Near-deterministic photon entanglement from a spin qudit in silicon using third quantization

Unlike other quantum hardware, photonic quantum architectures can produce millions of qubits from a single device. However, controlling photonic qubits remains challenging, even at small scales, due to their weak interactions, making nondeterministic gates in linear optics unavoidable. Nevertheless, a single photon can readily spread over multiple modes and create entanglement within the multiple modes deterministically. Rudolph’s concept of third quantization leverages this feature by evolving multiple single photons into multiple modes, distributing them uniformly and randomly to different parties, and creating multipartite entanglement without interactions between photons or nondeterministic gates. This method requires only classical communication and deterministic entanglement within multimode single-photon states and enables universal quantum computing. The multipartite entanglement generated within the third-quantization framework is nearly deterministic, where “deterministic” is achieved in the asymptotic limit of a large system size. In this work, we propose a near-term experiment using antimony donor in a silicon chip to realize third quantization. Utilizing the eight energy levels of antimony, one can generate two eight-mode single-photon states independently and distribute them to parties. This enables a random multipartite Bell-state experiment, achieving a Bell state with an upper-bound efficiency of 87.5% among 56 random pairs without nondeterministic entangling gates. This approach opens alternative pathways for silicon-based photonic quantum computing.