arXiv subjects

Edo Waks

Publications and source records attributed to Edo Waks.

At least 19 recordsLinked to original sources

arXiv2026

Surface passivation for narrowing optical linewidth of silicon T centers in nanophotonic devices

Silicon T centers are promising spin-photon interfaces in solid-state platforms for telecom-compatible, scalable quantum information technologies. A major challenge for T centers in nanophotonics is spectral diffusion, where fluctuations in the local electric-field environment from surface and bulk charge states broaden the optical transition and reduce photon indistinguishability. Strategies that directly suppress spectral diffusion are therefore critical for improving T-center-based quantum photonic devices. Here, we use atomic-layer-deposited Al2O3 to passivate the silicon surface and demonstrate a systematic narrowing of T center optical linewidths. Across our measurements, Al2O3 passivation reduces the T center emission linewidth by up to 57%. Complementary above-bandgap illumination and spectral hole burning measurements show that the remaining linewidth contains a significant spectral-diffusion component caused by adjacent charge traps, while placing an upper bound of approximately 75 MHz on the homogeneous linewidth. This work provides a CMOS-compatible path toward generating indistinguishable photons from silicon T centers for scalable quantum photonic applications.

quant-ph↗

arXiv2026

Bright Telecom Spin-Photon Interface in Silicon Photonics

Silicon is an attractive host for scalable quantum photonics, but the absence of bright telecom-band emitters with optically addressable spin states has limited its use for spin-photon interfaces. Here we demonstrate the Al1-center, an aluminum--carbon defect in silicon, as a bright waveguide-integrated single-photon emitter with a ground-state spin. Using isotopically purified silicon-on-insulator nanophotonic devices, we isolate individual Al1-centers and observe high-purity single-photon emission with $g^{(2)}(0)=0.04$ without background subtraction. Time-resolved photoluminescence spectroscopy reveals a fast excited-state lifetime of 135 ns, nearly an order of magnitude shorter than the benchmark provided by the well-studied T-center. Resonant photoluminescence excitation measurements further resolve the zero-phonon transition and reveal a narrow homogeneous linewidth reaching 47 MHz, threefold narrower than the T-center under comparable temperature. Through magneto-optical spectroscopy, we resolve the spin-dependent transitions of the bound-exciton manifold and achieve spin-selective optical pumping, fulfilling the prerequisite for quantum state initialization and readout. These results establish the Al1-center as a bright telecom-band spin-photon interface in silicon photonics and introduce a promising platform for integrated quantum networks.

quant-ph↗

arXiv2026

Optically Active Single Hole Spin in ZnSe

Semiconductor hole spins offer a pathway to extended coherence times by decoupling from nuclear magnetic noise, while their spin-orbit coupling enables fast all-electrical control. In ZnSe, however, realizing this potential has been limited by p-doping challenges. Here, we circumvent this limit by optically activating acceptors within the ZnSe quantum well. We isolate a single-hole spin bound to a shallow acceptor, confirmed by antibunching and accessed via the fast (244 ps) radiative recombination of a bound exciton. Magnetic and Raman spectroscopy of the ground state reveal an effective hole g-factor of 0.7 and an optical resonance linewidth of 26.7 GHz. Complementary first-principles simulations, together with the experimental results, provide evidence that points toward nitrogen as the most likely acceptor impurity. These results introduce a promising new platform for optically active spin qubits and single-photon sources in ZnSe.

quant-ph↗

arXiv2026

Quantization-aware Photonic Homodyne computing for Accelerated Artificial Intelligence and Scientific Simulation

