arXiv subjects

Mohamed Hatifi

Publications and source records attributed to Mohamed Hatifi.

11 recordsLinked to original sources

arXiv2026

The Effect of Geometry on Thermodynamic Response

At the nano- and microscale, various patterns influence and shape thermal and optical response, making them essential for the survival of various biological species. In addition, controlling thermal radiation is vital for a broad range of applications, such as thermal management, spectroscopy, optoelectronics, and energy conversion technologies. For this reason, there is strong pressure to elucidate the physics of thermal radiation at the nanoscale. In this article, we provide evidence that complex nanoscale geometries affect thermal management, leading to an unusual thermal response in heat-capacity measurements as a function of temperature. Beyond identifying the structural constraints associated with this unusual thermodynamic response, the current study introduces the possibility of shaping the apparent heat-capacity response through geometry without necessarily altering the system's chemistry.

cond-mat.mtrl-sci↗

arXiv2026

Self-Generated Chiral Rotation in Whispering-Gallery Optomechanics

Backscattering in whispering-gallery-mode resonators is usually a passive mode-splitting mechanism produced by a fixed defect. Here, we show that, when the backscatterer is a mechanical angular degree of freedom, the same process becomes an angular-recoil backaction channel capable of generating chirality under reciprocal driving. A localized movable scatterer coherently converts photons between clockwise and counterclockwise whispering-gallery modes, transferring angular recoil in each circulation-changing event. In a weak-scattering driven-dissipative model, reciprocal bidirectional pumping gives zero net torque at rest, but rotation Doppler-shifts the two opposite scattering rates in opposite directions. For suitable detuning, this feedback produces negative angular friction, destabilizes the nonrotating reciprocal state, and selects one of two symmetry-related steady rotations. The threshold scales inversely with the square of the WGM azimuthal index. The mechanically chiral state produces a direction-dependent weak-probe response, visible as a Doppler splitting of the backscattered spectra, turning passive WGM mode splitting into a minimal mechanism for autonomous chiral optomechanics.

quant-ph↗

arXiv2026

Velocity-Controlled Directional Readout of Single Photons

Photodetection is usually treated in the frame in which the detector is at rest relative to the optical apparatus. We show that uniform motion of an electric Glauber detector changes the single-click POVM realized on two counterpropagating single-photon modes. Motion Doppler-shifts the alternatives in the detector frame; finite bandwidth then converts propagation direction into a detection bias without decohering the photon. For a Lorentzian response near one Doppler branch, the readout crosses from phase-sensitive to direction-sensitive with a quality-factor-enhanced onset. Finite-time integration adds Doppler-beat visibility loss, separating passive covariance from measurement change.

quant-ph↗

arXiv2026

Basis- and Channel-Selective Quantum Photodetection

Photodetection converts optical quantum states into measurement events, but the usual electric-field response model becomes restrictive when the detector response is shaped by cavity, superconducting, or metamaterial engineering. We develop a generalized quantum photodetection framework in which electric and magnetic field amplitudes contribute coherently to the detection operator, and analyze it in a far-field two-source geometry, a two-mode single-photon setting, and a lossy resonant detector model. The far-field reference case exhibits complete detector-amplitude cancellation, absent in the electric-only Glauber response, while the single-photon model shows that the detector continuously rotates the effective measurement basis and controls the first-order visibility via an exact closed-form law. In the resonant realization, a monitored radiative output channel can be dark while the detector remains internally excited and absorptive, with unit absorption of the matched input mode at critical coupling. These results identify basis-selective readout and channel-selective absorption as experimentally relevant signatures of engineered electric-magnetic photodetection.

quant-ph↗

arXiv2026

Autonomous phonon maser in levitated spin-mechanics

Levitated nanodiamonds hosting a single nitrogen-vacancy (NV) center provide an ultra-low-frequency mechanical mode with widely tunable dissipation and spin backaction under microwave dressing and optical pumping. We demonstrate that the driven NV spin can be tuned to act as an inverted gain medium for the center-of-mass motion, thereby stabilizing an autonomous phonon maser. In the separation-of-timescales regime where spin dynamics is fast, adiabatic elimination yields a reduced mechanical master equation with closed-form, detuning-dependent transition rates and a sharp threshold given by the sign change of the phonon-number damping. For representative levitated-NV parameters, we find that a percent-level dressed-basis inversion is sufficient to reach the threshold, and the small-signal gain can exceed the intrinsic mechanical loss by orders of magnitude. Full master-equation simulations confirm above-threshold self-oscillation and a phase-diffusing, coherent steady state, whose saturation follows the Maxwell-Bloch prediction.

quant-ph↗

arXiv2026

Geometry-Controlled Freezing and Revival of Bell Nonlocality through Environmental Memory

