The interplay between quantum-mechanical and classical evolutions in a chirped driven Rydberg atom is discussed. It is shown that the system allows two continuing resonant excitation mechanisms, i.e., a successive two-level transitions (ladder climbing) and a continuing classical-like nonlinear phase locking (autoresonance). The persistent $1:1$ and $2:1$ resonances between the driving and the Keplerian frequencies are studied in detail and characterized in terms of two dimensionless parameters $P_{1,2}$ representing the driving strength and the nonlinearity in the problem, respectively. The quantum-mechanical rotating wave and the classical single resonance approximations are used to describe the regimes of efficient classical or quantum-mechanical excitation in this two-parameter space.
Entangled states are crucial for modern quantum enabled technology which makes their creation key for future developments. In this paper, a robust quantum control methodology is presented to create entangled states of two typical classes, the W and the Greenberger-Horne-Zeilinger (GHZ). It was developed from the analysis of a chain of alkali atoms $^{87}Rb $ interaction with laser pulses, which lead to the two-photon transitions from the ground to the Rydberg states with a predetermined magnetic quantum number. The methodology is based on the mechanism of two-photon adiabatic passage using ove…
Collective Chirped STIRAP in a Pair of Three-Level Atoms: Dressed-Manifold Dynamics and Compensation of the Rydberg-Rydberg Interaction-Induced Detuning
We analyze excitation of two ground state atoms to a double Rydberg state by a two-photon chirped optical pulse in the regime of adiabatic rapid passage. For intermediate Rydberg-Rydberg interaction strengths, relevant for atoms separated by $\sim$ten $μ$m, adiabatic excitation can be achieved at experimentally feasible Rabi frequencies and chirp rates of the pulses, resulting in high transfer efficiencies. We also study the adiabatic transfer between ground and Rydberg states as a means to realize a controlled phase gate between atomic qubits.
We considered the two-photon adiabatic rapid passage excitation of a single atom from the ground to a Rydberg state. Three schemes were analyzed: both pump and Stokes fields chirped and pulsed, only the pump field is chirped, and only the pump field is pulsed and chirped while the Stokes field is continuous wave (CW). In all three cases high transfer efficiencies $>99\%$ were achieved for the experimentally realizable Rabi frequencies and the pulse durations of the fields.
We develop a scheme for deterministic generation of an entangled state between two atoms on different Rydberg states via a chirped adiabatic passage, which directly connects the initial ground and target entangled states and also does not request the normally needed blockade effect. The occupancy of intermediate states suffers from a strong reduction via two pulses with proper time-dependent detunings and the electromagnetically induced transparency condition. By solving the analytical expressions of eigenvalues and eigenstates of a two-atom system, we investigate the optimal parameters for gu…
A chirped parametrically driven discrete nonlinear Schrodinger equation is discussed. It is shown that the system allows two resonant excitation mechanisms, i.e., successive two-level transitions (ladder climbing) or a continuous classical-like nonlinear phase-locking (autoresonance). Two-level arguments are used to study the ladder-climbing process, and semiclassical theory describes the autoresonance effect. The regimes of efficient excitation in the problem are identified and characterized in terms of three dimensionless parameters describing the driving strength, the dispersion nonlinearit…
Open Quantum Systems Driven by Chirped Pulses: Quantized versus Semiclassical Fields and the Validity of the Rotating-Wave Approximation
Nanyang Technological University（南洋理工大学）；Technische Universität Dresden（德累斯顿工业大学）；Zhejiang University of Science and Technology（浙江科技学院）；Hangzhou Dianzi University（杭州电子科技大学）
We propose an efficient free-space scheme to create single photons in a well-defined spatiotemporal mode. To that end, we first prepare a single source atom in an excited Rydberg state. The source atom interacts with a large ensemble of ground-state atoms via a laser-mediated dipole-dipole exchange interaction. Using an adiabatic passage with a chirped laser pulse, we produce a spatially extended spin wave of a single Rydberg excitation in the ensemble, accompanied by the transition of the source atom to another Rydberg state. The collective atomic excitation can then be converted to a propaga…
We propose schemes of controlled-Z and controlled-NOT gates with ultracold neutral atoms based on deterministic phase accumulation during double adiabatic passage of the Stark-tuned Förster resonance of Rydberg states. The effect of deterministic phase accumulation during double adiabatic passage in a two-level quantum system has been analyzed in detail. Adiabatic rapid passage using nonlinearly chirped pulses with rectangle intensity profile has been discussed. Nonlinear time dependence of the energy detuning from the Förster resonance is used to achieve a high fidelity of population transfer…
We propose to use adiabatic rapid passage with a chirped laser pulse in the strong dipole blockade regime to deterministically excite only one Rydberg atom from randomly loaded optical dipole traps or optical lattices. The chirped laser excitation is shown to be insensitive to the random number \textit{N} of the atoms in the traps. Our method overcomes the problem of the $\sqrt {N} $ dependence of the collective Rabi frequency, which was the main obstacle for deterministic single-atom excitation in the ensembles with unknown \textit{N}, and can be applied for single-atom loading of dipole trap…
