All-fiber Control of Entanglement:
Recovering Correlations via Mechanical Perturbations in a Multimode Fiber
In quantum optical communications, single photons can be used as a unit of quantum information. However, one can supercharge their capacity to carry information by encoding high-dimensional quantum dits, or qdits, into their transverse shape. They allow having more than two levels per unit of information as it is the case for bits. In fiber optical communications, it requires using multimode fibers to harness the spatial degrees of freedom to encode the qduts. However, when propagating through a real-life multimode fiber, the transverse shape of the photons gets scrambled because of mode mixing and modal interference. This scrambling of transverse shape is typically rectified using free-space spatial light modulators. But, this remedy prevents us from achieving a truly resilient all-fiber operation and requires a careful alignment and lab-graded stability hindering real-life implementation. In [R. Shekel et al., Arxiv 2306.02288 (2023)], the authors introduce an all-fiber method for controlling the shape of single photons and spatial correlations between entangled photon pairs. They do so by implementing carefully controlled mechanical perturbations to the fiber.
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