Remote creation of hybrid entanglement between particle-like and wave-like optical qubits

Abstract

The wave–particle duality of light has led to two different encodings for optical quantum information processing. Several approaches have emerged based either on particle-like discrete-variable states (that is, finite-dimensional quantum systems) or on wave-like continuous-variable states (that is, infinite-dimensional systems). Here, we demonstrate the generation of entanglement between optical qubits of these different types, located at distant places and connected by a lossy channel. Such hybrid entanglement, which is a key resource for a variety of recently proposed schemes, including quantum cryptography and computing, enables information to be converted from one Hilbert space to the other via teleportation and therefore the connection of remote quantum processors based upon different encodings. Beyond its fundamental significance for the exploration of entanglement and its possible instantiations, our optical circuit holds promise for implementations of heterogeneous network, where discrete- and continuous-variable operations and techniques can be efficiently combined. Optical entanglement between a particle-like subsystem and a wave-like one is generated through the heralding detection of a single photon in an indistinguishable fashion at a central station. This enables information to be converted from one Hilbert space to the other via teleportation, and hence permits remote quantum processors based on different encodings to be connected.