Free-Electron Qubits

Free-electron interactions with laser-driven nearfields can quantize the electrons' energy spectrum and provide control over this quantized degree of freedom. The study proposes to use such interactions to promote free electrons as carriers of quantum information and show how to create a qubit on a free electron, which holds promise for applications in electron microscopy and spectroscopy. A method to implement the qubit's noncommutative spin algebra, and to control and measure the qubit state with a universal set of 1-qubit gates is shown. These gates are within the current capabilities of ultrafast transmission electron microscopes. Laser-driven free-electron qubits promise configurability by the laser intensity, frequency, and polarizability, simultaneously with high-resolution temporal control on femtosecond timescales.