Atomic Entanglement Research Articles

Increased atom-cavity coupling through cooling-induced atomic reorganization

The strong coupling of atoms to optical cavities can improve optical lattice clocks as the cavity enables metrologically useful collective atomic entanglement and high-fidelity measurement. To this end, it is necessary to cool the ensemble to suppress motional broadening, and advantageous to maximize and homogenize the atom-cavity coupling. We demonstrate resolved Raman sideband cooling via the cavity as a method that can simultaneously achieve both goals. In 200 ms of Raman sideband cooling, we cool Yb171 atoms to an average vibration number 〈nx〉=0.23(7) in the tightly binding direction, resulting in 93% optical π-pulse fidelity on the clock transition S01→P03. During cooling, the atoms self-organize into locations with maximal atom-cavity coupling, which will improve quantum metrology applications. Published by the American Physical Society 2024

Entanglement of a three-level atom interacting with two-modes field in a cavity

Entanglement of a three-level atom interacting with two-modes field in a cavity

Analytical solution for Ξ-type qutrit interacting nonlinearly with a cavity field through Kerr-like medium with intrinsic noise present

This paper presents an analytical solution for the Milburn equation describing the interaction between a 3-level atom in a [Formula: see text]-configuration, a cavity field, and a nonlinear Kerr-like medium. The Hamiltonian of the model is presented in the rotating wave approximation (RWA) under specific conditions. The obtained analytical solution accounts for the impact of intrinsic decoherence and nonlinear terms on the dynamics of various physical phenomena. Specifically, we explore the behavior of atomic population, entropy functions, entanglement, negativity, and correlation, highlighting their dependence on the physical parameters of the [Formula: see text]-level atom-cavity system.

PROJECT PROPOSAL: REJUVENATION OF BRAIN NEURONS USING QUANTUM ENTANGLEMENT IN NUCLEOTIDES AND CRYPTOCHROMES

In this paper, we propose a novel and futuristic theoretical framework aimed at rejuvenating and repairing human brain neurons through the application of quantum entanglement. We hypothesize that by inducing atomic entanglement in nucleotides and photonic entanglement in cryptochromes, and subsequently reinjecting these entangled particles into brain neurons, we can exploit the unique properties of quantum entanglement to enhance neuronal repair and regeneration. Our study delves into the underlying quantum mechanisms, presents detailed mathematical formulations, and outlines comprehensive experimental protocols for achieving neuronal rejuvenation. Additionally, we explore the potential amplification of these effects by exposing entangled particles to the space environment, leveraging factors such as microgravity, cosmic radiation, vacuum conditions, temperature extremes, and electromagnetic isolation. This approach is specifically tailored for brain neurons, as other cells in the body do not process and transmit information in a manner that would benefit from quantum entanglement. Furthermore, we discuss the potential application of this method in treating blindness and neurodegenerative diseases such as Alzheimers disease.

Entangling Two Giant Atoms via a Topological Waveguide

AbstractThe entanglement generation of two two‐level giant atoms coupled to a photonic waveguide, which is formed by a Su–Schrieffer–Heeger (SSH) type coupled‐cavity array is studied. Here, each atom is coupled to the waveguide through two coupling points.The two‐atom separate‐coupling case is studied, and 16 coupling configurations are considered for the coupling‐point distributions between the two atoms and the waveguide. Quantum master equations are derived to govern the evolution of the two atoms and characterize atomic entanglement by calculating the concurrence of the two‐atom states. It is found that the two giant‐atom entanglement depends on the coupling configurations and the coupling‐point distance of the giant atoms. In particular, the entanglement dynamics of the two giant atoms in 14 coupling configurations depend on the dimerization parameter of the SSH waveguide. According to the self‐energies of the two giant atoms, it is found that ten of these 16 coupling configurations can be divided into five pairs. It is also showed that the delayed sudden birth of entanglement between the two giant atoms is largely enhanced in these five pairs of coupling configurations. This work will promote the study of quantum effects and coherent manipulation in giant‐atom topological‐waveguide‐QED.

Control and Entanglement of Individual Rydberg Atoms near a Nanoscale Device.

