arXiv subjects

Hadiseh Alaeian

Publications and source records attributed to Hadiseh Alaeian.

At least 19 recordsLinked to original sources

arXiv2026

Attosecond Control of Squeezed Light

Squeezed light is a key resource in quantum metrology and quantum information science. It is primarily generated through nonlinear optical interactions, where the degree of squeezing is set by the nonlinearity of the medium. Here, we modulate the third-order nonlinear response of a dielectric with strong ultrafast laser fields to control squeezed light generation on attosecond time scales. By tuning a sub-cycle phase delay between the input femtosecond pulses, we switch the generated light between amplitude-squeezed and phase-squeezed states. We measure the quantum noise using a frequency-resolved balanced homodyne detection scheme that extracts field quadratures in many frequency modes simultaneously. From these measurements we obtain the complete coherency matrix containing quadrature correlations across the frequency modes of the pulse. These results enable quantum light sources with sub-cycle control of squeezing and open a route to transduction of dynamical quantum correlations in matter to quantum correlations in electric fields.

quant-ph↗

arXiv2026

Nonlocal Quantum Phase Transitions

Phase transitions are paradigmatic examples of emergent phenomena, in which symmetries present at the microscopic level can be spontaneously broken in the thermodynamic limit. Two primary physical mechanisms can drive this symmetry breaking: thermal fluctuations in classical phase transitions and quantum fluctuations in quantum critical phenomena. Here, we introduce $nonlocal$ $quantum$ $fluctuations$ as a new fundamental mechanism to drive phase transitions. We show that entanglement shared between environmental modes can induce a correlated symmetry breaking in remote systems, independent of their spatial separation. Using the framework of driven-dissipative phase transitions, we theoretically investigate a system composed of two nonlinear quantum resonators placed at arbitrarily large spatial separations, each coupled to independent local Markovian baths. We consider the regime in which remote environmental modes are prepared in broadband entangled states. We show that near the critical point, where the susceptibility to weak perturbations diverges, quantum correlations in the environments govern the system critical behavior. While these correlations manifest locally only as effective thermal fluctuations, at the global level they give rise to an emergent nonlocal phase transition, marked by the spontaneous symmetry breaking of a collective mode shared by the two remote systems.

quant-ph↗

arXiv2026

Collective Strong Coupling of Thermal Atoms to Integrated Microring Resonators

Strong coupling between atomic ensembles and high-quality optical cavities enables collective and nonlinear phenomena that are central to cavity quantum electrodynamics (cQED). Although many experiments have been performed on this topic, most of them have focused on cold atoms. Here, we experimentally demonstrate collective strong coupling between thermal rubidium (Rb) vapor and high-quality silicon nitride microring resonators (MRRs) on an integrated photonic chip. We observe cavity mode splitting, with a measured collective coupling strength of $g_N/2π\approx 1\,\mathrm{GHz}$ and a collective cooperativity of $C_N\approx2$ at $110\,^\circ\mathrm{C}$, indicating coherent energy exchange between the atomic ensemble and the cavity mode despite rapid decoherence in the thermal vapor system. We infer an average of $20$ atoms participating in the collective interaction, yielding a single-atom cooperativity of $C_0=0.1$ and approaching the single-atom strong-coupling regime. Our results establish the integrated thermal vapor MRR platform as a robust, compact, and scalable system for studying collective and nonlinear phenomena in cQED.

physics.atom-ph↗

arXiv2026

Anticipating Decoherence for Enhancing Coherence in Quantum Systems

Large-scale quantum systems require optical coherence between distant quantum devices, necessitating spectral indistinguishability. Scalable solid-state platforms offer promising routes to this goal. However, environmental disorders, including dephasing, spectral diffusion, and spin-bath interactions, influence the emitters' spectra and deteriorate the coherence. Using statistical theory, we identify correlations in spectral diffusion from slowly varying environmental coupling, revealing predictable dynamics extendable to other disorders. Importantly, this could enable the development of an anticipatory framework for forecasting and decoherence engineering in remote quantum emitters. To validate this framework, we demonstrate that a machine learning model trained on limited data can accurately forecast unseen spectral behavior. Realization of such a model on distinct quantum emitters could reduce the spectral shift by factors $\approx$ 2.1 to 15.8, depending on emitter stability, compared to no prediction. This work presents, for the first time, the application of anticipatory systems and replica theory to quantum technology, along with the first experimental demonstration of internal prediction that generalizes across multiple quantum emitters. These results pave the way for real-time decoherence engineering in scalable quantum systems. Such capability could lead to enhanced optical coherence and multi-emitter synchronization, with broad implications for quantum communication, computation, imaging, and sensing.

