight into the process. In Sec. IV, we analyze the problem in terms of the adiabatic states and the dark and bright states and derive the adiabatic solution. In Sec. V, we illustrate our conclusions with numerical results for a realistic model. In Sec. VI, we derive an analytic approximation to the final-state population for Gaussian pulse shapes, which describes the effect of the incoherent channels in the case of effective twophoton resonance @7,8#. Finally, in Sec. VII, we present the conclusions. II. DEFINITION OF THE PROBLEM The problem of two bound states coupled by two laser fields via a common continuum has been studied intensively in the context of laser-induced continuum structure ~LICS @9#, and references therein!. The time evolution of the probability amplitudes cg(t) and ce(t) of the two bound states is governed by the equation @9#

We demonstrate that various properties of population transfer by delayed pulses in three-level systems on two-photon resonance can be deduced analytically and for general pulse shapes. We use the fact that the three-level system reduces to effective two-level problems at large intermediate-level detuning \ensuremath{\Delta}, on resonance (\ensuremath{\Delta}=0) and for completely overlapping pulses. Special attention is paid to the effect of the pulse order on the population transfer efficiency. We show that on resonance the transfer efficiency depends substantially on the pulse order, while at large \ensuremath{\Delta} it does not. We also find that under some natural restrictions on the symmetry of the problem, the population of the initial level does not depend on the pulse order at any \ensuremath{\Delta}. Furthermore, we demonstrate that the population transfer in the three-level system can be viewed as a level-crossing problem in an equivalent two-level system not only at large \ensuremath{\Delta} (which is known) but also on resonance, \ensuremath{\Delta}=0. The effective on-resonance two-level problem is interesting by itself as it shows that a level crossing and adiabatic evolution do not necessarily lead to complete population inversion. As examples throughout the paper, we present several analytically solvable models.

In atomic physics, adiabatic evolution is often used to achieve a robust and efficient population transfer. Many adiabatic schemes have also been implemented in optical waveguide structures. Recently there has been increasing interests in the influence of decay and absorption, and their engineering applications. Here it is shown that even a small decay can significantly influence the dynamical behaviour of a system, above and beyond a mere change of the overall norm. In particular, a small decay can lead to a breakdown of adiabatic transfer schemes, even when both the spectrum and the eigenfunctions are only sightly modified. This is demonstrated for the generalization of a STIRAP scheme that has recently been implemented in optical waveguide structures. Here the question how an additional absorption in either the initial or the target waveguide influences the transfer property of the scheme is addressed. It is found that the scheme breaks down for small values of the absorption at a relatively sharp threshold, which can be estimated by simple analytical arguments., 8 pages, 7 figures, revised and extended

We propose a potentially practical scheme to realize arbitrary quantum state transfer between two traveling atoms that go through a high-finesse cavity by using stimulated Raman adiabatic passage in an atom-cavity-laser system under a dissipative environment. By numerically simulating the dynamics of the system, we demonstrate quantitatively that the fidelities of the quantum state transferred between two atoms can be maximized by elaborately adjusting the peak amplitudes of the laser's Rabi frequency and the detuning of the Raman transition. Additionally, the noise effect from the atomic and cavity dissipation can reduce the fidelity. The experimental feasibility is justified using currently available technology.

We investigate the creation of stable homonuclear and heteronuclear $N$-body polymer molecules from ultracold atoms via a generalized stimulated Raman adiabatic passage scheme. The atom-molecule dark-state solutions for the system are obtained and are found to satisfy universal algebraic equations. We discuss the linear instability and the adiabatic fidelity of the dark state. We also explore the effects of the interparticle interactions, the atomic number of the polymer, and external field parameters on the conversion process.

We introduce a high-fidelity technique for coherent control of three-state quantum systems, which combines two popular control tools --- stimulated Raman adiabatic passage (STIRAP) and composite pulses. By using composite sequences of pairs of partly delayed pulses with appropriate phases the nonadiabatic transitions, which prevent STIRAP from reaching unit fidelity, can be canceled to an arbitrary order by destructive interference, and therefore the technique can be made arbitrarily accurate. The composite phases are given by simple analytic formulas, and they are universal for they do not depend on the specific pulse shapes, the pulse delay and the pulse areas., Comment: 5 pages, 5 figures

We derive an adiabatic technique that implements the most general SU($d$) transformation in a quantum system of $d$ degenerate states, featuring a qudit. This technique is based on the factorization of the SU($d$) transformation into $d$ generalized quantum Householder reflections, each of which is implemented by a two-shot stimulated Raman adiabatic passage with appropriate static phases. The energy of the lasers needed to synthesize a single Householder reflection is shown to be remarkably constant as a function of $d$. This technique is directly applicable to a linear trapped ion system with $d+1$ ions. We implement the quantum Fourier transform numerically in a qudit with $d=4$ (defined as a quartit) as an example.

Optical properties of ensembles of three-level quantum emitters coupled to plasmonic systems are investigated employing a self-consistent model. It is shown that stimulated Raman adiabatic passage (STIRAP) technique can be successfully adopted to control optical properties of hybrid materials with collective effects present and playing an important role in light-matter interactions. We consider a core-shell nanowire comprised of a silver core and a shell of coupled quantum emitters and utilize STIRAP scheme to control scattering efficiency of such a system in a frequency and spatial dependent manner. After the STIRAP induced population transfer to the final state takes place, the core-shell nanowire exhibits two sets of Rabi splittings with Fano lineshapes indicating strong interactions between two different atomic transitions driven by plasmon near-fields., Comment: 11 pages, 6 figures, accepted, Physical Review A

