arXiv subjects

Darmindra Arumugam

Publications and source records attributed to Darmindra Arumugam.

9 recordsLinked to original sources

arXiv2026

Giant Resonant Reflection Gain from Injection-Induced Quenching in a Tunnel Diode

Negative-resistance microwave oscillators can simultaneously sustain autonomous oscillations and coherently scatter electromagnetic waves, enabling active reflection beyond conventional linear amplification. Here we demonstrate giant resonant reflection gain from synchronization-induced phase localization in a self-sustained tunnel diode oscillator operating near 2.96 GHz. Weak resonant RF injection drives a transition from a broadband free running state to a phase localized narrowband reflected carrier. The resulting reflected enhancement reaches 83.1dB relative to the injected signal and is accompanied by greater than order of magnitude linewidth collapse, nonlinear injection pulling, and a synchronization bandwidth of 15.84 kHz. Time resolved spectrograms directly resolve injection locking and frequency entrainment, while noisy Stuart Landau simulations reproduce the observed spectral concentration and detuning dependent gain roll off near the Hopf instability. Artificially increasing phase diffusion with broadband bias noise suppresses the reflected enhancement, confirming synchronization-induced quenching of phase fluctuations as the origin of the giant coherent reflection gain.

physics.app-ph↗

arXiv2026

Microwave Power-to-Frequency Transduction via Injection Pulling of a Self-Sustained Oscillator for Rydberg Superheterodyne Sensing

A Rydberg superheterodyne sensing architecture is demonstrated in which a self-sustained oscillator (SSO) serves as a dynamically perturbed local oscillator (LO) for microwave detection. The SSO is realized by a phase-controlled radio-frequency (RF) feedback loop coupled to a transverse electromagnetic (TEM) cavity containing a Rydberg vapor cell. The system operates near 5.49 GHz using a cesium ladder scheme with an 852 nm probe and 510 nm coupling laser addressing the 6S to 6P to 49D transition, with microwave coupling to the 50P state. Injection of a microwave signal pulls the SSO frequency via nonlinear dynamics, converting input power into a measurable frequency shift read out optically as a Rydberg probe intermediate-frequency (IF) signal. The response follows Adler-type injection-pulling behavior, with continuous IF tuning with input power. A peak responsivity of 35 kHz/dB is observed, with enhanced sensitivity near synchronization. These results demonstrate power-to-frequency transduction using a dynamically perturbed LO combined with Rydberg atomic readout.

quant-ph↗

arXiv2026

Polarization-Aware DoA Detection Relying on a Single Rydberg Atomic Receiver

A polarization-aware direction-of-arrival (DoA) detection scheme is conceived that leverages the intrinsic vector sensitivity of a single Rydberg atomic vapor cell to achieve quantum-enhanced angle resolution. Our core idea lies in the fact that the vector nature of an electromagnetic wave is uniquely determined by its orthogonal electric and magnetic field components, both of which can be retrieved by a single Rydberg atomic receiver via electromagnetically induced transparency (EIT)-based spectroscopy. To be specific, in the presence of a static magnetic bias field that defines a stable quantization axis, a pair of sequential EIT measurements is carried out in the same vapor cell. Firstly, the electric-field polarization angle is extracted from the Zeeman-resolved EIT spectrum associated with an electric-dipole transition driven by the radio frequency (RF) field. Within the same experimental cycle, the RF field is then retuned to a magnetic-dipole resonance, producing Zeeman-resolved EIT peaks for decoding the RF magnetic-field orientation. This scheme exhibits a dual yet independent sensitivity on both angles, allowing for precise DoA reconstruction without the need for spatial diversity or phase referencing. Building on this foundation, we derive the quantum Fisher-information matrix (QFIM) and obtain a closed-form quantum Cramér-Rao bound (QCRB) for the joint estimation of polarization and orientation angles. Finally, simulation results spanning various quantum parameters validate the proposed approach and identify optimal operating regimes. With appropriately chosen polarization and magnetic-field geometries, a single vapor cell is expected to achieve sub-0.1$^\circ$ angle resolution at moderate RF-field driving strengths.

