Laser Trapping of Circular Rydberg Atoms

Slowing Down a Coherent Superposition of Circular Rydberg States of Strontium

Rydberg alkaline earth atoms are promising tools for quantum simulation and metrology. When one of the two valence electrons is promoted to long-lived circular states, the second valence electron can be optically manipulated without significant autoionization. We harness this feature to demonstrate laser slowing of a thermal atomic beam of circular strontium atoms. By driving the main ion core 422 nm wavelength resonance, we observe a velocity reduction of 50  m/s without significant autoionization. We also show that a superposition of circular states undergoes very weak decoherence during the cooling process, up to the scattering of more than 1000 photons. This robustness opens new perspectives for quantum simulations over long timescales with circular atoms, while simultaneously cooling their motional state. It makes it possible to mitigate the harmful effects of unavoidable heating due to spin-motion coupling during a quantum simulation.

Direct Laser Cooling of Rydberg Atoms with an Isolated-Core Transition

We propose a scheme to directly laser cool Rydberg atoms by laser cooling the residual ion core within the Rydberg-electron orbit. The scheme is detailed for alkaline-earth-metal Rydberg atoms, whose ions can be easily laser cooled. We demonstrate that a closed optical cooling cycle can be found despite the perturbations caused by the Rydberg electron and that this cycle can be driven over more than 100  μs to achieve laser cooling. The cooling dynamics with and without the presence of magnetic fields are discussed in detail.

Array of Individual Circular Rydberg Atoms Trapped in Optical Tweezers

Circular Rydberg atoms (CRAs), i.e., Rydberg atoms with maximal orbital momentum, are highly promising for quantum computation, simulation, and sensing. They combine long natural lifetimes with strong interatomic interactions and coupling to electromagnetic fields. Trapping individual CRAs is essential to harness these unique features. We report the first demonstration of CRAs laser trapping in a programmable array of optical bottle beams. We observe the decay of a trapped rubidium circular level over 5 ms using a novel optical detection method. This first optical detection of alkali CRAs is both spatially and level selective. We finally observe the mechanical oscillations of the CRAs in the traps. This work opens the route to the use of circular levels in quantum devices. It is also promising for quantum simulation and information processing using the full extent of Rydberg manifolds.

Millisecond-Lived Circular Rydberg Atoms in a Room-Temperature Experiment

Circular Rydberg states are excellent tools for quantum technologies, with large mutual interactions and long lifetimes in the tens of milliseconds range, 2 orders of magnitude larger than those of laser-accessible Rydberg states. However, such lifetimes are observed only at zero temperature. At room temperature, blackbody-radiation-induced transfers cancel this essential asset of circular states, which have thus been used mostly so far in specific, complex cryogenic experiments. We demonstrate here, on a laser-cooled atomic sample, a circular state lifetime of more than 1 millisecond at room temperature for a principal quantum number 60. A simple plane-parallel capacitor efficiently inhibits the blackbody-radiation-induced transfers. One of the capacitor electrodes is fully transparent and provides large optical access to the atoms. This result paves the way to a wide range of quantum metrology and quantum simulation room-temperature experiments with long-lived, trapped circular Rydberg atoms in inhibition capacitors with full optical access.

Few generalized entropic relations related to Rydberg atoms

We calculate the analytical and numerical values of the position space Shannon entropy, momentum space Shannon entropy, and total Shannon entropy, [Formula: see text], [Formula: see text], and [Formula: see text], respectively, of free and trapped Rydberg hydrogen-like atoms. The influence of atomic number Z, the principal quantum number n, and energy E on the Shannon entropy of the Rydberg atoms are illustrated. The scaling properties of Shannon entropy with energy of states E and the principal quantum number n have been reported for the first time to the best of our knowledge. Our work explains how Shannon entropy indicates localization-delocalization of the wavefunction. The total Shannon entropy as a measure of the number of nodes in the trapped Rydberg atom's wavefunction is also discussed. We show why an uncertainty relation based on Shannon entropy is superior to Heisenberg uncertainty for Rydberg atoms.

