Nonlinear feedforward enabling quantum computation.

Sakaguchi, Atsushi; Konno, Shunya; Hanamura, Fumiya; Asavanant, Warit; Takase, Kan; Ogawa, Hisashi; Marek, Petr; Filip, Radim et al. · Nat Commun · 2023

basic_science · Level V

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Abstract

Measurement-based quantum computation with optical time-domain multiplexing is a promising method to realize a quantum computer from the viewpoint of scalability. Fault tolerance and universality are also realizable by preparing appropriate resource quantum states and electro-optical feedforward that is altered based on measurement results. While linear feedforward has been realized and become a common experimental technique, nonlinear feedforward was unrealized until now. In this paper, we demonstrate that a fast and flexible nonlinear feedforward realizes the essential measurement required for fault-tolerant and universal quantum computation. Using non-Gaussian ancillary states, we observed 10% reduction of the measurement excess noise relative to classical vacuum ancilla.