Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

General Signal Model and Capacity Limit for Rydberg Quantum Information System

Jieao Zhu, Linglong Dai

TL;DR

This work addresses the lack of dynamic signal modeling for Rydberg atomic receivers, where existing static, steady-state models fail to describe time-varying RF signals. It develops a general dynamic model by applying small-signal perturbation to the quantum master equation, yielding closed-form Laplace-domain transfer functions $T_{kl}(s)$ that map RF perturbations to density-matrix variations and optical output, and introduces the quantum transconductance $g_q(x,i\omega)$ to describe RF-to-photocurrent conversion. Key contributions include Doppler-averaged transfer functions $T_{kl}^{\rm D}(s)$, a Doppler-aware intrinsic gain $\kappa(i\omega)$, and a BBR-noise analysis via a spatial coherence factor $\zeta(\ell)$, supported by SISO and MIMO simulations showing potential performance gains over classical receivers. The results establish a rigorous, physics-based framework for dynamic quantum RF sensing and communication, enabling accurate end-to-end baseband modeling and capacity analyses while highlighting fundamental noise limits set by blackbody radiation and quantum projection noise.

Abstract

Rydberg atomic receivers represent a transformative approach to achieving high-sensitivity, broadband, and miniaturized radio frequency (RF) reception. However, existing static signal models for Rydberg atomic receivers rely on the steady-state assumption of atomic quantum states, which cannot fully describe the signal reception process of dynamic signals. To fill in this gap, in this paper, we present a general model to compute the dynamic signal response of Rydberg atomic receivers in closed form. Specifically, by applying small-signal perturbation techniques to the quantum master equation, we derive closed-form Laplace domain transfer functions that characterize the receiver's dynamic responses to time-varying signal fields. To gain more insights into the quantum-based RF-photocurrent conversion process, we further introduce the concept of quantum transconductance that describes the quantum system as an equivalent classical system. By applying quantum transconductance, we quantify the influence of in-band blackbody radiation (BBR) noise on the atomic receiver sensitivity. Extensive simulations for Rydberg atomic receivers validate the proposed signal model, and demonstrate the possibility of quantum receivers to outperform classical electronic receivers through the improvement of quantum transconductance.

General Signal Model and Capacity Limit for Rydberg Quantum Information System

TL;DR

This work addresses the lack of dynamic signal modeling for Rydberg atomic receivers, where existing static, steady-state models fail to describe time-varying RF signals. It develops a general dynamic model by applying small-signal perturbation to the quantum master equation, yielding closed-form Laplace-domain transfer functions that map RF perturbations to density-matrix variations and optical output, and introduces the quantum transconductance to describe RF-to-photocurrent conversion. Key contributions include Doppler-averaged transfer functions , a Doppler-aware intrinsic gain , and a BBR-noise analysis via a spatial coherence factor , supported by SISO and MIMO simulations showing potential performance gains over classical receivers. The results establish a rigorous, physics-based framework for dynamic quantum RF sensing and communication, enabling accurate end-to-end baseband modeling and capacity analyses while highlighting fundamental noise limits set by blackbody radiation and quantum projection noise.

Abstract

Rydberg atomic receivers represent a transformative approach to achieving high-sensitivity, broadband, and miniaturized radio frequency (RF) reception. However, existing static signal models for Rydberg atomic receivers rely on the steady-state assumption of atomic quantum states, which cannot fully describe the signal reception process of dynamic signals. To fill in this gap, in this paper, we present a general model to compute the dynamic signal response of Rydberg atomic receivers in closed form. Specifically, by applying small-signal perturbation techniques to the quantum master equation, we derive closed-form Laplace domain transfer functions that characterize the receiver's dynamic responses to time-varying signal fields. To gain more insights into the quantum-based RF-photocurrent conversion process, we further introduce the concept of quantum transconductance that describes the quantum system as an equivalent classical system. By applying quantum transconductance, we quantify the influence of in-band blackbody radiation (BBR) noise on the atomic receiver sensitivity. Extensive simulations for Rydberg atomic receivers validate the proposed signal model, and demonstrate the possibility of quantum receivers to outperform classical electronic receivers through the improvement of quantum transconductance.

Paper Structure

This paper contains 28 sections, 1 theorem, 80 equations, 12 figures, 2 tables.

Table of Contents

  1. Introduction
  2. Prior works
  3. Our contributions
  4. Organization and Notation
  5. System Model
  6. Overall system description
  7. Quantum mechanisms for Rydberg atoms
  8. Static DC and dynamic AC responses
  9. Dynamic Models
  10. Reformulation of the master equation
  11. Small-signal transfer function
  12. Incorporating the thermal Doppler effect
  13. Quantum transconductance
  14. Alternative definition of the Rydberg intrinsic gain
  15. Noise Models
  16. ...and 13 more sections

Key Result

Theorem 1

For any given $s\in\mathbb{C}$, the Doppler-averaged transfer function $T_{k\ell}^{\rm D}(s)$ equals the 2nd component of the following expression where $(\lambda_j(s), {\bf s}_j(s), {\bf t}_j(s))$ are respectively the $j$-th eigenvalue, right eigenvector, and left eigenvector of the matrix $(s{\bf I}-{\bf C}_0)^{-1}{\bf C}_v$. The expectation $\mathbb{E}_X[\cdot]$ is taken with respect to a stan

Figures (12)

  • Figure 1: Signal reception pipeline of Rydberg atomic receivers. The Rydberg atoms act as an electro-optical mixer that down-converts the passband RF signal to the IF. The Rydberg atomic receiver is composed of one atomic vapor cell and the subsequent analog-to-digital conversion (A/D) and digital signal processing (DSP) devices.
  • Figure 2: DC probe transmission $\bar{P}/P_0$ as a function of the LO E-field $E_{\rm LO}\,{\rm [V/m]}$ ($T=0\,{\rm K}$). Curves of the same color are respectively the $\bar{P}/P_0$-$E_{\rm LO}$ curve (solid) and its derivative (dashed). The value of $\gamma_4$ is proportionally adjusted with $\gamma_3$ during simulation. These curves show a strong dependence of the DC gain $\kappa$ on the inverse of Rydberg state lifetimes $\gamma_{3,4}$.
  • Figure 3: Coherence factor $\zeta(\ell)$ and normalized noise correlation $R_{\rm n}(\ell, {\mathrm{i}} 0)$ as a function of normalized interaction length $\ell$. The fluctuation of $\zeta(\ell)$ in the large-$\ell$ regime is caused by the long-tail effect in the noise correlation.
  • Figure 4: Analog signal processing pipeline for Rydberg atomic receivers: Photo-atomic interaction, transimpedance amplification (TIA), and IQ down-conversion.
  • Figure 5: Noise factor and power gain of the quantum LNA (qLNA) and the transimpedance amplifier (TIA) as a function of the PD bias resistor $R_s$.
  • ...and 7 more figures

Theorems & Definitions (4)

  • Theorem 1: Analytical dynamic response
  • Remark 1
  • Remark 2
  • Remark 3