We demonstrate two-dimensional robust Raman cooling in a four-level tripod system, in which velocity-selective population transfer is achieved by a STIRAP pulse. In contrast to basic 2D Raman cooling with square envelope pulses [Phys. Rev. A 83, 023407 (2011)], the technique presented here allows for a wide variation in the pulse duration and amplitude once the adiabaticity criterion is satisfied. An efficient population transfer together with attaining of a narrow spread of the resonant-velocity group leads to the narrowing of the velocity-distribution spread down to $0.1v_\mathrm{rec}$, corresponding to an effective temperature equal to $0.01 T_\mathrm{rec}$. This robust method opens new possibilities for cooling of neutral atoms., 8 pages, 3 figures

We investigate the solitary propagation effect of a well-defined chirped femtosecond laser pulse in a resonance-absorbing medium which is modeled by a two-level quantum dot ensemble. Employing full time-dependent and space-dependent Maxwell-Bloch equations, the evolution of the pulse and the population inversion as well as the spectrum are obtained. The results reveal that the special chirped pulse can retain its shape and resist breakup while propagating through the absorbing medium. Besides, the spectrum does not exhibit obvious broadening but the central and near-central frequency components tend to vanish. Moreover, the stable soliton formed by the special chirped-pulse design based on stimulated Raman adiabatic passage does not obey the area theorem.

We report and propose a simple scheme to achieve efficient and fast coherent population transfer (CPT) by utilizing either a nonlinearly chirped Gaussian shaped few-cycle laser pulse or an unchirped sinc-shaped few-cycle laser pulse. The proposed scheme is shown to be fairly robust against the variation of the laser parameters such as temporal pulse width, chirp rates, carrier envelope phases and Rabi frequencies. We find that compared to the so-called stimulated Raman adiabatic passage (STIRAP) technique, our scheme for complete population transfer with few-cycle Gaussian shaped laser pulses requires less pulse area.

A technique for complete population transfer between the two end states $|1\ensuremath{\rangle}$ and $|3\ensuremath{\rangle}$ of a three-state quantum system with a train of $N$ pairs of resonant and coincident pump and Stokes pulses is introduced. A simple analytic formula is derived for the ratios of the pulse amplitudes in each pair for which the maximum transient population ${P}_{2}(t)$ of the middle state $|2\ensuremath{\rangle}$ is minimized, ${P}_{2}^{\mathrm{max}}={\mathrm{sin}}^{2}(\ensuremath{\pi}/4N)$. It is remarkable that, even though the pulses are on exact resonance, ${P}_{2}(t)$ is damped to negligibly small values even for a small number of pulse pairs. The population dynamics resembles generalized $\ensuremath{\pi}$ pulses for small $N$ and stimulated Raman adiabatic passage for large $N$ and therefore this technique can be viewed as a bridge between these well-known techniques.

We demonstrate one-dimensional robust Raman cooling in a three-level $\ensuremath{\Lambda}$-type atom, where the velocity-selective transfer is carried out by a STIRAP pulse. In contrast to the standard Raman method, the excitation profile is insensitive to variations in the pulse duration, whereas its position and width are nevertheless under control. Two different cooling variants are examined and we show that subrecoil temperatures are attainable in both cases.

We consider the optimal control problem of transferring population between states of a quantum system where the coupling proceeds only via intermediate states that are subject to decay. We pose the question whether it is generally possible to carry out this transfer. For a single intermediate decaying state, we recover the Stimulated Raman Adiabatic Passage (STIRAP) process which we identify as the global optimum in the limit of infinite control time. We also present analytic solutions for the case of transfer that has to proceed via two consecutive intermediate decaying states. We show that in this case, for finite power the optimal control does not approach perfect state transfer even in the infinite time limit. We generalize our findings to characterize the topologies of paths that can be achieved by coherent control under the assumption of finite power., 12 pages

We present a fully quantum-mechanical theory of the mutual light-matter effects when two laser pulses interact with three discrete states coupled to a (quasi)continuum. Our formulation uses a single set of equations to describe the time dependence of the discrete and continuum populations, as well as pulse propagation in electromagnetically induced transparency (EIT) and stimulated Raman adiabatic passage (STIRAP) situations, for both weak and strong laser pulses. The theory gives a mechanistic picture of the ``slowing down of light'' and the state of spontaneously emitted photons during this process. Surprising features regarding the time dependence of material and radiative transients as well as limitations on quantum light storage and retrieval are unraveled.

We study the dynamics of chirped adiabatic passage (CHIRAP) with temporally delayed pulses to selectively and fully transfer population in atoms and molecules. We show that the transfer of population via stimulated Raman adiabatic passage (STIRAP) and stimulated two-photon adiabatic absorption with temporally delayed laser pulses is not adversely affected by applying a chirp to the pulses, provided the intensity of the laser is sufficiently large to allow adiabatic passage. We then proceed to consider systems in which a near degeneracy of terminal state levels results in nonselective population of the terminal levels using nonchirped STIRAP or two-photon absorption stimulated passage, because the dynamics within the nearly degenerate pair of levels is not adiabatic. However, the CHIRAP process selectively populates only one of the terminal levels.

We theoretically study an extension of the Dicke model, where the single-particle Hamiltonian has three energy levels in Lambda-configuration, i.e. the excited state is coupled to two non-degenerate ground states via two independent quantized light fields. The corresponding many-body Hamiltonian can be diagonalized in the thermodynamic limit with the help of a generalized Holstein--Primakoff transformation. Analyzing the ground-state energy and the excitation energies, we identify one normal and two superradiant phases, separated by phase transitions of both first and second order. A phase with both superradiant states coexisting is not stable. In addition, in the limit of two degenerate ground states a dark state emerges, which seems to be analogous to the dark state appearing in the well known stimulated Raman adiabatic passage scheme., 9 pages, 6 figures