A practical high-dimensional quantum key distribution (QKD) protocol is demonstrated over a 52-km deployed multicore fiber link in L'Aquila, Italy. The protocol uses a 4-dimensional hybrid time-path encoding scheme, achieving a secret key rate (SKR) of 51.5 kbps despite 22 dB of channel loss. This experiment shows that robust high-dimensional QKD can be implemented in realistic environments by combining standard telecom equipment with emerging multicore fiber technology. The system uses four cores of a 26-km 4-core fiber, with two cores looped back to form a 52-km link. The protocol is a 4D generalization of the BB84 protocol, using weak coherent pulses and a two-decoy-state protocol to detect photon-number splitting attacks. The experiment demonstrates the stability of the QKD system, with the Z basis showing greater stability than the X basis, which is affected by mechanical vibrations. The results indicate that the 4D protocol has higher noise tolerance and a higher secret key generation rate compared to a reference 2D scheme. The work paves the way for the practical implementation of future high-dimensional QKD systems. The protocol uses a phase-locked loop (PLL) to stabilize the phase of the multicore fiber, which is crucial for maintaining the stability of the quantum states. The experiment also highlights the advantages of path-encoding over other high-dimensional encoding methods, as it avoids the fragility of quantum states seen in other protocols. The results show that path-encoding based on multicore fibers is a robust scheme for high-dimensional QKD, with the potential for future deployment in real-world scenarios. The study also compares the performance of 4D and 2D QKD protocols, showing that the 4D protocol has higher noise tolerance and a higher secret key generation rate. The experiment demonstrates the feasibility of high-dimensional QKD in realistic environments, with the potential for future applications in secure communication. The results are significant for the development of quantum communication networks, as they show that high-dimensional QKD can be implemented in practical scenarios with the use of multicore fibers. The study also highlights the importance of phase stabilization in maintaining the stability of the quantum states, which is essential for the success of high-dimensional QKD. The experiment provides a foundation for future research in high-dimensional QKD, demonstrating the potential of multicore fibers for quantum communication. The results show that high-dimensional QKD can be implemented in practical scenarios, with the potential for future applications in secure communication. The study also highlights the importance of phase stabilization in maintaining the stability of the quantum states, which is essential for the success of high-dimensional QKD. The experiment provides a foundation for future research in high-dimensional QKD, demonstrating the potential of multicore fibers for quantum communication.A practical high-dimensional quantum key distribution (QKD) protocol is demonstrated over a 52-km deployed multicore fiber link in L'Aquila, Italy. The protocol uses a 4-dimensional hybrid time-path encoding scheme, achieving a secret key rate (SKR) of 51.5 kbps despite 22 dB of channel loss. This experiment shows that robust high-dimensional QKD can be implemented in realistic environments by combining standard telecom equipment with emerging multicore fiber technology. The system uses four cores of a 26-km 4-core fiber, with two cores looped back to form a 52-km link. The protocol is a 4D generalization of the BB84 protocol, using weak coherent pulses and a two-decoy-state protocol to detect photon-number splitting attacks. The experiment demonstrates the stability of the QKD system, with the Z basis showing greater stability than the X basis, which is affected by mechanical vibrations. The results indicate that the 4D protocol has higher noise tolerance and a higher secret key generation rate compared to a reference 2D scheme. The work paves the way for the practical implementation of future high-dimensional QKD systems. The protocol uses a phase-locked loop (PLL) to stabilize the phase of the multicore fiber, which is crucial for maintaining the stability of the quantum states. The experiment also highlights the advantages of path-encoding over other high-dimensional encoding methods, as it avoids the fragility of quantum states seen in other protocols. The results show that path-encoding based on multicore fibers is a robust scheme for high-dimensional QKD, with the potential for future deployment in real-world scenarios. The study also compares the performance of 4D and 2D QKD protocols, showing that the 4D protocol has higher noise tolerance and a higher secret key generation rate. The experiment demonstrates the feasibility of high-dimensional QKD in realistic environments, with the potential for future applications in secure communication. The results are significant for the development of quantum communication networks, as they show that high-dimensional QKD can be implemented in practical scenarios with the use of multicore fibers. The study also highlights the importance of phase stabilization in maintaining the stability of the quantum states, which is essential for the success of high-dimensional QKD. The experiment provides a foundation for future research in high-dimensional QKD, demonstrating the potential of multicore fibers for quantum communication. The results show that high-dimensional QKD can be implemented in practical scenarios, with the potential for future applications in secure communication. The study also highlights the importance of phase stabilization in maintaining the stability of the quantum states, which is essential for the success of high-dimensional QKD. The experiment provides a foundation for future research in high-dimensional QKD, demonstrating the potential of multicore fibers for quantum communication.