Converting Quantum Sensing Noise into Erasures

Abstract

Erasures are more favorable for quantum sensing than unflagged errors such as Pauli errors. However, realistic sensing noise does not usually appear as erasures; it often acts within the same sensing Hilbert space as the signal, making it difficult to identify and mitigate. For such noise, we establish a noise-model-agnostic necessary and sufficient condition for erasure conversion, identifying the noise components that can be converted into erasures and removed without damaging the signal. For components satisfying the condition, conversion can be realized by a passive dimension-lifted scheme requiring neither detailed noise knowledge nor active control. Theoretically, the protocol remains effective over a broad range of noise strengths and approaches the corresponding precision limit. Experimentally, in single-photon phase sensing, we recover standard-quantum-limit precision in a Pauli-noise channel with erasure-convertible weight 0.5, using orbital angular momentum as the ancilla. These results provide a practical route to robust quantum sensing under realistic noise.