LO-Free Phase and Amplitude Recovery of an RF Signal with a DC-Stark-Enabled Rydberg Receiver
2026-03-31 • Information Theory
Information Theory
AI summaryⓘ
The authors developed a theoretical method to measure both the strength and phase of a single radio frequency (RF) signal using Rydberg atoms without needing an extra local oscillator signal. They apply a steady electric bias to the atoms, which creates a new interaction pathway that encodes the signal's phase into measurable light harmonics. By analyzing these harmonics, they can directly extract the signal's phase and amplitude, and they identify optimal settings for the bias to improve accuracy. They also explore how uneven bias affects measurement quality and confirm their theory with numerical examples. Overall, the work shows a simpler way to get detailed RF signal information using Rydberg atoms alone.
Rydberg atomsRF signalcarrier phaseStark effectlocal oscillatorprobe harmonicfour-level HamiltonianFloquet theoryphase estimationDC bias
Authors
Vladislav Katkov, Nikola Zlatanov
Abstract
We present a theoretical framework for recovering the amplitude and carrier phase of a single received RF field with a Rydberg-atom receiver, without injecting an RF local oscillator (LO) into the atoms. The key enabling mechanism is a static DC bias applied to the vapor cell: by Stark-mixing a near-degenerate Rydberg pair, the bias activates an otherwise absent upper optical pathway and closes a phase-sensitive loop within a receiver driven only by the standard probe/coupling pair and the received RF field. For a spatially uniform bias, we derive an effective four-level rotating-frame Hamiltonian of Floquet form and show that the periodic steady state obeys an exact harmonic phase law, so that the $n$th probe harmonic carries the factor $e^{inΦ_S}$. This yields direct estimators for the signal phase and amplitude from a demodulated probe harmonic, with amplitude recovery obtained by inverting an injective harmonic response map. In the high-SNR regime, we derive explicit RMSE laws and use them to identify distinct phase-optimal and amplitude-optimal bias-controlled mixing angles, together with a weighted joint-design criterion and a balanced compromise angle that equalizes the fractional phase and amplitude penalties. We then extend the analysis to nonuniform DC bias through quasistatic spatial averaging and show that bias inhomogeneity reduces coherent gain for phase readout while also reshaping the amplitude-response slope. Numerical examples validate the phase law, illustrate response-map inversion and mixing-angle trade-offs, and quantify the penalties induced by bias nonuniformity. The results establish a minimal route to coherent Rydberg reception of a single RF signal without an auxiliary RF LO in the atoms.