Structured Electron Interferometry

The goal of this project is to enable and expand quantum-inspired measurements with electrons. The vast majority of modern developments in quantum measurement and quantum information technologies use photons, the smallest unit of light, as a central component. Yet the wavelike nature of photons still places fundamental limits on the smallest lengthscale at which this can be applied. Many of these quantum measurement protocols can be implemented with matter waves as well, but the technologies used to generate, manipulate, apply, and detect matter waves are not as well-developed as those for photons. This project develops new quantum techniques in the electron microscope, such as interaction-free measurements using electrons, and applies them to explore various phenomenon at the nanoscale. This will provide new quantum electron microscopy tools that can be used to reduce the size of quantum devices, similar to how conventional electron microscopes enabled the reduction in size of classical computing components. In addition to providing training to graduate and undergraduate students in advanced microscopy and nanoscience, this project will engage first-year STEM majors as well, providing a “bridge” over the summer into their second year by introducing them to programming, data analysis, electron microscopy, nanofabrication, and optical physics. The project develops and uses tools to both prepare and measure coherence and phase of free electron wavefunctions inside electron microscopes. Nanoscale diffraction holograms provide a way to coherently manipulate the phase profile of individiual electrons as well as measure them. For example, diffraction holograms can produce free electron wavefunctions with helical phase profiles that provide a new way to probe the chirality and spatial coherence of nanoscale plasmonics. Electron-transparent phase gratings can also serve as optimized beamsplitters for electrons, which are used in this project to create electron interferometers with large path separation, useful for measuring electric and magnetic fields at the nanoscale. Interaction-free measurement protocols are also explored, which could enable high resolution electron microscopy of easily damaged materials. The project connects with a broad spectrum of sciences and applications, enabling unique opportunities for project participants in a range of disciplines and industries. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.