Modern problems in high-performance computing, ranging from training and inferencing deep learning models in computer vision and language models to simulating complex physical systems with nonlinearly-coupled equations, require exponential growth of computational resources. Photonic analog systems are emerging with solutions of intrinsic parallelism, high bandwidth, and low propagation loss. However, their application has been hindered by the low analog accuracy due to the electro-optic distortion, material nonlinearities, and signal-to-noise ratios. Here we overcome this barrier with a quantization-aware digital-photonic mixed-precision framework across chiplets for accelerated AI processing and physical simulation. Using Lithium Niobate photonics with channel equalization techniques, we demonstrate linear multiplication (9-bit amplitude-phase decoupling) in homodyne optical logics with 6-bit precision at the clock rate of 128 giga-symbol-per-second (128 GS/s), enabling AI processing with 6 ns latency. Codesign hardware-algorithms, including iterative solvers, sparse-dense quantization, and bit-sliced matrix multiplication, explore photonic amplitude and phase coherence for complex-valued, physics-inspired computation. In electromagnetic problems, our approach yields 12-bit solutions for partial differential equations (PDEs) in scattering problems that would conventionally require up to 32-bit and often even 64-bit precision. These results preserve digital-level fidelity while leveraging the high-speed low-energy photonic hardware, establishing a pathway toward general-purpose optical acceleration for generative artificial intelligence, real-time robotics, and accurate simulation for climate challenges and biological discoveries.

cs.ET↗

arXiv2025

Electrical Control of Optically Active Single Spin Qubits in ZnSe

Electrons bound to shallow donors in ZnSe quantum wells are promising candidates for optically addressable spin qubits and single-photon sources. However, their optical coherence and indistinguishability are often limited by spectral broadening arising from charge fluctuations in the local environment. Here, we report electrical control of single donor qubits in ZnSe quantum wells. The applied field induces a DC Stark shift that tunes the emission energy over a range exceeding 30 times the inhomogeneous linewidth, effectively compensating for emitter-to-emitter variations. Concurrently, the field stabilizes trap occupancy, yielding a twofold reduction in optical linewidth and the suppression of spectral wandering. A statistical model based on trap dynamics qualitatively reproduces these observations and elucidates the mechanism of field-assisted charge noise suppression. Our results identify electrical control as a versatile pathway to significantly improve optical and spin addressability.

quant-ph↗

arXiv2025

Cavity Enhanced Emission from Telecom Rare-Earth System in Colloidal Host

Erbium incorporated in a ceria (CeO2) host offers strong potential as a spin qubit platform, providing a pathway toward telecom-compatible quantum memory. But erbium is a dim emitter due to its long excited state lifetime. Methods to enhance its emission rate and efficiency through nanophotonic cavity integration are therefore essential. In this work, we demonstrate cavity-enhanced emission from erbium doped CeO2. We couple colloidally synthesized erbium doped CeO2 nanocrystals to a silicon nanobeam cavity and show a 30-fold improvement in emitter brightness combined with a 2-fold lifetime enhancement. We estimate a lower bound of 12 for the Purcell factor of cavity-coupled emitters after accounting for non-radiative decay. These results pave the way towards utilizing colloidally synthesized optically addressable spin qubits emitting at telecom wavelength for quantum networking and distributed quantum computing.

physics.optics↗

arXiv2025

Inverse-Designed Photonic Crystal Cavities with Controllable Far-Field Numerical Aperture

Photonic crystal cavities confine light to subwavelength volumes, enabling strong light-matter interactions for applications in low-power photonics, opto-electronics, nonlinear optics, and quantum information. These applications demand cavities that combine high quality factors, low mode volumes, and high coupling efficiencies. However, optimizing across these metrics requires exploring a large design space, motivating the use of inverse design strategies. Previous inverse design efforts targeted high quality factors and low mode volumes, sacrificing the coupling efficiency or lacking the ability to precisely control the far-field radiation pattern. In this work, we present an inverse design framework that simultaneously optimizes cavity quality factor and far-field numerical aperture, both specified as design targets. Using this method, we design L3 photonic crystal cavities, with different far-field numerical apertures, in the visible wavelength and fabricate them in silicon nitride. Photoluminescence measurements confirm experimental control of the far-field numerical aperture and reveal a 28-fold and 3.9-fold improvement in the coupling efficiency and quality factor respectively when compared to the standard L3 cavity. Disorder analysis further shows that the designs retain significant performance despite nanofabrication imperfections. Our work demonstrates a versatile inverse design framework for multi-objective optimization of photonic crystal cavities to attain high quality factors and coupling efficiency.

physics.optics↗

arXiv2025

Hardware-Efficient Universal Linear Transformations for Optical Modes in the Synthetic Time Dimension

