Dynamic generation of photonic spatial quantum states with an all-fiber platform

Abstract

Photonic spatial quantum states are a subject of great interest for applications in quantum communication. One important challenge has been how to dynamically generate these states using only fiber-optical components. Here we propose and experimentally demonstrate an all-fiber system that can dynamically switch between any general transverse spatial qubit state based on linearly polarized modes. Our platform is based on a fast optical switch based on a Sagnac interferometer combined with a photonic lantern and few-mode optical fibers. We show switching times between spatial modes on the order of 5 ns and demonstrate the applicability of our scheme for quantum technologies by demonstrating a measurement-device-independent (MDI) quantum random number generator based on our platform. We run the generator continuously over 15 hours, acquiring over 13.46 Gbits of random numbers, of which we ensure that at least 60.52% are private, following the MDI protocol. Our results show the use of photonic lanterns to dynamically create spatial modes using only fiber components, which due to their robustness and integration capabilities, have important consequences for photonic classical and quantum information processing.

All-in-Fiber Dynamically Reconfigurable Orbital Angular Momentum Mode Sorting

“…Further studies are needed to quantify these effects and evaluate the sorting performance of the degraded OAM states. At last, if one wishes to recover the OAM spatial information at each output, it is possible to split the beam into two paths and interferometrically reconstruct the OAM state with a photonic lantern . Our results show how the use of space-division multiplexing technology (i.e., few-mode fibers and photonic lanterns) can be used to implement a fast and reconfigurable OAM mode sorter that is fully compatible with optical fiber networks, further paving the way for this popular degree of freedom to be used as a reliable transport medium for information in classical and quantum networks.…”

“…We generate the OAM ±1 modes using the well-known technique based on a computer-generated hologram on a spatial light modulator (SLM) mimicking the desired optical element capable of converting a Gaussian laser beam into a helical mode . Although this is done in free space for convenience, our mode-sorting system is completely in-fiber, and it would work equally well if the OAMs were generated with an in-fiber method . A continuous wave (CW) laser operating at 1546.92 nm is spatially filtered through a single-mode fiber (SMF) and collimated with a 10x objective lens to reach a waist of ω p ≈ 1250 μm.…”

“…The mode sorter consists of a few-mode fiber connected to a photonic lantern . The physical principle behind our experiment relies on the fact that any OAM ± scriptl mode within a few-mode fiber can be decomposed into the following LP modal superposition: ,,, OAM ± scriptl = LP scriptl 1 ( even ) ± normali · LP scriptl 1 ( odd ) …”

“…49 Although this is done in free space for convenience, our mode-sorting system is completely in-fiber, and it would work equally well if the OAMs were generated with an in-fiber method. 14 A continuous wave (CW) laser operating at 1546.92 nm is spatially filtered through a single-mode fiber (SMF) and collimated with a 10x objective lens to reach a waist of ω p ≈ 1250 μm. A polarizing beam splitter (PBS) is used to set the laser's polarization state to horizontal for the optimal operation of the SLM.…”

“…Although some efforts have been made to generate OAM modes using fiber systems, − the efficient detection of OAM modes using all-in-fiber platforms remains an ongoing challenge. An ideal OAM mode sorter is a device capable of deterministically demultiplexing different incoming electromagnetic fields that carry OAM.…”