We present effects of an external driving on the tunneling dynamics of interacting bosons confined in a double well potential. At large values of a periodic driving potential, the dynamics become chaotic, with a distinct difference between tuning of the amplitude or the phase of the driving term with regard to the route leading to chaos. For example, we find that a controlled increase in the amplitude of the driving term with a fixed phase leads to quasiperiodic route to chaos. While tuning of the frequency with a fixed (large) amplitude leads to a crisis induced intermittency route to a chaot…
Recent experiments have shown that (quasi-)crystalline phases of Rydberg-dressed quantum many-body systems in optical lattices (OL) are within reach. Rydberg systems naturally possess strong long-range interactions due to the large polarizability of Rydberg atoms. Thus a wide range of quantum phases have been predicted, such as a devil's staircase of lattice incommensurate density wave phases as well as more exotic lattice supersolid order for bosonic systems, as considered in our work. Guided by results in the "frozen" gas limit, we study the ground state phase diagram at finite hopping ampli…
Decoupling of the STIRAP and Microwave-Dressing paths in Trapped Rydberg Ion Gates
Center for Quantum Technologies, Department of Physics, Sofia University（索非亚大学量子技术中心物理系）；Georgi Nadjakov Institute of Solid State Physics, Bulgarian Academy of Sciences（保加利亚科学院格奥尔基·纳德贾科夫固体物理研究所）；Department of Physics, Stockholm University（斯德哥尔摩大学物理系）
We study the impact of dephasing on the excitation dynamics of a cloud of ultracold two-level Rydberg atoms for both resonant and off-resonant laser excitation, using the wave function Monte Carlo (MCWF) technique. We find that while for resonant laser driving, dephasing mainly leads to an increase of the Rydberg population and a decrease of the Mandel Q parameter, at off-resonant driving strong dephasing toggles between direct excitation of pairs of atoms and subsequent excitation of single atoms, respectively. These two excitation mechanisms can be directly quantified via the pair correlatio…
In an atomic ensemble, quantum information is typically carried as single collective excitations. It is very advantageous if the creation of single excitations is efficient and robust. Rydberg blockade enables deterministic creation of single excitations via collective Rabi oscillation by precisely controlling the pulse area, being sensitive to many experimental parameters. In this paper, we implement the adiabatic rapid passage technique to the Rydberg excitation process in a mesoscopic atomic ensemble. We make use of a two-photon excitation scheme with an intermediate state off-resonant and …
Classical and quantum-mechanical phase locking transition in a nonlinear oscillator driven by a chirped frequency perturbation is discussed. Different limits are analyzed in terms of the dimensionless parameters $% P_{1}=ε/\sqrt{2m\hbar ω_{0}α}$ and $P_{2}=(3\hbar β)/(4m\sqrtα)$ ($ε,$ $α,$ $β$ and $ω_{0}$ being the driving amplitude, the frequency chirp rate, the nonlinearity parameter and the linear frequency of the oscillator). It is shown that for $P_{2}\ll P_{1}+1$, the passage through the linear resonance for $P_{1}$ above a threshold yields classical autoresonance (AR) in the system, eve…
The collective effect of large amounts of atoms exhibit an enhanced interaction between light and atoms. This holds great interest in quantum optics, and quantum information. When a collective excited state of a group of atoms during Rabi oscillation is varying, the oscillation exhibits rich dynamics. Here, we experimentally observe a size-reduction effect of the Rydberg collective state during Rabi oscillation in cold atomic dilute gases. The Rydberg collective state was first created by the Rydberg quantum memory, and we observed a decreased oscillation frequency effect by measuring the time…
We examine the adiabatic preparation of spatially-ordered Rydberg excitations of atoms in finite one-dimensional lattices by frequency-chirped laser pulses, as realized in a number of recent experiments simulating quantum Ising model. Our aims are to unravel the microscopic mechanism of the phase transition from the unexcited state of atoms to the antiferromagnetic-like state of Rydberg excitations by traversing an extended gapless phase, and to estimate the preparation fidelity of the target state in a moderately sized system amenable to detailed numerical analysis. We find that, in the basis…
Successful execution of a quantum information processing (QIP) task on a quantum processing device depends on the availability of high-quality entangling gates. Two important goals in the design and implementation of any entangling gate are low error rates and high connectivity. The former minimizes unintended perturbations to the quantum state during application of that gate, while the latter maximizes the set of qubits that can interact directly without remapping the QIP task through intermediary qubits -- a step that can require many additional gates. Unfortunately, these goals can sometime…
We develop and study quantum and semi-classical models of Rydberg-atom spectroscopy in amplitude-modulated optical lattices. Both initial- and target-state Rydberg atoms are trapped in the lattice. Unlike in any other spectroscopic scheme, the modulation-induced ponderomotive coupling between the Rydberg states is spatially periodic and perfectly phase-locked to the lattice trapping potentials. This leads to a novel type of sub-Doppler mechanism, which we explain in detail. In our exact quantum model, we solve the time-dependent Schrödinger equation in the product space of center-of-mass (COM)…
