arXiv subjects

Chee Wei Wong

Publications and source records attributed to Chee Wei Wong.

At least 37 records · Page 2Linked to original sources

arXiv2023

High-dimensional time-frequency entanglement in a singly-filtered biphoton frequency comb

High-dimensional quantum entanglement is a cornerstone for advanced technology enabling large-scale noise-tolerant quantum systems, fault-tolerant quantum computing, and distributed quantum networks. The recently developed biphoton frequency comb (BFC) provides a powerful platform for high-dimensional quantum information processing in its spectral and temporal quantum modes. Here we propose and generate a singly-filtered high-dimensional BFC via spontaneous parametric down-conversion by spectrally shaping only the signal photons with a Fabry-Perot cavity. High-dimensional energy-time entanglement is verified through Franson-interference recurrences and temporal correlation with low-jitter detectors. Frequency- and temporal- entanglement of our singly-filtered BFC is then quantified by Schmidt mode decomposition. Subsequently, we distribute the high-dimensional singly-filtered BFC state over a 10 km fiber link with a post-distribution time-bin dimension lower bounded to be at least 168. Our demonstrations of high-dimensional entanglement and entanglement distribution show the capability of the singly-filtered quantum frequency comb for high-efficiency quantum information processing and high-capacity quantum networks.

quant-ph↗

arXiv2023

A chip-scale polarization-spatial-momentum quantum SWAP gate in silicon nanophotonics

Recent progress in quantum computing and networking enables high-performance large-scale quantum processors by connecting different quantum modules. Optical quantum systems show advantages in both computing and communications, and integrated quantum photonics further increases the level of scaling and complexity. Here we demonstrate an efficient SWAP gate that deterministically swaps a photon's polarization qubit with its spatial-momentum qubit on a nanofabricated two-level silicon-photonics chip containing three cascaded gates. The on-chip SWAP gate is comprehensively characterized by tomographic measurements with high fidelity for both single-qubit and two-qubit operation. The coherence preservation of the SWAP gate process is verified by single-photon and two-photon quantum interference. The coherent reversible conversion of our SWAP gate facilitates a quantum interconnect between different photonic subsystems with different degrees of freedom, demonstrated by distributing four Bell states between two chips. We also elucidate the source of decoherence in the SWAP operation in pursuit of near-unity fidelity. Our deterministic SWAP gate in the silicon platform provides a pathway towards integrated quantum information processing for interconnected modular systems.

quant-ph↗

arXiv2023

Non-Binary LDPC Code Design for Energy-Time Entanglement Quantum Key Distribution

In energy-time entanglement Quantum Key Distribution (QKD), two users extract a shared secret key from the arrival times (discretized as symbols) of entangled photon pairs. In prior work, Zhou et al. proposed a multi-level coding (MLC) scheme that splits the observed symbols into bit layers and utilizes binary Low-Density Parity-Check (LDPC) codes for reconciliation of the symbols. While binary LDPC codes offer low latency for key generation, splitting the symbols into bits results in a loss of key generation rate due to error propagation. Additionally, existing LDPC codes do not fully utilize the properties of the QKD channel to optimize the key rates. In this paper, we mitigate the above issues by first generalizing the MLC scheme to a non-binary(NB) MLC scheme that has layers with non-binary symbols and utilizes NB-LDPC codes. We show the NB-MLC scheme offers flexibility in system design. Additionally, we show that the NB-MLC scheme with a small symbol size per layer offers the best trade-off between latency and key rate. We then propose a framework to jointly optimize the rate and degree profile of the NB-LDPC codes that is tailored towards the QKD channel resulting in higher key rates than prior work.

cs.IT↗

arXiv2023

Polarization-diverse soliton transitions and deterministic switching dynamics in strongly-coupled and self-stabilized microresonator frequency combs

