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Significant progress has been achieved in leveraging atomic systems for the effective operation of quantum networks, which are essential for secure and long-distance quantum communication protocols. The key elements of such networks are quantum nodes that can store or generate both single and entangled photon pairs. The primary mechanisms leading to the production of single and entangled photon pairs revolve around established techniques such as parametric down-conversion, four-wave mixing, and stimulated Raman scattering. In contrast to solid-state platforms, atomic platforms offer a more controlled approach to the generation of single and entangled photon pairs, owing to the progress made in atom manipulation techniques such as trapping, cooling, and precise excitation schemes facilitated by the use of lasers. This review article delves into the techniques implemented for generating single and entangled photon pairs in atomic platforms, starting with a detailed discussion of the fundamental concepts associated with single and entangled photons and their characterization techniques. The aim is to evaluate the strengths and limitations of these methodologies and offer insights into potential applications. Additionally, the article will review the extent to which these atomic-based systems have been integrated into operational quantum communication networks. [ABSTRACT FROM AUTHOR]

Significant progress has been achieved in leveraging atomic systems for the effective operation of quantum networks, which are essential for secure and long-distance quantum communication protocols. The key elements of such networks are quantum nodes that can store or generate both single and entangled photon pairs. The primary mechanisms leading to the production of single and entangled photon pairs revolve around established techniques such as parametric down-conversion, four-wave mixing, and stimulated Raman scattering. In contrast to solid-state platforms, atomic platforms offer a more controlled approach to the generation of single and entangled photon pairs, owing to the progress made in atom manipulation techniques such as trapping, cooling, and precise excitation schemes facilitated by the use of lasers. This review article delves into the techniques implemented for generating single and entangled photon pairs in atomic platforms, starting with a detailed discussion of the fundamental concepts associated with single and entangled photons and their characterization techniques. The aim is to evaluate the strengths and limitations of these methodologies and offer insights into potential applications. Additionally, the article will review the extent to which these atomic-based systems have been integrated into operational quantum communication networks.

In this paper, we carry out the non-Hermitian stimulated Raman shortcut-to-adiabatic passage (NH-STIRSAP) to create ultracold deeply-bound molecules. The open three-level molecular system is supposed to have irreversible decays out of all levels. Under the assumption of large single-photon detuning and/or strong loss rate of the excited level, the NH three-level system can be theoretically reduced to an effective two-level system. By continuously using the counter-diabatic driving of the shortcut-to-adiabaticity, an auxiliary field is produced to couple the Feshbach level with the ground level. In the numerical calculations, we firstly consider the case of decaying only from the excited level, which is the main loss of the system. Under the NH-STIRSAP, the calculations reveal that complete population transfer from the Feshbach to the ground level can occur even if the adiabatic condition is not fulfilled. Therefore, the creation efficiency of ultracold deeply-bound molecules is greatly improved. The results hold equally for counter-intuitive and intuitive time sequence of the Stokes and pump pulse. If the decays from the Feshbach and ground level are also included, the NH-STIRSAP can still restore most of that efficiency, which performs much better than typical stimulated Raman adiabatic passage. Finally, we point out that the robustness and fast transfer speed of the NH-STIRSAP facilitate the creation and detection of ultracold deeply-bound molecules.

Multi-photon bundle states are crucial for a broad range of applications such as quantum metrology, quantum lithography, quantum communication, and quantum biology. Here we propose a scheme that generates multi-photon bundles via virtual excitations in a quantum Rabi model. Our approach utilizes a Ξ-type three-level atom, where the upper two levels are coupled to a cavity field to form a quantum Rabi model with ultrastrong coupling, and the transition between the lower two levels is driven by two sequences of Gaussian pulses. We show that the driving pulses induce deterministic emission of multiple photons from the eigenstates of the quantum Rabi model via the stimulated Raman adiabatic passage technique, and hence can create bundles of multiple photons on-demand in the cavity output field. We calculate the generalized second-order correlation functions of the output photons, which reveal that the emitted photons form antibunched multi-photon bundles. [ABSTRACT FROM AUTHOR]

We use optimal control theory to obtain shortcuts to adiabaticity which maximize population transfer in a three-level stimulated Raman adiabatic passage system, for a given finite duration of the process and a specified dissipation rate at the intermediate state. We fix the sum of the intensities of the pump and Stokes pulses and use the mixing angle of the fields as the sole control variable. We determine the optimal variation of this angle and reveal the role of the singular arc in the optimal trajectory, in order to minimize the effect of dissipation. This article is part of the theme issue 'Shortcuts to adiabaticity: theoretical, experimental and interdisciplinary perspectives'. [ABSTRACT FROM AUTHOR]

