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arXiv:2605.26377

Single-Ensemble Multiparameter Squeezing with Qudits

Xiaoshui Lin, Chunlei Qu, Chong Zu, Chuanwei Zhang

quant-phSubmitted May 25, 2026• Announced May 27, 2026• 0 citations• Revised Sep 19, 2026 (v2)
v1 · May 25, 2026v2 · Sep 19, 2026
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Abstract

Conventional spin squeezing enhances a single sensing channel. Here, we show how internal qudit levels enable simultaneous multiparameter squeezing within one ensemble. In two-component magnetometry, a qutrit sensor provides two orthogonal and weakly compatible channels. A collective twisting interaction squeezes both responses while preserving joint attainability of the ultimate sensitivity. The sensing gain is quantified by using a matrix generalization of the Wineland sensitivity that retains both noise correlations and cross-channel response. An interaction-based echo amplifies the signal to overcome noise from a fixed local joint readout, yielding a simulated $13~\mathrm{dB}$ gain over the product-state standard quantum limit for $N=128$ qutrits. More generally, we use the single-site quantum Fisher information matrix to select reference states and channel quadratures for prescribed sensing tasks. The tangent geometry permits at most $d-1$ independent, weakly compatible channels around a common pure reference state for a $d$-level sensor. Our work provides a constructive task-to-protocol map for multiparameter squeezing in a single qudit ensemble.

Comments
9+16 pages; 4+2 figures

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Conventional spin squeezing enhances a single sensing channel. Here, we show how internal qudit levels enable simultaneous multiparameter squeezing within one ensemble. In two-component magnetometry, a qutrit sensor provides two orthogonal and weakly compatible channels. A collective twisting interaction squeezes both responses while preserving joint attainability of the ultimate sensitivity. The sensing gain is quantified by using a matrix generalization of the Wineland sensitivity that retains both noise correlations and cross-channel response. An interaction-based echo amplifies the signal to overcome noise from a fixed local joint readout, yielding a simulated 13 dB13~\mathrm{dB}13 dB gain over the product-state standard quantum limit for N=128N=128N=128 qutrits. More generally, we use the single-site quantum Fisher information matrix to select reference states and channel quadratures for prescribed sensing tasks. The tangent geometry permits at most d−1d-1d−1 independent, weakly compatible channels around a common pure reference state for a ddd-level sensor. Our work provides a constructive task-to-protocol map for multiparameter squeezing in a single qudit ensemble.
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