High-dimensional quantum states of light, such as photons entangled in their spatial or temporal structure, can carry significantly more information than qubits. Also known as “qudits,” such states offer the potential for noise-robust and high-capacity quantum communication networks. A central challenge in the realisation of such networks is the ability to precisely control and measure photonic qudits. In this talk, I will show how we can harness complex scattering processes inside a commercial multi-mode fiber to program arbitrary quantum circuits and measurements for photonic qudits encoded in space and time. First, I will present our “top-down” approach where a smaller unitary is embedded inside the larger modal space of the fiber, with the auxiliary modes serving as an additional resource. I will demonstrate how this capability allows us to turn the multi-mode fibre into a generalised multi-outcome device, enabling us to simultaneously transport, manipulate, and certify entanglement within the transmission channel itself. I will also discuss how this technique allows us to implement a programmable, fully connected four-user multiplexed quantum network for entanglement routing and swapping. Finally, I will show how spatio-temporal coupling inside a multi-mode fiber can be harnessed to program generalised projective measurements for photonic time-bins in dimensions up to seven.