Distribution of entangled photon pairs over few-mode fibers

Abstract

Few-mode fibers (FMFs) have been recently employed in classical optical communication to increase the data transmission capacity. Here we explore the capability of employing FMF for long distance quantum communication. We experimentally distribute photon pairs in the forms of time-bin and polarization entanglement over a 1-km-long FMF. We find the time-bin entangled photon pairs maintain their high degree of entanglement, no matter what type of spatial modes they are distributed in. For the polarization entangled photon pairs, however, the degree of entanglement is maintained when photon pairs are distributed in LP 01 mode but significantly declines when photon pairs are distributed in LP 11 mode due to a mode coupling effect in LP 11 mode group. We propose and test a remedy to recover the high degree of entanglement. Our study shows, when FMFs are employed as quantum channels, selection of spatial channels and degrees of freedom of entanglement should be carefully considered.

Experimental space-division multiplexed polarization-entanglement distribution through 12 paths of a multicore fiber

“…Quantum SDM in optical fibers opens access to implementing QKD schemes for high throughput quantum communications. Besides this, our implementation of the SDM with polarization-entangled photons can be combined with other degrees of freedom, e.g., wavelength [40] or timebin [25], for enhancing communication capacity, and can be adapted for multi-user quantum network applications [22,41]. Furthermore, it provides a feasible way of implementing QKD based on position-momentum variables without timeconsuming fiber scans [42] as all modes are guided simultaneously through the fiber.…”

“…In terms of fibers links, single-mode fibers (SMF) are not suitable for SDM implementations since only one spatial mode can be carried. In contrast, the fibers capable of transmitting multiple spatial modes, such as a multiand few-mode fibers, require a complex system [24] to avoid the mode-coupling effects [25] and are susceptible to external influences [26] inhibiting long-term stability. A multicore fiber (MCF) is superior in this sense because all the spatial modes are guided through individual cores that share the same cladding [27].…”

Self-testing mutually unbiased bases in higher dimensions with space-division multiplexing optical fiber technology

“…Recently, the new technology developed for SDM has become a new platform for high-dimensional quantum information processing [30]. Initial efforts, based on pathencoded qudits and multi-core fibers [52][53][54][55][56], have now been expanded to different types of fibers and encoding schemes [57][58][59][60]. Nonetheless, up to our knowledge, this new platform has not yet been demonstrated to be compatible with modern self-testing protocols of quantum states and circuits.…”

Multi-core fiber integrated multi-port beam splitters for quantum information processing

“…The benefit of MCFs for QI has been further reinforced by showing that they can support propagation of entangled photons [23,24]. Similar research has begun for FMFs [25][26][27][28][29][30]. HD entanglement is advantageous in this regard, as it can be more resistant to noise [31].…”