Papers by Hadiseh Alaeian
arXiv (Cornell University), Dec 21, 2021
Strong light-induced interactions between atoms are known to cause nonlinearities at a fewphoton ... more Strong light-induced interactions between atoms are known to cause nonlinearities at a fewphoton 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 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.
Physical Review Letters, Sep 2, 2021
APS Division of Atomic, Molecular and Optical Physics Meeting Abstracts, 2020
Communications physics, Dec 7, 2022
The existence of multistability in quantum systems beyond the mean-field approximation remains an... more The existence of multistability in quantum systems beyond the mean-field approximation remains an intensely debated open question. Quantum fluctuations are finite-size corrections to the mean-field as the full exact solution is unobtainable and they usually destroy the multistability present on the mean-field level. Here, by identifying and using exact modulated dynamical symmetries in a driven-dissipative fermionic chain we exactly prove multistability in the presence of quantum fluctuations. Further, unlike common cases in our model, rather than destroying multistability, the quantum fluctuations themselves exhibit multistability, which is absent on the mean-field level for our systems. Moreover, the studied model acquires additional thermodynamic dynamical symmetries that imply persistent periodic oscillations, constituting the first case of a boundary time crystal,to the best of our knowledge, a genuine extended many-body quantum system with the previous cases being only in emergent single-or few-body models. The model can be made into a dissipative time crystal in the limit of large dissipation (i.e. the persistent oscillations are stabilized by the dissipation) making it both a boundary and dissipative time crystal.
Journal of Lightwave Technology, Jul 1, 2009
In this paper, a new method based on the complex images technique is presented for analysis of 2-... more In this paper, a new method based on the complex images technique is presented for analysis of 2-D periodic devices such as waveguides, directional couplers, and coupled cavity waveguides (CCW). The main idea of this method lies in representing the infinite summation of the periodic Green's functions of such kind of structures in terms of finite terms of complex images. The electric field integral equation has been used to formulate the problem and the method of moments has been applied afterward for solving the equation. The method has been used successfully in the analysis of different waveguides, directional couplers, and CCWs in both rectangular and triangular lattices. Fast convergence, simple formulations, and flexibility of the method in analyzing different structures are the main advantages of the proposed method.
Journal of Physics: Condensed Matter, Jun 10, 2022
Topological Quantum Chemistry (TQC) has recently emerged as a instrumental tool to characterize t... more Topological Quantum Chemistry (TQC) has recently emerged as a instrumental tool to characterize the topological nature of both fermionic and bosonic band structures. TQC is based on the study of band representations and the localization of maximally localized Wannier functions. In this article, we study various two-dimensional photonic crystal structures analyzing their topological character through a combined study of TQC, their Wilson-loop spectra and the electromagnetic energy density. Our study demonstrates that the analysis of the spatial localization of the energy density complements the study of the topological properties in terms of the spectrum of the Wilson-loop operator and TQC.
arXiv (Cornell University), Sep 23, 2022
In this work, we study the magnetic phases of a spatially-modulated chain of spin-1 Rydberg excit... more 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.
arXiv (Cornell University), Dec 23, 2014
We investigate the effect of parity-time (PT)-symmetric optical potentials on the radiation of ac... more We investigate the effect of parity-time (PT)-symmetric optical potentials on the radiation of achiral and chiral emitters. Mode coalescence and the appearance of exceptional points lead to orders-of-magnitude enhancements in the emitted dipole power. Further, the emitter can be tuned to behave as a strong optical source or absorber based on the non-Hermiticity parameter. Chiral enantiomers radiating near PT metamaterials exhibit a 4.5-fold difference in their decay rate. The results of this work could enable new atom-cavity interactions for quantum optics, as well as alloptical enantio-specific separation.
