arXiv subjects

Ivan Cojocaru

Publications and source records attributed to Ivan Cojocaru.

5 recordsLinked to original sources

arXiv2026

Tune-out wavelength for the thulium atom near 576 nm

We report the theoretical prediction and measurement of a tune-out wavelength for the ground state of the thulium atom in a linearly polarized optical dipole trap with a wavelength of approximately 576 nm. The measurements were conducted using a combination of trap frequency and RF loss spectroscopy, thus making it possible to separate the scalar and tensor parts of the total polarizability without measurements in the range of negative total polarizability. The calculated tune-out wavelength is consistent with the measured one of $575.646_{-0.014}^{+0.016}$ nm in air. The existence of the zero in the polarizability for the Tm ground state was confirmed by the trap loss experiment, which also made it possible to refine the tune-out wavelength to $575.646_{-0.004}^{+0.004}$. Despite the presence of an imaginary part of the polarizability at some wavelengths, it was experimentally demonstrated that, with a proper choice of the dipole trap polarization, it was possible to achieve Bose-Einstein condensation of thulium atoms in the range from 575.348 to 575.689 nm, covering the tune-out wavelength.

physics.atom-ph↗

arXiv2025

Modular Design and Experimental Evaluation of 5G Mobile Cell Architectures Based on Overlay and Integrated Models

This paper presents the concept, architectural design, and performance evaluation of a 5G Mobile Cell (MC) used to provide 5G wireless connectivity to User Equipment (UE) in areas with limited fixed 5G infrastructures or subject to adverse radio conditions. We consider two main approaches to MC design: an overlay model, where the MC obtains backhaul connectivity from a 5G overlay network, and an Integrated Access and Backhaul (IAB)-based model, discussing their protocol stacks and architectural implications. In order to validate the MC's performance, we employ an emulation-based testbed using the OpenAirInterface (OAI) implementation, considering different MC positions. The results validate the MC concept and demonstrate that MC positioning significantly influences network performance. This paper has the potential to aid network operators and service providers in selecting and deploying MC architectures for temporary coverage extension and capacity reinforcement in different environments, including seaports, industrial scenarios, and public safety.

cs.NI↗

arXiv2024

Transport of magnetically sensitive atoms in a magnetic environment

Among interesting applications of cold atoms, quantum simulations attract a lot of attention. In this context, rare-earth ultracold atoms are particularly appealing for such simulators due to their numerous Fano-Feshbach resonances and magnetic dipole moments in the ground state. Creating a quantum gas microscope requires a large optical access that may be achieved using transport of atoms between separate vacuum volumes. We demonstrate that in case of the transport of magnetic atoms the magnetic field can be directly measured and adjusted to reduce additional losses after the transport therefore increasing the efficiency of subsequent evaporation cooling. This approach allows to transfer over 85% of the atoms from the main chamber to the scientific chamber, located 38 cm away with moderate laser power of 26 W without atomic polarization decay.

cond-mat.quant-gas↗

arXiv2020

Free-standing silicon nitride nanobeams with efficient fiber-chip interface for cavity QED

We present the design, fabrication and characterization of high quality factor silicon nitride nanobeam PhC cavities at visible wavelengths for coupling to diamond color centers in a cavity QED system. We demonstrate devices with a quality factor of about 24;000 around the zero-phonon line of the germanium-vacancy center in diamond. We also present an efficient fiber-to-waveguide coupling platform for suspended nanophotonics. By gently changing the corresponding effective indices at the fiber-waveguide interface, we achieve an efficiency of about 96% at the cavity resonance.

physics.optics↗

arXiv2017

Germanium-Vacancy Color Center in Diamond as a Non-invasive Temperature Sensor

We present high-resolution, all-optical thermometry based on ensembles of GeV color center in diamond. Due to the unique properties of diamond, an all-optical approach using this method opens a way to produce non-invasive, back-action-free temperature measurements in a wide range of temperatures, from a few Kelvin to 1100 Kelvin.

cond-mat.mtrl-sci↗