Quantum vs. Classical Complementary PNT

Due to its accuracy and availability, dependency on GPS has become commonplace in all domains, from civil aviation and critical infrastructure to cellular communications, global finance, and the military. However, to maintain robust positioning, navigation, and timing (PNT) capabilities, it is crucial to develop techniques and technologies that do not rely on GPS. The field of complementary PNT aims to provide PNT solutions that are complementary or alternative to GPS, which is often treated as the primary source of PNT.

Complementary PNT may be needed when GPS signals are unavailable (e.g., underground or underwater), in the event of GPS interference, or in case of GPS satellite failures. Currently, no complementary PNT capabilities can offer the same level of global availability and accuracy as GPS, but many techniques serve as critical complements or alternatives to GPS in a wide range of applications.

Emerging quantum sensors are often cited as promising technologies to enable complementary PNT solutions with improved capabilities or reduced cost. Atomic clocks are already widely used for precision timing, and emerging quantum inertial sensors, magnetometers, and gravimeters may also play a role for positioning and navigation as they are developed further. However, quantum sensors are just a subset of the broader complementary PNT ecosystem, which comprises a wide range of sensing and timing technologies with varying technological maturity and attributes. To determine the optimal solution for a given complementary PNT need, it is necessary to consider both quantum and classical technologies and analyze their advantages and limitations. This report provides a summary of various complementary PNT techniques and identifies where quantum technologies are likely to fit within the broader complementary PNT ecosystem.