Initial Atomic State Research Articles

Microscopic electronic structure tomography of Rydberg macrodimers

Precise control and study of molecules is challenging due to the variety of internal degrees of freedom and local coordinates that are typically not controlled in an experiment. Employing quantum gas microscopy to position and resolve the atoms in Rydberg macrodimer states solves almost all of these challenges and enables unique access to the molecular frame. Here, we demonstrate the power of this approach and present first photoassociation studies for different molecular symmetries in which the molecular orientation relative to an applied magnetic field, the polarization of the excitation light and the initial atomic state are fully controlled. The observed characteristic dependencies allow for an electronic structure tomography of the molecular state. We additionally observe an orientation-dependent Zeeman shift and reveal a significant influence on it caused by the hyperfine interaction of the macrodimer state. Finally, we demonstrate controlled engineering of the electrostatic binding potential by opening a gap in the energetic vicinity of two crossing pair potentials.

Driven Qubit by Train of Gaussian-Pulses

The simplest non-dissipative 2-level atom system, a qubit, excited by a train of resonant n-Gaussian laser pulses is investigated. This concerns examination of the averaged atomic variables, the intensity-intensity correlation function, and the transient fluorescent radiation. Analytical formulas for the above expressions are obtained. Computational results show that the transient spectra with the initial ground and coherent atomic states exhibit asymmetric Mollow structure with dip structure, dense oscillation, and narrowing, and depends on the pulse number (n), the repetition time (τR), and the observed time.

A strong-field approach with realistic wave functions to the above-threshold ionization of Ba+

We study the above-threshold ionization of atoms in intense circularly polarized laser pulses. In order to compute photoelectron energy spectra, we apply the strong-field approximation with different models for the initial state wave function. Specifically, we compare the spectra for singly ionized Barium (Ba+) using hydrogenic wave functions and realistic one-particle wave functions obtained by multiconfiguration Dirac–Hartree–Fock computations, respectively. As a particular example, we discuss the dependence of the photoelectron spectra on the magnetic quantum number m of the initial state and we reproduce the well known m-selectivity in strong-field ionization. Here, we show that the photoelectron spectra exhibit noticeable differences for the two models of the initial state and that the m-selectivity is enhanced when realistic wave functions are used. We conclude that the description of strong-field processes within the strong-field approximation will benefit from a realistic description of the initial atomic state.

Theoretical Realization of a Two Qubit Quantum Controlled-NOT Logic Gate and a Single Qubit Quantum Hadamard Logic Gate in the Anti-Jaynes-Cummings Model

Quantum gates are fundamental in Quantum computing for their role in manipulating elementary information carriers referred to as quantum bits. In this paper, a theoretical scheme for realizing a quantum Hadamard and a quantum controlled-NOT logic gates operations in the anti-Jaynes-Cummings interaction process is provided. Standard Hadamard operation for a specified initial atomic state is achieved by setting a specific sum frequency and photon number in the normalized anti-Jaynes-Cummings qubit state transition operation with the interaction component of the anti-Jaynes-Cummings Hamiltonian generating the state transitions. The quantum controlled-NOT logic gate is realized when a single atomic qubit defined in a two-dimensional Hilbert space is the control qubit and two non-degenerate and orthogonal polarized cavities defined in a two-dimensional Hilbert space make the target qubit. With precise choice of interaction time in the anti-Jaynes-Cummings qubit state transition operations defined in the anti-Jaynes-Cummings sub-space spanned by normalized but non-orthogonal basic qubit state vectors, ideal unit probabilities of success in the quantum controlled-NOT operations is determined.

Stable entanglement in a quadripartite cavity optomechanics

In this paper, making use of negativity, we study bipartite entanglements in a quadripartite system composed of two two-level atoms and a cavity optomechanics. An atom is inside a single-mode cavity with a movable mirror and the other one is isolated outside, i.e., there is no direct interaction between this atom and cavity optomechanics with the atom therein. The entanglement dynamics of various types of bipartite systems obtained has been numerically investigated to understand the roles of initial state of cavity field, movable mirror and atoms, the ratio of the atom-field coupling strength to the optomechanical coupling coefficient on physical properties. The results amazingly show the bipartite entanglement between the interior and exterior isolated atoms. Depending on the above-mentioned ratio and different initial states adopted to the system, the relatively stable entanglement can be generated between the atoms. Furthermore, the so-called atomic entanglement sudden death, which is independent of the degree of entanglement of the initial state, occurs in some situations.

