arXiv subjects

Chetan Sriram Madasu

Publications and source records attributed to Chetan Sriram Madasu.

6 recordsLinked to original sources

arXiv2025

Topological optical skyrmion transfer to matter

The ability of structured light to mimic exotic topological skyrmion textures, encountered in high-energy physics, cosmology, magnetic materials, and superfluids has recently received considerable attention. Despite their promise as mechanisms for data encoding and storage, there has been a lack of studies addressing the transfer and storage of the topology of optical skyrmions to matter. Here, we demonstrate a high-fidelity mapping of skyrmion topology from a laser beam onto a gas of cold atoms, where it is detected in its new non-propagating form. Within the spatial overlap of the beam and atom cloud, the skyrmion topological charge is preserved, with a reduction from $Q \simeq 0.91$ to $Q \simeq 0.84$ mainly due to the beam width exceeding the sample size. Our work potentially opens novel avenues for topological photonics state storage and the analysis of more complex structured light topologies.

physics.optics↗

arXiv2024

Geometric Ramsey Interferometry with a Tripod Scheme

Ramsey interferometry is a key technique for precision spectroscopy and to probe the coherence of quantum systems. Typically, an interferometer is constructed using two quantum states and involves a time-dependent interaction with two short resonant electromagnetic pulses. Here, we explore a different type of Ramsey interferometer where we perform quantum state manipulations by geometrical means, eliminating the temporal dependence of the interaction. We use a resonant tripod scheme in ultracold strontium atoms where the interferometric operation is restricted to a two-dimensional dark-state subspace in the dressed-state picture. The observed interferometric phase accumulation is due to an effective geometric scalar term in the dark-state subspace, which remarkably does not vanish during the free evolution time when the light-matter interaction is turned off. This study opens the door for more robust interferometers operating on multiple input-output ports.

quant-ph↗

arXiv2022

Datta-Das transistor for atomtronic circuits using artificial gauge fields

Spin-dependent electrical injection has found useful applications in storage devices, but fully operational spin-dependent semiconductor electronics remain a challenging task because of weak spin-orbit couplings and/or strong spin relaxations. These limitations are lifted considering atoms instead of electrons or holes as spin carriers. In this emerging field of atomtronics, we demonstrate the equivalent of a Datta-Das transistor using a degenerate Fermi gas of strontium atoms as spin carriers in interaction with a tripod laser-beams scheme. We explore the dependence of spin rotation, and we identify two key control parameters which we interpret as equivalent to the gate-source and drain-source voltages of a field effect transistor. Our finding broadens the spectrum of atomtronics devices for implementation of operational spin-sensitive circuits.

cond-mat.mes-hall↗

arXiv2022

Evolution of an ultracold gas in a non-Abelian gauge fields: Finite temperature effect

We detail the cooling mechanisms of a Fermionic strontium-87 gas in order to study its evolution under a non-Abelian gauge field. In contrast to our previous work reported in Ref. [1], we emphasize here on the finite temperature effect of the gas. In addition, we provide the detail characterization for the efficiency of atoms loading in the cross-dipole trap, the quantitative performance of the evaporative cooling, and the characterization of a degenerate Fermi gas using a Thomas-Fermi distribution.

cond-mat.quant-gas↗

arXiv2022

Wave-packet Dynamics in Synthetic Non-Abelian Gauge Fields

It is generally admitted that in quantum mechanics, the electromagnetic potentials have physical interpretations otherwise absent in classical physics as illustrated by the Aharonov-Bohm effect. In 1984, Berry interpreted this effect as a geometrical phase factor. The same year, Wilczek and Zee generalized the concept of Berry phases to degenerate levels and showed that a non-Abelian gauge field arises in these systems. In sharp contrast with the Abelian case, spatially uniform non-Abelian gauge fields can induce particle noninertial motion. We explore this intriguing phenomenon with a degenerated Fermionic atomic gas subject to a two-dimensional synthetic SU(2) non-Abelian gauge field. We reveal the spin Hall nature of the noninertial dynamic as well as its anisotropy in amplitude and frequency due to the spin texture of the system. We finally draw the similarities and differences of the observed wave packet dynamic and the celebrated Zitterbewegung effect of the relativistic Dirac equation.

cond-mat.quant-gas↗

arXiv2022

Homodyne detection of a two-photon resonance assisted by cooperative emission

Focusing on the transient regime, we explore atomic two-photon spectroscopy with self-aligned homodyne interferometry in a $Λ$-system with large optical depth. The two light sources at the origin of the interference are the single-photon transient transmission of the probe, and the slow light of the electromagnetically induced transparency. By switching off the probe laser abruptly (flash effect), the transient transmission signal is reinforced by cooperativity, showing enhanced sensitivity to the two-photon frequency detuning. If the probe laser is periodically switched on and off, the amplitude of the transmission signal varies and remains large even for high modulation frequency. This technique has potential applications in sensing, such as magnetometry and velocimetry, and in coherent population trapping clocks.

quant-ph↗