arXiv subjects

Nithiwadee Thaicharoen

Publications and source records attributed to Nithiwadee Thaicharoen.

10 recordsLinked to original sources

arXiv2026

Simple Magneto-Optical and Magnetic Traps for Dysprosium

Dysprosium (Dy) is the most magnetic element on the periodic table, making it excellent for studying dipolar atom-atom interactions. We report on a simple Dy MOT that captures atoms directly from the thermal beam using a single diode-laser system to generate the light. Additionally, the atoms are magnetically confined by the quadrupole magnetic field that also facilitates the MOT. The MOT loading time is $τ_\text{b} = 26~\text{ms}$. Atoms can decay to a dark state that is magnetically trapped. The time constant for loading into this magnetic trap is $τ_\text{d} = 410~\text{ms}$. The total magnetically trapped population is $1.14\times10^{5}$ atoms, with $85\%$ residing in the dark states. The magnetically trapped atoms have a temperature of $28~μ\text{K}$, significantly below the Doppler limit. This population fulfills the requirements for a range of future experiments.

physics.atom-ph↗

arXiv2025

Gravitational Wave Effects on Radio Spectral Lines of Atomic Hydrogen: Hyperfine Splitting and Broadening Mechanisms

We explore the effects of gravitational waves (GWs) on hydrogen's radio spectral lines, focusing on the ground-state hyperfine transition and radiative transitions in highly excited Rydberg states. To analyze GW impacts on hyperfine structure, we derive Maxwell's equations in a gravitational-wave background using linearized gravity and the $3+1$ formalism. Our findings reveal that GWs induce energy shifts in hyperfine magnetic substates, modifying the 21 cm line. However, these energy shifts fall well below the detection limits of current radio astronomical instruments. For transitions in highly excited states, which produce radio recombination lines (RRL), the influence of GW manifests itself as spectral broadening, with the fractional linewidth for $\mathrm{H}n\alpha$ scaling as $\Delta\nu/\nu_0 \sim n^7\omega^2_{\mathrm{gw}}h(t)$. This suggests that RRLs could serve as probes for ultra-high-frequency GWs, particularly given that Rydberg atoms in the interstellar medium can reach quantum numbers above $n=100$. As an example of possibly detectable high frequency GW source, We investigate GWs emitted during the inspiral of planetary-mass primordial black hole binaries, where GW-induced broadening in RRLs could exceed natural broadening effects. Additionally, we examine the influence of the recently detected stochastic gravitational-wave background on hydrogen spectral lines.

gr-qc↗

arXiv2024

Rydberg electromagnetically induced transparency of $^{85}$Rb vapor in Ar, Ne and N$_2$ gases

An experimental study on Rydberg electromagnetically induced transparency (EIT) in rubidium (Rb) vapor cells containing inert gases at pressures $\le 5$ Torr is reported. Using an inert-gas-free Rb vapor cell as a reference, we measure frequency shift and line broadening of the EIT spectra in Rb vapor cells with argon, neon or nitrogen gases at pressures ranging from a few mTorr to 5 Torr. The results qualitatively agree with a pseudo-potential model that includes $s$-wave scattering between the Rydberg electron and the inert-gas atoms, and the effect of polarization of the inert-gas atoms by the Rydberg atoms. Our results are important for establishing Rydberg-EIT as an all-optical and non-intrusive spectroscopic probe for field diagnostics in low-pressure radio-frequency discharges.

physics.atom-ph↗

arXiv2024

Observation of anisotropy-independent magnetization dynamics in spatially disordered Heisenberg spin systems

An important step towards a comprehensive understanding of far-from-equilibrium dynamics of quantum many-body systems is the identification of unifying features that are independent of microscopic details of the system. We experimentally observe such robust features in the magnetization relaxation dynamics of disordered Heisenberg XX-, XXZ- and Ising Hamiltonians. We realize these Heisenberg spin models with tunable anisotropy parameter and power-law interactions in an ensemble of Rydberg atoms by encoding the spin in suitable Rydberg state combinations. We consistently observe stretched-exponential relaxation of magnetization for all considered spin models, collapsing onto a single curve after appropriate rescaling of time. This robust short-time relaxation behavior is explained by a perturbative treatment that exploits the strong disorder in pairwise couplings, which leads to a description in terms of approximately independent pairs of spins. In numerical simulations of small systems, we show that these pairs of spins constitute approximate local integrals of motion, which remain at least partially conserved on a timescale exceeding the duration of the relaxation dynamics of the magnetization.

quant-ph↗

arXiv2024

Emergent pair localization in a many-body quantum spin system

Understanding how closed quantum systems dynamically approach thermal equilibrium presents a major unresolved problem in statistical physics. Generically, non-integrable quantum systems are expected to thermalize as they comply with the Eigenstate Thermalization Hypothesis. However, in the presence of strong disorder, the dynamics can possibly slow down to a degree that systems fail to thermalize on experimentally accessible timescales, as in spin glasses or many-body localized systems. In general, particularly in long-range interacting quantum systems, the specific nature of the disorder necessary for the emergence of a prethermal, metastable state--distinctly separating the timescales of initial relaxation and subsequent slow thermalization--remains an open question. We study an ensemble of Heisenberg spins with a tunable distribution of random coupling strengths realized by a Rydberg quantum simulator. We observe a drastic change in the late-time magnetization when increasing disorder strength. The data is well described by models based on pairs of strongly interacting spins, which are treated as thermal for weak disorder and isolated for strong disorder. Our results indicate a crossover into a pair-localized prethermal regime in a closed quantum system of thousands of spins in the critical case where the exponent of the power law interaction matches the spatial dimension.

