Path Entanglement of Continuous-Variable Quantum Microwaves

Phys Rev Lett. 2012 Dec 21;109(25):250502. doi: 10.1103/PhysRevLett.109.250502. Epub 2012 Dec 18.


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.