quant-ph↗

arXiv2025

Collective Enhancement of Photon Blockade via Two-Photon Interactions

Analogous to Coulomb blockade for electrons, photon blockade is a key quantum optical effect in which the presence of one photon prevents the transmission of subsequent ones through a nonlinear medium. Beyond its fundamental interest, photon and multi-photon blockade are actively studied as mechanisms for generating technologically-relevant quantum states of light. Although photon blockade typically requires achieving strong light-matter coupling, increasing the number of atoms fails to enhance antibunching. Here, we analyze the optical transmission properties of a quantum resonator that embeds a two-photon-coupled ensemble of emitters, combining an approximate analytical approach with full quantum numerical simulations. We show that when light and matter are coupled via a two-photon interaction, both single- and multi-photon blockade can benefit from a collective enhancement. We propose different driving schemes in which the second or third-order correlation functions are strongly suppressed with increasing atom number. Differently from established methods, this collective enhancement of non-classical properties occurs with unitary transmission and is ultimately constrained only by decoherence. This demonstrates that collective two-photon couplings are a powerful mechanism for realizing photon blockade even in platforms where individual strong coupling is not achievable.

quant-ph↗

arXiv2025

Topology-Optimized Dielectric Cavities for Enhanced Excitonic Light Emission from $\rm WSe_{2}$

Photonic inverse design and, especially, topology optimization, enable dielectric cavities with deeply sub-diffraction mode volumes and high quality factors, thus offering a powerful platform for enhanced light-matter coupling. Here, we design and fabricate arrays of CMOS-compatible silicon cavities on sapphire with extreme subwavelength transverse mode sizes of only 30-40 nm ($\rm V\simλ^3/2500$). These cavities are engineered for deterministic coupling to a monolayer (or few-layer) excitonic material, producing strong near-field localization directly beneath the 2D material. Photoluminescence (PL) measurements show reproducible tenfold enhancements relative to bare silicon, consistent with numerical simulations that account for material absorption and fabrication tolerances. Furthermore, time-resolved PL measurements reveal pronounced lifetime shortening and non-exponential dynamics, indicating cavity-mediated exciton-exciton interactions. The optimized cavity geometry enhances the far-field collection efficiency and supports scalable integration with van der Waals semiconductors. Our results show that the arrays of topology-optimized dielectric cavities are a versatile, scalable platform for controlling excitonic emission and interactions, which creates new opportunities in nonlinear optics, optoelectronics, and quantum photonics.

physics.optics↗

arXiv2025

Engineering nonlinear activation functions for all-optical neural networks via quantum interference

All-optical neural networks (AONNs) promise transformative gains in speed and energy efficiency for artificial intelligence (AI) by leveraging the intrinsic parallelism and wave nature of light. However, their scalability has been fundamentally limited by the high power requirements of conventional nonlinear optical elements. Here, we present a low-power nonlinear activation scheme based on a three-level quantum system driven by dual laser fields. This platform introduces a two-channel nonlinear activation matrix with both self- and cross-nonlinearities, enabling true multi-input, multi-output optical processing. The system supports tunable activation behaviors, including sigmoid and ReLU functions, at ultralow power levels (17 uW per neuron). We validate our approach through theoretical modeling and experimental demonstration in rubidium vapor cells, showing the feasibility of scaling to deep AONNs with millions of neurons operating under 20 W of total optical power. Crucially, we also demonstrate the all-optical generation of gradient-like signals with backpropagation, paving the way for all optical training. These results mark a major advance toward scalable, high-speed, and energy-efficient optical AI hardware.

physics.optics↗

arXiv2025

Cooperative Effects in Thin Dielectric Layers: Long-Range Dicke Superradiance

The realization and control of collective effects in quantum emitter ensembles have predominantly focused on small, ordered systems, leaving their extension to larger, more complex configurations as a significant challenge. Quantum photonic platforms, with their engineered Green's functions and integration of advanced solid-state quantum emitters, provide opportunities to explore new regimes of light-matter interaction beyond the scope of atomic systems. In this study, we examine the interaction of quantum emitters embedded within a thin dielectric layer. Our results reveal that the guided optical modes of the dielectric layer mediate extended-range interactions between emitters, enabling both total and directional superradiance in arrays spanning several wavelengths. Additionally, the extended interaction range facilitated by the dielectric layer supports Dicke superradiance in regimes where collective effects cannot be obtained in a homogeneous environment. This work uncovers a distinctive interplay between environmental dimensionality and collective quantum dynamics, paving the way for exploring novel many-body quantum optical phenomena in engineered photonic environments.

