arXiv subjects

Rafi Weill

Publications and source records attributed to Rafi Weill.

11 recordsLinked to original sources

arXiv2025

Fast collisional $\sqrt{\mathrm{SWAP}}$ gate for fermionic atoms in an optical superlattice

Collisional gates in optical superlattices have recently achieved record fidelities, but their operation times are typically limited by tunneling. Here we propose and analyze an alternative route to a fast $\sqrt{\mathrm{SWAP}}$ gate for two fermionic atoms in an optical superlattice based on optimized, time-dependent control of the short and long lattice depths. The gate is implemented by transiently releasing the atoms into a quasi-harmonic confinement centered between the two sites. With an appropriately chosen contact interaction strength, a controlled collision accumulates the exchange phase required for $\sqrt{\mathrm{SWAP}}$ and generates entanglement. We employ a continuum, time-dependent Schr\"odinger-equation simulation that goes beyond a two-site Fermi--Hubbard description and benchmark it against experimentally implemented tunneling-based protocols, reproducing the observed single-particle tunneling and spin-exchange dynamics. For experimentally accessible lattice depths, we find that the proposed gate operates in $\sim 21\,\mu\mathrm{s}$, more than an order of magnitude faster than tunneling-based implementations, while achieving fidelities $\gtrsim 99\%$. We further analyze sensitivity to lattice-depth variations and show that a composite sequence improves robustness. Our results establish fast, collision-mediated entangling gates in superlattices as a promising building block for scalable neutral-atom quantum computation.

cond-mat.quant-gas↗

arXiv2023

Atomic interferometer based on optical tweezers

Atomic interferometers measure forces and acceleration with exceptional precision. The conventional approach to atomic interferometry is to launch an atomic cloud into a ballistic trajectory and perform the wave-packet splitting in momentum space by Raman transitions. This places severe constraints on the possible atomic trajectory, positioning accuracy and probing duration. Here, we propose and analyze a novel atomic interferometer that uses micro-optical traps (optical tweezers) to manipulate and control the motion of atoms. The new interferometer allows long probing time, sub micrometer positioning accuracy, and utmost flexibility in shaping of the atomic trajectory. The cornerstone of the tweezer interferometer are the coherent atomic splitting and combining schemes. We present two adiabatic schemes with two or three tweezers that are robust to experimental imperfections and work simultaneously with many vibrational states. The latter property allows for multi-atom interferometry in a single run. We also highlight the advantage of using fermionic atoms to obtain single-atom occupation of vibrational states and to eliminate mean-field shifts. We examine the impact of tweezer intensity noise and demonstrate that, when constrained by shot noise, the interferometer can achieve a relative accuracy better than $10^{-11}$ in measuring Earth's gravitational acceleration. The sub-micrometer resolution and extended measurement duration offer promising opportunities for exploring fundamental physical laws in new regimes. We discuss two applications well-suited for the unique capabilities of the tweezer interferometer: the measurement of gravitational forces and the study of Casimir-Polder forces between atoms and surfaces. Crucially, our proposed tweezer interferometer is within the reach of current technological capabilities.

quant-ph↗

arXiv2023

Spatial adiabatic passage of ultracold atoms in optical tweezers

Spatial adiabatic passage (SAP) is a process that facilitates the transfer of a wave packet between two localized modes that are not directly coupled, but rather interact through an intermediate third mode. By employing a counter-intuitive adiabatic pulse sequence, this technique achieves minimal population in the intermediate state and high transfer efficiency. Here, we report the implementation of SAP for transferring massive particles between three micro-optical traps. We begin by preparing ultracold fermionic atoms in low vibrational eigenstates of one trap and then manipulate the distance between the three traps to execute the SAP protocol. We observe a smooth transfer of atoms between the two outer traps, accompanied by a low population in the central trap. We validate our findings and underscore the significance of the counter-intuitive sequence by reversing the order of the pulse sequence. Additionally, we investigate the influence of the tunneling rate and the time delay between the motion of the two external tweezers on the fidelity of the process. Our results open up new possibilities for advanced control and manipulation schemes in optical tweezer array platforms.

cond-mat.quant-gas↗

arXiv2021

Generalization of Kirchhoff's Law: The inherent relations between quantum efficiency and emissivity

Planck's law of thermal radiation depends only on the temperature T and emissivity $\varepsilon$. It is one of the most fundamental discoveries about light-matter interaction that led to the development of quantum physics. Another basic property of a body is its ability to absorb incoming light, characterized by absorptivity $\alpha$. Kirchhoff's law of thermal radiation equals these two properties at thermodynamic equilibrium, i.e., $\varepsilon$=$\alpha$. The generalized Planck's equation extends Kirchhof's law out of equilibrium by scaling the absorptivity with the pump-dependent chemical potential $\mu$, obscuring emissivity as a material property. Quantum efficiency (QE) is a material property, defined out of equilibrium, describing the statistics of absorption followed by emission of a photon. Both emissivity and QE depend on the interplay between radiative and non-radiative rates. Here we theoretically and experimentally demonstrate a prime equation for emissivity as a material property in and out of equilibrium in the form of $\varepsilon$=$\alpha$(1-QE), which at equilibrium is reduced to Kirchhoff's law. Our work lays out the fundamental evolution of non-thermal emission with temperature, which is critical for the development of lighting and energy devices.

physics.atom-ph↗

arXiv2021

High-temperature photoluminescence reveals the inherent relations between quantum efficiency and emissivity