We study experimentally and theoretically the transfer of population between the ground state and the second excited state in a transmon circuit by the use of superadiabatic stimulated Raman adiabatic passage (saSTIRAP). We show that the transfer is remarkably resilient against variations in the amplitudes of the pulses (scaling errors), thus demostrating that the superadiabatic process inherits certain robustness features from the adiabatic one. In particular, we provide new evidence of a plateau that appears at high values of the counterdiabatic pulse strength, which goes beyond the usual framework of saSTIRAP. This article is part of the theme issue 'Shortcuts to adiabaticity: theoretical, experimental and interdisciplinary perspectives'. [ABSTRACT FROM AUTHOR]

Stimulated Raman adiabatic passage is a well-known technique for quantum population transfer due to its robustness again various sources of noises. Here we consider quantum population transfer from one spin to another via an intermediate spin which is under dephasing noise. We obtain an analytic expression for the transfer efficiency under a specific driving protocol, showing that dephasing could reduce the transfer efficiency, but the effect of dephasing could also be suppressed with a stronger laser coupling or a longer laser duration. We also consider another commonly used driving protocol, which shows that this analytic picture is still qualitatively correct. [ABSTRACT FROM AUTHOR]

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 pumpâ€"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 pumpâ€"dump and the STIRAP schemes are 16% and 99%, respectively. [ABSTRACT FROM AUTHOR]

Shortcuts to adiabaticity (STA) are the fast routes to the final results of slow, adiabatic changes of the controlling parameters of a system. In this work, we investigate a theoretical model in which two Λ-type atoms embedded in a single mode cavity, and a shortcut was proposed to speed up the adiabatic process. In the spirit of non-Hermitian (NH) shortcut approach, by adding several imaginary terms in the original Hamilton, a modified Hamiltonian is provided and we find it’s Hermitian. Numerical simulation demonstrates that compared with the previous works using the stimulated Raman adiabatic passage, the evolution of the quantum state transfer can be significantly sped up with our present scheme. Also, the efficiency of population transfer with respect to changes in various parameters of laser fields has been numerically studied. Furthermore, the physical realization of the modified Hamiltonian is discussed in the conclusion. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate spatial confinement of atomic excitation by adiabatic passage processes in a rare-earth ion-doped Pr3+:Y2SiO5 crystal. In particular, we apply stimulated Raman adiabatic passage (STIRAP) and compare its performance with electromagnetically induced transparency (EIT). Using a Stokes beam with Gaussian and a pump beam with donut shape we localize the atomic population in the zero-intensity center of the latter. Our data confirm that adiabatic passage confines excitation far below the diameter of the driving laser beams, and that this localization rapidly increases with laser intensity. We find, that STIRAP significantly outperforms EIT, as it was predicted by previous theory proposals, i.e., STIRAP reaches small excitation volumes with much lower laser intensity. The experimental data agree very well with numerical simulations. The findings serve as a step towards new applications for STIRAP, to prepare excitation regions or population patterns in space with large resolution. [ABSTRACT FROM AUTHOR]

Shortcuts to adiabaticity (STA) are channels that can fast prepare a desired quantum state with high fidelity which obtains more and more research in the atomic domain. Based on stimulated Raman shortcut-to-adiabatic passage (STIRSAP), we propose a frequency conversion technique which works through a non-adiabatic route and produces the same energy distribution as in adiabatic evolution. Numerical simulation results show that the conversion is efficient and robust. Our results reveal a novel scenario for frequency conversion and relax the strict limitations on system parameters in adiabatic frequency conversion.

Engineering multiphoton resources is of importance in quantum metrology, quantum lithography, and biological sensing. Here we propose a concept of dynamical emission of N strongly-correlated photons. This is realized in a circuit quantum electrodynamical system driven by two Gaussian-pulse sequences. The underlying physical mechanism relies on the stimulated Raman adiabatic passage that allows efficient and selective preparation of target multiphoton states. Assisted by the photon decay, a highly pure N -photon bundle emission takes place in this system. In particular, the dynamical N -photon bundle emission can be tuned by controlling the time interval between consecutive pulses so that the device behaves as an N -photon gun, which can be triggered on demand. Our work opens up a route to achieve multiphoton source devices, which have wide potential applications in quantum information processing and quantum metrology.