quant-ph↗

arXiv2023

Rydberg-EIT of $^{85}$Rb vapor in a cell with Ne buffer gas

We investigate Rydberg electromagnetically induced transparency (EIT) of $^{85}$Rb atomic vapor in a glass cell that contains a 5-Torr neon buffer gas. At low probe power, EIT lines exhibit a positive frequency shift of about 70~MHz and a broadening of about 120~MHz, with minimal dependence on the principal quantum number of the Rydberg states. The EIT line shift arises from s-wave scattering between the Rydberg electron and the Ne atoms, which induces a positive shift near 190~MHz, and from the polarization of the Ne atoms within the Rydberg atom, which adds a negative shift near -120~MHz. The line broadening is largely due to the Ne polarization. Our experimental results are in good qualitative agreement with our theoretical model, in which the shift is linear in buffer-gas density. Our results suggest that Rydberg-EIT can serve as a direct spectroscopic probe for buffer-gas density at low pressure, and that it is suitable for non-invasive measurement of electric fields in low-pressure noble-gas discharge plasmas and in dusty plasmas.

physics.atom-ph↗

arXiv2021

Floquet Hamiltonian Engineering of an Isolated Many-Body Spin System

Controlling interactions is the key element for quantum engineering of many-body systems. Using time-periodic driving, a naturally given many-body Hamiltonian of a closed quantum system can be transformed into an effective target Hamiltonian exhibiting vastly different dynamics. We demonstrate such Floquet engineering with a system of spins represented by Rydberg states in an ultracold atomic gas. Applying a sequence of spin manipulations, we change the symmetry properties of the effective Heisenberg XYZ Hamiltonian. As a consequence, the relaxation behavior of the total spin is drastically modified. The observed dynamics can be qualitatively captured by a semi-classical simulation. Synthesising a wide range of Hamiltonians opens vast opportunities for implementing quantum simulation of non-equilibrium dynamics in a single experimental setting.

cond-mat.quant-gas↗

arXiv2014

Millimeter Wave Detection via Autler-Townes Splitting in Rubidium Rydberg Atoms

In this paper we demonstrate the detection of millimeter waves via Autler-Townes splitting in 85Rb Rydberg atoms. This method may provide an independent, atom-based, SI-traceable method for measuring mm-wave electric fields, which addresses a gap in current calibration techniques in the mm-wave regime. The electric- field amplitude within a rubidium vapor cell in the WR-10 waveguide band is measured for frequencies of 93 GHz, and 104 GHz. Relevant aspects of Autler-Townes splitting originating from a four-level electromagnetically induced transparency scheme are discussed. We measure the E-field generated by an open-ended waveguide using this technique. Experimental results are compared to a full-wave finite element simulation.

physics.atom-ph↗

arXiv2014

Broadband Rydberg Atom-Based Electric-Field Probe: From Self-Calibrated Measurements to Sub-Wavelength Imaging

We discuss a fundamentally new approach for the measurement of electric (E) fields that will lead to the development of a broadband, direct SI-traceable, compact, self-calibrating E-field probe (sensor). This approach is based on the interaction of radio frequency (RF) fields with alkali atoms excited to Rydberg states. The RF field causes an energy splitting of the Rydberg states via the Autler-Townes effect and we detect the splitting via electromagnetically induced transparency (EIT). In effect, alkali atoms placed in a vapor cell act like an RF-to-optical transducer, converting an RF E-field strength measurement to an optical frequency measurement. We demonstrate the broadband nature of this approach by showing that one small vapor cell can be used to measure E-field strengths over a wide range of frequencies: 1 GHz to 500 GHz. The technique is validated by comparing experimental data to both numerical simulations and far-field calculations for various frequencies. We also discuss various applications, including: a direct traceable measurement, the ability to measure both weak and strong field strengths, compact form factors of the probe, and sub-wavelength imaging and field mapping.

physics.atom-ph↗

arXiv2014

Sub-Wavelength Imaging and Field Mapping via EIT and Autler-Townes Splitting In Rydberg Atoms

We present a technique for measuring radio-frequency (RF) electric field strengths with sub-wavelength resolution. We use Rydberg states of rubidium atoms to probe the RF field. The RF field causes an energy splitting of the Rydberg states via the Autler-Townes effect, and we detect the splitting via electromagnetically induced transparency (EIT). We use this technique to measure the electric field distribution inside a glass cylinder with applied RF fields at 17.04 GHz and 104.77 GHz. We achieve a spatial resolution of $\bf{\approx}$100 $\bfμ$m, limited by the widths of the laser beams utilized for the EIT spectroscopy. We numerically simulate the fields in the glass cylinder and find good agreement with the measured fields. Our results suggest that this technique could be applied to image fields on a small spatial scale over a large range of frequencies, up into the sub-THz regime.

physics.atom-ph↗