Adiabatic Population Transfer Research Articles

Full optical preparation of an absolute ground-state ultracold CsYb molecule via laser-assisted self-induced Feshbach resonance

We investigate theoretically the formation of an ultracold CsYb molecule in the absolute ground state by full optical control. The laser-assisted self-induced Feshbach resonance takes place when the trap state in the optical lattice is coupled with a rovibrational state of the ground electronic state. The Feshbach molecule is formed in the resonant rovibrational state via an adiabatic population transfer by ramping the frequency of a chirped pulse. Two schemes are designed to prepare the absolute ground-state molecule starting from the Feshbach molecule: a pump–dump scheme controlled by short pulses and a stimulated-Raman-adiabatic-passage (STIRAP) scheme steered by long pulses. The probabilities of converting the Feshbach molecule to the absolute ground state molecule by using the pump–dump and the STIRAP schemes are 16% and 99%, respectively.

Geometric representation of adiabatic distributed-Bragg-reflectors and broadening the photonic bandgap

Adiabatic following has been an widely-employed technique for achieving near-complete population transfer in a ‘two-level’ quantum mechanical system. The theoretical basis, however, could be generalized to a broad class of systems exhibiting SU(2) symmetry. In the present work, we present an analogy of population transfer dynamics of a two-level atomic system with that of light propagation in a classical ‘one-dimensional’ photonic crystal, commonly known as distributed-Bragg-reflector (DBR). This formalism facilitates in adapting the idea of adiabatic following, more precisely the rapid adiabatic passage (RAP) which is usually encountered in a broad class of quantum-mechanical systems. We present a chirped DBR configuration in which the adiabatic constraints are satisfied by virtue of optimally chirping the DBR. The reflection spectrum of the configuration exhibit broadening of photonic bandgap (PBG) in addition to a varying degree of suppression of sharp reflection peaks in the transmission band. The intermodal coupling between counter-propagating modes as well as their phase-mismatch, for the DBR configuration, exhibits a longitudinal variation which is usually observed in ‘Allen-Eberly’ scheme of adiabatic population transfer in two-level atomic systems.

Photodissociation of [Ar–N2]+ induced by near-IR femtosecond laser fields by ion-trap time-of-flight mass spectrometry

Photodissociation of [Ar-N2]+ induced by a near-IR (800 nm) femtosecond laser pulse is investigated using ion-trap time-of-flight mass spectrometry. The intra-complex charge transfer proceeding in the course of the decomposition of the electronically excited Ar+(2P3/2)⋯N2(X1Σg +), prepared by the photoexcitation of the electronic ground Ar(1S0)⋯N2 +(X2Σg +), is probed by the ion yields of Ar+ and N2 +. The yield ratio γ of N2 + with respect to the sum of the yields of Ar+ and N2 + is determined to be γ = 0.62, which is much larger than γ ∼ 0.2 determined before when the photodissociation is induced by a nano-second laser pulse in the shorter wavelength region between 270 and 650 nm. This enhancement of γ at 800 nm and the dependence of γ on the excitation wavelength are interpreted by numerical simulations, in which the adiabatic population transfer from Ar+(2P3/2)⋯N2(X1Σg +) to Ar(1S0)⋯N2 +(X2Σg +) at the avoided crossings is accompanied by the vibrational excitation in the N2 +(X2Σg +) moiety followed by the intra-complex vibrational energy transfer from the N2 +(X2Σg +) moiety to the intra-complex vibrational mode leading to the dissociation.

Stimulated Raman Adiabatic Passage in Optomechanics

In multimode optomechanical systems, the mechanical modes can be coupled via the radiation pressure of the common optical mode, but the fidelity of the state transfer is limited by the optical cavity decay. Here we demonstrate stimulated Raman adiabatic passage (STIRAP) in optomechanics, where the optical mode is not populated during the coherent state transfer between the mechanical modes avoiding this decay channel. We show a state transfer of a coherent mechanical excitation between vibrational modes of a membrane in a high-finesse optical cavity with a transfer efficiency of 86%. Combined with exceptionally high mechanical quality factors, STIRAP between mechanical modes can enable generation, storage, and manipulation of long-lived mechanical quantum states, which is important for quantum information science and for the investigation of macroscopic quantum superpositions.

Stabilization of adiabatic population transfer by strong coupling to a phonon bath

We investigate the influence of the environment on the rapid adiabatic passage scheme for optimal population transfer in a two-level system. To cope with strong coupling to an external phonon bath with super-Ohmic spectral density, we are solving the time-dependent Schr\odinger equation of the extended system, including a finite number of bath modes using the multi-Davydov D2 ansatz. This allows for the treatment of the non-Markovian reduced dynamics of the two-level subsystem. Surprisingly, it is found that strong system-bath coupling stabilizes the transition probability from the lower to the upper level as a function of the area under the laser pulse. This dissipative engineering effect could only be uncovered by a non-Markovian treatment. For strong coupling, the transition probability then becomes a monotonically increasing function of the pulse area at zero temperature of the heat bath. Finite temperatures break the monotonicity in the range of pulse areas that we studied, but not the stability of the observed effect.