Generally, stimulated Raman adiabatic passage technology has been used to generate the Greenberger–Horne–Zeilinger state. Due to decoherence caused by long operation time, it is almost impossible to implement experimentally. To reduce the operation time, we propose a scheme to construct the shortcut to adiabatic passage based on deep reinforcement learning (DRL). Moreover, in order to facilitate the implementation, we have performed Gaussian fitting on the pulse sequence. Numerical analysis shows that our scheme has better performance than the Gradient Ascent Pulse Engineering and the Genetic Algorithm, and is robust to the leakage of the optical cavity as well as the spontaneous emission of atoms. Besides, we apply the DRL algorithm to another model and give the pulse sequence for the preparation of the three-atom singlet state with high fidelity and robustness. [ABSTRACT FROM AUTHOR]

We study the stimulated Raman adiabatic passage for a pair of interacting cold atoms driven into the Y-type configuration with two adjacent Rydberg states. The results show that the self and cross dipole-dipole interactions will cause the blockade effect of states |rr〉 (|ll〉) and |rl〉 (|lr〉), respectively. However, it is viable to overcome the blockade effect and achieve efficient population transfer to different Rydberg states |r〉 and |l〉 by choosing appropriate single-photon and two-photon detunings to fully compensate dipole-induced shifts. Moreover, a maximal entangled state composed of two Rydberg states will generate with the proper detunings of coherent fields. [ABSTRACT FROM AUTHOR]

The methods of quickly achieving the adiabatic effect through a non-adiabatic process has recently drawn widely attention both in quantum and classical regime. In this work,we study the classical adiabatic shortcut for two- and three-Level atoms by transforming the quantum version into classical one via quantum-classical corresponding theory. The results shows that, the additional couplings between the oscillators can be used to speed up the adiabatic evolution of coupled oscillators. Furthermore, we find that the quantum-classical correspondence theory still holds for the couter-adiabatic driving Hamiltonian for the TQD. This means that, we can obtain the counter-adiabatic driving Hamiltonian for a classical system by averaging over its quantum correspondence in a quantum system. This provides a feasible way to study the classical adiabatic shortcut and the simulation for the quantum adiabatic shortcut in a classical system. [ABSTRACT FROM AUTHOR]

We show how a quantum state in a microwave cavity mode can be transferred to and stored in a phononic mode via an intermediate magnon mode in a magnomechanical system. For this we consider a ferrimagnetic yttrium iron garnet (YIG) sphere inserted in a microwave cavity, where the microwave and magnon modes are coupled via a magnetic-dipole interaction and the magnon and phonon modes in the YIG sphere are coupled via magnetostrictive forces. By modulating the cavity and magnon detunings and the driving of the magnon mode in time, a stimulated Raman adiabatic passage-like coherent transfer becomes possible between the cavity mode and the phonon mode. The phononic mode can be used to store the photonic quantum state for long periods as it possesses lower damping than the photonic and magnon modes. Thus our proposed scheme offers a possibility of using magnomechanical systems as quantum memory for photonic quantum information.

The best upper limit for the electron electric dipole moment was recently set by the ACME collaboration. This experiment measures an electron spin-precession in a cold beam of ThO molecules in their metastable $H\,{(}^{3}{{\rm{\Delta }}}_{1})$ state. Improvement in the statistical and systematic uncertainties is possible with more efficient use of molecules from the source and better magnetometry in the experiment, respectively. Here, we report measurements of several relevant properties of the long-lived $Q\,{(}^{3}{{\rm{\Delta }}}_{2})$ state of ThO, and show that this state is a very useful resource for both these purposes. The Q state lifetime is long enough that its decay during the time of flight in the ACME beam experiment is negligible. The large electric dipole moment measured for the Q state, giving rise to a large linear Stark shift, is ideal for an electrostatic lens that increases the fraction of molecules detected downstream. The measured magnetic moment of the Q state is also large enough to be used as a sensitive co-magnetometer in ACME. Finally, we show that the Q state has a large transition dipole moment to the $C\,{(}^{1}{{\rm{\Pi }}}_{1})$ state, which allows for efficient population transfer between the ground state $X\,{(}^{1}{{\rm{\Sigma }}}^{+})$ and the Q state via $X-C-Q$ Stimulated Raman Adiabatic Passage (STIRAP). We demonstrate 90 % STIRAP transfer efficiency. In the course of these measurements, we also determine the magnetic moment of C state, the $X\to C$ transition dipole moment, and branching ratios of decays from the C state.