quant-ph↗

arXiv2024

Dissipative Phase Transition in the Two-Photon Dicke Model

We explore the dissipative phase transition of the two-photon Dicke model, a topic that has garnered significant attention recently. Our analysis reveals that while single-photon loss does not stabilize the intrinsic instability in the model, the inclusion of two-photon loss restores stability, leading to the emergence of superradiant states which coexist with the normal vacuum states. Using a second-order cumulant expansion for the photons, we derive an analytical description of the system in the thermodynamic limit which agrees well with the exact calculation results. Additionally, we present the Wigner function for the system, shedding light on the breaking of the Z4-symmetry inherent in the model. These findings offer valuable insights into stabilization mechanisms in open quantum systems and pave the way for exploring complex nonlinear dynamics in two-photon Dicke models.

quant-ph↗

arXiv2024

Single-Photon Generation: Materials, Techniques, and the Rydberg Exciton Frontier

Due to their quantum nature, single-photon emitters generate individual photons in bursts or streams. They are paramount in emerging quantum technologies such as quantum key distribution, quantum repeaters, and measurement-based quantum computing. Many such systems have been reported in the last three decades, from Rubidium atoms coupled to cavities to semiconductor quantum dots and color centers implanted in waveguides. This review article highlights different material systems with deterministic and controlled single photon generation. We discuss and compare the performance metrics, such as purity and indistinguishability, for these sources and evaluate their potential for different applications. Finally, a new potential single-photon source, based on the Rydberg exciton in solid state metal oxide thin films, is introduced, briefly discussing its promising qualities and advantages in fabricating quantum chips for quantum photonic applications.

quant-ph↗

arXiv2024

Bottom-up Fabrication of 2D Rydberg Exciton Arrays in Cuprous Oxide

Solid-state platforms provide exceptional opportunities for advancing on-chip quantum technologies by enhancing interaction strengths through coupling, scalability, and robustness. Cuprous oxide ($\text{Cu}_{2}\text{O}$) has recently emerged as a promising medium for scalable quantum technology due to its high-lying Rydberg excitonic states, akin to those in hydrogen atoms. To harness these nonlinearities for quantum applications, the confinement dimensions must match the Rydberg blockade size, which can reach several microns in $\text{Cu}_{2}\text{O}$. Using a CMOS-compatible growth technique, this study demonstrates the bottom-up fabrication of site-selective arrays of $\text{Cu}_{2}\text{O}$ microparticles. We observed Rydberg excitons up to the principal quantum number $n$=5 within these $\text{Cu}_{2}\text{O}$ arrays on a quartz substrate and analyzed the spatial variation of their spectrum across the array, showing robustness and reproducibility on a large chip. These results lay the groundwork for the deterministic growth of $\text{Cu}_{2}\text{O}$ around photonic structures, enabling substantial light-matter interaction on integrated photonic platforms and paving the way for scalable, on-chip quantum devices.

quant-ph↗

arXiv2024

Reducing system dimensionality with long-range collective dipole-dipole interactions

Dimensionality plays a crucial role in long-range dipole-dipole interactions (DDIs). We demonstrate that a resonant nanophotonic structure modifies the apparent dimensionality in an interacting ensemble of emitters, as revealed by population decay dynamics. Our measurements on a dense ensemble of interacting quantum emitters in a resonant nanophotonic structure with long-range DDIs reveal an effective dimensionality reduction to $\bar{d} = 2.20 (12)$, despite the emitters being distributed in 3D. This contrasts the homogeneous environment, where the apparent dimension is $\bar{d} = 3.00$. Our work presents a promising avenue to manipulate dimensionality in an ensemble of interacting emitters.

physics.optics↗

arXiv2024

Manipulating the Dipolar Interactions and Cooperative Effects in Confined Geometries

To facilitate the transition of quantum effects from the controlled laboratory environment to practical real-world applications, there is a pressing need for scalable platforms. One promising strategy involves integrating thermal vapors with nanostructures designed to manipulate atomic interactions. In this tutorial, we aim to gain deeper insights into this by examining the behavior of thermal vapors that are confined within nanocavities or waveguides and exposed to near-resonant light. We explore the interactions between atoms in confined dense thermal vapors. Our investigation reveals deviations from the predictions of continuous electrodynamics models, including density-dependent line shifts and broadening effects. In particular, our results demonstrate that by carefully controlling the saturation of single atoms and the interactions among multiple atoms using nanostructures, along with controlling the geometry of the atomic cloud, it becomes possible to manipulate the effective optical nonlinearity of the entire atomic ensemble. This capability renders the hybrid thermal atom-nanophotonic platform a distinctive and valuable one for manipulating the collective effect and achieving substantial optical nonlinearities.