We show that the distance between two qubits coupled to a structured reservoir acts as a single geometric control that can store, revive, or suppress Bell nonlocality. In a mirror-terminated guide, quantum correlations lost to the bath return at discrete recurrence times, turning a product state into a Bell-violating one without any entangling drive (only local basis rotations/readout). In the continuum limit, we derive closed-form criteria for the emergence of nonlocality from backflow, and introduce a Bell-based analogue of the BLP measure to quantify this effect. We also show how subwavelength displacements away from a decoherence-free node quadratically reduce the lifetime of a dark state or bright state, enabling highly sensitive interferometric detection. All results rely on analytically solvable models and are compatible with current superconducting and nanophotonic platforms, offering a practical route to passive, geometry-controlled non-Markovian devices.

quant-ph↗

arXiv2025

Quantum Gravity Without Metric Quantization: From Hidden Variables to Hidden Spacetime Curvatures

Bohmian mechanics offers a deterministic alternative to conventional quantum theory through well-defined particle trajectories. While successful in nonrelativistic contexts, its extension to curved spacetime-and hence quantum gravity-remains unresolved. Here, we develop a covariant extension of Bohmian mechanics in curved spacetime that removes the need for metric quantization. From a Lagrangian formulation, we derive a generalized guidance equation in which Bohmian trajectories generate hidden curvature, replacing metric superposition with a statistical ensemble constrained by Heisenberg uncertainty, offering a novel perspective on quantum gravity. Consequently, in our approach, measuring the gravitational potential at a point unveils a pre-existing trajectory and its associated curvature-a departure from the observer-centric paradigm of standard quantum mechanics-providing an alternative in which gravitational effects emerge from deterministic quantum trajectories rather than wavefunction collapse. Numerical simulations in Robertson-Walker and cigar soliton spacetimes reveal that while quantum interference is curvature-sensitive, Zitterbewegung remains invariant, distinguishing fundamental quantum effects. Moreover, deviations from the Born rule in inhomogeneous spacetimes are observed and suggest gravity-induced quantum non-equilibrium. This new approach has far-reaching implications for the role of determinism and potential observational signatures of quantum non-equilibrium in cosmology.

gr-qc↗

arXiv2024

Spin-mechanical thermal machines

We introduce a method to construct a quantum battery and a quantum Otto heat engine using a Nitrogen-Vacancy (NV) center spin coupled to a mechanical oscillator in a highly detuned regime. By precisely controlling the NV spin, we enable efficient energy exchange despite significant detuning, challenging conventional assumptions. This leads to a robust mechanical quantum battery and a cooling scheme driving the oscillator toward its ground state. Leveraging this, we implement a quantum Otto engine that produces mechanical work at maximum efficiency without decoupling from the hot bath, paving the way for practical quantum thermal machines.

quant-ph↗

arXiv2023

Revealing self-gravity in a Stern-Gerlach Humpty-Dumpty experiment

There is no consensus among today's physicists about how to describe the gravitational interaction properly in a quantum framework. We propose in this paper an experimental test aimed at revealing the existence of a non-linear self-interaction à la Schrodinger-Newton (S-N). In this test, a mesoscopic spin 1/2 microsphere is freely falling in a Humpty-Dumpty Stern-Gerlach interferometer. After clarifying the role of the scaling of the interaction in function of the amplitudes of the up and down spin components of the microsphere, it is shown that self-gravity induces a measurable phase shift between them, which paves the way to experimental tests. It is also shown that if we consider two distinct microspheres falling in parallel, the entangling power of the S-N interaction is exactly equal to zero.

quant-ph↗

arXiv2018

Bouncing oil droplets, de Broglie's quantum thermostat and convergence to equilibrium

Recently, the properties of bouncing oil droplets, also known as "walkers", have attracted much attention because they are thought to offer a gateway to a better understanding of quantum behaviour. They constitute indeed a macroscopic realization of wave-particle duality, in the sense that their trajectories are guided by a self-generated surrounding wave. The aim of this paper is to develop a phenomenological theory for the behavior of walkers in terms of de Broglie-Bohm and Nelson dynamics. We study in particular how modifications of the de Broglie pilot-wave theory, à la Nelson, affect the process of relaxation to quantum equilibrium, and prove an H-theorem for the relaxation to quantum equilibrium under Nelson dynamics. We compare the onset of equilibrium in the Nelson and de Broglie-Bohm approaches and we also propose some simple experiments by which one can test the applicability of our theory to the context of bouncing oil droplets.

quant-ph↗

arXiv2017

Quantum walk hydrodynamics

A simple Discrete-Time Quantum Walk on the line is revisited and given an hydrodynamic interpretation through a novel relativistic generalization of the Madelung transform. Numerical results are presented which show that suitable initial conditions indeed produce hydrodynamical shocks. An analytical computation of the asymptotic quantum shock structure is presented. The non-relativistic limit is explored in the Supplementary Material (SM).

quant-ph↗