The fragility of quantum metrological advantages under loss remains a major barrier to practical quantum sensing. For a two-photon-driven (TPD) Kerr resonator (TPD-Kerr model) subject to unavoidable single-photon loss (SPL), both the quantum Fisher information gain and squeezing level exhibit hard-to-track long-lived damped oscillations, restricting useful sensing and squeezing to extremely short time windows. We show that adding engineered two-photon loss (ETPL) -- forming a TPD-Kerr-ETPL hybrid model -- significantly mitigates these oscillations and converts the decay into a smooth, monotonic drop. This extends the high-sensitivity windows by over an order of magnitude. Moreover, we reveal a temporal hierarchy of quantum resources: the initial boost in metrological sensitivity arises from Gaussian squeezing, while sustained high-precision sensing stems from dissipatively stabilized non-Gaussian even-parity cat states. Crucially, only in models that include ETPL -- such as the TPD-Kerr-ETPL and TPD-ETPL systems -- does the dynamics actively mitigate SPL's detrimental effects, transforming damped oscillation into a smooth, easily trackable trajectory and enabling a prolonged, usable metrological window. Our approach transcends encoding-based or feedback-controlled schemes, offering a fully autonomous route to high-precision measurement without real-time feedback control. This establishes a general design principle: engineered loss, combined with appropriate driving, can actively preserve metrologically useful non-Gaussian quantum resources even in the presence of SPL -- paving the way toward robust, scalable quantum sensors in superconducting circuits, optomechanics, and trapped-ion platforms.
The fragility of quantum metrological advantages under loss remains a major barrier to practical quantum sensing. For a two-photon-driven (TPD) Kerr resonator (TPD-Kerr model) subject to unavoidable single-photon loss (SPL), both the quantum Fisher information gain and squeezing level exhibit hard-to-track long-lived damped oscillations, restricting useful sensing and squeezing to extremely short time windows. We show that adding engineered two-photon loss (ETPL) -- forming a TPD-Kerr-ETPL hybrid model -- significantly mitigates these oscillations and converts the decay into a smooth, monotonic drop. This extends the high-sensitivity windows by over an order of magnitude. Moreover, we reveal a temporal hierarchy of quantum resources: the initial boost in metrological sensitivity arises from Gaussian squeezing, while sustained high-precision sensing stems from dissipatively stabilized non-Gaussian even-parity cat states. Crucially, only in models that include ETPL -- such as the TPD-Kerr-ETPL and TPD-ETPL systems -- does the dynamics actively mitigate SPL's detrimental effects, transforming damped oscillation into a smooth, easily trackable trajectory and enabling a prolonged, usable metrological window. Our approach transcends encoding-based or feedback-controlled schemes, offering a fully autonomous route to high-precision measurement without real-time feedback control. This establishes a general design principle: engineered loss, combined with appropriate driving, can actively preserve metrologically useful non-Gaussian quantum resources even in the presence of SPL -- paving the way toward robust, scalable quantum sensors in superconducting circuits, optomechanics, and trapped-ion platforms.
In this work, we investigate the dissipative generation of metrologically useful steady states in a generalized atom-cavity system that incorporates two-photon exchange, diamagnetic interactions, and auxiliary nonlinearities inherent to superconducting circuits. By quantifying the normalized Quantum Fisher Information (QFI), we demonstrate that the interplay between coherent driving and Kerr–Stark anharmonicity allows for the autonomous preparation of states that surpass the Standard Quantum Limit (SQL). Our results reveal that unlike simple Gaussian squeezing, the introduction of realistic nonlinearities induces non-Gaussian phase-space distortions, accompanied by small but finite Wigner negativity, that maximise the information content for photon-number encoding while maintaining a mean photon number below unity throughout. The Mandel Q M parameter is found to exceed the thermal-state reference 〈 n ^ 〉 across all dynamical regimes and coupling strengths, providing a stringent quantitative demonstration that the observed super-Poissonian statistics originate from non-classical correlations rather than thermal fluctuations. Crucially, a rigorous spectral decomposition of the Liouvillian superoperator confirms that these high-sensitivity regimes are protected by a finite spectral gap, precluding critical slowing down and ensuring that state preparation occurs on timescales significantly shorter than typical qubit decoherence times. These findings establish a viable blueprint for engineering always-on quantum sensors that are both metrologically superior and dynamically robust.
We study the squeezing dynamics in a Kerr-nonlinear oscillator, and quantify the metrological usefulness of the resulting states. Even if the nonlinearity limits the attainable squeezing by making the evolution non-Gaussian, the states obtained still have a high quantum Fisher information for sensing displacements. However, contrary to the Gaussian case, the amplitude of the displacement cannot be estimated by simple quadrature measurements. Therefore, we propose the use of a measurement-after-interaction protocol where a linear quadrature measurement is preceded by an additional nonlinear evolution, and show the significant sensitivity enhancement that can be obtained. Our results are robust when considering realistic imperfections such as energy relaxation, and can be implemented in state-of-the-art experimental setups.
