Deterministic Entanglement as a Prerequisite for Scalable Quantum Photonic Resource State Generation

ABSTRACT As demonstrated experimentally by Prevedel et al., active feed‐forward can render one‐way quantum computation deterministic. An analogous principle applies to the scalable generation of photonic resource states: because each probabilistic photonic fusion operation branches the construction process, the overall success probability shrinks exponentially unless entanglement is generated deterministically. A simple comparative combinatorial resource estimate illustrates the practical consequences of this principle. State‐of‐the‐art fault‐tolerant optical quantum computing architectures incur an unreasonably high single‐photon overhead when relying solely on probabilistic fusion. In contrast, deterministic sources of entangled multi‐photon states, such as semiconductor quantum dots, can reduce the number of required attempts dramatically. Assuming realistic system efficiencies, on average only 15 attempts are needed to generate a 4‐qubit resource state (4‐star), and 89 attempts for a 6‐qubit state (6‐ring), bringing efficient resource state generation in reach with near‐term photonic systems.