Q-TAGG: Quantum Trapped-Atom Gravity Gradiometer

The Quantum Trapped-Atom Gravity Gradiometer (Q‑TAGG), developed at Los Alamos National Laboratory, is a compact sensing platform designed to achieve extended atom interferometer interrogation times without the height required by conventional free‑fall instruments. Ultracold atoms remain guided during interferometric evolution, providing a pathway to increased sensitivity within a compact architecture. The platform uses spatially multiplexed sensing, with multiple atomic sensing sites across one or more sensor heads operated under common or phase-referenced interrogation conditions. The resulting site-resolved phase measurements support estimation of spatially varying gravitational signals and differential processing of correlated disturbances. By combining a compact guided-atom architecture, spatial multiplexing, and suppression of correlated disturbances, Q‑TAGG provides a pathway toward deployable quantum sensing for subsurface imaging, resource exploration, safeguards, and security applications.

Overview

Q‑TAGG measures spatial variations in gravity using atom interferometric phase measurements acquired at distinct sensing locations. Optical pulses split, redirect, and recombine guided atomic wave packets. The resulting interferometric phase is sensitive to gravity and inertial acceleration along the relevant measurement axis, as well as to optical, trapping, and other instrument‑related contributions. Multiple sensing locations are interrogated during a common measurement cycle, producing a synchronized spatial data set. After calibration and differential processing, relative phase measurements are used to estimate gravity field gradients and related spatial modes. The architecture also supports multiple spatially separated sensor heads for longer‑baseline or distributed measurements.

Technology Description

Each sensor head prepares one or more ultracold atomic ensembles at respective locations within an optical guiding or trapping structure. The atomic ensembles are subjected to a common or phase‑referenced interferometric pulse sequence and are read out on a site‑resolved basis. Guiding the atoms during interrogation permits longer interaction times in a lower profile system than would be required for an equivalent free‑fall distance. Because the sensing locations share common timing and an optical phase reference, their outputs are analyzed jointly. Differential and global estimation approaches are used to extract relative phase information, evaluate spatial consistency, and estimate gravity gradient signals. Common interrogation also suppresses disturbances correlated among the sensing locations. Multiple sensor heads can be arranged in linear, planar, or distributed configurations, providing flexibility in the selection of baselines and measurement geometries. Multi-axes sensing arrangements can also access additional components of the gravity gradient tensor.

Advantages

• Guided atom interferometer operation supports extended interrogation without a tall free‑fall structure.
• Spatial multiplexing provides multiple simultaneous phase samples within each measurement cycle.
• Joint processing of multi‑site data supports gradient estimation, consistency checks, and systematic error diagnostics.
• Common or phase‑referenced interrogation reduce sensitivity to correlated disturbances.
• Atom‑based phase measurements support a repeatable, model‑based calibration framework.
• Configurable sensor arrangements support different baselines and measurement geometries.

Market Applications

• Geothermal and resource exploration (gravity gradient surveys of geological boundaries and density contrasts).
• Subsurface imaging and infrastructure (detection and characterization of tunnels, voids, buried structures, and changes around engineered sites).
• Environmental and storage monitoring (repeat surveys of groundwater, subsurface reservoirs, carbon storage sites, and changing mass distributions).
• Security and nuclear safeguards (passive detection or monitoring of gravity anomalies associated with dense objects).
• Mobile surveying and navigation (moving platform gravity mapping and gravity-referenced positioning following dynamic validation).
• Space-based Earth observation (gravity mapping for geodesy, hydrology and climate monitoring).

TRL 4

U.S. Patent pending

LA-UR-26-29523

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