Recent progress in photonic information processing has spurred strong demand in scalable and reconfigurable photonic circuitry. Conventional spatially-meshed multi-port interferometers require a number of components growing quadratically with the system size, posing a fundamental scaling challenge ahead. Here, we introduce a hardware-efficient synthetic time-domain photonic processor that achieves at least an exponential reduction in hardware component count for implementing arbitrary linear transformations. The processor's dynamic connectivity allows systematic pruning, minimizing optical loss while preserving all-to-all connectivity. We benchmark our architecture on the task of boosted Bell state measurements -- a protocol essential for linear optical quantum computation, and show that it exceeds thresholds for universal cluster-state quantum computation under realistic hardware constraints. We link the device performance to the geometry of multi-photon transport, showing that localization effects from redundant, imperfect hardware may enhance robustness to coherent errors. Our design establishes a practical pathway toward near-term, scalable, and reconfigurable photonic processors in the synthetic time dimension.

quant-ph↗

arXiv2025

Quantum simulation of interacting bosons with propagating waveguide photons

Optical networks composed of interconnected waveguides are a versatile platform to simulate bosonic physical phenomena. Significant work in the non-interacting regime has demonstrated the capabilities of this platform to simulate many exotic effects such as photon transport in the presence of gauge fields, dynamics of quantum walks, and topological transition and dissipation phenomena. However, the extension of these concepts to simulating interacting quantum many-body phenomena such as the Bose-Hubbard and the fractional quantum Hall (FQH) physics has remained elusive. In this work, we address this problem and demonstrate a framework for quantum many-body simulation as well as drive and dissipation in photonic waveguides. Specifically, we show that for waveguide photons, a tunable on-site interaction can be simulated using a photon-number-selective phase gate. We propose an implementation of such a phase gate based on a three-level-atom-mediated photon subtraction and addition. We apply this approach to bosonic lattice models and propose circuits that can accurately simulate the Bose-Hubbard and FQH Hamiltonian as benchmarking examples. Moreover, we show how to simulate the Lindbladian evolution with engineered dissipators such that the steady state of the Lindbadlian corresponds to the ground state of desired Hamiltonians. Our scheme extends the waveguide photonic simulation platform to the strongly interacting quantum many-body regime while retaining all of its crucial advantages, such as single-site addressability, Hamiltonian parameter controllability, and hardware efficiency.

quant-ph↗

arXiv2024

Bright and Purcell-enhanced single photon emission from a silicon G center

Silicon G centers show significant promise as single photon sources in a scalable silicon platform. But these color centers have large non-radiative decay and a low Debye-Waller factor, limiting their usability in quantum applications. In this work, we demonstrate bright Purcell-enhanced emission from a silicon G center by coupling it to a nanophotonic cavity. The nanobeam cavity enhances the spontaneous emission rate of a single G center by a factor of 6, corresponding to a Purcell factor greater than 31 when accounting for decay into the phonon sideband. We obtain a spontaneous emission rate of 0.97 ns, which is the fastest single photon emission rate reported in silicon. With this radiative enhancement, we achieve an order of magnitude improvement in emitter brightness compared to previously reported values. These results pave the way for scalable quantum light sources on a silicon photonic chip.

physics.optics↗

arXiv2024

Generation of Coherent Quantum Light from a Single Impurity-Bound Exciton

Impurity-bound excitons in II-VI direct-bandgap semiconductors are promising optically active solid-state spin qubits that combine exceptional optical quantum efficiency with an ultra-low spin noise environment. Previous studies on single impurities relied on incoherent optical excitation to generate photons. However, many quantum applications require resonant driving of quantum emitters to precisely control optical transitions and maintain coherence of the emission. Here, we demonstrate coherent optical emission of quantum light from a resonantly driven single impurity-bound exciton in ZnSe. The resonantly driven emitter exhibits bright quantum light emission that preserves the phase of the resonant drive, validated through polarization interferometry. Resonant excitation enables us to directly measure the Debye-Waller factor, determined to be 0.94, which indicates high efficiency emission to the zero-phonon line. Time-resolved resonance fluorescence measurements reveal a fast optically-driven ionization process that we attribute to Auger recombination, along with a slower spontaneous ionization process having a lifetime of 21 {\mu}s due to charge tunneling from the impurity. We show that incoherent, low-power laser pumping efficiently stabilizes the charge of the impurity-bound exciton on the timescale of 9.3 ns, recovering the resonance fluorescence emission from the bound exciton. These results pave the way for coherent optical and spin control of the single impurity states through resonant excitation of impurity-bound excitons in II-VI semiconductors.

