Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2607.02962

Entanglement Drives Common Noise into the Strong-Coupling Regime

Yizhe Zhou·Xusheng Lei·Xing Heng·Zuoxian Wang·Danyue Ma
View original source ↗Read source document ↗Export metadata ↓

Abstract

Under Gaussian collective dephasing parallel to the signal, the superdecoherence of an $N$-atom Greenberger--Horne--Zeilinger (GHZ) state cancels its gain in Fisher information, so GHZ frequency sensitivity is limited to an atom-number-independent floor. We demonstrate that this floor is a property of Gaussian diffusion: a single common phase kick can at most randomize the phase of an $N$-atom coherence, so discrete events at rate $Γ$ cannot dephase any coherence order faster than $2Γ$. At the same single-atom coherence time, finite-rate Poisson kicks with an absolutely continuous amplitude law therefore saturate the order-$N$ decay rate and restore Heisenberg scaling. We prove that Gaussian diffusion is the worst case for GHZ and Dicke-cat probes under this calibration, that only the Brownian component of Lévy phase noise sets the asymptotic floor, and that the $1/N$ exponent is optimal for parallel Ramsey protocols. These results identify the counting statistics of the common noise, rather than its spectrum, as the property that bounds superdecoherence.

Explore related subjects

quant-ph

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Yizhe Zhou, Xusheng Lei, Xing Heng, Zuoxian Wang, Danyue Ma. 2026-09-12. Entanglement Drives Common Noise into the Strong-Coupling Regime. https://arxiv.org/abs/2607.02962

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Measurement-Induced Local Dephasing Generates Symmetrically Located Entangled Sites in a Fermionic Tight-Binding Lattice

We investigate an odd-sized fermionic open tight-binding chain subjected to stochastic projective measurements at its central site, effectively inducing localized dephasing. Focusing initially on the single-particle regime, we demonstrate that when the system is prepared in an even-parity state, the dynamics under central-site dephasing drive it toward a nontrivial steady state, which we characterize through both analytical and numerical approaches. Remarkably, this steady state exhibits long-range quantum correlations in the form of symmetrically positioned, pairwise entangled sites across the chain. We further show that the degree of pairwise mode entanglement can be significantly enhanced by increasing the particle number, provided the system is initialized within a specific symmetry sector associated with an underlying strong symmetry operator. Our results identify a minimal measurement-induced route for generating symmetry-selected long-range pairwise mode entanglement, with possible implications for quantum communication and distributed quantum information processing.

quant-ph↗
arXiv2026

Role of scrambling and noise in temporal information processing with quantum systems

Scrambling quantum systems have attracted attention as effective substrates for temporal information processing. Here we consider a quantum reservoir processing framework that captures a broad range of physical computing models with quantum systems. We examine the scalability and memory retention of the model with scrambling reservoirs modelled by high-order unitary designs in both noiseless and noisy settings. In the former regime, we show that measurement readouts become exponentially concentrated with increasing reservoir size, yet strikingly do not worsen with the reservoir iterations. Thus, while repeatedly reusing a small scrambling reservoir with quantum data might be viable, scaling up the problem size deteriorates generalization unless one can afford an exponential shot overhead. In contrast, the memory of early inputs and initial states decays exponentially in both reservoir size and reservoir iterations. In the noisy regime, we also prove that memory decays exponentially in time for local noisy channels. These results required us to introduce new proof techniques for bounding concentration in temporal quantum models. Beyond this extreme scrambling regime, we numerically demonstrate that exponential concentration can still exist even with a physical reservoir such as an Ising model whenever the reservoir operates in a quantum-chaotic phase. In contrast, physical reservoirs in a many-body localized phase and at the edge of chaos appear to not suffer from such phenomena

quant-ph↗
arXiv2026

Superpositions of Quantum Gaussian Processes

We generalise the Gaussian formalism of Continuous Variable (CV) systems to describe their entanglement with Discrete Variable (DV) systems, leading to superpositions of CV Gaussian states. A new class of CV-DV entangled states, named Gaussian-Branched Cat States (GBCSs), yields an analytical formalism to describe quantum hybrid systems. GBCSs are fully characterised by their superposed phase-space parameters: sets of generalised complex first moments and covariance matrices, along with the DV reduced density matrix (phases and contrasts). These states arise in all the instances where Gaussian dynamics, operations, and measurements are performed conditionally on a DV state. The time evolution of the GBCS phase-space parameters allows one -- via a new set of equations in closed form -- to analytically treat a large set of unitary and open dynamics, generated by Gaussian Hamiltonians labelled by DV eigenvalues. Conditional operations, such as displacements and rotations, and Gaussian measurements (homodyne/heterodyne) jointly with DV projectors, can be both described as maps on GBCS's parameters. A phase-space perturbation theory is given to extend the analysis to non-orthogonal DV super-operators, e.g. DV decay. We showcase our general formalism with two paradigmatic examples of experimental modelling: (i) a dispersively coupled qubit to a driven parametric amplifier; (ii) a levitated nanoparticle undergoing Stern-Gerlach matter-wave interferometry in a diffusive environment. Both examples highlight the generation of novel Wigner negativities through qubit measurements.

quant-ph↗