cs.IT↗

arXiv2026

Rydberg-State Hopping in a Wavemeter-Locked Dissipative Time-Crystal System

Rydberg-state hopping is demonstrated in a wavemeter-locked two-photon rubidium system (Rb D2 probe at 780 nm and 480 nm coupler), enabling rapid and repeatable switching between the 65S1/2 and 63D5/2 states without cavity or frequency-comb stabilization. A Fizeau-interferometer wavemeter provides the error signal for a digital feedback loop that simultaneously stabilizes the coupler and commands discrete Rydberg-state changes. The lock achieves sub MHz frequency stability and acquisition rates up to 6.5 GHz/s (0.4283 GHz engaged in 66 ms), extrapolating to ~0.93 s for a ~6 GHz 65S to 63D transition. Time resolved spectra reveal reemergent dissipative time-crystal oscillations after each hop, with distinct state dependent fundamentals and harmonics. This approach addresses the need for dynamically reconfigurable Rydberg state control for on resonant multi band field detection, while the DTC frequency reconfigurability enables adaptive, low frequency E field sensing in compact, cavity free architectures.

physics.atom-ph↗

arXiv2026

Stabilization of Rydberg Dissipative Time Crystals Using a Scanning Fabry Perot Interferometer Transfer Lock

Stabilization of laser frequencies is critical for sensitive Rydberg measurements, including in applications such as dissipative time crystal (DTC) dynamics, yet conventional approaches often require complex or costly hardware. We demonstrate a compact, low cost stabilization method using a scanning Fabry Perot interferometer (SFPI) to transfer lock a 960nm coupler laser to an 852nm probe. The lock suppresses coupler multi MHz free running drift and improves the Allan deviation by up to an order of magnitude, reaching <75kHz at 66s. Applied to DTC oscillations using a Rb 2 photon D2 transition, the second harmonic generated 480nm (from 960nm lock) reduces DTC frequency drift from >20kHz to a few kHz and lowers instability by more than an order of magnitude with a minimum Allan deviation of 0.2kHz at <10s. These results establish SFPI-based transfer locking as a practical and accurate approach for scalable multi laser Rydberg experiments requiring long-term stability in a compact and low cost system.

physics.atom-ph↗

arXiv2025

Injection locking of Rydberg dissipative time crystals

Non-equilibrium Rydberg gases exhibit exotic many-body phases stabilized by the interplay of coherent interactions and dissipation. Strong Rydberg interactions drive sustained limit cycle oscillations, whose robustness, long-range temporal order, and spontaneous time-translation symmetry breaking establish a dissipative time crystal (DTC). Collective self-entrainment in driven ensembles leads to global synchronization and a dominant oscillation frequency. Here, injection locking of a Rydberg DTC is demonstrated using a radio-frequency (RF) electric field that gradually pulls the intrinsic oscillation toward the injected frequency. Above a critical threshold, full synchronization occurs, with the locking bandwidth scaling linearly with RF amplitude. This includes synchronization of higher-order harmonics, revealing entrainment of the system nonlinear temporal dynamics. The phenomenon parallels injection locking in classical nonlinear systems, but emerges here in a strongly interacting quantum medium. This approach establishes a new method for stabilizing and controlling quantum temporal order, with applications in precision sensing, quantum metrology, and timekeeping.

quant-ph↗

arXiv2025

Stark-modulated Rydberg dissipative time crystals at room-temperature applied to sub-kHz electric-field sensing

