Frequency-Encoded Photonic Bell-State Generation

High-quality entangled states are a fundamental resource in quantum information science. In fusion-based quantum computation, such states can be combined via entangling measurements called fusions to create larger entangled states, forming a substrate for quantum computation. Bell states are the simplest entangled resource state, making modeling their generation crucial for guiding early experiments and as a starting point in modeling larger resource state generation.

Here we analyze heralded protocols for generating frequency-encoded photonic Bell states in an integrated optics platform, contrasting their efficiencies, fidelities, and error robustness. We focus on biphoton sources using spontaneous four-wave mixing in microring resonators and coupled-ring-resonator-based interferometric elements, including frequency beam splitters. We characterize the dominant error mechanisms within these protocols, including photon loss and multi-photon errors. Strong linear optical simulation of the lossy circuits is performed using Quandela’s Perceval software along with custom modeling capabilities for reducing the overhead in simulating loss and multi-photon sources.