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Restoring Heisenberg scaling in noisy quantum metrology by monitoring the environment

We study quantum frequency estimation for $N$ qubits subjected to independent Markovian noise, via strategies based on time-continuous monitoring of the environment. Both physical intuition and an extended convexity property of the quantum Fisher …

Ultimate limits for quantum magnetometry via time-continuous measurements

We address the estimation of the magnetic field B acting on an ensemble of atoms with total spin J subjected to collective transverse noise. By preparing an initial spin coherent state, for any measurement performed after the evolution, the …

Non-Markovianity by undersampling in quantum optical simulators

Continuous-time quantum walks on spatially correlated noisy lattices

We address memory effects and diffusive properties of a continuous-time quantum walk on a one-dimensional percolation lattice affected by spatially correlated random telegraph noise. In particular, by introducing spatially correlated time-dependent …

Effective description of the short-time dynamics in open quantum systems

We address the dynamics of a bosonic system coupled to either a bosonic or a magnetic environment and derive a set of sufficient conditions that allow one to describe the dynamics in terms of the effective interaction with a classical fluctuating …

All-optical quantum simulator of qubit noisy channels

We suggest and demonstrate an all-optical quantum simulator for single-qubit noisy channels originating from the interaction with a fluctuating field. The simulator employs the polarization degree of freedom of a single photon and exploits its …

Probing the diamagnetic term in light-matter interaction

Should the Dicke model of light-matter interaction include a diamagnetic term? This question has generated intense debate in the literature, and is particularly relevant in the modern contexts of cavity and circuit quantum electrodynamics. We design …

Quantum metrology beyond the quantum Cramér-Rao theorem

A usual assumption in quantum estimation is that the unknown parameter labels the possible states of the system, while it influences neither the sample space of outcomes nor the measurement aimed at extracting information on the parameter itself. …

Probing deformed quantum commutators

Quantum gravity theories predict a minimal length at the order of magnitude of the Planck length, under which the concepts of space and time lose every physical meaning. In quantum mechanics, the insurgence of such minimal length can be described by …

Enhanced estimation of loss in the presence of Kerr nonlinearity

We address the characterization of dissipative bosonic channels and show that estimation of the loss rate by Gaussian probes (coherent or squeezed) is improved in the presence of Kerr nonlinearity. In particular, enhancement of precision may be …