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David Vitali

Publications and source records attributed to David Vitali.

At least 19 recordsLinked to original sources
arXiv2026

Multimode Gaussian steady state engineering in optomechanical systems with a squeezed reservoir

We investigate a theoretical protocol for the dissipative stabilization of mechanical quantum states in a multimode optomechanical system composed of multiple optical and mechanical modes. The scheme employs a single squeezed reservoir that drives one of the optical modes, while the remaining optical modes mediate an effective phonon-phonon interaction Hamiltonian. The interplay between these coherent interactions and the dissipation provided by the squeezed bath enables the steady-state preparation of targeted quantum states of the mechanical modes. In the absence of significant uncontrolled noise sources, the resulting dynamics closely approximate the model introduced in [Phys. Rev. Lett. 126, 020402 (2021)]. We analyze the performance of this protocol in generating mechanical cluster states defined on rectangular graphs.

quant-ph↗
arXiv2026

Can gravity mediate the transmission of quantum information?

We propose an experiment to test the non-classicality of the gravitational interaction. We consider two optomechanical systems that are perfectly isolated, except for a weak gravitational coupling. If a suitable resonance condition is satisfied, an optical signal can be transmitted from one system to the other over a narrow frequency band, a phenomenon that we call gravitationally induced transparency. In this framework, the challenging problem of testing the quantum nature of gravity is mapped to the easier task of determining the non-classicality of the gravitationally-induced optical channel: If the optical channel is not entanglement-breaking, then gravity must have a quantum nature. This approach is applicable without making any assumption on the, currently unknown, correct model of gravity in the quantum regime. In the second part of this work, we model gravity as a quadratic Hamiltonian interaction (e.g. a weak Newtonian force), resulting in a Gaussian thermal attenuator channel between the two systems. Depending on the strength of thermal noise, the system presents a sharp transition from an entanglement-breaking to a non-classical channel capable not only of entanglement preservation but also of asymptotically perfect quantum communication.

quant-ph↗
arXiv2025

Deep-learned error mitigation via partially knitted circuits for the variational quantum eigensolver

The variational quantum eigensolver (VQE) is generally regarded as a promising quantum algorithm for near-term noisy quantum computers. However, when implemented with the deep circuits that are in principle required for achieving a satisfactory accuracy, the algorithm is strongly limited by noise. Here, we show how to make VQE functional via a tailored error mitigation technique based on deep learning. Our method employs multilayer perceptrons trained on the fly to predict ideal expectation values from noisy outputs combined with circuit descriptors. Importantly, a circuit knitting technique with partial knitting is adopted to substantially reduce the classical computational cost of creating the training data. We also show that other popular general-purpose quantum error mitigation techniques do not reach comparable accuracies. Our findings highlight the power of deep-learned quantum error mitigation methods tailored to specific circuit families, and of the combined use of variational quantum algorithms and classical deep learning.

quant-ph↗
arXiv2025

Large amplitude mechanical coherent states and detection of weak nonlinearities in cavity optomechanics

The generation of large-amplitude coherent states of a massive mechanical resonator, and their quantum-limited detection represent useful tools for quantum sensing and for testing fundamental physics theories. In fact, any weak perturbation may affect the coherent quantum evolution of the prepared state, providing a sensitive probe for such a perturbation. Here we consider a cavity optomechanical setup and the case of the detection of a weak mechanical nonlinearity. We consider different strategies, first focusing on the stationary dynamics in the presence of multiple tones driving the system, and then focusing on non-equilibrium dynamical strategies. These methods can be successfully applied for measuring Duffing-like material nonlinearities, or effective nonlinear corrections associated with quantum gravity theories.

quant-ph↗
arXiv2025

Mechanical characterization of a membrane with an on-chip loss shield in a cryogenic environment

The quantum transduction of an rf/microwave signal to the optical domain, and vice versa, paves the way for technologies that exploit the advantages of each domain to perform quantum operations. Since electro-optomechanical devices implement a simultaneous coupling of a mechanical oscillator to both an rf/microwave field and an optical field, they are suitable for the realization of a quantum transducer. The membrane-in-the-middle setup is a possible solution, once its vibrational mode is cooled down to ultra cryogenic temperature for achieving quantum operation. This work is focused on the mechanical characterization via an optical interferometric probe, down to T=18mK, of a loss-shielded metalized membrane designed for this purpose. A stroboscopic technique has been exploited for revealing a mechanical quality factor up to 64 millions at the lowest temperature. In fact, with continuous illumination and a cryostat temperature below 1K, the heat due to optical absorption is not efficiently dissipated anymore, and the membrane remains hotter than its environment.

quant-ph↗
arXiv2025

Full dynamics of two-membrane cavity optomechanics

In a two-membrane cavity optomechanical setup, two semi-transparent membranes placed within an optical Fabry-Pérot cavity yield a nontrivial dependence of the frequency of a mode of the optical cavity on the membranes' positions, which is due to interference. However, the system dynamics is typically described by a radiation pressure force treatment in which the frequency shift is expanded stopping at first order in the membrane displacements. In this paper, we study the full dynamics of the system obtained by considering the exact nonlinear dependence of the optomechanical interaction between two membranes' vibrational modes and the driven cavity mode. We then compare this dynamics with the standard treatment based on the Hamiltonian linear interaction, and we find the conditions under which the two dynamics may significantly depart from each other. In particular, we see that a parameter regime exists in which the customary first-order treatment provides distinct and incorrect predictions for the synchronization of two self-sustained mechanical limit-cycles, and for Gaussian entanglement of the two membranes in the case of two-tone driving.