physics.atom-ph↗

arXiv2022

Highly-Excited Rydberg Excitons in Synthetic Thin-Film Cuprous Oxide

Cuprous oxide (Cu${}_2$O) has recently been proposed as a promising solid-state host for excitonic Rydberg states with large principal quantum numbers ($n$), whose exaggerated wavefunction sizes ($\propto n^2)$ facilitate gigantic dipole-dipole ($\propto n^4$) and van der Waals ($\propto n^{11}$) interactions, making them an ideal basis for solid-state quantum technology. Synthetic, thin-film Cu${}_2$O samples are of particular interest because they can be made defect-free via carefully controlled fabrication and are, in principle, suitable for the observation of extreme single-photon nonlinearities caused by the Rydberg blockade. Here, we present spectroscopic absorption and photoluminescence studies of Rydberg excitons in synthetic Cu${}_2$O grown on a transparent substrate, reporting yellow exciton series up to $n = 7$. We perform these studies at powers up to 2 mW and temperatures up to 150 K, the highest temperature where Rydberg series can be observed. These results open a new portal to scalable and integrable on-chip Rydberg-based quantum devices.

quant-ph↗

arXiv2022

Magnetic Phases of Spatially-Modulated Spin-1 Chains in Rydberg Excitons: Classical and Quantum Simulations

In this work, we study the magnetic phases of a spatially-modulated chain of spin-1 Rydberg excitons. Using the Density Matrix Renormalization Group (DMRG) technique we study various magnetic and topologically nontrivial phases using both single-particle properties like local magnetization and quantum entropy as well as many-body ones like pair-wise Néel and long-range string correlations. In particular, we investigate the emergence and robustness of Haldane phase, a topological phase of anti-ferromagnetic spin-1 chains. Further, we devise a hybrid quantum algorithm employing Restricted Boltzmann Machine to simulate the ground state of such a system which shows very good agreement with the results of exact diagonalization (ED) and DMRG.

cond-mat.mtrl-sci↗

arXiv2022

Transient Density-Induced Dipolar Interactions in a Thin Vapor Cell

We exploit the effect of light-induced atomic desorption to produce high atomic densities ($n\gg k^3$) in a rubidium vapor cell. An intense off-resonant laser is pulsed for roughly one nanosecond on a micrometer-sized sapphire-coated cell, which results in the desorption of atomic clouds from both internal surfaces. We probe the transient atomic density evolution by time-resolved absorption spectroscopy.With a temporal resolution of $\approx1\,\mathrm{ns}$, we measure the broadening and line shift of the atomic resonances. Both broadening and line shift are attributed to dipole-dipole interactions. This fast switching of the atomic density and dipolar interactions could be the basis for future quantum devices based on the excitation blockade.

physics.atom-ph↗

arXiv2022

Exact bistability and time pseudo-crystallization of driven-dissipative fermionic lattices

The existence of bistability in quantum optical systems remains a intensely debated open question beyond the mean-field approximation. Quantum fluctuations are finite-size corrections to the mean-field approximation used because the full exact solution is unobtainable. Usually, quantum fluctuations destroy the bistability present on the mean-field level. Here, by identifying and using exact modulated semi-local dynamical symmetries in a certain quantum optical models of driven-dissipative fermionic chains we exactly prove bistability in precisely the quantum fluctuations. Surprisingly, rather than destroying bistability, the quantum fluctuations themselves exhibit bistability, even though it is absent on the mean-field level for our systems. Moreover, the models studied acquire additional thermodynamic dynamical symmetries that imply persistent periodic oscillations in the quantum fluctuations, constituting pseudo-variants of boundary time crystals. Physically, these emergent operators correspond to finite-frequency and finite-momentum semi-local Goldstone modes. Our work therefore provides to the best of our knowledge the first example of a provably bistable quantum optical system.

quant-ph↗

arXiv2021

Purcell-enhanced dipolar interactions in nanostructures

Strong light-induced interactions between atoms are known to cause nonlinearities at a few-photon level which are crucial for applications in quantum information processing. Compared to free space, the scattering and the light-induced dipolar interaction of atoms can be enhanced by a dielectric environment. For this \emph{Purcell effect}, either a cavity or a waveguide can be used. Here, we combine the high densities achievable in thermal atomic vapors with an efficient coupling to a slot waveguide. In contrast to free-space interactions, atoms aligned within the slot exhibit repulsive interactions that are further enhanced by a factor of 8 due to the Purcell effect. The corresponding blueshift of the transition frequency of atoms arranged in the essentially one-dimensional geometry vanishes above the saturation, providing a controllable nonlinearity at the few-photon level. The experimental results are in good agreement with Monte-Carlo simulations that include the dielectric environment, dipolar interactions, and motional effects. The results pave the way towards a robust scalable platform for quantum nonlinear optics and all-optical quantum information processing at room temperature.

quant-ph↗