Quantum network functionalities rely on the distribution of entangled photons to remote nodes interconnected by optical fibers. Polarization dependent loss (PDL) could potentially impair transmissions of entangled photon pairs. We propose a compact model that accounts for the deleterious effect of PDL of any orientation.
Quantum networking brings together several diverse research areas, such as fiber-optic communication, quantum optics, and quantum information, to achieve capabilities in security, secret sharing, and authentication which are unavailable classically. The development of practical fiber-based quantum networks requires an understanding of the reach, rates, and quality of the entanglement of distributed quantum states. Here, we present a theoretical model describing how the magnitude and orientation of polarization dependent loss (PDL), a common impairment in fiber-optic networks, affects the entanglement quality of distributed quantum states. Furthermore, we theoretically characterize how PDL in one fiber channel can be optimally applied in order to nonlocally compensate for the PDL present in another channel. We present experimental results that verify our theoretical model.
Abstract Quantum networks entangle remote nodes by distributing quantum states, which inevitably suffer from decoherence while traversing quantum channels. Pertinent decoherence mechanisms govern the reach, quality, and rate of distributed entanglement. Hence recognizing, understanding, and modeling those mechanisms is a crucial step in building quantum networks. Here, we study real-life fiber-optic quantum channels that partially filter individual modes of transmitted polarization-entangled states and are capable of introducing dephasing. First, we theoretically model and experimentally demonstrate the combined effect of two independent and arbitrarily oriented polarization-dependent loss elements experienced by each photon of an entangled photon pair. Then, we showcase the compensation of lost entanglement by properly adjusting the channels’ properties and discuss the resulting tradeoff between the entanglement quality and rate. Our results provide insights into the robustness of fiber-optic quantum channels, thus taking an important step toward the realization of quantum networks.