quantum compass

Quantum 'compass' enables global navigation without satellites and GPS

Image credit: imperial college london

A quantum accelerometer has been developed that could pave the way for global navigation technologies, without having to rely on satellites and GPS technology.

The device, built by Imperial College London and Glasgow-based photonics company M Squared, uses an accelerometer to measure how an object’s velocity changes over time. Using this, and the starting point of the object, the new position can be calculated.

Most navigation today relies on global navigation satellite systems, such as GPS, which send and receive signals from satellites orbiting the Earth. The quantum accelerometer is a self-contained system that does not rely on any external signals. This technology is useful because satellite signals can become unavailable due to blockages such as tall buildings, or can be jammed, imitated or denied - preventing accurate navigation. One day of denial of the satellite service would cost the UK an estimated £1bn.

Accelerometers have existed for decades, and are widely used in everyday technologies such as mobile phones and laptops. However, these devices cannot maintain their accuracy over longer periods without an external reference.

The quantum accelerometer relies on the precision and accuracy possible by measuring properties of supercooled atoms. At extremely low temperatures, the atoms exhibit quantum behaviour, demonstrating properties of both waves and particles.

Dr Joseph Cotter, from the Centre for Cold Matter at Imperial, said: “When the atoms are ultra-cold we have to use quantum mechanics to describe how they move, and this allows us to make what we call an atom interferometer.”

As the atoms fall, their wave properties are affected by the acceleration of the vehicle. Using an ‘optical ruler’, the accelerometer can measure these minute changes very accurately. To make the atoms cold enough, and to probe their properties as they respond to acceleration, very powerful lasers that can be precisely controlled are needed.

Dr Joseph Thom, Quantum Technology Scientist at M Squared, said: “As part of our work in commercialising cold atom quantum sensors, we developed a universal laser system for cold atom-based sensors that we have already implemented in our quantum gravimeter. This laser is now also used in the quantum accelerometer we have built in collaboration with Imperial. Combining high power, exceptionally low noise and frequency tunability, the laser system cools the atoms and provides the optical ruler for the acceleration measurements.”

The current system is designed for navigation of large vehicles, such as ships and even trains. However, the principle can also be used for fundamental science research, such as in the search for dark energy and gravitational waves, which the Imperial team are also working on.

Professor Ed Hinds, from the Centre for Cold Matter at Imperial College, said: “I think it’s tremendously exciting that this quantum technology is now moving out of the basic science lab and being applied to problems in the wider world, all from the fantastic sensitivity and reliability that you can only get from these quantum systems.”

Dr Graeme Malcolm, founder and CEO of M Squared, said: “This commercially viable quantum device, the accelerometer, will put the UK at the heart of the coming quantum age. The collaborative efforts to realise the potential of quantum navigation illustrate Britain’s unique strength in bringing together industry and academia - building on advancements at the frontier of science, out of the laboratory to create real-world applications for the betterment of society.”

In August the UK government announced it would spend £92m on funding its own satellite navigation system after being shut out from being involved in development on the EU’s Galileo programme. 

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