We show that a significant quantum gain corresponding to squeezed or over-squeezed spin states can be obtained in multiparameter estimation by measuring the Hadamard coefficients of a 1D or 2D signal. The physical platform we consider consists of twolevel atoms in an optical lattice in a squeezed-Mott configuration, or more generally by correlated spins distributed in spatially separated modes. Our protocol requires the possibility to locally flip the spins, but relies on collective measurements. We give examples of applications to scalar or vector field mapping and compressed sensing.We show that a significant quantum gain corresponding to squeezed or over-squeezed spin states can be obtained in multiparameter estimation by measuring the Hadamard coefficients of a 1D or 2D signal. The physical platform we consider consists of twolevel atoms in an optical lattice in a squeezed-Mott configuration, or more generally by correlated spins distributed in spatially separated modes. Our protocol requires the possibility to locally flip the spins, but relies on collective measurements. We give examples of applications to scalar or vector field mapping and compressed sensing.

arXiv:2208.00640Aug 1, 20220 citations

Quantum enhanced sensing of a spatially extended field

Alice Sinatra

The nonlocal correlations that exist in quantum physics can be used in a sensor network to improve the sensitivity of the measurement of an extended field or some of its spatial features. Taking an atomic ensemble in a spin squeezed state distributed in different spatial modes (the sensors) as a resource, I will show what kind of gain can be obtained in two different cases. First, assuming that local manipulations can be made on the sensors but all measurements are collective [1], and second, including some experimental results [2], assuming that both local manipulations and local measurements are possible on each sensor. Generalising to the case of a large number of sensors, we show applications to imaging and compressed sensing. --- References : [1] "Quantum-enhanced multiparameter estimation and compressed sensing of a field" Y. Baamara, M. Gessner, A. Sinatra, SciPost Physics 14, 050 (2023) https://scipost.org/SciPostPhys.14.3.050 ; [2] "Multiparameter estimation with an array of entangled atomic sensors" Yifan Li, Lex Joosten, Youcef Baamara, Paolo Colciaghi, Alice Sinatra, Philipp Treutlein, Tilman Zibold, https://arxiv.org/abs/2504.08677.The nonlocal correlations that exist in quantum physics can be used in a sensor network to improve the sensitivity of the measurement of an extended field or some of its spatial features. Taking an atomic ensemble in a spin squeezed state distributed in different spatial modes (the sensors) as a resource, I will show what kind of gain can be obtained in two different cases. First, assuming that local manipulations can be made on the sensors but all measurements are collective [1], and second, including some experimental results [2], assuming that both local manipulations and local measurements are possible on each sensor. Generalising to the case of a large number of sensors, we show applications to imaging and compressed sensing. --- References : [1] "Quantum-enhanced multiparameter estimation and compressed sensing of a field" Y. Baamara, M. Gessner, A. Sinatra, SciPost Physics 14, 050 (2023) https://scipost.org/SciPostPhys.14.3.050 ; [2] "Multiparameter estimation with an array of entangled atomic sensors" Yifan Li, Lex Joosten, Youcef Baamara, Paolo Colciaghi, Alice Sinatra, Philipp Treutlein, Tilman Zibold, https://arxiv.org/abs/2504.08677.

Optical and Quantum Sensing and Precision Metrology IIMar 5, 20260 citations

Multiparameter quantum metrology and mode entanglement with spatially split nonclassical spin ensembles

Matteo Fadel, Benjamin Yadin, Yuping Mao +2 more

Abstract We identify the multiparameter sensitivity of entangled spin states, such as spin-squeezed and Dicke states that are spatially distributed into several addressable spatial modes. Analytical expressions for the spin-squeezing matrix of families of states that are accessible by current atomic experiments reveal the quantum gain in multiparameter metrology, as well as the optimal strategies to maximize the sensitivity gain for the estimation of any linear combination of parameters. We further study the mode entanglement of these states by deriving a witness for genuine k-partite mode entanglement from the spin-squeezing matrix. Our results highlight the advantage of mode entanglement for distributed sensing, and outline optimal protocols for multiparameter estimation with nonclassical spatially-distributed spin ensembles. We illustrate our findings with the design of a protocol for gradient sensing with a Bose–Einstein condensate in an entangled spin state in two modes.Abstract We identify the multiparameter sensitivity of entangled spin states, such as spin-squeezed and Dicke states that are spatially distributed into several addressable spatial modes. Analytical expressions for the spin-squeezing matrix of families of states that are accessible by current atomic experiments reveal the quantum gain in multiparameter metrology, as well as the optimal strategies to maximize the sensitivity gain for the estimation of any linear combination of parameters. We further study the mode entanglement of these states by deriving a witness for genuine k-partite mode entanglement from the spin-squeezing matrix. Our results highlight the advantage of mode entanglement for distributed sensing, and outline optimal protocols for multiparameter estimation with nonclassical spatially-distributed spin ensembles. We illustrate our findings with the design of a protocol for gradient sensing with a Bose–Einstein condensate in an entangled spin state in two modes.