High-fidelity multistate stimulated Raman adiabatic passage assisted by shortcut fields

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 $J_g=2$ and $J_e=1$ or $J_e=2$ 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.

Speeding up the Generation of Entangled State between a Superconducting Qubit and Cavity Photons via Counterdiabatic Driving

AbstractOptimal generation of entangled states is of critical significance for robust quantum information processing. An effective scheme is presented for speeding up the generation of an entangled state between a superconducting qubit and microwave photons via counterdiabatic driving. At a magic bias point, the first three levels of a charge‐phase quantum circuit constitute an effective qutrit. An entangled state based on adiabatic population transfer is first achieved. By the technique of shortcuts to adiabaticity, a counterdiabatic driving is applied to the qutrit, which then accelerates the entanglement generation significantly. Moreover, with the accessible decoherence rates, the rapid operations in a shortcut way are highly robust when compared with adiabatic manipulations. The scheme could offer a promising approach toward optimal preparation of entangled states with superconducting artificial atoms in circuit quantum electrodynamics, experimentally.

Adiabatic population transfer of dressed spin states with quantum optimal control

We report theoretical studies of adiabatic population transfer using dressed spin states. Quantum optimal control using the algorithm of Chopped Random Basis (CRAB) has been implemented in a negatively charged diamond nitrogen vacancy center that is coupled to a strong and resonant microwave field. We show that the dressed spin states are highly effective in suppressing effects of spin dephasing on adiabatic population transfer. The numerical simulation also demonstrates that CRAB-based quantum optimal control can enable an efficient and robust adiabatic population transfer.

Superadiabatic population transfer in a three-level superconducting circuit

Adiabatic manipulation of the quantum state is an essential tool in modern quantum information processing. Here, we demonstrate the speedup of the adiabatic population transfer in a three-level superconducting transmon circuit by suppressing the spurious nonadiabatic excitations with an additional two-photon microwave pulse. We apply this superadiabatic method to the stimulated Raman adiabatic passage, realizing fast and robust population transfer from the ground state to the second excited state of the quantum circuit.

Adiabatic Evolution: The Influence of Non‐Markovian Characters on Quantum Adiabatic Evolution (Ann. Phys. 1/2019)

In article number 1800234, Ye-Xiong Zeng, Chong Li, and coworkers investigate the influence of the memory effect of the environments on adiabatic evolution and show that the memory can protect the adiabatic process and decrease the dependence of the classical lasers on adiabatic population transfer. The cover image illustrates an atom ensemble controlled by two classical optical fields in two environments. The yellow and purple straight lines represent two classical optical fields. Furthermore, two multicolor coils are considered as two environments which surround an atom ensemble.

The Influence of Non‐Markovian Characters on Quantum Adiabatic Evolution

AbstractThe influence of non‐Markovian characters on the adiabatic evolution is investigated. The adiabatic Raman process is simulated in a three‐level system coupled to two independent environments. The results show that the memory effect of environments can restrain the decoherence effect of the system. Even if the system has strong decay rates in the non‐Markovian environments, the adiabatic population transfer can be still completed efficiently. Moreover, the memory effect can reduce the dependence of the adiabatic evolution on the Rabi frequency. Specifically, the two independent non‐Markovian baths can suppress the decoherence more effectively than a single non‐Markovian bath.

Proposal for the formation of ultracold deeply bound RbSr dipolar molecules by all-optical methods

Ultracold paramagnetic and polar diatomic molecules are among the promising systems for quantum simulation of lattice-spin models. Unfortunately, their experimental observation is still challenging. Based on our recent \textit{ab-initio} calculations, we analyze the feasibility of all-optical schemes for the formation of ultracold $^{87}$Rb$^{84}$Sr bosonic molecules. First, we have studied the formation by photoassociation followed by spontaneous emission. The photoassociation rates to levels belonging to electronic states converging to the $^{87}$Rb$(5s\,^2S)$+$^{84}$Sr($5s5p\,^3P_{0,1,2}$) asymptotes are particularly small close to the asymptote. The creation of molecules would be more interesting by using deeply levels that preferentially relaxes to the $v''=0$ level of the ground state. On the other hands, the photoassociation rates to levels belonging to electronic states converging to the Rb$(5p\,^2P_{1/2,3/2})$+Sr($5s^2\,^1S$) asymptotes have high value close to the asymptote. The relaxation from the levels close to the asymptotes creates weakly-bound molecules in mosty only one vibrational level. Second, stimulated Raman adiabatic passage (STIRAP) achieved in a tight optical trap efficiently creates weakly-bound ground-state molecules in a well-defined level, thus providing an alternative to magnetic Feshbach resonances to implement several schemes for an adiabatic population transfer toward the lowest ground-state level of RbSr. Finally, we have studied STIRAP process for transferring the weakly-bound molecules into the $v''=0$ level of the RbSr ground state.

