Path Entanglement of Continuous-Variable Quantum Microwaves
Path entanglement constitutes an essential resource in quantum information
and communication protocols. Here, we demonstrate frequency-degenerate
entanglement between continuous-variable quantum microwaves propagating along
two spatially separated paths. We combine a squeezed and a vacuum state using a
microwave beam splitter. Via correlation measurements, we detect and quantify
the path entanglement contained in the beam splitter output state. Our
experiments open the avenue to quantum teleportation, quantum communication, or
quantum radar with continuous variables at microwave frequencies.