Journal of Optics, Jan 12, 2012
Zenodo (CERN European Organization for Nuclear Research), Nov 3, 2022
Physical review applied, Aug 31, 2022
We propose the encoding of memristive quantum dynamics on a digital quantum computer. Using a set... more We propose the encoding of memristive quantum dynamics on a digital quantum computer. Using a set of auxiliary qubits, we simulate an effective non-Markovian environment inspired by a collisional model, reproducing memristive features between expectation values of different operators in a single qubit. We numerically test our proposal in an IBM quantum simulator with 32 qubits, obtaining the pinched hysteresis curve that is characteristic of a quantum memristor. Furthermore, we extend our method to the case of two coupled quantum memristors, opening the door to the study of neuromorphic quantum computing in the NISQ era.
arXiv (Cornell University), May 8, 2023
Dimensionality plays a crucial role in long-range dipole-dipole interactions (DDIs). We demonstra... more 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 tod = 2.20(12), despite the emitters being distributed in 3D. This contrasts the homogeneous environment, where the apparent dimension isd = 3.00. Our work presents a promising avenue to manipulate dimensionality in an ensemble of interacting emitters.
We experimentally demonstrate reduced dimensionality in a interacting ensemble of emitters. The w... more We experimentally demonstrate reduced dimensionality in a interacting ensemble of emitters. The well-known stretched exponential decay dynamics, I(t)/I0 =exp(−γ D t)exp(−αt β ) with β = 0.5 in 3D geometries, is strikingly modified in a nanophotonic environment that supports long-range interaction to β ∼ 0.3
Bulletin of the American Physical Society, Mar 17, 2021
Physical Review Letters
We exploit the effect of light-induced atomic desorption to produce high atomic densities (n ≫ k ... more We exploit the effect of light-induced atomic desorption to produce high atomic densities (n ≫ k 3) in a rubidium vapor cell. An intense off-resonant laser is pulsed for roughly one nanosecond on a micrometersized 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 ≈ 1 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.
The Journal of Chemical Physics
In this work, we study the magnetic phases of a spatially modulated chain of spin-1 Rydberg excit... more 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, such as local magnetization and quantum entropy, and many-body ones, such as pair-wise Néel and long-range string correlations. In particular, we investigate the emergence and robustness of the Haldane phase, a topological phase of anti-ferromagnetic spin-1 chains. Furthermore, we devise a hybrid quantum algorithm employing restricted Boltzmann machine to simulate the ground state of such a system that shows very good agreement with the results of exact diagonalization and DMRG.
Cornell University - arXiv, Oct 28, 2022
Cuprous oxide (Cu2O) has recently been proposed as a promising solid-state host for excitonic Ryd... more Cuprous oxide (Cu2O) has recently been proposed as a promising solid-state host for excitonic Rydberg states with large principal quantum numbers (n), whose exaggerated wavefunction sizes (∝ n 2) facilitate gigantic dipole-dipole (∝ n 4) and van der Waals (∝ n 11) interactions, making them an ideal basis for solid-state quantum technology. Synthetic, thin-film Cu2O 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 Cu2O 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.
Cornell University - arXiv, Jun 8, 2021
Driven-dissipative quantum many-body systems have been the subject of many studies in recent year... more Driven-dissipative quantum many-body systems have been the subject of many studies in recent years. They possess unique, novel classes of dissipation-stabilized quantum many-body phases including the limit cycle. For a long time it has been speculated if such a behavior, a recurring phenomenon in non-linear classical and quantum many-body systems, can be classified as a time crystal. However, the robustness of these periodic dynamics, against quantum fluctuations is an open question. In this work we seek the answer to this question in a canonical yet important system, i.e., a multi-mode cavity with self and cross-Kerr non-linearity, including the fluctuation effects via higher order correlations. Employing the Keldysh path integral, we investigate the Green's function and correlation of the cavity modes in different regions. Furthermore, we extend our analysis beyond the mean-field by explicitly including the effect of two-body correlations via the 2 nd-cumulant expansion. Our results shed light on the emergence of dissipative phase transitions in open quantum systems and clearly indicate the robustness of limit-cycle oscillations in the presence of the quantum fluctuations.
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Papers by Hadiseh Alaeian