Optimal Gain Sensing of Quantum-Limited Phase-Insensitive Amplifiers

Nair, Ranjith; Tham, Guo Yao; Gu, Mile

doi:10.1103/physrevlett.128.180506

Cited by 6 publications

(7 citation statements)

References 58 publications

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“…Indeed, if we have a constraint on the total power, then the larger the bandwidth the better is the achievable precision. This effect is similar to what happens in the quantum estimation of the amplifier gain, as analysed in reference [46]. In the amplifier case, this happens also at zero temperature, as amplification is an active operation for any temperature value.…”

Section: Optimal Total Qfisupporting

confidence: 76%

Gaussian quantum estimation of the loss parameter in a thermal environment

Jonsson¹,

Candia²

2022

J. Phys. A: Math. Theor.

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Lossy bosonic channels play an important role in a number of quantum information tasks, since they well approximate thermal dissipation in an experiment. Here, we characterize their metrological power in the idler-free and entanglement-assisted cases, using respectively single- and two-mode Gaussian states as probes. In the problem of estimating the loss parameter, we study the power-constrained quantum Fisher information (QFI) for generic temperature and loss parameter regimes, showing qualitative behaviours of the optimal probes. We show semi-analytically that the two-mode squeezed-vacuum state optimizes the QFI for any value of the loss parameter and temperature. We discuss the optimization of the {\it total} QFI, where the number of probes is allowed to vary by keeping the total power constrained. In this context, we elucidate the role of the ``shadow-effect'', or passive signature, for reaching a quantum advantage. Finally, we discuss the implications of our results for the quantum illumination and quantum reading protocols.

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Section: Optimal Total Qfisupporting

confidence: 76%

Gaussian quantum estimation of the loss parameter in a thermal environment

Jonsson¹,

Candia²

2022

J. Phys. A: Math. Theor.

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“…where n j i ¼ M ℓ¼1 n ℓ j i is the number state basis of the M-mode signal S, p n 's are probabilities and normalized to unity and ancilla states f χ n j ig are normalized but not necessarily orthogonal 26,27 . We adopt the vector notation n = {n 1 , ⋯ , n M }.…”

Section: General Noise Sensing Strategiesmentioning

confidence: 99%

“…The ultimate precision limit of DM search can therefore be understood from the ultimate precision limit of additive noise sensing. However, while the ultimate limits of phase sensing 22 , displacement sensing 23,24 , loss sensing 25,26 and amplifier gain sensing 27 have been explored, little is known about the limit of noise sensing 28 in bosonic quantum channels when there is energy constraint.…”

Section: Introductionmentioning

confidence: 99%

“…In this paper, we derive the ultimate precision limit of energyconstrained 26,27 noise sensing in covariant bosonic quantum channels, and therefore reveal the DM search performance limit allowed by quantum physics. Via quantum Fisher information (QFI) calculations, we show that entangled source in the form of two-mode squeezed vacuum (TMSV) is optimal for noise sensing in the parameter region of interest.…”

Section: Introductionmentioning

confidence: 99%

“…npj Quantum Information (2023)27 Published in partnership with The University of New South Wales 1234567890():,;…”

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confidence: 99%

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Ultimate precision limit of noise sensing and dark matter search

Shi

Zhuang

2023

npj Quantum Inf

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The nature of dark matter is unknown and calls for a systematical search. For axion dark matter, such a search relies on finding feeble random noise arising from the weak coupling between dark matter and microwave haloscopes. We model such process as a quantum channel and derive the fundamental precision limit of noise sensing. An entanglement-assisted strategy based on two-mode squeezed vacuum is thereby demonstrated optimal, while the optimality of a single-mode squeezed vacuum is found limited to the lossless case. We propose a “nulling” measurement (squeezing and photon counting) to achieve the optimal performances. In terms of the scan rate, even with 20-decibel of strength, single-mode squeezing still underperforms the vacuum limit which is achieved by photon counting on vacuum input; while the two-mode squeezed vacuum provides large and close-to-optimum advantage over the vacuum limit, thus more exotic quantum resources are no longer required. Our results highlight the necessity of entanglement assistance and microwave photon counting in dark matter search.

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Optimal quantum metrology of two-photon absorption

Karsa,

Nair,

Chia

et al. 2024

Quantum Sci. Technol.

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Two-photon absorption (TPA) is a nonlinear optical process with wide-ranging applications from spectroscopy to super-resolution imaging. Despite this, the precise measurement and characterisation of TPA parameters are challenging due to their inherently weak nature. We study the potential of single-mode quantum light to enhance TPA parameter estimation through the quantum Fisher information (QFI). Discrete variable (DV) quantum states (defined to be a finite superposition of Fock states) are optimised to maximise the QFI for given absorption, revealing a quantum advantage compared to both the coherent state (classical) benchmark and the single-mode squeezed vacuum state. For fixed average energy ̄n ∈ 2N, the Fock state is shown to be optimal for large TPA parameters, while a superposition of vacuum and a particular Fock state is optimal for small absorption for all ̄n. This differs from single-photon absorption where the Fock state is always optimal. Notably, photon counting is demonstrated to offer optimal or nearly optimal performance compared to the QFI bound for all levels of TPA parameters for the optimised quantum probes, and their quantum advantage is shown to be robust to single-photon loss. Our findings provide insight into known limiting behaviours of Gaussian probes and their different Fisher information (FI) scalings under photon counting (∝ ̄n2 for squeezed vacuum states versus ̄n3 for coherent states). The squeezed state outperforms coherent states for small TPA parameters but underperforms in the intermediate regime, becoming comparable in the large absorption limit. This can be explained through fundamental differences between behaviours of even and odd number Fock states: the former’s QFI diverges in both large and small absorption limits, while the latter diverges only in the small absorption limit, dominating at intermediate scales.

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Optimal Gain Sensing of Quantum-Limited Phase-Insensitive Amplifiers

Cited by 6 publications

References 58 publications

Gaussian quantum estimation of the loss parameter in a thermal environment

Gaussian quantum estimation of the loss parameter in a thermal environment

Ultimate precision limit of noise sensing and dark matter search

Optimal quantum metrology of two-photon absorption

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