Demonstration of a logical Bell-state measurement beyond the linear-optical limit

• URL: http://arxiv.org/abs/2609.10698v1
• Date: Wed, 09 Sep 2026 18:00:13 GMT
• Title: Demonstration of a logical Bell-state measurement beyond the linear-optical limit
• Abstract summary: We show that error-correction codes can be used to surpass the linear-optics limit of Bell-state measurements.<n>This is an important step towards practical, fault-tolerant, and scalable photonic quantum technologies.
• Score: 0.04666493857924356
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Fault tolerance is essential for scalable quantum technologies and is enabled by quantum error-correction codes. Bell-state measurements (BSMs) are a fundamental building block for modern quantum technologies such as measurement-based quantum computation and fusion-based quantum computation, as well as quantum networks. Therefore, performing BSMs on error-corrected qubits is a necessary step for achieving fault tolerance in these applications. In this work, we realise a logical BSM using linear optics, based on a two-qubit repetition code, an instance of a quantum parity code that allows detection of bit-flip errors, and experimentally achieve a mean success probability of (70.8 +/- 0.4)%. While standard linear-optical BSMs are fundamentally limited to a maximum success probability of 50%, this increased success probability enables higher secure key rates in quantum communication and facilitates the generation of large graph states for quantum computation. Since fault-tolerant schemes require error-correction codes regardless, this improvement comes at no additional resource overhead. Our results demonstrate that error-correction codes can be used to surpass the linear-optics limit of BSMs, which is an important step towards practical, fault-tolerant, and scalable photonic quantum technologies.

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