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Journal of Physics B: Atomic, Molecular and Optical Physics - latest papers

Latest articles for Journal of Physics B: Atomic, Molecular and Optical Physics

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  • Quantum state transfer in a magnetic atoms chain using a scanning tunneling microscope
    The electric control of quantum spin chains has been an outstanding goal for the few last years due to its potential use in technologies related to quantum information processing. In this work, we show the feasibility of the different steps necessary to perform controlled quantum state transfer and excitation transmission in a titanium atoms chain employing the electric field produced by a scanning tunneling microscope (STM). Our results show that the initialization and transmission of a single excitation state is achievable in short times, and with high fidelity. Our study uses spin Hamiltonians to model the magnetic atoms chain, the tip of the STM, the interaction between it and the atoms chain and the electronic response to the fields applied by the tip, employing sets of parameters compatible with the latest experiments and ab initio calculations. The time dynamical evolution is considered in the full Hilbert space and the control pulses frequencies exerted by the tip of the microscope are within the reach of present day technology.

  • W-state generation and verification in linearly coupled waveguide arrays
    W states are maximally entangled states with excellent robustness to loss. They have been studied in ion, photon and waveguide-mode bases, however the entanglement verification has remained challenging. Here, we theoretically study W-state generation by the quantum walk of a single photon through a linearly coupled waveguide array (WGA) that supports self-imaging of light. We design W states in symmetric and asymmetric arrays with even and odd number of waveguides. Bipartite entanglement is formally proven using the von Neumann entropy of the reduced density matrix. We further use the self-imaging to construct an entanglement witness based on the exclusion principle. A key to verification is the interferometer which extends the length of a W-state generator to the revival length where the photon is fully recombined into a single waveguide mode. In addition, W-state coherence is proven by numerically demonstrating the far-field interference. The sensitivities of the proposed W-state generation and verification protocols to the fabrication tolerances are numerically evaluated in glass, silicon nitride and silicon-on-insulator WGAs, indicating the feasibility of their realisation by high-precision e-beam lithography and laser writing.

  • A method to determine the phase-space distribution of a pulsed molecular beam
    We demonstrate a method to determine the longitudinal phase-space distribution of a cryogenic buffer gas cooled beam of barium-fluoride molecules based on a two-step laser excitation scheme. Temporal resolution is achieved by a transversely aligned laser beam that drives molecules from the ground state to the state around 860  nm, while the velocity resolution is obtained by a laser beam that is aligned counter-propagating with respect to the molecular beam and that drives the Doppler shifted to transition around 797  nm. Molecules in the D-state are detected background-free by recording the fluorescence from the D − X transition at 413 nm. A temporal resolution of 11  μs and a velocity resolution of 6  m s−1 is obtained. In order to calibrate the absolute velocity, we have determined the Doppler free transition frequencies for the X − A and X − D transitions with an absolute accuracy below 0.3  MHz. The high resolution of the phase-space distributions allows us to observe a variation of the average velocity and velocity spread over the duration of the molecular beam pulse. Our method hence gives valuable insight into the dynamics in the source.

  • Quantum correlations dynamics in qubit–qutrit system under magnetic and dephasing field
    We investigate a hybrid qubit–qutrit system exposed to both a magnetic field and classical dephasing noise. The quantum system’s characteristics encompass diverse parameters, including spin-exchange interaction, dephasing, and the magnetic field. To incorporate thermal effects, we employ the system’s Hamiltonian to generate an initial qubit–qutrit density matrix within the framework of the Gibbs density operator. Furthermore, we model dephasing effects on the initial thermal state of the system using an Ornstein–Uhlenbeck process. We employ geometric discord, negativity, and entropic coherence functions to depict the quantum correlations across various parameter settings. Our results reveal that initially, quantum correlations attain non-maximal values, with their dynamics intricately reliant on the underlying system parameters. Specifically, when the system is primarily characterized by the magnetic field, we observe heightened levels of quantum correlations. Additionally, temperature-based characterization is found to have the most detrimental effect on the state. Geometric discord is observed to capture a higher degree of quantum correlations, albeit saturating rapidly at zero compared to entanglement and coherence. Finally, we investigated the effects of common environmental coupling and more pronounced non-Markovian dynamics in the system, revealing an enhanced preservation of quantum correlations. These modifications allow for prolonged coherence and entanglement, underscoring the potential of structured environmental interactions to mitigate decoherence effects and sustain quantum correlations over time.

  • Cr3+ doped ZnGa2O4 micro-flowers as stable saturable absorber media
    Micro-flowers of Cr3+ doped ZnGa2O4, a spinel compound with high chemical and thermal stability is synthesized by hydrothermal method. Flower-like structures in the micrometer range made up of secondary nanoflakes are evident from the field emission scanning electron microscope images. X-ray photoelectron spectroscopy studies confirm the presence of Cr3+ dopants. The steady-state optical characterizations show higher absorbance of the samples in the ultraviolet (UV) region. Due to introduction of the d–d electron transition states of Cr3+ ions, ZnGa2O4:Cr3+ exhibits a prominent red near infrared (NIR) luminescence. Optical nonlinearity studies show that Cr3+ doping changes the nonlinear absorption from reverse saturable absorption to saturable absorption. This is due to the introduction of an excitation band owing to 4T1-4A2 transition of Cr3+ ion.