Photoluminescence (PL) is a light-matter quantum interaction associated with the chemical potential of light formulated by the Generalized Planck's law. Without knowing the inherent temperature dependence of chemical potential, the Generalized Planck's law is insufficient to characterize PL(T). Recent experiments showed that PL at low temperatures conserves the emitted photon rate, accompanied by a blue-shift and transition to thermal emission at a higher temperature. Here, we theoretically study temperature-dependent PL by including phononic interactions in a detailed balance analysis. Our solution validates recent experiments and predicts important relations, including i) An inherent relation between emissivity and the quantum efficiency of a system, ii) A universal point defined by the pump and the temperature where the emission rate is fixed to any material, iii) A new phonon-induced quenching mechanism, and iv) Thermalization of the photon spectrum. These findings are relevant to and important for all photonic fields where the temperature is dominant.

physics.atom-ph↗

arXiv2020

Temperature-dependent photoluminescence: A theoretical study

Photoluminescence (PL) is a light matter quantum interaction associated with the chemical potential of light formulated by the Generalized Planck's law. Without knowing the inherent temperature dependence of chemical potential, the Generalized Planck's law is insufficient in order to characterize PL vs. T. Recent experiments showed that PL at a critical temperature abruptly shifts from a conserved rate, accompanied by a blue-shift, to thermal emission. Here, we theoretically study temperature dependent PL by including phononic interactions in a detailed balance analysis. We show that in a three-level system, both chemical potential and T are defined in the case of fast thermalization. Our solution validates recent experiments and predicts new features, including an inherent relation between emissivity and external quantum efficiency of a system, a universal point defined by the pump and the temperature where the emission rate is fixed to any material, a new phonon induced quenching mechanism, and thermalization of the photon spectrum. Our high temperature luminescence solution is relevant to and important for all photonic fields where the temperature is dominant

physics.optics↗

arXiv2017

Thermalization of one-dimensional photon gas and thermal lasers in erbium-doped fibers

We demonstrate thermalization and Bose-Einstein (BE) distribution of photons in standard erbium-doped fibers (edf) in a broad spectral range up to ~200nm at the 1550nm wavelength regime. Our measurements were done at a room temperature ~300K and 77K. It is a special demonstration of thermalization of photons in fiber cavities and even in open fibers. They are one-dimensional (1D), meters-long, with low finesse, high loss and small capture fraction of the spontaneous emission. Moreover, we find in the edf cavities coexistence of thermal equilibrium (TE) and lasing without an overall inversion. The experimental results are supported by a theoretical analysis based on the rate equations.

physics.optics↗

arXiv2012

When does lasing become a condensation phenomenon?

We present a generic classical light condensation (LC) phenomenon in linear photonic mode systems, such as cw laser cavities, in a noisy environment (spontaneous emission, etc.), based on weighting the modes in a loss-gain scale rather than in photon energy. It is characterized by a sharp transition from multi- to single-mode oscillation. The study uses a linear multivariate Langevin formulation which gives a mode occupation hierarchy that functions like Bose-Einstein statistics. We find that condensation occurs when the spectral filtering has near the lowest loss mode a power law dependence with exponent smaller than 1. We then discuss how and when condensation occurs in photon systems, how it relates to lasing, and the difficulties to observe regular photon Bose-Einstein condensation (BEC) in laser cavities. We raise the possibility that recent experiments on photon condensation in optical cavities fall in a classical LC or lasing category rather than being a thermal-quantum BEC phenomenon.

physics.optics↗

arXiv2011

Spectral Sidebands and Multi-Pulse Formation in Passively Mode Locked Lasers

Pulse formation in passively mode locked lasers is often accompanied with dispersive waves that form of spectral sidebands due to spatial inhomogoneities in the laser cavity. Here we present an explicit calculation of the amplitude, frequency, and precise shape of the sidebands accompanying a soliton-like pulse. We then extend the study to the global steady state of mode locked laser with a variable number of pulses, and present experimental results in a mode locked fiber laser that confirm the theory. The strong correlation between the temporal width of the sidebands and the measured spacing between the pulses in multipulse operation suggests that the sidebands have an important role in the inter-pulse interaction.

physics.optics↗

arXiv2005

Critical Behavior of Light

Light is shown to exhibit critical and tricritical behavior in passive mode-locked lasers with externally injected pulses. It is a first and unique example of critical phenomena in a one-dimensional many body light-mode system. The phase diagrams consist of regimes with continuous wave, driven para-pulses, spontaneous pulses via mode condensation, and heterogeneous pulses, separated by phase transition lines which terminate with critical or tricritical points. Enhanced nongaussian fluctuations and collective dynamics are observed at the critical and tricritical points, showing a mode system analog of the critical opalescence phenomenon. The critical exponents are calculated and shown to comply with the mean field theory, which is rigorous in the light system.

cond-mat.stat-mech↗

arXiv2004

Formation and annihilation of laser light pulse quanta in thermodynamic-like pathway

We present a theoretical and experimental study of multiple pulse formation in passively mode-locked (PML) lasers. Following a statistical mechanics approach, the study yields a thermodynamic-like "phase diagram" with boundaries representing cascaded first order phase transitions. They correspond to abrupt creation or annihilation of pulses and a quantized RF power behavior, as system parameters (noise and/or pumping levels) are varied, in excellent accordance with the experiments. Remarkably, individual pulses carry an almost constant quantum of energy.

cond-mat.stat-mech↗