Impairments Characterisation for Deployable Rydberg Atomic Quantum Receivers

Abstract

Rydberg atomic quantum receivers (RAQRs) recently gained significant interest. However, their impairments characterisation, which is critical for practical deployments, remains under-examined. In this paper, we evaluate how deviations in five operational parameters (atomic density, EIT linewidth, local oscillator (LO) amplitude, laser frequency, and probe power) impact the signal-to-noise ratio (SNR), third-order intercept (IIP3), 1 dB compression $\left(P_{1 \mathrm{~dB}}\right)$, and spurious-free dynamic range (SFDR). By expanding the atomic coherence in powers of signal amplitude, we classify deviation responses into three distinct categories. All three categories remain robust under Doppler broadening from $200 \mu \mathrm{~K}$ to 300 K. Crucially, the LO amplitude falls into a regime where IIP3 degrades linearly while the SNR changes only quadratically. As this linearity loss can go easily undetected during standard sensitivity checks, LO amplitude requires tightest control (+7% tolerance). We further derive two closed-form relationships governing the RAQRs. The first one features how much the SNR can be improved as atomic density increases, yielding improvement equal to or less than 20 dB for every tenfold increase in atomic density. The second one shows that a laser frequency drift of about 55 kHz reduces the SNR by an order of 1 dB.