Out-of-equilibrium Rydberg gases exhibit emergent many-body phases due to mode competition. Sustained limit cycle oscillations (OSC) emerge when driven by B-fields at room-temperature, forming robust Rydberg dissipative time crystals (DTC). These driven-dissipative Rydberg DTC have recently been shown to develop an effective transition centered at the OSC frequency (-10dB bandwidth of ~1.7kHz, centered at 9.8kHz). Weak RF signals injected within this emergent transition perturb and emerge on the OSC spectrum, from which sensitive and high-resolution sensing of E-fields (~1.6-2.3 uVcm-1Hz-1/2) near the OSC frequencies can be achieved. In this article, it is demonstrated that DC and AC Stark fields in the sub-kHz regime can be used effectively to shift (DC) or modulate (AC) the OSC frequency of Rydberg DTC at room-temperature. The AC-Stark driven modulation of the OSC is shown as an effective technique to sense weak AC E-fields in the sub-kHz regime. With a modest setup, a sensitivity of ~7.8 uVcm-1Hz-1/2 for AC signals at 300Hz (~8.7x improvement over state-of-art Rydberg atom techniques), and high-resolution detection to as low as sub-Hz is demonstrated. This approach enables the development of ultra-compact, extremely low-frequency E-field detectors for applications in remote sensing, communications, navigation, and bio-medical technologies.

physics.atom-ph↗

arXiv2025

Electric-field sensing with driven-dissipative time crystals in room-temperature Rydberg vapor

Mode competition in nonequilibrium Rydberg gases enables the exploration of emergent many-body phases. This work leverages this emergent phase for electric field detection at room temperature. Sensitive frequency-resolved electric field measurements at very low-frequencies (VLF) are of central importance in a wide range of applications where deep-penetration is required in communications, navigation and imaging or surveying. The long wavelengths on order of 10-100 km (3-30 kHz) limit the efficiency, sensitivity, and bandwidth of compact classical detectors that are constrained by the Chu limit. Rydberg-atom electrometers are an attractive approach for microwave electric-field sensors but have reduced sensitivity at lower-frequencies. Very recent efforts to advance the standard Rydberg-atoms approach is based on DC electric-field (E-field) Stark shifting and have resulted in sensitivities between 67.9-2.2 uVcm-1Hz-1/2 (0.1-10 kHz) by fine optimization of the DC E-field. A major challenge in these approaches is the need for embedded electrodes or plates due to DC E-field Stark screening effect, which can perturb coupling of VLF signals when injected from external sources. In this article, it is demonstrated that state-of-art sensitivity (~1.6-2.3 uVcm-1Hz-1/2) can instead be achieved using limit-cycle oscillations in driven-dissipative Rydberg atoms by using a magnetic field (B-field) to develop mode-competition between nearby Rydberg states. The mode-competition between nearby Rydberg-states develop an effective transition centered at the oscillation frequency capable of supporting external VLF E-field coupling in the ~10-15kHz regime without the requirement for fine optimization of the B-field magnitude.

physics.atom-ph↗

arXiv2024

Remote sensing of soil moisture using Rydberg atoms and satellite signals of opportunity

Spaceborne radar remote sensing of the earth system is essential to study natural and man-made changes in the ecosystem, water and energy cycles, weather and air quality, sea level, and surface dynamics. A major challenge with current approaches is the lack of broad spectrum tunability due to narrow band microwave electronics, that limit systems to specific science variable retrievals. This results in a significant limitation in studying dynamic coupled earth system processes such as surface and subsurface hydrology, where broad spectrum radar remote sensing is needed to sense multiple variables simultaneously. Rydberg atomic sensors are highly sensitive broad-spectrum quantum detectors that can be dynamically tuned to cover micro-to-millimeter waves with no requirement for band-specific electronics. Rydberg atomic sensors can use existing transmitted signals such as navigation and communication satellites to enable remote sensing. We demonstrate remote sensing of soil moisture, an important earth system variable, via ground-based radar reflectometry with Rydberg atomic systems. To do this, we sensitize the atoms to XM satellite radio signals and use signal correlations to demonstrate use of these satellite signals for remote sensing of soil moisture. Our approach provides a step towards satellite-based broad-spectrum Rydberg atomic remote sensing.

physics.app-ph↗