We investigate the coherence generation in dense two-level systems under detuning-induced stimulated Raman adiabatic passage (D-STIRAP). In the dense two-level system, the near dipole-dipole (NDD) interaction should be taken into consideration. With the increase in the strength of the NDD interaction, it is found that a switchlike transition of the generated coherence from maximum value to zero appears. Meanwhile, the adiabatic condition of the D-STIRAP is destroyed in the presence of the NDD interaction. In order to avoid the sudden decrease in the generated coherence and maintain the maximum value, we can use stronger detuning pulse or pump pulse, between which increasing the intensity of the detuning pulse is of more efficiency. Except for taking advantage of such maximum coherence in the high density case into areas like enhancing the four-wave mixing process, we also point out that the phenomenon of the coherence transition can be applied as an optical switch. [ABSTRACT FROM AUTHOR]

In this paper, we use stimulated Raman adiabatic passage technique to implement single-qutrit quantum gates in tripod systems. It is shown by using the Morris-Shore (MS) transformation, the six-state problem with 5 pulsed fields can be reduced to a basis that decouples two states from the others. This imposes three pulses not connected to the initial condition with have the same shape. Using this method, the six-state penta-pod system is reduced to a tripod system. We can design single-qutrit quantum gates by ignoring the fragile dynamical phase, and by suitable design of Rabi frequencies of the effective Hamiltonian

In this paper, we carry out the non-Hermitian stimulated Raman shortcut-to-adiabatic passage (NH-STIRSAP) to create ultracold deeply-bound molecules. The open three-level molecular system is supposed to have irreversible decays out of all levels. Under the assumption of large single-photon detuning and/or strong loss rate of the excited level, the NH three-level system can be theoretically reduced to an effective two-level system. By continuously using the counter-diabatic driving of the shortcut-to-adiabaticity, an auxiliary field is produced to couple the Feshbach level with the ground level. In the numerical calculations, we firstly consider the case of decaying only from the excited level, which is the main loss of the system. Under the NH-STIRSAP, the calculations reveal that complete population transfer from the Feshbach to the ground level can occur even if the adiabatic condition is not fulfilled. Therefore, the creation efficiency of ultracold deeply-bound molecules is greatly improved. The results hold equally for counter-intuitive and intuitive time sequence of the Stokes and pump pulse. If the decays from the Feshbach and ground level are also included, the NH-STIRSAP can still restore most of that efficiency, which performs much better than typical stimulated Raman adiabatic passage. Finally, we point out that the robustness and fast transfer speed of the NH-STIRSAP facilitate the creation and detection of ultracold deeply-bound molecules. • The STIRSAP scheme is extended from closed system to open NH system. • The NH-STIRSAP is employed to create ultracold deeply-bound molecules. • Adiabatic elimination conditions of large single-photon detuning and/or strong loss rate of the excited state are used to help us designing the auxiliary field coupling the Feshbach and the ground state. • Compared with the common stimulated Raman adiabatic passage (STIRAP), high creation efficiency of ultracold deeply-bound molecules can still be obtained under the NH-STIRSAP even if the adiabatic condition is not fulfilled. • The transfer speed from weakly-bound to deeply-bound molecules is much faster under the NH-STIRSAP. • The creation and detection of ultracold deeply-bound molecules occurs regardless the pulse sequence of the pump and Stokes pulse, which allows minimizing the off-resonant scattering. [ABSTRACT FROM AUTHOR]

We propose a scheme for creation and transfer of coherence among ground state and indirect exciton states of triple quantum dots via the technique of stimulated Raman adiabatic passage. Compared with the traditional stimulated Raman adiabatic passage, the Stokes laser pulse is replaced by the tunneling pulse, which can be controlled by the externally applied voltages. By varying the amplitudes and sequences of the pump and tunneling pulses, a complete coherence transfer or an equal coherence distribution among multiple states can be obtained. The investigations can provide further insight for the experimental development of controllable coherence transfer in semiconductor structure and may have potential applications in quantum information processing. [ABSTRACT FROM AUTHOR]

We propose a scheme to synthesize atom-photon hybrid controlled-not (CNOT) gate by combining atomic single-qubit operations via stimulated Raman adiabatic passage and photonic Faraday rotation in cavity QED system. Benefiting from its hybrid characteristic, we utilize atom-photon CNOT gate to construct quantum CNOT gate for remote atoms and photons, respectively. As our scheme works in the bad cavity regime and only involves virtual excitation of atoms, it may be robust against both cavity decay and atomic spontaneous emission, thus can be realized with less demanding technology than that previously mentioned. [ABSTRACT FROM AUTHOR]