Dissipative Kerr soliton microcombs in microresonators has enabled fundamental advances in chip scale precision metrology, communication, spectroscopy, and parallel signal processing. Here we demonstrate polarization diverse soliton transitions and deterministic switching dynamics of a self stabilized microcomb in a strongly coupled dispersion-managed microresonator driven with a single pump laser. The switching dynamics are induced by the differential thermorefractivity between coupled transverse magnetic and transverse electric supermodes during the forward backward pump detunings. The achieved large soliton existence range and deterministic transitions benefit from the switching dynamics, leading to the cross polarized soliton microcomb formation when driven in the transverse magnetic supermode of the single resonator. Resultantly the pump laser always exists at the effective blue detuning of the transverse magnetic resonance, fundamentally mitigating the thermal destabilization barrier and improving accessibility of the soliton formation regime. Subsequently and secondly, we demonstrate two distinct polarization diverse soliton formation routes arising from chaotic or periodically modulated waveforms via pump power selection. The generated self stabilized supermode microcomb features an extraordinarily large soliton existence range, a variety of soliton state transitions with well defined pump laser tuning, high pump microcomb conversion efficiency, and low repetition rate phase noise.

physics.optics↗

arXiv2022

PhotoFourier: A Photonic Joint Transform Correlator-Based Neural Network Accelerator

The last few years have seen a lot of work to address the challenge of low-latency and high-throughput convolutional neural network inference. Integrated photonics has the potential to dramatically accelerate neural networks because of its low-latency nature. Combined with the concept of Joint Transform Correlator (JTC), the computationally expensive convolution functions can be computed instantaneously (time of flight of light) with almost no cost. This 'free' convolution computation provides the theoretical basis of the proposed PhotoFourier JTC-based CNN accelerator. PhotoFourier addresses a myriad of challenges posed by on-chip photonic computing in the Fourier domain including 1D lenses and high-cost optoelectronic conversions. The proposed PhotoFourier accelerator achieves more than 28X better energy-delay product compared to state-of-art photonic neural network accelerators.

cs.AR↗

arXiv2022

Parametrically driven inertial sensing in chip-scale optomechanical cavities at the thermodynamical limits with extended dynamic range

Recent scientific and technological advances have enabled the detection of gravitational waves, autonomous driving, and the proposal of a communications network on the Moon (Lunar Internet or LunaNet). These efforts are based on the measurement of minute displacements and correspondingly the forces or fields transduction, which translate to acceleration, velocity, and position determination for navigation. State-of-the-art accelerometers use capacitive or piezo resistive techniques, and micro-electromechanical systems (MEMS) via integrated circuit (IC) technologies in order to drive the transducer and convert its output for electric readout. In recent years, laser optomechanical transduction and readout have enabled highly sensitive detection of motional displacement. Here we further examine the theoretical framework for the novel mechanical frequency readout technique of optomechanical transduction when the sensor is driven into oscillation mode [8]. We demonstrate theoretical and physical agreement and characterize the most relevant performance parameters with a device with 1.5mg/Hz acceleration sensitivity, a 2.5 fm/Hz1/2 displacement resolution corresponding to a 17.02 ug/Hz1/2 force-equivalent acceleration, and a 5.91 Hz/nW power sensitivity, at the thermodynamical limits. In addition, we present a novel technique for dynamic range extension while maintaining the precision sensing sensitivity. Our inertial accelerometer is integrated on-chip, and enabled for packaging, with a laser-detuning-enabled approach.

eess.SY↗

arXiv2022

AtOMICS: A neural network-based Automated Optomechanical Intelligent Coupling System for testing and characterization of silicon photonics chiplets

Recent advances in silicon photonics promise to revolutionize modern technology by improving performance of everyday devices in multiple fields. However, as the industry moves into a mass fabrication phase, the problem of effective testing of integrated silicon photonics devices remains to be solved. A cost-efficient manner that reduces schedule risk needs to involve automated testing of multiple devices that share common characteristics such as input-output coupling mechanisms, but at the same time needs to be generalizable to multiple types of devices and scenarios. In this paper we present a neural network-based automated system designed for in-plane fiber-chip-fiber testing, characterization, and active alignment of silicon photonic devices that use process-design-kit library edge couplers. The presented approach combines state-of-the-art computer vision techniques with time-series analysis, in order to control a testing setup that can process multiple devices and can be easily tuned to incorporate additional hardware. The system can operate at vacuum or atmospheric pressures and maintains stability for fairly long time periods in excess of a month.

eess.IV↗

arXiv2022

Spontaneous microwave platicon frequency microcomb in dispersion-managed microresonators

