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Using quantum physics, researchers are on the cusp of creating sensors that will see further, deeper, and around corners.
Since its inception at the start of the 20th Century, quantum physics has changed how we see the microscopic world. Thanks to advances in sensor technology, this revolutionary and counter-intuitive branch of physics could change our view of the everyday world.
Quantum sensors could be employed in medical scanners, self-driving vehicles, weather pattern assessments, and seismic activity analysis. Therefore, our understanding of the sometimes strange subatomic world is poised to change our everyday lives forever.
Such sensors manipulate aspects of quantum mechanics such as entanglement — the idea that a particle change can instantly influence its entangled partner despite the distance between them — and the energy levels that electrons can occupy in atoms to assess the environment around them in devastatingly imaginative ways.
Going Deeper Underground
Beneath the surface of urban areas is a mass of utility infrastructures such as pipes, cables and sewers, transport utilities, and even mine shafts, old foundations, and sinkholes.
Public work in these areas is not just delayed and made more expensive by these buried obstacles, they can often pose a legitimate danger to workers and the general public. There are sensors that can probe beneath the ground without penetration. However, technology such as Ground Penetrating Radars (GPR) can only probe a few centimeters beneath the surface before its signal is stifled and pipes and cables can be meters deep.
One possible alternative comes from the quantum realm.
Quantum technology could create a gravity sensor which can detect much deeper beneath the surface. Theoretically, such a sensor could probe to the center of the Earth. Quantum gravity sensors are more useful as they do not send a signal through the ground. Instead, they measure density variations by using a facet of quantum physics known as ‘superposition.’
Superposition arises from particles' wave-like behavior and means that a quantum system can technically exist in two contradictory states at once. This contradictory existence continues until measurements are made.
A quantum gravity sensor would drop a cloud of supercooled atoms in a superposition of two different states into an area to be probed. Changes in the atomic cloud and how it passes through the ground are then observed, giving density measurements to the operators above the surface. These changes in density indicate buried obstacles such as pipes and cables, and voids caused by tunnels.
The application of such a system goes way beyond assisting in road works. A quantum gravity sensor could be used in volcanic activity areas to monitor lava flow and help geologists uncover water and mineral deposits. Self-piloted ships could also use the system to navigate and probe the depths of the ocean.
In the UK, the University of Birmingham has teamed with engineering services firm RSK on ‘Gravity Pioneer’ a project that aims to make quantum gravity sensors a reality.
Just Around the Corner
Self-navigation is a major problem for the car industry. The Insurance Institute for Highway Safety recently produced a report concluding that only one-third of crashes would be avoided by autonomous cars despite being impervious to human error, distraction or driver incapacitation.
The tendency of light to refract off walls and other surfaces can be used to build 3D images, as long as the sensors used to detect light are sensitive enough. This rebounded light could allow self-driving cars to ‘see’ around corners. More sensitive sensors could also allow these vehicles to see through fog and smoke.
Improving the sensitivity of quantum sensors is one of the primary goals of scientists at the Pritzker School of Molecular Engineering (PME) at the University of Chicago.
The team believes that using a physics phenomenon called non-Hermitian dynamics can prevent a string of photonic cavities that prevent light from ‘leaking’ from sensors. This results in an improvement in sensitivity without expending extra energy or vastly increasing the photon collection area of sensors.
Video Credit: University of Birmingham/YouTube.com
Right on Time
While quantum computers and even a quantum internet could be on the horizon, these improved information networks will rely heavily on accurate synchronized time-keeping. All the innovations discussed above will also hinge on hyper-accurate clocks over a geographically distributed network.
This precision timing is currently achieved using atomic clocks, which keep time with quantum phenomena and the randomness that lies at the heart of this field of physics. As such, they were probably the first piece of ‘quantum tech’ to become widely available and probably warrant a mention in any discussion about such advance.
In addition to this, atomic clocks form the foundation of the Global Positioning Systems (GPS) technology that our satnavs and mobile phones rely on every day.
Atomic clocks combine a quartz crystal oscillator with an ensemble of atoms to achieve greater stability. To give you an idea of how accurate this makes them in comparison to a wristwatch that uses a quartz crystal oscillator alone, NASA’s Deep Space Atomic Clock will be off by less than a nanosecond after four days and less than a microsecond — one-millionth of a second — after 10 years. This is equal to around one second every 10 million years.
Atomic clocks operate because electrons can only occupy certain energy levels while orbiting an atomic nucleus. They ‘step’ from one level to another by absorbing or emitting a photon of specific energy.
Atomic clocks have incredible accuracy as photons come in precise ‘packets’ of energy and it takes an exact amount of energy to make an electron step up.
However, that does not mean atomic clocks cannot be improved. NASA-funded researchers are attempting to use entanglement to create the most precise clock known to man. Entangling atoms in an atomic clock with enough atoms could produce an atomic clock so stable that it would lose a second about once every 30 billion years.
Small Science. Big Money
At the moment, these applications — barring atomic clocks — are strictly in development phases, with some modalities further along than others. But the phenomena that inform these techniques are well established, and it is a matter of time before quantum sensors are market-ready.
In a recent Scientific American article, it was estimated that such sensors could be available in around 3–5 years.
To get a sense of how important quantum sensors are for the future, the University of Birmingham is leading an £80 million consortium, the UK Quantum Technology Hub for Sensors and Metrology, using quantum effects to build next-generation sensors for gravity, magnetic fields, rotation, time, THz radiation and quantum light.
Professor Kai Bongs, Director of Innovation at the College of Engineering and Physical Sciences at the University of Birmingham, is the consortium's principal investigator. He and his team have identified a market potential for quantum sensors of £4 billion per year, with the possibility of improving the UK’s Gross Domestic Product by 10%.
Elsewhere in the UK, the government and private sector has invested £315 million into the second phase of its National Quantum Computing Program (2019–2024).
It is ironic perhaps that quantum physics — the science of the very small, could, via quantum sensors, improve our lives in a very big way.
References and Further Reading
C Freier, M Hauth, V Schkolnik, B Leykauf, M Schilling, H Wziontek, H-G Scherneck, J Muller, and A Peters, (2020), ‘Mobile quantum gravity sensor with unprecedented stability,’ Journal of Physics: Conference Series, doi:10.1088/1742–6596/723/1/012050
Young. J, (2020), ‘Self-driving vehicles could struggle to eliminate most crashes,’ Insurance Institute for Highway Safety, https://www.iihs.org/news/detail/self-driving-vehicles-could-struggle-to-eliminate-most-crashes
McDonald. A., Clerk. A. A., (2020), ‘Exponentially-enhanced quantum sensing with non-Hermitian lattice dynamics,’ Nature Communications, https://doi.org/10.1038/s41467-020-19090-4
‘What is an Atomic Clock?’ NASA JPL, https://www.nasa.gov/feature/jpl/what-is-an-atomic-clock
‘Are quantum sensors the key to transforming our lives?’ (2020), The University of Birmingham, https://www.birmingham.ac.uk/research/quest/emerging-frontiers/quantum-sensors.aspx