quant-ph↗

arXiv2024

Opportunities and Challenges of Solid-State Quantum Nonlinear Optics

Nonlinear interactions between single quantum particles are at the heart of any quantum information system, including analog quantum simulation and fault-tolerant quantum computing. This remains a particularly difficult problem for photonic qubits, as photons do not interact with each other. While engineering light-matter interaction can effectively create photon-photon interaction, the required photon number to observe any nonlinearity is very high, where any quantum mechanical signature disappears. However, with emerging low-dimensional materials, and engineered photonic resonators, the photon number can be potentially reduced to reach the quantum nonlinear optical regime. In this review paper, we discuss different mechanisms exploited in solid-state platforms to attain quantum nonlinear optics. We review emerging materials and optical resonator architecture with different dimensionalities. We also present new research directions and open problems in this field.

physics.optics↗

arXiv2024

Universal Logical Quantum Photonic Neural Network Processor via Cavity-Assisted Interactions

Encoding quantum information within bosonic modes offers a promising direction for hardware-efficient and fault-tolerant quantum information processing. However, achieving high-fidelity universal control over the bosonic degree of freedom using native photonic hardware remains a challenge. Here, we propose an architecture to prepare and perform logical quantum operations on arbitrary multimode multi-photon states using a quantum photonic neural network. Central to our approach is the optical nonlinearity, which is realized through strong light-matter interaction with a three-level Lambda atomic system. The dynamics of this interaction are confined to the single-mode subspace, enabling the construction of high-fidelity quantum gates. This nonlinearity functions as a photon-number selective phase gate, which facilitates the construction of a universal gate set and serves as the element-wise activation function in our neural network architecture. Through numerical simulations, we demonstrate the versatility of our approach by executing tasks that are key to logical quantum information processing. The network is able to deterministically prepare a wide array of multimode multi-photon states, including essential resource states. We also show that the architecture is capable of encoding and performing logical operations on bosonic error-correcting codes. Additionally, by adapting components of our architecture, error-correcting circuits can be built to protect bosonic codes. The proposed architecture paves the way for near-term quantum photonic processors that enable error-corrected quantum computation, and can be achieved using present-day integrated photonic hardware.

quant-ph↗

arXiv2024

Efficient, indistinguishable telecom C-band photons using a tapered nanobeam

Telecom C-band single photons exhibit the lowest attenuation in optical fibers, enabling long-haul quantum-secured communication. However, efficient coupling with optical fibers is crucial for these single photons to be effective carriers in long-distance transmission. In this work, we demonstrate an efficient fiber-coupled single photon source at the telecom C-band using InAs/InP quantum dots coupled to a tapered nanobeam. The tapered nanobeam structure facilitates directional emission that is mode-matched to a lensed fiber, resulting in a collection efficiency of up to 65% from the nanobeam to a single-mode fiber. Using this approach, we demonstrate single photon count rates of 575 $\pm$ 5 Kcps and a single photon purity of $g^2$ (0) = 0.015 $\pm$ 0.003. Additionally, we demonstrate Hong-Ou Mandel interference from the emitted photons with a visibility of 0.84 $\pm$ 0.06. From these measurements, we determine a photon coherence time of 450 $\pm$ 20 ps, a factor of just 8.3 away from the lifetime limit. This work represents an important step towards the development of telecom C-band single-photon sources emitting bright, pure, and indistinguishable photons, which are necessary to realize fiber-based long-distance quantum networks

quant-ph↗

arXiv2024

Dynamic control of 2D non-Hermitian photonic corner states in synthetic dimensions

