Generating and verifying entangled itinerant microwave fields with efficient and independent measurements

摘要

By combining a squeezed propagating microwave field and an unsqueezed vacuum field on a hybrid (microwave beam splitter), we generate entanglement between the two output modes. We verify that we have generated entangled states by making independent and efficient single-quadrature measurements of the two output modes. We observe the entanglement witness E-W = -0.263(-0.036)(+0.001) and the negativity N = 0.0824(-0.0004)(+0.01) with measurement efficiencies at least 26 +/- 0.1% and 41 +/- 0.2% for channels 1 and 2, respectively. These measurements show that the output two-mode state violates the separability criterion and therefore demonstrates entanglement. This shared entanglement between propagating microwaves provides an important resource for building quantum networks with superconducting microwave systems.