Angle-Dependent Magic Optical Trap for the 6S1/2↔nP3/2 Rydberg Transition of Cesium Atoms

The existence of an anisotropic tensor part of atomic states with an angular momentum greater than 1/2 causes their dynamic polarizabilities to be very sensitive to the polarization direction of the laser field. Therefore, the magic wavelength of the transition between two atomic states also depends on the polarization angle between the quantized axis and the polarization vector. We perform a calculation of the magic conditions of the 6S1/2↔nP3/2 (n = 50–90) Rydberg transition of cesium atoms by introducing an auxiliary electric diople transition connected to the target Rydberg state and a low-excited state. The magic condition is determined by the intersection of dynamic polarizabilities of the 6S1/2 ground state and the nP3/2 Rydberg state. The dynamic polarizability is calculated by using the sum-over-states method. Furthermore, we analyze the dependence of magic detuning on the polarization angle for a linearly polarized trapping laser and establish the relationship between magic detuning and a principal quantum number of the Rydberg state at the magic angle. The magic optical dipole trap can confine the ground-state and Rydberg-state atoms simultaneously, and the differential light shift in the 6S1/2↔nP3/2 transition can be canceled under the magic condition. It is of great significance for the application of long-lifetime high-repetition-rate accurate manipulation of Rydberg atoms on high-fidelity entanglement and quantum logic gate operation.

Trapping Alkaline Earth Rydberg Atoms Optical Tweezer Arrays

Neutral atom qubits with Rydberg-mediated interactions are a leading platform for developing large-scale coherent quantum systems. In the majority of experiments to date, the Rydberg states are not trapped by the same potential that confines ground state atoms, resulting in atom loss and constraints on the achievable interaction time. In this Letter, we demonstrate that the Rydberg states of an alkaline earth atom, ytterbium, can be stably trapped by the same red-detuned optical tweezer that also confines the ground state, by leveraging the polarizability of the Yb^{+} ion core. Using the previously unobserved ^{3}S_{1} series, we demonstrate trapped Rydberg atom lifetimes exceeding 100  μs, and observe no evidence of auto- or photoionization from the trap light for these states. We measure a coherence time of T_{2}=59  μs between two Rydberg levels, exceeding the 28  μs lifetime of untrapped Rydberg atoms under the same conditions. These results are promising for extending the interaction time of Rydberg atom arrays for quantum simulation and computing, and are vital to capitalize on the extended Rydberg lifetimes in circular states or cryogenic environments.

Synthetic Dimension-Induced Conical Intersections in Rydberg Molecules

We observe a series of conical intersections in the potential energy curves governing both the collision between a Rydberg atom and a ground-state atom and the structure of Rydberg molecules. By employing the electronic energy of the Rydberg atom as a synthetic dimension we circumvent the von Neumann-Wigner theorem. These conical intersections can occur when the Rydberg atom's quantum defect is similar in size to the electron-ground-state atom scattering phase shift divided by π, a condition satisfied in several commonly studied atomic species. The conical intersections have an observable consequence in the rate of ultracold l-changing collisions of the type Rb(nf)+Rb(5s)→Rb(nl>3)+Rb(5s). In the vicinity of a conical intersection, this rate is strongly suppressed, and the Rydberg atom becomes nearly transparent to the ground-state atom.

Efficient microwave-to-optical single-photon conversion with a single flying circular Rydberg atom

We propose a scheme for converting a microwave (mw) single photon in a mw cavity to a flying optical photon. The conversion is realized by using a flying circular Rydberg atom, which plays a role of the "data bus" as an excellent memory to connect the mw and optical cavities. To link the energy levels of atom in optical domain and mw domain, we use fast decircularization method and three-photon Raman transition method. Thank to these low loss processes and the super long lifetime of circular Rydberg states, this scheme can efficiently convert single mw photons into the optical domain. Based on existing experiments and data, the conversion efficiency is simulated as 60%. The theoretical limit of the conversion efficiency is about 87%.

Entanglement and entropy squeezing in the system of two qubits interacting with a two-mode field in the context of power low potentials

We study the dynamics of two non-stationary qubits, allowing for dipole-dipole and Ising-like interplays between them, coupled to quantized fields in the framework of two-mode pair coherent states of power-low potentials. We focus on three particular cases of the coherent states through the exponent parameter taken infinite square, triangular and harmonic potential wells. We examine the possible effects of such features on the evolution of some quantities of current interest, such as population inversion, entanglement among subsystems and squeezing entropy. We show how these quantities can be affected by the qubit-qubit interaction and exponent parameter during the time evolution for both cases of stationary and non-stationary qubits. The obtained results suggest insights about the capability of quantum systems composed of nonstationary qubits to maintain resources in comparison with stationary qubits.