Coherent control of Rydberg atoms near dielectric surfaces is a major challenge due to the large sensitivity of Rydberg states to electric fields. We demonstrate coherent single-atom operations and two-qubit entanglement as close as 100 μm from a nanophotonic device. Using the individual atom control enabled by optical tweezers to study the spatial and temporal properties of the electric field from the surface, we employ dynamical decoupling techniques to characterize and cancel the electric-field noise with submicrosecond temporal resolution. We further use entanglement-assisted sensing to accurately map magnitude and direction of electric-field gradients on a micrometer scale. Our observations open a path for integration of Rydberg arrays with micro- and nanoscale devices for applications in quantum networking and quantum information science.

A photonic engine fueled by entangled two atoms

Entangled states are an important resource for quantum information processing and for the fundamental understanding of quantum physics. An intriguing open question would be whether entanglement can improve the performance of quantum heat engines in particular. One of the promising platforms to address this question is to use entangled atoms as a non-thermal bath for cavity photons, where the cavity mirror serves as a piston of the engine. Here we theoretically investigate a photonic quantum engine operating under an effective reservoir consisting of quantum-correlated pairs of atoms. We find that maximally entangled Bell states alone do not help extract useful work from the reservoir unless some extra populations in the excited states or ground states are taken into account. Furthermore, high efficiency and work output are shown for the non-maximally entangled superradiant state, while negligible for the subradiant state due to lack of emitted photons inside the cavity. Our results provide insights in the role of quantum-correlated atoms in a photonic engine and present new opportunities in designing a better quantum heat engine.

Optimal control of entanglement in atom pairs with dipole-dipole interaction by quantum phase space formalism

We investigate the entanglement in a two-particle system with continuous degree of freedom constituted by trapped neutral atoms interacting via tunable dipole-dipole interaction. We describe the system in the quantum Wigner phase space representation. The atom entanglement is measured in terms of violation of the non separability condition or of some Bell inequalities. By an optimal control procedure, we design the control parameters that steer the system toward a maximally entangled state. We estimate the robustness of the control by considering the presence of an external source of noise weakly interacting with the atoms.

Non-local temporal interference

Although position and time have different mathematical roles in quantum mechanics, with one being an operator and the other being a parameter, there is a space–time duality in quantum phenomena—a lot of quantum phenomena that were first observed in the spatial domain were later observed in the temporal domain as well. In this context, we propose a modified version of the double-double-slit experiment using entangled atom pairs to observe a non-local interference in the arrival time distribution, which is analogous to the non-local interference observed in the arrival position distribution. However, computing the arrival time distribution in quantum mechanics is a challenging open problem, and so to overcome this problem we employ a Bohmian treatment. Based on this approach, we numerically demonstrate that there is a complementary relationship between the one-particle and two-particle interference visibilities in the arrival time distribution, which is analogous to the complementary relationship observed in the position distribution. These results can be used to test the Bohmian arrival time distribution in a strict manner, i.e., where the semiclassical approximation breaks down. Moreover, our approach to investigating this experiment can be applied to a wide range of phenomena, and it seems that the predicted non-local temporal interference and associated complementary relationship are universal behaviors of entangled quantum systems that may manifest in various phenomena.

Spatial entanglement in two-dimensional artificial atoms

Semiconductor quantum dots (QDs) are one of the leading candidates for realizable qubits, as well as for many other advances in quantum computing and quantum communication. The spatial overlapping of wavefunctions describing each single electron in these nanoscale devices results in tunable spatial entanglement. In this article, we explore the case of two electrons in two-dimensional double quantum dot systems. We compute the two-particle wavefunction through a variational method combined with Hermite finite elements and study the spatial entanglement of electrons. We show that symmetry in the geometry of the double quantum dots plays a role in obtaining optimal entanglement, while a broken symmetry can lead to additional resonances in entanglement that are associated with the crossings of states. We also show that one can finely tune the level of spatial entanglement by altering the geometry of the quantum dots or by applying external fields, which corresponds to an “entanglement spectroscopy.” Finally, we study how impurities in the potential profile of the QDs affect the level of entanglement.