Entanglement of atoms induced by thermal noise in the presence of initial atomic coherence

In this article, author investigated the dynamics of entanglement of two dipole-coupled natural or artificial two-level atoms (qubits) interacting nonresonantly with the intensive one-mode cavity thermal field. Author found an exact solution of the quantum Liouville equation for the full density matrix of the system two atoms + field mode for a coherent initial state of atoms in the dressed states representation. The full system density matrix is used to calculate the two-atom reduced density matrix and to calculate the quantitative criterion for atom-atom entanglement ‒ negativity. The results of computer simulation of the time dependence of negativity showed that in the case of a model with nonresonant interaction, the presence of initial atomic coherence leads to a significant decrease in the maximum degree of atomic entanglement, in contrast to the model with resonant interaction of atoms and a field. For the resonance model, the initial atomic coherence greatly enhances the degree of atomic entanglement.

Precision protection through cosmic string in quantum metrology

The dynamics of the quantum Fisher information of the parameters of the initial atomic state and atomic transition frequency is studied, in the framework of open quantum systems, for a static polarizable two-level atom coupled in the multipolar scheme to a bath of fluctuating vacuum electromagnetic fields in cosmic string space-time. Our results show that with the presence of cosmic string, the quantum Fisher information becomes position and atomic polarization dependent. It may be enhanced or depressed as compared to that in flat space-time case. Remarkably, when the atom is extremely close to the cosmic string and the polarization direction of the atom is perpendicular to the direction of the cosmic string, the quantum Fisher information has been totally protected from the fluctuating vacuum electromagnetic fields. So on the one hand, near a cosmic string, precision of estimation can be enhanced by ranging the radial distance between the probe atom and the cosmic string; on the other hand, the cosmic string can be sensed by studying the distribution of parameter induced state-separation.

Steady and optimal entropy squeezing for three types of moving three-level atoms coupled with a single-mode coherent field* *Project supported by the National Natural Science Foundation of China (Grant Nos. 12064012 and 11374096).

The entropy squeezing properties of different types of moving three-level atoms coupled with a single-mode coherent field are studied. The influences of the moving velocity and initial states of the three-level atom on the entropy squeezing are discussed. The results show that, the entropy squeezing properties of the three-level atom depend on its initial state, moving velocity, and the type. A stationary three-level atom can not obtain a steady entropy squeezing whatever initial conditions are chosen, while a moving three-level atom can achieve a steady and optimal entropy squeezing through choosing higher velocity and appropriate initial state. Our result provides a simple method for preparing squeezing resources with ultra-low quantum noise of the three-level atomic system without additional any complex techniques.

Nondestructive photon counting in waveguide QED

Number-resolving single-photon detectors represent a key technology for a host of quantum optics protocols, but despite significant efforts, state-of-the-art devices are limited to few photons. In contrast, state-dependent atom counting in arrays can be done with extremely high fidelity up to hundreds of atoms. We show that in waveguide QED, the problem of photon counting can be reduced to atom counting, by entangling the photonic state with an atomic array in the collective number basis. This is possible as the incoming photons couple to collective atomic states and can be achieved by engineering a second decay channel of an excited atom to a metastable state. Our scheme is robust to disorder and finite Purcell factors, and its fidelity increases with atom number. Analyzing the state of the re-emitted photons, we further show that if the initial atomic state is a symmetric Dicke state, dissipation engineering can be used to implement a nondestructive photon-number measurement, in which the incident state is scattered into the waveguide unchanged. Our results generalize to related platforms, including superconducting qubits.

Observation of Quantum Phase Synchronization in Spin-1 Atoms.

With growing interest in quantum technologies, possibilities of synchronizing quantum systems have garnered significant recent attention. In experiments with dilute ensemble of laser cooled spin-1 ^{87}Rb atoms, we observe phase difference of spin coherences to synchronize with phases of external classical fields. An initial limit-cycle state of a spin-1 atom localizes in phase space due to dark-state polaritons generated by classical two-photon tone fields. In particular, when the two couplings fields are out of phase, the limit-cycle state synchronizes only with two artificially engineered, anisotropic decay rates. Furthermore, we observe a blockade of synchronization due to quantum interference and emergence of Arnold-tongue-like features. Such anisotropic decay induced synchronization of spin-1 systems with no classical analog can provide insights in open quantum systems and find applications in synchronized quantum networks.

