Multi-user distribution of polarization entangled photon pairs

Abstract

We experimentally demonstrate multi-user distribution of polarization entanglement using commercial telecom wavelength division demultiplexers. The entangled photon pairs are generated from a broadband source based on spontaneous parametric down conversion in a periodically poled lithium niobate crystal using a double path setup employing a Michelson interferometer and active phase stabilisation. We test and compare demultiplexers based on various technologies and analyze the effect of their characteristics, such as losses and polarization dependence, on the quality of the distributed entanglement for three channel pairs of each demultiplexer. In all cases, we obtain a Bell inequality violation, whose value depends on the demultiplexer features. This demonstrates that entanglement can be distributed to at least three user pairs of a network from a single source. Additionally, we verify for the best demultiplexer that the violation is maintained when the pairs are distributed over a total channel attenuation corresponding to 20 km of optical fiber. These techniques are therefore suitable for resource-efficient practical implementations of entanglement-based quantum key distribution and other quantum communication network applications.

Multi-User Quantum Key Distribution with Entangled Photons from a Semiconductor Chip

“…Thus, standard telecom dense wavelength division multiplexers (DWDM) can be used to separate them. An entangled state can then be shared between two users who receive the photons from symmetric channels with respect to the degeneracy wavelength p  2 [5]. In our experiment, we use an 8-channel commercial DWDM with a channel width and channel separation of 0.8 nm (100 GHz).…”

Multi-user quantum key distribution with entangled photons from an AlGaAs chip

“…The temporal overlap between two orthogonal polarization modes was thus limited to η = f A (t)f B (τ PMD − t)dt ≈ 84% (where f A (t) and f B (t) are the normalized temporal transmission functions of the DWDM channels). As a result, the visibility of the measured entangled state is upper bounded by V max tot = 1+η 2 ≈ 92% [12].…”

Exploiting Faraday Rotation to Jam Quantum Key Distribution via Polarized Photons

“…Two sets of measurements found a = 0.159 ± 0.008 [31] and a = 0.142 ± 0.004 [32]. QKD via optical fiber typically uses photons with λ = 1550 nm [21,[33][34][35]; adopting the lower (more conservative) measurement of V from Ref. [32], this corresponds to V fiber = 0.53 rad T −1 m −1 .…”