quant-ph↗
arXiv2025

Two-membrane etalon

Optomechanics with semi-transparent membrane multi-oscillators in a high-finesse cavity is an established solution for designing the dispersive interaction, and reaching many achievements, such as the study of non-linear dynamics, heat transfer, and so on. The multi-oscillators are dielectric slabs, usually with low reflectivity, constituting an etalon. Here we propose the theoretical and experimental investigation of a low-finesse optical cavity formed by two (nominally identical) parallel semi-transparent membranes. The experiment consists in laser-driving the cavity, detecting interferometrically the field reflected by the etalon, and measuring the intensity of the transmitted field, for different distances within the two membranes. A complete characterization of the membrane sandwich is provided. On the other hand, we developed an analytical model to describe the fields, which reproduces all the experimental results, under specific approximations. As expected, the model reproduces the known results when high-reflectivity, and/or fixed mirrors conditions are restored. This work paves the way for a complete and analytical model to describe multi-oscillators "membrane-in-the-middle" optomechanics.

quant-ph↗
arXiv2024

Optics-assisted enhanced sensing at radio-frequencies in an optoelectromechanical system

We investigate a scheme to enhance the sensitivity in detecting weak variations in a parameter of an optoelectromechanical system by detecting the system response at radio frequencies. We consider a setup, where either one or two mechanical modes mediate the interaction between an optical cavity and an rf resonator. This system can be operated in a regime of impedance matching where thermal fluctuations are redistributed among the system elements, and, in particular, rf output noise can be reduced to the quantum vacuum noise level. We show that this effect can be used to boost the sensitivity in detecting parameter variations also in regimes of high thermal noise. We characterize the performance of this protocol in detecting variations in the capacitance of the rf resonator.

quant-ph↗
arXiv2024

Noise level of a ring laser gyroscope in the femto-rad/s range

Absolute angular rotation rate measurements with sensitivity better than prad/s would be beneficial for fundamental science investigations. On this regard, large frame Earth based ring laser gyroscopes are top instrumentation as far as bandwidth, long--term operation, and sensitivity are concerned. Here, we demonstrate that the GINGERINO active--ring laser upper limiting noise is close to $2 \times 10^{-15}$ rad/s for $\sim 2 \times 10^5$ s of integration time, as estimated by the Allan deviation evaluated in a differential measurement scheme. This is more than a factor 10 better than the theoretical prediction so far accounted for ideal ring lasers shot--noise with the two beams counter--propagating inside the cavity considered as two independent propagating modes. This feature is related to the peculiarity of real ring laser system dynamics that causes phase cross--talking among the two counter--propagating modes. In this context, the independent beam model is, then, not applicable and the measured noise limit falls below the expected one.

quant-ph↗
arXiv2024

Synergy between noisy quantum computers and scalable classical deep learning

We investigate the potential of combining the computational power of noisy quantum computers and of classical scalable convolutional neural networks (CNNs). The goal is to accurately predict exact expectation values of parameterized quantum circuits representing the Trotter-decomposed dynamics of quantum Ising models. By incorporating (simulated) noisy expectation values alongside circuit structure information, our CNNs effectively capture the underlying relationships between circuit architecture and output behaviour, enabling predictions for circuits with more qubits than those included in the training set. Notably, thanks to the quantum information, our CNNs succeed even when supervised learning based only on classical descriptors fails. Furthermore, they outperform a popular error mitigation scheme, namely, zero-noise extrapolation, demonstrating that the synergy between quantum and classical computational tools leads to higher accuracy compared with quantum-only or classical-only approaches. By tuning the noise strength, we explore the crossover from a computationally powerful classical CNN assisted by quantum noisy data, towards rather precise quantum computations, further error-mitigated via classical deep learning.

quant-ph↗
arXiv2024

Engineering Entangled Schrodinger Cat States of Separated Cavity Modes in Cavity-QED

We provide a scheme by utilizing a two-cavity setup to generate useful quantum mechanically entangled states of two cavity fields, which themselves are prepared in Schrodinger cat states. The underlying atom-field interaction is considered off-resonant and three atoms are successively sent through the cavities, initially fed with coherent fields. Analytical solution of the protocol, followed by conditional measurements on the atoms, produce a family of eight such entangled states. Entanglement properties of the obtained states are characterized by the Von Neumann entropy. We reveal the parameter domain for tuning the entanglement, the prime tuning parameters being the atom-field interaction time and the field amplitudes. The parameter domains for both quasi-Bell and non quasi-Bell states are discussed. We also present a Wigner phase space representation of the reduced state of the cavity, showing negative values and interference patterns similar to those of a compass state, used in quantum precision measurements, and despite its large entropy.

