The mysterious X-37B space-plane — the U.S. military's orbital test vehicle — "serves partly as a platform for cutting-edge experiments," writes Space.com
And "one of these experiments is a potential alternative to GPS that makes use of quantum science as a tool for navigation: a quantum inertial sensor."
This technology could revolutionize how spacecraft, airplanes, ships and submarines navigate in environments where GPS is unavailable or compromised. In space, especially beyond Earth's orbit, GPS signals become unreliable or simply vanish. The same applies underwater, where submarines cannot access GPS at all. And even on Earth, GPS signals can be jammed (blocked), spoofed (making a GPS receiver think it is in a different location) or disabled — for instance, during a conflict... Traditional inertial navigation systems, which use accelerometers and gyroscopes to measure a vehicle's acceleration and rotation, do provide independent navigation, as they can estimate position by tracking how the vehicle moves over time... Eventually though, without visual cues, small errors will accumulate and you will entirely lose your positioning...
At very low temperatures, atoms obey the rules of quantum mechanics: they behave like waves and can exist in multiple states simultaneously — two properties that lie at the heart of quantum inertial sensors. The quantum inertial sensor aboard the X-37B uses a technique called atom interferometry, where atoms are cooled to the temperature of near absolute zero, so they behave like waves. Using fine-tuned lasers, each atom is split into what's called a superposition state, similar to Schrödinger's cat, so that it simultaneously travels along two paths, which are then recombined.
Since the atom behaves like a wave in quantum mechanics, these two paths interfere with each other, creating a pattern similar to overlapping ripples on water. Encoded in this pattern is detailed information about how the atom's environment has affected its journey. In particular, the tiniest shifts in motion, like sensor rotations or accelerations, leave detectable marks on these atomic "waves". Compared to classical inertial navigation systems, quantum sensors offer orders of magnitude greater sensitivity. Because atoms are identical and do not change, unlike mechanical components or electronics, they are far less prone to drift or bias. The result is long duration and high accuracy navigation without the need for external references.
The upcoming X-37B mission will be the first time this level of quantum inertial navigation is tested in space.
The article points out that a quantum navigation system could be crucial "for future space exploration, such as to the Moon, Mars or even deep space," where autonomy is key and when signals from Earth are unavailable.
"While quantum computing and quantum communication often steal headlines, systems like quantum clocks and quantum sensors are likely to be the first to see widespread use."
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