Linear multiport photonic interferometers: loss analysis of temporally-encoded architectures

Implementing spatially-encoded universal linear multiport interferometers on integrated photonic platforms with high controllability becomes increasingly difficult as the number of modes increases. In this work, we consider an architecture in which temporally-encoded modes are injected into a chain of reconfigurable beamsplitters and delay loops, and provide a detailed loss analysis for this and other comparable architectures. This analysis also yields a straightforward and explicit description of the control sequence needed for implementing an arbitrary temporally-encoded transformation. We consider possible physical implementations of these architectures and compare their performance. We conclude that implementing a chain of reconfigurable beamsplitters and delay loops on an integrated lithum niobate platform could outperform comparable architectures in the near future.