Adiabatic population transfer between electronic states of LiH molecule in two picosecond laser pulses

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.

Accelerated and robust population transfer in a transmon qutrit via $$\Delta $$ Δ -type driving

We propose an efficient protocol to implement accelerated and robust population transfer in a transmon qutrit via $$\Delta $$ -type driving. By means of stimulated Raman adiabatic passage, we first show an adiabatic population transfer in the qutrit under a two-photon resonance. By taking advantage of the weak level anharmonicity of the qutrit, only two drivings are needed to be applied to the qutrit, forming a $$\Delta $$ -type interaction. With the Gaussian-shaped Rabi couplings, target population transfer can be accelerated substantially when compared to the adiabatic process. Moreover, we analyze the negligible leakages and distinct fidelity enhancement with the accessible parameters. The present scheme could offer a promising application in experimentally performing population transfer with the transmon-regime quantum circuits.

Experimental demonstration of efficient and robust second harmonic generation using the adiabatic temperature gradient method

We propose a way of achieving efficient and robust second-harmonic generation. The technique proposed is similar to the adiabatic population transfer in a two-state quantum system with crossing energies. If the phase mismatching changes slowly, e.g., due to a temperature gradient along the crystal, and makes the phase match for second-harmonic generation to occur, then the energy would be converted adiabatically to the second harmonic. As an adiabatic technique, the second-harmonic generation scheme presented is stable to variations in the crystal parameters, as well as in the input light, crystal length, input intensity, wavelength and angle of incidence.

Speeding up adiabatic population transfer in a Josephson qutrit via counter-diabatic driving

We propose a theoretical scheme to speed up adiabatic population transfer in a Josephson artificial qutrit by transitionless quantum driving. At a magic working point, an effective three-level subsystem can be chosen to constitute our qutrit. With Stokes and pump driving, adiabatic population transfer can be achieved in the qutrit by means of stimulated Raman adiabatic passage. Assisted by a counter-diabatic driving, the adiabatic population transfer can be sped up drastically with accessible parameters. Moreover, the accelerated operation is flexibly reversible and highly robust against decoherence effects. Thanks to these distinctive advantages, the present protocol could offer a promising avenue for optimal coherent operations in Josephson quantum circuits.

Dressed-state scheme for a fast CNOT gate

A dressed-state scheme, which aims to speed up the adiabatic population transfer, is applied for constructing a fast controlled-not (CNOT) gate in a cavity quantum electrodynamics system. Numerical simulations indicate that the average fidelity for constructing the CNOT gate is quite high and the gate operation time is relatively short. Moreover, the effects of the atomic spontaneous emissions and the photon leakages from the system on the average fidelity are discussed and the results show the scheme is robust against decoherence.

Speeding up adiabatic passage by adding Lyapunov control

We propose a scheme to speed up adiabatic passage by using Lyapunov control theory. This is a good choice to solve the problem that may emerge in Berry's transitionless quantum driving [M. V. Berry, J. Phys. A 42, 365303 (2009)]. That is, the extra couplings in the counterdiabatic driving Hamiltonian can be avoided by choosing the available control Hamiltonian in an actual physical system. As examples, we shorten the evolution time of adiabatic population transfer in a three-level system and the entanglement generation in a cavity quantum electrodynamics system. Moreover, the occupation of an intermediate state can be sharply suppressed by properly choosing the control Hamiltonian in the three-level system. The scheme can also be generalized to a complex system where the exact expressions of adiabatic eigenstates are difficult to obtain.

Shortcut to adiabatic population transfer in quantum three-level systems: Effective two-level problems and feasible counterdiabatic driving

Shortcut to adiabaticity in various quantum systems has attracted much attention with the wide applications in quantum information processing and quantum control. In this paper, we concentrate on stimulated Raman shortcut-to-adiabatic passage in quantum three-level systems. To implement counter-diabatic driving but without additional coupling, we first reduce the quantum three-level systems to effective two-level problems at large intermediate-level detuning, or on resonance, apply counter-diabatic driving along with the unitary transformation, and eventually modify the pump and Stokes pulses for achieving fast and high-fidelity population transfer. The required laser intensity and stability against parameter variation are further discussed, to demonstrate the advantage of shortcuts to adiabaticity.

Robust population transfer in atomic beams induced by Doppler shifts

The influence of photon-momentum recoil on adiabatic population transfer in an atomic three-level lambda system is studied. It is shown that the Doppler frequency shifts, due to atomic motion can play an important role in adiabatic population transfer processes of atomic internal states by a pair of laser fields. For the limiting case of slow atoms ( Doppler shift much smaller than the photon recoil energy) the atoms occupy the same target state regardless of the order of switching of laser fields, while for the case of fast atoms interacting with the intuitive sequence of pulses, the target state is the intermediate atomic state. It is shown that these processes are robust with respect to parameter fluctuations, such as the laser pulse area and the relative spatial offset (delay) of the laser beams. The obtained results can be used for the control of temporal evolution of atomic populations in atomic beams by externally adjustable Doppler shifts.