Coherent Electron Optics with Ballistically Coupled Quantum Point Contacts

The realization of integrated quantum circuits requires precise on-chip control of charge carriers. Aiming at the coherent coupling of distant nanostructures at zero magnetic field, here we study the ballistic electron transport through two quantum point contacts (QPCs) in series in a three terminal configuration. We enhance the coupling between the QPCs by electrostatic focusing using a field effect lens. To study the emission and collection properties of QPCs in detail we combine the electrostatic focusing with magnetic deflection. Comparing our measurements with quantum mechanical and classical calculations we discuss generic features of the quantum circuit and demonstrate how the coherent and ballistic dynamics depend on the details of the QPC confinement potentials.