quant-ph↗
arXiv2023

Amplitude and phase noise in Two-membrane cavity optomechanics

Cavity optomechanics is a suitable field to explore quantum effects on macroscopic objects and develop quantum technology applications. A perfect control of the laser noise is required to operate the system in such extreme conditions necessary to reach the quantum regime. In this paper, we consider a Fabry-Perót cavity, driven by two laser fields, with two partially reflective SiN membranes inside it. We describe the effects of amplitude and phase noise on the laser introducing two additional noise terms in the Langevin equations of the system's dynamics. Experimentally, we add an artificial source of noise on the laser. We calibrate the intensity of the noise, inject it into the system, and check the validity of the theoretical model. This procedure provides an accurate description of the effects of a noisy laser in the optomechanical setup and allows for quantifying the amount of noise.

quant-ph↗
arXiv2023

Low Noise Opto-Electro-Mechanical Modulator for RF-to-Optical Transduction in Quantum Communications

In this work, we present an Opto-Electro-Mechanical Modulator (OEMM) for RF-to-optical transduction realized via an ultra-coherent nanomembrane resonator capacitively coupled to an rf injection circuit made of a microfabricated read-out able to improve the electro-optomechanical interaction. This device configuration can be embedded in a Fabry-Perot cavity for electromagnetic cooling of the LC circuit in a dilution refrigerator exploiting the opto-electro-mechanical interaction. To this aim, an optically measured steady-state frequency shift of 380 Hz was seen with a polarization voltage of 30 V and a $Q$-factor of the assembled device above $10^6$ at room temperature. The rf-sputtered titanium nitride layer can be made superconductive to develop efficient quantum~transducers.

quant-ph↗
arXiv2023

Enhancing strength and range of atom-atom interaction in a coupled-cavity array via parametric drives

Coherent long-range interactions between atoms are a prerequisite for numerous applications in the field of quantum information science, but they usually decrease exponentially with the increase in atomic separation. Here we present an appealing method to dramatically enhance the long-range atom-atom interaction mediated by a coupled-cavity array that is subjected to two-photon (parametric) drives. Our method allows one to greatly amplify both the localization length of the single-photon bound-state wavefunction and the effective atom-photon coupling strength, resulting in a significant improvement of photon-mediated coherent interaction between two distant atoms. Additionally, we illustrate this effect by analyzing how it facilitates the transfer of information and the creation of entanglement between the atoms.

quant-ph↗
arXiv2023

Dissipative stabilization of entangled qubit pairs in quantum arrays with a single localized dissipative channel

We study the dissipative stabilization of entangled states in arrays of quantum systems. Specifically, we are interested in the states of qubits (spin-1/2) which may or may not interact with one or more cavities (bosonic modes). In all cases only one element, either a cavity or a qubit, is lossy and irreversibly coupled to a reservoir. When the lossy element is a cavity, we consider a squeezed reservoir and only interactions which conserve the number of cavity excitations. Instead, when the lossy element is a qubit, pure decay and a properly selected structure of XY-interactions are taken into account. We show that in all cases, in the steady state, many pairs of distant, non-directly interacting qubits, which cover the whole array, can get entangled in a stationary way, by means of the interplay of dissipation and local interactions.

quant-ph↗
arXiv2023

Microwave quantum illumination with correlation-to-displacement conversion

Entanglement is vulnerable to degradation in a noisy sensing scenario, but surprisingly, the quantum illumination protocol has demonstrated that its advantage can survive. However, designing a measurement system that realizes this advantage is challenging since the information is hidden in the weak correlation embedded in the noise at the receiver side. Recent progress in a correlation-to-displacement conversion module provides a route towards an optimal protocol for practical microwave quantum illumination. In this work, we extend the conversion module to accommodate experimental imperfections that are ubiquitous in microwave systems. To mitigate loss, we propose amplification of the return signals. In the case of ideal amplification, the entire six-decibel error-exponent advantage in target detection error can be maintained. However, in the case of noisy amplification, this advantage is reduced to three-decibel. We analyze the quantum advantage under different scenarios with a Kennedy receiver in the final measurement. In the ideal case, the performance still achieves the optimal one over a fairly large range with only on-off detection. Empowered by photon number resolving detectors, the performance is further improved and also analyzed in terms of receiver operating characteristic curves. Our findings pave the way for the development of practical microwave quantum illumination systems.

quant-ph↗
arXiv2022

The ASIMOV Prize for scientific publishing -- HEP researchers trigger young people toward science

This work presents the ASIMOV Prize for scientific publishing, which was launched in Italy in 2016. The prize aims to bring the young generations closer to scientific culture, through the critical reading of popular science books. The books are selected by a committee that includes scientists, professors, Ph.D. and Ph.D. students, writers, journalists and friends of culture, and most importantly, over 800 school teachers. Students are actively involved in the prize, according to the best practices of public engagement: they read, review the books and vote for them, choosing the winner. The experience is quite successful: 12,000 students from 270 schools all over Italy participated in the last edition. The possibility of replicating this experience in other countries is indicated, as was done in Brazil in 2020 with more than encouraging results.

physics.soc-ph↗