Quantum Applications of an Atomic Ensemble Inside a Laser Cavity

Many quantum device signals are proportional to the number of the participating atoms that take part in the detection devices. Among these are optical magnetometers, atomic clocks, quantum communications and atom interferometers. One way to enhance the signal-to-noise ratio is to introduce atom entanglement that increases the signal in a super-radiant-like effect. A coherent em field inside a laser cavity is suggested to achieve atoms’ correlation/entanglement. This may also play an important role in the basic quantum arena of many-body physics. An initial novel experiment to test the realization of atoms’ correlation is described here. A Cs optical magnetometer is used as a tool to test the operation of a cell-in-cavity laser and its characteristics. A vapor cell is inserted into an elongated external cavity of the pump laser in Littrow configuration. Higher atom polarization and reduced laser linewidth are obtained leading to better magnetometer sensitivity and signal-to-noise ratio. The Larmor frequency changes of the Free Induction Decay of optically pumped Cs atomic polarization in the ambient earth magnetic field at room temperature is measured. Temporal changes in the magnetic field of less than 10 pT/√Hz are measured. The first-order dependence of the magnetic field on temperature and temperature gradients is eliminated, important in many practical applications. Single and gradiometric magnetometer configurations are presented.

Fast nuclear-spin gates and electrons-nuclei entanglement of neutral atoms in weak magnetic fields

Fast nuclear-spin gates and electrons-nuclei entanglement of neutral atoms in weak magnetic fields

Entanglement and quantum teleportation conditions from non-local quantum computing theory

Entanglement and quantum teleportation are two inter-related subjects and can be explained through four fundamental non-local quantum computing diagonal operator-state relations, which model the conservative phase-interaction between two adjacent atoms of an entangled atomic chain. Each model atom possesses four eigen-states. There exists a minimum focus distance between the two atoms for the entanglement to exist. Consequently, there exist perpetual elastic phase-changing events on the entire entangled chain at every discrete time interval that is evaluated and shown here. It is analogous to Newton’s first law of motion in discrete time. Quantum teleportation means every extra $2\pi$ phase between the atoms can be translated in Fourier space into an additional separation distance, a quantized value.

Quantum memory and entanglement dynamics induced by interactions of two moving atoms with a coherent cavity

This study explores the dynamics of atomic entanglement of formation and entropic uncertainty relation (EUR) of two moving atoms interacting with an even coherent cavity during a two-photon interaction. We investigate the impact of the initial even coherent amplitude, the atom–photon coupling strengths, and the atomic motion coupling on the dynamics of quantum memory (QM) entropic uncertainty and entanglement. The dynamics of the entropic uncertainty and entanglement of formation are significantly altered by the atom-photon-atom interaction parameters. By increasing the initial mean photon number, the QM entropic uncertainty and the atomic entanglement can be improved. Bob’s capacity to limit his uncertainty regarding Alice’s measurement results depends on the initial even coherent state, the atom–photon couplings, and the atomic motion parameter. The atomic location couplings produce QM entropic uncertainty and entanglement with regular oscillatory behavior. The system parameters control the sudden death-birth entanglement phenomenon, which is improved by increasing the atomic location coupling.

Thermal states of two identical two-level atoms interacting with the single-mode fields of the Arik–Coon and Biedenharn–Macfarlane q-oscillators

We consider the Jaynes–Cummings models (JCMs) of two identical two-level atoms interacting with a single mode of the Arik–Coon and Biedenharn–Macfarlane [Formula: see text]-boson fields in a cavity. It is shown that there is a constant of motion, so-called the total number of excitation, which leads to decomposition of the total Hilbert space of [Formula: see text]-deformed system into three invariant subspaces. So, we have the block diagonal structure with three blocks as the Hamiltonian matrices. The exact energy spectrum and eigenstates of the [Formula: see text]-deformed models are obtained by diagonalizing each block. Assuming that the cavity fields and atoms are in thermal equilibrium, the partition function and thermal density matrix of the models are calculated. Finally, the influence of deformation parameters of the Arik–Coon and Biedenharn–Macfarlane [Formula: see text]-oscillator light fields at low-temperatures on the entropy and internal energy of the Jaynes–Cummings models as well as on the atom–atom entanglement via the concurrence measure is analyzed.

Generation of Stable Entanglement in an Optomechanical System with Dissipative Environment: Linear-and-Quadratic Couplings

In this paper, we present a theoretical scheme for the generation and manipulation of bipartite atom–atom entanglement in a dissipative optomechanical system containing two atoms in the presence of linear and nonlinear (quadratic) couplings. To achieve the goal of paper, we first obtain the interaction Hamiltonian in the interaction picture, and then, by considering some resonance conditions and applying the rotating wave approximation, the effective Hamiltonian, which is independent of time, is derived. In the continuation, the system solution was obtained via solving the Lindblad master equation, which includes atomic, optical and mechanical dissipation effects. Finally, bipartite atom–atom entanglement is quantitatively discussed, by evaluating the negativity, which is a well-known measure of entanglement. Our numerical simulations show that a significant degree of entanglement can be reached via adjusting the system parameters. It is noticeable that the optical and mechanical decay rates play an important role in the quasi-stability and even stability of the obtained atom–atom entanglement.