Quantum Fisher information and nonclassical properties of a two-atom interacting with a radiation field in squeezed coherent states

In this paper, we consider the problem of the interaction between a two atoms and a radiation field in the squeezed coherent states with one- and two-photon processes. The analytic solution for the wavefunction of the whole system is used to describe various quantum measures. The article investigates the dynamics of entanglement between the squeezed coherent field with two atoms measured by quantum entropy. On the other side, the negativity is used to detect the atom–atom entanglement. The influence of the multiphoton transitions, the initial atomic state and intensity dependent function on the entanglement and Quantum Fisher Information (QFI) for the system under consideration is examined. Furthermore, we show how the QFI of the system states is affected and changed according to the main physical parameters. Finally, our results have reported some important phenomena such as entanglement sudden death and birth and its link with the dynamical behavior of the QFI.

Violation of Svetlichny inequality in Triple Jaynes-Cummings Models

We study the genuine tripartite nonlocality of some qubit states in a triple JCM. In this model, each atom state (A, B or C) was initially prepared with an independent cavity (a, b or c). By using two kinds of GHZ-like states as the atomic initial states, we investigate the genuine tripartite nonlocality as the time evolutions for the non-interaction three-qubit subsystems. We also study the genuine tripartite nonlocality of the subsystems by using the Svetlichny inequality. For the subsystems of three atoms ABC and three cavity modes abc, we show that they are genuinely nonlocal at certain period intervals of time. The states of all the other inequivalent subsystems satisfy the Svetlichny inequality for two types of GHZ-like states.

Dynamics of entanglement of atoms with two-photon transitions induced by a thermal field

In this paper, we investigate the entanglement between two two-level atoms non-resonantly in-teracting with a thermal field of a lossless one-mode resonator via degenerate two-photon transi-tions. On the basis of the exact solution of the time-dependent density matrix we calculate the negativity as a measure of atomic entanglement. We show that for separable initial atomic states a slight atom-field detuning may generate the high amount of atom-atom entanglement. The re-sults also show that for non-resonant atom-field interaction the entanglement induced by nonlin-ear two-photon interaction is smaller than that induced by one-photon interaction in contrast to the resonant interaction situation. For a Bell-type entangled initial atomic state we obtain that if the detuning increases, there is an appreciable decrease in the amplitudes of the negativity oscilla-tions. The results also show that elimination of the sudden death of entanglement for non-resonant two-photon atom-field interaction may take place.

Collinear laser spectroscopy of stable palladium isotopes at the IGISOL facility

Collinear laser spectroscopy on stable palladium isotopes was performed at the IGISOL facility in Jyväskylä in preparation for an experiment on its neutron-rich isotopes. Five transitions from different initial atomic states were tested, with the goal of finding the most spectroscopically efficient. The observed intensities afforded a comparison with atomic-level population predictions based on charge-exchange calculations. For some transitions hyperfine parameters of 105Pd were measured, which were found to be in good agreement with literature values. A King plot analysis was performed using the measured isotope shifts and known charge radii from literature to determine the atomic field and mass shift factors.

Atomic nonclassicality in the Jaynes-Cummings model

The Jaynes-Cummings model, a fundamental and ideal paradigm for the study of atom-field interaction with remarkable beauty and complexity, plays an instrumental role in cavity quantum electrodynamics and related experiments. The dynamics of both the atom and the field in this ubiquitous model, which exhibit a number of intriguing nonclassical effects, have been widely studied and engineered from various perspectives. In particular, the collapses and revivals for several physical quantities have been revealed, with important implications for quantum foundations and technologies. In this work, we study the atomic nonclassicality in the Jaynes-Cummings model in terms of an information-theoretic quantifier, reveal its basic features, and compare them with various well known observations of atomic dynamics. The sensitivity of the dynamics on both the initial atomic states and field states indicates rich patterns of atom-field interaction, and may be exploited to estimate, prepare, and engineer atomic states via fields, or vice versa.

