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Quantum sensors, measurement devices with unrivaled precision

​While quantum computers have become the Holy Grail in the quantum field, there is a much more advanced branch which harnesses the same properties, that of quantum sensors. In fact, these have become one of the key technological solutions in the quantum computer quest, not just to detect encoded information, but also in telecommunications or medical imaging, and numerous other applications.  

Published on 31 March 2022

​What are quantum sensors? 

“By definition, sensors are tools that help measure one or several physical values,” explains Preden Roulleau, Director of Research at CEA-Iramis. “They are said to be ‘quantum’ when they use quantum properties to operate, such as in the principle of superposition, quantum interference, or the entanglement of quantum states.” These sensors can contain different particle types (photons or electrons) or atoms, which physicists can place in a given quantum state. This has the distinction of being extremely sensitive, as the slightest disruption in its surrounding environment can alter it. It explains the unrivaled precision and sensitivity of these sensors.  

When was the notion of quantum sensors first developed? 

The origin of quantum sensors is quite old. As early as the 1950s, atomic clocks had demonstrated the value in using a system that was quantified and perfectly replicable to carry out frequency standards - a property that led to redefining seconds based on the transition of a cesium atom. Today, atomic clocks help establish time scales and keep them in sync throughout the world. 

At CEA-Leti: quantum sensors serving advanced medical imagery

Recently created in 2021, Mag4Health, a CEA-Leti startup, designed a new generation of magnetoencephalography (MEG) operating at room temperature, based on quantum sensors developed at CEA-Leti. MEG is a neuroimaging method which involves recording the brain’s electromagnetic activity in real time, thereby improving the diagnosis of some neuronal diseases. Due to their cost, which can reach 4 million euros per device, and to their weight (over 5 tons), about a hundred MEG devices are currently in use in hospitals. Mag4Health intends to revolutionize access to MEG by introducing a non-invasive device that would cost five times less and only weigh about 150 kg. This democratization will give rise to new clinical uses, such as rehabilitation after a stroke, or early Alzheimer’s diagnoses. Since 2021, the startup has been rolling out its quantum sensor prototypes in university hospitals. 

Do quantum sensors involve any R&D issues?

The extremely high sensitivity of quantum sensors goes hand-in-hand with very high vulnerability to decoherence sources, explaining why using most of these sensors is still limited to very specific dates at this stage. R&D issues stated in their national strategy on quantum technologies will involve consolidating France’s position regarding cold atom detectors and developing the next generation of inertial sensors, magnetic sensors, and atomic clocks. 
Particularly, in terms of quantum sensors developed at CEA, areas of research involve, on one hand, exploring systems that would sidestep the need to use very low temperatures, and on the other, to create larger scale circuits than lab-scale ones. Progress is being made, for example with CEA-Leti’s development in 2016 of Qubit silicon in Grenoble - mature silicon technology that makes it possible to create circuits more easily and to facilitate scaling up. Research on the ERC Synergy QuCube, project also continues, led by CEA and CNRS researchers, and on the H2020 QLSI project headed by CEA-Leti. The French quantum plan will offer QuantAlps great opportunities in this field, with fantastic projects within the PEPR (Programme et Équipement Prioritaire de Recherche, Priority Research Equipment and Program) framework due to begin shortly.

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