Fundamental Research Division
The DRF at the CEA assemble approximately 6,000 scientists since January 2016.
Découvertes et avancées | Scientific result | Quantum Physics | Spintronics
According to researchers from the CEA-Iramis, it is now possible to detect spins thanks to an original method using a single photon sensor that is insensitive to noise. This is a major step forward for the measurement of spin quantum bits or their conversion into photons.
The leading technique to probe electron spins is Electron Paramagnetic Resonance (EPR; see below), although its sensitivity is not sufficient for small numbers of spins.
Using their experience in the field of superconducting circuits, physicists from Iramis were able to lower the EPR detection sensitivity to about ten electrons for an integration time of one second. To go beyond this, it was necessary to overcome the quantum fluctuations of the lowest possible energy state (known as the zero point). The researchers have now achieved this feat by using photon counting.
For this, they couple a few thousand electron spins of impurities implanted in silicon to a resonant cavity. This configuration allows these quantum systems with two close energy levels to deexcite according to the Purcell effect, by emitting single microwave photons. This very small number of photons can then be detected thanks to an ingenious single microwave photon detector (see below).
This remarkable sensitivity, which stands in contrast to conventional EPR, opens the way to multiple applications in quantum information processing, as well as the analysis of individual biological objects such as cells or proteins.
Electron spin resonance spectroscopy with femtoliter detection volume, Applied Physics Letters
Irreversible qubit-photon coupling for the detection of itinerant microwave photons, Physical Review X
Detecting spins by their fluorescence with a microwave photon counter, Nature
CEA is a French government-funded technological research organisation in four main areas: low-carbon energies, defense and security, information technologies and health technologies. A prominent player in the European Research Area, it is involved in setting up collaborative projects with many partners around the world.