Quantum Resource States from Post-Selected Classical Mixed States

Resource state generators form the fundamental building blocks of fusion-based quantum computing (FBQC). Each produces a relatively small multi-qubit entangled state that is combined with others into larger states via fusion gates. In this paper we discuss a novel efficient procedure for classically mimicking resource states that offers comparable fidelity and experimental relevance. Such a procedure may be useful in developing a quantum-inspired classical approach to computation implementing FBQC. To validate our procedure, we employ tomographic state reconstruction to demonstrate close agreement with quantum mechanical predictions. We evaluate the statistics of the four-star and six-ring resource states, achieving respectively a quantum fidelity of 94.7% and a worst classical fidelity of 84.0%, and demonstrate an eight-qubit Greenberger-Horne-Zeilinger (GHZ) state fidelity of 70.6 ± 4.6%. We estimate that resource state realizations can be generated at a rate of hundreds of MHz on a digital parallelized compute cluster, and we discuss the feasibility of improving this with analog architectures.