Non-Hermitian models describe the physics of ubiquitous open systems with gain and loss. One intriguing aspect of non-Hermitian models is their inherent topology that can produce intriguing boundary phenomena like resilient higher-order topological insulators (HOTIs) and non-Hermitian skin effects (NHSE). Recently, time-multiplexed lattices in synthetic dimensions have emerged as a versatile platform for the investigation of these effects free of geometric restrictions. Despite holding broad applications, studies of these effects have been limited to static cases so far, and full dynamical control over the non-Hermitian effects has remained elusive. Here, we demonstrate the emergence of topological non-Hermitian corner states with remarkable temporal controllability and robustness in a two-dimensional photonic synthetic time lattice. Specifically, we showcase various dynamic control mechanisms for light confinement and flow, including spatial mode tapering, sequential non-Hermiticity on-off switching, dynamical corner state relocation, and light steering. Moreover, we establish the corner state's robustness in the presence of intensity modulation randomness and quantitatively determine its breakdown regime. Our findings extend non-Hermitian and topological photonic effects into higher synthetic dimensions, offering remarkable flexibility and real-time control possibilities. This opens avenues for topological classification, quantum walk simulations of many-body dynamics, and robust Floquet engineering, free from the limitations of physical geometries.

physics.optics↗

arXiv2024

Cavity-enhanced narrowband spectral filters using rare-earth ions doped in thin-film lithium niobate

On-chip optical filters are fundamental components in optical signal processing. While rare-earth ion-doped crystals offer ultra-narrow optical filtering via spectral hole burning, their applications have primarily been limited to those using bulk crystals, restricting their utility. In this work, we demonstrate cavity-enhanced spectral filtering based on rare-earth ions in an integrated nonlinear optical platform. We incorporate rare-earth ions into high quality-factor ring resonators patterned in thin-film lithium niobate. By spectral hole burning at 4K in a critically coupled resonance mode, we achieve bandpass filters ranging from 7 MHz linewidth, with 13.0 dB of extinction, to 24 MHz linewidth, with 20.4 dB of extinction. By reducing the temperature to 100 mK to eliminate phonon broadening, we achieve an even narrower linewidth of 681 kHz, which is comparable to the narrowest filter linewidth demonstrated in an integrated photonic device, while only requiring a small device footprint. Moreover, the cavity enables reconfigurable filtering by varying the cavity coupling rate. For instance, as opposed to the bandpass filter, we demonstrate a bandstop filter utilizing an under-coupled ring resonator. Such versatile integrated spectral filters with high extinction ratio and narrow linewidth could serve as fundamental components for optical signal processing and optical memories on-a-chip.

physics.optics↗

arXiv2023

Purcell enhanced emission and saturable absorption of cavity-coupled CsPbBr$_3$ quantum dots

Halide perovskite semiconductors have emerged as promising materials for the development of solution-processed, scalable, high performance optoelectronic devices such as light-emitting diodes (LEDs) as well as coherent single photon emitters. Their integration to nanophotonic cavities for radiative enhancement and strong nonlinearity is underexplored. In this work, we demonstrate cavity-enhanced emission and saturable absorption using colloidal CsPbBr$_3$ perovskite quantum dots coupled to a high-Q cavity mode of a circular Bragg grating structure designed to facilitate integration of solution-processed materials . We achieve an order of magnitude increase in brightness and 8-fold increase in the spontaneous emission rate for the cavity-coupled emitters. This result indicates the possibility of achieving transform-limited photon coherence for the halide perovskites at cryogenic temperatures. We also observe saturable absorption of the emitters through intensity-dependent cavity quality factor. These results pave the way towards achieving improved photon indistinguishability and strong optical nonlinearities for cavity coupled perovskite systems.

physics.optics↗

arXiv2023

Optimizing the quality factor of InP nanobeam cavities using atomic layer deposition

Photonic crystal nanobeam cavities are valued for their small mode volume, CMOS compatibility, and high coupling efficiency crucial features for various low-power photonic applications and quantum information processing. However, despite their potential, nanobeam cavities often suffer from low quality factors due to fabrication imperfections that create surface states and optical absorption. In this work, we demonstrate InP nanobeam cavities with up to 140% higher quality factors by applying a coating of Al$_2$O$_3$ via atomic layer deposition to terminate dangling bonds and reduce surface absorption. Additionally, changing the deposition thickness allows precise tuning of the cavity mode wavelength without compromising the quality factor. This Al$_2$O$_3$ atomic layer deposition approach holds great promise for optimizing nanobeam cavities that are well-suited for integration with a wide range of photonic applications.

physics.optics↗