Magnetoencephalography (MEG) is a noninvasive brain-imaging technology that measures the tiny magnetic signals created when groups of brain cells communicate with each other. Unlike the better-known EEG, the magnetic fields recorded by MEG are not blurred by the skull, which means MEG can identify functional locations in the brain very precisely. And, unlike functional magnetic resonance imaging which has good localization accuracy but poor time resolution, MEG can be used to image brain processes in real-time. It is used for early diagnosis of Parkinson’s and Alzheimer’s, can localize changes in brain activity in patients with epilepsy or concussion, and can be used to study the development of brain networks as they form during childhood.
So, why haven’t most of us heard of this wonder diagnostic? Likely because only approximately 200 medical clinics around the world have an MEG machine. The magnetometers in MEG are superconducting quantum interference devices (SQUIDs) that must be submerged in helium to maintain cryogenic temperatures (-269°C). That makes an MEG machine very heavy, expensive, and stationary by necessity.
Recently, a research group from the University of Nottingham spun off a new company called Cerca to manufacture and market a helmet-sized MEG system. This group managed to reduce the size of the MEG by using a quantum technology called optically pumped magnetometers (OPM), which are just as sensitive as SQUIDs but don’t have to be kept at cryogenic temperatures. The OPM-MEGs are lightweight and allow subjects to wear them while freely moving. While this system has not yet received regulatory approval for use in a clinical setting, it’s easy to imagine how such a device could become a standard piece of medical equipment in every hospital and clinic in the world.
Quantum technologies like these were likely not in the minds of De Broglie, Heisenberg, Dirac, Bohr, Schrödinger, and other giants at the forefront of modern quantum mechanics in the mid-1920s. Their work provided a mathematical framework for later experimental validation of pre-modern theories of quantum physics, but they were still very far from imagining practical uses for such ideas.
One hundred years later, in 2025, the UNESCO International Year of Quantum Science and Technology recognizes the tremendous advances in the field. Quantum sensors, quantum computing, and quantum communication are opening new opportunities for innovation in medicine, cybersecurity, clean energy, and materials discovery—all of them end goals aligned with the United Nation’s 17 Sustainable Development Goals.
In keeping with the sustainability theme, I am excited to announce the launch of a new column in Photonics Focus, “Photonics for a Better World.” The column will spotlight specific applications of photonics technology that are making a tangible difference in our world.
The feature stories for this first issue of 2025—in keeping with the International year of Quantum Science and Technology—explore astounding developments in quantum, including space-based quantum communications, new generations of quantum sensors, and the quest for the elusive holy grail of a reliable single-photon source.
I hope you enjoy getting entangled with the fascinating quantum world in this issue of Photonics Focus.
Gwen Weerts, Editor-in-chief
