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arXiv:2605.08341

Quantum metrology via partial quantum error correction

Yinan Chen, Zongyuan Wang, Sisi Zhou

quant-phSubmitted May 8, 2026• Announced May 12, 2026• 0 citations• Revised Sep 29, 2026 (v3)
v1 · May 8, 2026v2 · Jun 10, 2026v3 · Sep 29, 2026
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Abstract

We introduce a quantum metrology scheme in which partial quantum error correction suppresses local noise while preserving sensitivity beyond the standard quantum limit. The probes are superpositions of energetically distinct stabilizer sectors, whose sensing coherence is protected by measuring only a subset of local checks. We propose an adaptive weight strategy to balance two competing effects. Increasing the stabilizer-generator weight suppresses parallel noise to $O(p^δ)$, with $δ$ increasing with the weight, but also increases susceptibility to perpendicular noise. Our main theorem establishes a sufficient noise condition under which adapting this weight to the system size preserves superlinear quantum Fisher information under simultaneous independent $X$ and $Z$ noise. We illustrate this strategy using repetition, Bacon-Shor, and toric codes, and analyze noise both before and after phase imprinting. In all examples, the error-correction checks and phase-imprinting operators are local and require no nonlocal connectivity.

Comments
Substantially revised version. Added Theorem 1, providing a general performance guarantee for super-SQL scaling; reorganized the presentation and updated the figures

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We introduce a quantum metrology scheme in which partial quantum error correction suppresses local noise while preserving sensitivity beyond the standard quantum limit. The probes are superpositions of energetically distinct stabilizer sectors, whose sensing coherence is protected by measuring only a subset of local checks. We propose an adaptive weight strategy to balance two competing effects. Increasing the stabilizer-generator weight suppresses parallel noise to O(pδ)O(p^δ)O(pδ), with δδδ increasing with the weight, but also increases susceptibility to perpendicular noise. Our main theorem establishes a sufficient noise condition under which adapting this weight to the system size preserves superlinear quantum Fisher information under simultaneous independent XXX and ZZZ noise. We illustrate this strategy using repetition, Bacon-Shor, and toric codes, and analyze noise both before and after phase imprinting. In all examples, the error-correction checks and phase-imprinting operators are local and require no nonlocal connectivity.
Quantum metrology surpasses the classical precision limit by encoding signals in a probe state such that signal contributions are indistinguishable and their phases accumulate coherently as a collective response. In realistic settings, scalable quantum metrology requires quantum error correction to protect the probe against noise. However, quantum error correction relies on syndrome information that distinguishes errors for identification and correction. Because signals and errors act on the same physical degrees of freedom, there is a structural incompatibility between signal-sensitivity and noise-protection in quantum-error-corrected metrology. We quantify this incompatibility by establishing trade-offs between code distance and the quantum Fisher information of code states for non-degenerate codes, quantum low-density parity-check codes, and generalized Shor codes. We bypass this limitation with asymmetric quantum error correction, in which protection is relaxed along the signal direction while being maintained in complementary directions. We construct such codes for local sensing Hamiltonians, restoring Heisenberg-limited precision while retaining a growing distance and hence protection against local perturbations in complementary directions. Strongly asymmetric quantum low-density parity-check and concatenated asymmetric constructions make the framework sparse, scalable, and continuously tunable. The associated probe states can be prepared by constant-depth adaptive circuits with optimal resource scaling.
Quantum error correction has become an indispensable tool for restoring Heisenberg-limited precision in noisy quantum metrology. Existing protocols, however, almost exclusively focus on correcting noise during the signal-encoding stage and implicitly assume that the probe is measured immediately after sensing. In many quantum information processing tasks, the encoded probe must instead be stored before subsequent quantum operations, during which environmental noise can significantly degrade the accumulated metrological information. Here, we propose a correlated-noise correction (CNC) protocol for protecting quantum probes during the storage stage. By correlating probe errors with auxiliary qubits through fixed two-body entangling gates, memory errors are converted into measurable syndromes that are extracted only once after storage. We show that the protocol naturally extends from single-qubit to multi-qubit probes and protects the stored quantum Fisher information against dephasing, bit-flip, and amplitude-damping noise. Furthermore, we demonstrate that preserving the quantum Fisher information does not necessarily require restoring the entire quantum state when the probe is measured immediately after storage, whereas full state recovery becomes essential for subsequent rounds of quantum signal processing. Our results establish correlated-noise correction as a practical framework for protecting metrological information during quantum memory and provide a useful building block for sensing-enabled quantum information processing.
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Fragile quantum features such as entanglement are employed to improve the precision of parameter estimation and as a consequence the quantum gain becomes vulnerable to noise. As an established tool to subdue noise, quantum error correction is unfortunately overprotective because the quantum enhancement can still be achieved even if the states are irrecoverably affected, provided that the quantum Fisher information, which sets the ultimate limit to the precision of metrological schemes, is preserved and attained. Here, we develop a theory of robust metrological schemes that preserve the quantum Fisher information instead of the quantum states themselves against noise. After deriving a minimal set of testable conditions on this kind of robustness, we construct a family of 2t+12t+12t+1 qubits metrological schemes being immune to ttt-qubit errors after the signal sensing. In comparison at least five qubits are required for correcting arbitrary 1-qubit errors in standard quantum error correction.
Fragile quantum features such as entanglement are employed to improve the precision of parameter estimation and as a consequence the quantum gain becomes vulnerable to noise. As an established tool to subdue noise, quantum error correction is unfortunately overprotective because the quantum enhancement can still be achieved even if the states are irrecoverably affected, provided that the quantum Fisher information, which sets the ultimate limit to the precision of metrological schemes, is preserved and attained. Here we develop a theory of robust metrological schemes that preserve the quantum Fisher information instead of the quantum states themselves against noise. After deriving a minimal set of testable conditions on this kind of robustness, we construct a family of 2t+1 qubits metrological schemes being immune to t-qubit errors after the signal sensing. In comparison, at least five qubits are required for correcting arbitrary 1-qubit errors in standard quantum error correction. Quantum features such as entanglement can be used to improve metrological precision, but noise affects their performances. Here the authors construct schemes for exploiting quantum error correction to preserve the quantum Fisher information, thereby shielding quantum gain efficiently.
Distributed quantum sensing requires spatially separated probes to acquire local parameters while maintaining compatibility with network-level quantum information processing. We develop an entanglement-assisted stabilizer framework based on the extended structure of entanglement-assisted quantum error-correcting (EAQEC) codes, in which the remote halves of pre-shared ebits are used directly as local phase probes while the joint state simultaneously carries an encoded logical subsystem. Each remote probe acquires a local Z-axis phase and subsequently returns through an X-type noise channel. Within the extended EAQEC stabilizer structure, the stabilizer containing XBjX_{B_j}XBj​​ provides phase-dependent measurement statistics, whereas its partner containing ZBjZ_{B_j}ZBj​​ records the corresponding return-error syndrome. A graph-code formulation is introduced to make this structure explicit, together with an illustrative [[5,1,3;2]] construction. We further show that, conditioned on the joint sensing-and-syndrome measurement record, the post-sensing state differs from the original encoded state only by a known Pauli transformation, so that the logical information remains available for subsequent encoded operations. For the local-phase model considered here, the stabilizer readout attains the available quantum Fisher information, while the finite-shot estimator approaches the corresponding 1/M1/\sqrt{M}1/M​ scaling as the number of repetitions increases. The framework therefore provides a common entanglement-assisted stabilizer structure for distributed local-phase sensing, restricted return-error identification, and post-sensing logical-state retention, without relying on an intrinsic metrological enhancement from EAQEC itself.