Anisotropic Quantum Inertial Sensor Using Semi-Dirac Lattice and Cryogenically Stabilized BEC Interferometry

We present a hybrid quantum inertial sensor, that integrates a high-precision Rb-87 Bose–Einstein condensate (BEC) interferometer with the stable anisotropic optical properties of semi-Dirac fermions in ZrSiS thin films. Two orthogonally oriented ZrSiS films (operated at 1. 8–2. 1 K in a superfluid helium bath), serve as a fixed, high-stability polarimetric reference frame. Their intrinsic birefringence, arising from the large static optical conductivity anisotropy (Δσ ∼ 10²–10³ Ω⁻¹ cm⁻¹) of the semi-Dirac band structure, defines crystal-fixed coordinate axes. This enables gimbal-free decomposition of the acceleration vector measured by the co-located BEC into the sensor platform (body) frame, eliminating the need for a separate gyroscope or mechanical gimbal for body-to-navigation-frame transformations in dead-reckoning navigation. The Rb-87 BEC provides the absolute, isotropic acceleration measurement, with a projected sensitivity of 10^-9–10^-10 g/√Hz (BEC atom-shot-noise limited). Acceleration-induced carrier momentum shifts, and elasto-optical modulation in the ZrSiS films are negligible at target sensitivities, and are not required for operation. The architecture cleanly separates roles: the BEC delivers metrological precision while the ZrSiS films supply a robust, low-drift optical orientation reference. The manuscript includes a detailed noise budget, cryogenic thermal isolation analysis, systematic error mitigation, and a realistic four-phase experimental pathway. Key challenges addressed are thin-film anisotropy retention, reference-frame angular stability, and nanokelvin BEC operation in proximity to a 2 K lattice domain. This hybrid approach offers a promising route toward compact, high-stability quantum inertial sensors for GPS-denied navigation, submarine/underground exploration, and precision geodesy. Keywords quantum sensing, semi-Dirac materials, ZrSiS, atom interferometry, Bose-Einstein condensate, inertial navigation, gimbal-free orientation reference, topological quantum materials, hybrid quantum systems, polarimetric sensing