Towards quantum sensing at ultrafast speeds

Quantum sensing is a powerful tool that uses the exceptional sensitivity of quantum systems to detect physical changes with incredible precision. One of the most exciting methods in this field involves nitrogen vacancy (NV) centers in diamond - a special type of spin defect in the diamond structure. These NV centers can measure changes in electromagnetic fields with exceptional sensitivity, very high spatial resolution (nanometer range), and in a wide range of environments. As a result, NV-based sensing has been useful across various fields, including physics, biology, chemistry, and quantum computing. However, like many quantum sensing techniques, NV centers have a limitation: they cannot capture in real time processes that take place on an ultrafast timescale. Current NV-based sensors can only capture changes that occur on nanosecond (billionth of a second) timescales. Unfortunately, this falls short of the timescales needed to observe many rapid natural processes such as vibrations in materials, fast chemical reactions, and even electronic phase transitions which usually take place within femtoseconds (fs, millionths of a billionth of a second) or even faster. In our project, we aim to break this barrier and enable NV-based sensing on ultrafast timescales, improving its time resolution by over 100,000 times. By combining femtosecond lasers with microwave technology, we hope to trigger rapid changes in materials and capture these events through a quantum lock-in technique. First, we will benchmark our approach on a thin film of ferromagnetic material, observing how it demagnetizes at ultrafast speeds after being illuminates with a femtosecond laser pulse. Afterwards, we will apply it to explore the unique magnetic behavior of 2D materials, where magnetic phases are influenced by excitons (quasiparticles consisting of a hole and an electron held together by the Coulomb interaction). Our work connects the fields of ultrafast spectroscopy which investigates extremely fast transformations in matter in real-time and quantum sensing. This new method will allow us to capture fleeting electromagnetic changes and electric currents in real time and at very small spatial scales. This approach could lead to new insights in fields as diverse as material science, electronics, chemistry, and even biology, opening up a new way to study light-matter interactions and the fundamental workings of many natural and technological processes.