Optical and atomic decoherence in quantum nondemolition measurement induced atomic ensemble entanglement

We study the effects of optical and atomic decoherence in entangled atomic ensembles produced via quantum nondemolition (QND) measurements. We examine potentially experimentally detrimental effects, such as optical phase diffusion, photon loss and gain, and atomic dephasing. For the optical decoherence channels, we use the technique of integration within ordered operators to obtain the associated Kraus operators. We analyze the effect of different decoherence channels on various quantities, such as the variances of the spin operators, entanglement and correlation criteria, logarithmic negativity, and the Bell–CHSH inequality. We generally find a smooth decay of correlations and entanglement in the presence of decoherence. In the short interaction time range, we find that various quantities show signals consistent with, and showing that entanglement exists under all three types of decoherence. Our results show that QND measurements are one of the most promising methods for entanglement generation between two Bose–Einstein condensates.

Scalable Multipartite Entanglement Created by Spin Exchange in an Optical Lattice.

Ultracold atoms in optical lattices form a competitive candidate for quantum computation owing to the excellent coherence properties, the highly parallel operations over spins, and the ultralow entropy achieved in qubit arrays. For this, a massive number of parallel entangled atom pairs have been realized in superlattices. However, the more formidable challenge is to scale up and detect multipartite entanglement, the basic resource for quantum computation, due to the lack of manipulations over local atomic spins in retroreflected bichromatic superlattices. In this Letter, we realize the functional building blocks in quantum-gate-based architecture by developing a cross-angle spin-dependent optical superlattice for implementing layers of quantum gates over moderately separated atoms incorporated with a quantum gas microscope for single-atom manipulation and detection. Bell states with a fidelity of 95.6(5)% and a lifetime of 2.20±0.13 s are prepared in parallel, and then connected to multipartite entangled states of one-dimensional ten-atom chains and two-dimensional plaquettes of 2×4 atoms. The multipartite entanglement is further verified with full bipartite nonseparability criteria. This offers a new platform toward scalable quantum computation and simulation.

Classical and quantum correlations between two qubits interacting with a field in thermal spin states

In this manuscript, we introduce a quantum physical model consisting of two-atom system that interact with a quantized field initially prepared in the thermal spin states (TSSs). We study the effect of the main parameters of the model on the dynamical behavior atom–atom coherence, atoms-field entanglement, atom–atom entanglement and classical correlation. We show how the quantumness measures can be influenced by the spin number and thermal noise in the absence and presence of time-dependent coupling effect. We obtain that, despite the destructive influence of thermal noise, a considerable amount of coherence, entanglement and classical correlation still remain during the time evolution according the values of spin number. The results also show that the TSSs can offer the advantage of generating the maximal amount of coherence, entanglement and classical correlation during the dynamics.

Enhancing the atomic correlation dynamics under the effects of Stark shift and Kerr medium through multi-photon transitions

Enhancing and preserving the atomic correlation and entanglement is of significant utility in quantum information. To this aim, we study the temporal evolution of uncertainty-induced nonlocality ([Formula: see text]) and logarithmic negativity ([Formula: see text]) as measures of quantum correlations (QCs) and quantum entanglement (QE) between two effective atoms coupled to a bosonic reservoir in the absence of thermal fluctuations and in the presence of Kerr medium (KM) and Stark shift (SS) under which n-photon transitions are permitted. We explore how Markovian and non-Markovian regimes affect the temporal dynamics of atomic correlation and entanglement and its limitations. Our findings indicate that by adjusting the KM and SS parameters, the quantum correlations between the two atoms can be enhanced and maintained while displaying similar qualitative behavior. Notably, it was observed that the QCs and QE quantities are at their highest magnitudes in the non-Markovian regime when the strengths of both SS and KM are increased, implying that QCs and QE are well protected. In contrast to the typical view that protecting the QCs from decoherence that may be observed owing to environmental noise, we proposed a gainful way to reduce the atomic decoherence by adjusting the number of n-photon transitions. Our investigation reveals that in the non-Markovian regime, the considered system exhibits better resistance against decoherence in comparison to the Markovian regime, as evidenced by the significant amount of quantum correlations detected among the two effective atoms at a specific point in time.