arXiv:2201.11081New Journal of PhysicsJun 26, 202330 citations

Multiparameter squeezing for optimal quantum enhancements in sensor networks

Manuel Gessner, Augusto Smerzi, Luca Pezzè

Squeezing currently represents the leading strategy for quantum enhanced precision measurements of a single parameter in a variety of continuous- and discrete-variable settings and technological applications. However, many important physical problems including imaging and field sensing require the simultaneous measurement of multiple unknown parameters. The development of multiparameter quantum metrology is yet hindered by the intrinsic difficulty in finding saturable sensitivity bounds and feasible estimation strategies. Here, we derive the general operational concept of multiparameter squeezing, identifying metrologically useful states and optimal estimation strategies. When applied to spin- or continuous-variable systems, our results generalize widely-used spin- or quadrature-squeezing parameters. Multiparameter squeezing provides a practical and versatile concept that paves the way to the development of quantum-enhanced estimation of multiple phases, gradients, and fields, and for the efficient characterization of multimode quantum states in atomic and optical sensor networks.Squeezing currently represents the leading strategy for quantum enhanced precision measurements of a single parameter in a variety of continuous- and discrete-variable settings and technological applications. However, many important physical problems including imaging and field sensing require the simultaneous measurement of multiple unknown parameters. The development of multiparameter quantum metrology is yet hindered by the intrinsic difficulty in finding saturable sensitivity bounds and feasible estimation strategies. Here, we derive the general operational concept of multiparameter squeezing, identifying metrologically useful states and optimal estimation strategies. When applied to spin- or continuous-variable systems, our results generalize widely-used spin- or quadrature-squeezing parameters. Multiparameter squeezing provides a practical and versatile concept that paves the way to the development of quantum-enhanced estimation of multiple phases, gradients, and fields, and for the efficient characterization of multimode quantum states in atomic and optical sensor networks.

arXiv:1910.14014Nature CommunicationsJul 30, 202088 citations

Multiparameter estimation with an array of entangled atomic sensors

Yifan Li, Lex E. Joosten, Youcef Baamara +4 more

In quantum metrology, entangled states of many-particle systems are investigated to enhance measurement precision of the most precise clocks and field sensors. Whereas single-parameter quantum metrology is well established, joint multiparameter estimation poses conceptual challenges and has been explored only theoretically. We experimentally demonstrated multiparameter quantum metrology with an array of entangled atomic ensembles. By splitting a spin-squeezed ensemble, we created an atomic sensor array featuring intersensor entanglement that can be flexibly configured to enhance measurement precision of multiple parameters jointly. Using an optimal estimation protocol, we achieved substantial gains over the standard quantum limit in key multiparameter estimation tasks, thus grounding the concept of quantum enhancement of field sensor arrays and imaging devices.In quantum metrology, entangled states of many-particle systems are investigated to enhance measurement precision of the most precise clocks and field sensors. Whereas single-parameter quantum metrology is well established, joint multiparameter estimation poses conceptual challenges and has been explored only theoretically. We experimentally demonstrated multiparameter quantum metrology with an array of entangled atomic ensembles. By splitting a spin-squeezed ensemble, we created an atomic sensor array featuring intersensor entanglement that can be flexibly configured to enhance measurement precision of multiple parameters jointly. Using an optimal estimation protocol, we achieved substantial gains over the standard quantum limit in key multiparameter estimation tasks, thus grounding the concept of quantum enhancement of field sensor arrays and imaging devices.

arXiv:2504.08677ScienceJan 22, 20266 citations

Single-Ensemble Multiparameter Squeezing with Qudits

Xiaoshui Lin, Chunlei Qu, Chong Zu +1 more

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.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.

quant-pharXiv:2605.26377May 27, 20260 citations

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.