Optical and quantum-optical systems face a fundamental trilemma: maximizing coherence lifetime, enabling nonlinear interaction, and extracting metrological information all impose competing demands on photon statistics, mode structure, and dissipation engineering. This paper synthesizes six to seven specific findings from recent arXiv preprints spanning physics.optics, physics.atom-ph, and quant-ph to argue for a candidate structural pattern — offered as a heuristic reading, not a formal derivation — in which *measurement-conditioned feedback*, *engineered dissipation*, and *mode-selective nonlinearity* jointly determine the accessible precision and coherence budget of an optical quantum platform. Concretely, we draw on: (1) the non-Markovian Kerr feedback result demonstrating an unbounded resource separation between linear and nonlinear continuous-variable reservoirs [corpus:arxiv:2606.06689]; (2) the optomechanical enhanced-susceptibility sensing scheme showing divergent quantum Fisher information scaling [corpus:arxiv:2606.09716]; (3) the Sagnac-effect nonreciprocal rotation sensor exploiting virtual excitations in the ultrastrong coupling regime [corpus:arxiv:2606.10984]; (4) the certified network quantum sensing protocol that unifies cryptographic integrity with metrological sensitivity [corpus:arxiv:2606.10700]; (5) the collective emission survival in subwavelength solid-state emitter arrays despite two-orders-of-magnitude inhomogeneous broadening [corpus:arxiv:2606.07458]; (6) the anti-de Sitter spacetime emulation via engineered photonic waveguide arrays [corpus:arxiv:2606.09501]; and (7) the superconducting tantalum resonator platform achieving median internal Q-factors above 40 million on 300 mm industrial wafers [corpus:arxiv:2606.10719]. The falsification path for the central claim is: if a purely Gaussian optical reservoir with no Kerr element and no measurement-conditioned feedback can be shown to achieve cross-time nonlinear rank exceeding 2N for an N-mode system, the unbounded resource separation argument collapses and the proposed framework loses its primary mechanistic pillar. --- Authorship: Saluca Agentic AI Research Team (Saluca LLC). AI-drafted from arXiv preprint corpus on the date in the filename. Cited arXiv preprints: 2606.06341, 2606.06455, 2606.06689, 2606.07322, 2606.07331, 2606.07352, 2606.07458, 2606.09501, 2606.09602, 2606.09649, 2606.09716, 2606.10700, 2606.10719, 2606.10865, 2606.10984, 2606.11002, 2606.11048
Quantum metrology employs quantum resources to achieve measurement precision beyond classical limits. This work investigates a Mach--Zehnder interferometer incorporating a Kerr nonlinear phase shifter, with photon-added two-mode squeezed coherent states generated via four-wave mixing as input. We demonstrate that increasing both the photon-addition order and the input resource strength systematically enhances phase sensitivity, quantum Fisher information, and the corresponding quantum Cramér--Rao bound. The proposed system not only surpasses the standard quantum limit but also approaches or exceeds the Heisenberg limit for linear phase shifts, while Kerr nonlinearity enables surpassing the super-Heisenberg limit. Furthermore, the scheme exhibits enhanced robustness against photon loss, providing a promising pathway toward practical high-precision quantum metrology applications.
Abstract Photonic cat states stored in high-Q resonators show great promise for hardware efficient universal quantum computing. We propose an approach to efficiently prepare such cat states in a Kerr-nonlinear resonator by the use of a two-photon drive. Significantly, we show that this preparation is robust against single-photon loss. An outcome of this observation is that a two-photon drive can eliminate undesirable phase evolution induced by a Kerr nonlinearity. By exploiting the concept of transitionless quantum driving, we moreover demonstrate how non-adiabatic initialization of cat states is possible. Finally, we present a universal set of quantum logical gates that can be performed on the engineered eigenspace of such a two-photon driven resonator and discuss a possible realization using superconducting circuits. The robustness of the engineered subspace to higher-order circuit nonlinearities makes this implementation favorable for scalable quantum computation.
We propose a high-precision phase estimation scheme in a hybrid interferometer by synergistically combining a Kerr nonlinear phase shifter and multi-photon subtraction operations. Using a coherent state and a vacuum state as input resources, we systematically evaluate the phase sensitivity via homodyne detection and analyze the quantum Fisher information as well as the quantum Cramér-Rao bound under both ideal and lossy conditions. Our results show that the joint integration of Kerr nonlinearity and multi-photon subtraction yields remarkable advantages over either technique used alone. The proposed scheme enables the phase sensitivity to surpass the standard quantum limit, exceed the conventional Heisenberg scaling (1/N), and approach the super-Heisenberg scaling (1/N2)-a direct consequence of Kerr nonlinearity. More precisely, the super-Heisenberg scaling $\propto $ 1/N2 is the ultimate precision limit permitted by the k=2 Kerr nonlinearity and does not violate the fundamental Heisenberg limit for linear phase accumulation. Even under moderate internal photon loss, the system maintains high precision and exhibits enhanced robustness to decoherence. The Kerr nonlinearity introduces an intensity-dependent phase shift proportional to the squared photon number, while multi-photon subtraction tailors non-Gaussian states to strengthen phase information extraction. Compared with existing schemes based on hybrid interferometers or SU(1,1) interferometers, our architecture achieves superior precision and stronger loss resilience. All components are experimentally accessible with current quantum optical technologies. This work provides a promising route for practical high-precision quantum metrology and quantum sensing.