New properties of a pure bipartite system in presence of dissipative environments

We investigate some new properties of the model of a pure bipartite system in dissipative environments. The mathematical model of bipartite system with the interaction cavity field in the presence of dissipative environment is designed. The systems is assumed to be initially in the Warner state. The system is analytically solved using master equation method. We quantified the dynamics of quantum correlation between the system, under the influence of the mean photon numbers, type of the initial state and spontaneous emission rate of atom using several measures are, measurement-induced disturbance (MID) and Geometric measure of quantum discord (GQD), negativity (N) and concurrence (C). The effect of the system parameters on dynamics of entanglement is investigated, it is found that the spontaneous emission rate of atom number have much effect on all measures. Moreover the Geometric measure of quantum discord (GQD) have different behavior rather than the others and more influenced by the mean photon number and type of the initial state.

Entanglement and geometric phase of the coherent field interacting with a three two-level atoms in the presence of non-linear terms

We study the interaction of a three two-level atoms with a one-mode optical coherent field in coherent state in the presence of non-linear Kerr medim. The three atoms are initially prepared in upper and entangled states while the field mode is in a coherent state. The constants of motion, three two-level atoms and field density matrix are obtained. The analytic results are employed to perform some investigations of the temporal evolution of the von Neumann entropy as measure of the degree of entanglement between the three two-level atoms and optical coherent field. The effect of the detuning and the initial atomic states on the evolution of geometric phase and entanglement is analyzed. Also, we demonstrate the link between the geometric phase and non-classical properties during the evolution time. Additionally the effect of detuning and initial conditions on the Mandel parameter is studied. The obtained results are emphasize the impact of the detuning and the initial atomic states of the feature of the entanglement, geometric phase and photon statistics of the optical coherent field.

Entanglement and geometric phase of the coherent field interacting with a three two-level atoms in the presence of non-linear terms

We study the interaction of a three two-level atoms with a one-mode optical coherent field in coherent state in the presence of non-linear Kerr medim. The three atoms are initially prepared in upper and entangled states while the field mode is in a coherent state. The constants of motion, three two-level atoms and field density matrix are obtained. The analytic results are employed to perform some investigations of the temporal evolution of the von Neumann entropy as measure of the degree of entanglement between the three two-level atoms and optical coherent field. The effect of the detuning and the initial atomic states on the evolution of geometric phase and entanglement is analyzed. Also, we demonstrate the link between the geometric phase and non-classical properties during the evolution time. Additionally the effect of detuning and initial conditions on the Mandel parameter is studied. The obtained results are emphasize the impact of the detuning and the initial atomic states of the feature of the entanglement, geometric phase and photon statistics of the optical coherent field.

Entanglement and geometric phase of the coherent field interacting with a three two-level atoms in the presence of non-linear terms

We study the interaction of a three two-level atoms (3-2LA) with a one-mode op?tical coherent field in coherent state in the presence of non-linear Kerr medium. The three atoms are initially prepared in upper and entangled states while the field mode is in a coherent state. The constants of motion, 3-2LA and field density matrix are obtained. The analytic results are employed to perform some investigations of the temporal evolution of the von Neumann entropy as measure of the degree of entanglement between the 3-2LA and optical coherent field. The effect of the detuning and the initial atomic states on the evolution of geometric phase and en?tanglement is analyzed. Also, we demonstrate the link between the geometric phase and non-classical properties during the evolution time. Additionally the effect of detuning and initial conditions on the Mandel parameter is studied. The obtained results are emphasize the impact of the detuning and the initial atomic states of the feature of the entanglement, geometric phase and photon statistics of theoptical coherent field.

In uence of Stark shift and detuning on atomic entanglement induced by a thermal eld of one-mode cavity

We considered a quantum model consisting of two effective two-level atoms not resonantly interacting with a single-mode thermal cavity eld through two-photon transitions. We explored the entanglement dynamics between two atoms, and studied the effect of the Stark shift and detuning on the entanglement. The results showed that for a separable initial atomic state the Stark shift and detuning enhance the amount of atom-atom entanglement induced by the thermal eld. For entangled atomic state these reduce the atom-atom entanglement oscillations.