Temporally stabilized optical pules, confined in microresonators driven by a continuous-wave laser, have attracted tremendous attention due to their fascinating features with many applications. Here we report the observations of mode-locked platicon frequency microcomb formation in normal dispersion dispersion-managed microresonators operating at microwave K-band repetition rate for the first time. Facilitated by the thermally controllable modulated background induced by avoided mode-crossings, various platicon bound state patterns with regular and irregular temporal separation are stably generated due to an additional balance between repulsive and attractive forces resulting from non-trivial interpulse and background electromagnetic field interactions. The number of mode-locked pulses can be switched by forward- and backward-cavity pump detuning and, with increasing pump power, result in stationary bound-state complexes. These experimental observations are in accordance with our nonlinear numerical simulations that includes avoided mode-crossing, anomalous fourth-order dispersion and quality-factor spectral filtering. The observed platicon mode-locked pulses have broad spectral profiles overlapping Kelly-sideband-like parametric oscillation. The single-sideband phase noise of microcomb repetition rate is characterized for the different mode-locked states, comparable with electronic microwave oscillators. The ability to achieve mode-locking in dispersion-managed microresonators provides a platform to reduce pulse timing jitter and enrich the exploration of ultrafast phenomena in microresonators.

physics.optics↗

arXiv2022

Coherent terahertz radiation with 2.8-octave tunability through chip-scale photomixed microresonator optical parametric oscillation

High spectral purity frequency agile room temperature sources in the terahertz spectrum are foundational elements for imaging, sensing, metrology, and communications. Here we present a chip scale optical parametric oscillator based on an integrated nonlinear microresonator that provides broadly tunable single frequency and multi frequency oscillators in the terahertz regime. Through optical to terahertz down conversion using a plasmonic nanoantenna array, coherent terahertz radiation spanning 2.8 octaves is achieved from 330 GHz to 2.3 THz, with 20 GHz cavity mode limited frequency tuning step and 10 MHz intracavity mode continuous frequency tuning range at each step. By controlling the microresonator intracavity power and pump resonance detuning, tunable multi frequency terahertz oscillators are also realized. Furthermore, by stabilizing the microresonator pump power and wavelength, sub 100 Hz linewidth of the terahertz radiation with 10-15 residual frequency instability is demonstrated. The room temperature generation of both single frequency, frequency agile terahertz radiation and multi frequency terahertz oscillators in the chip scale platform offers unique capabilities in metrology, sensing, imaging and communications.

physics.optics↗

arXiv2022

Nonlinear Optical Joint Transform Correlator for Low Latency Convolution Operations

Convolutions are one of the most relevant operations in artificial intelligence (AI) systems. High computational complexity scaling poses significant challenges, especially in fast-responding network-edge AI applications. Fortunately, the convolution theorem can be executed on-the-fly in the optical domain via a joint transform correlator (JTC) offering to fundamentally reduce the computational complexity. Nonetheless, the iterative two-step process of a classical JTC renders them unpractical. Here we introduce a novel implementation of an optical convolution-processor capable of near-zero latency by utilizing all-optical nonlinearity inside a JTC, thus minimizing electronic signal or conversion delay. Fundamentally we show how this nonlinear auto-correlator enables reducing the high $O(n^4)$ scaling complexity of processing two-dimensional data to only $O(n^2)$. Moreover, this optical JTC processes millions of channels in time-parallel, ideal for large-matrix machine learning tasks. Exemplary utilizing the nonlinear process of four-wave mixing, we show light processing performing a full convolution that is temporally limited only by geometric features of the lens and the nonlinear material's response time. We further discuss that the all-optical nonlinearity exhibits gain in excess of $>10^{3}$ when enhanced by slow-light effects such as epsilon-near-zero. Such novel implementation for a machine learning accelerator featuring low-latency and non-iterative massive data parallelism enabled by fundamental reduced complexity scaling bears significant promise for network-edge, and cloud AI systems.

physics.optics↗

arXiv2022

Stimulated generation of deterministic platicon frequency microcombs

Dissipative Kerr soliton generation in chip-scale nonlinear resonators has recently observed remarkable advances, spanning from massively-parallel communications, self-referenced oscillators, to dual-comb spectroscopy. Often working in the anomalous dispersion regime, unique driving protocols and dispersion in these nonlinear resonators have been examined to achieve the soliton and soliton-like temporal pulse shapes and coherent frequency comb generation. The normal dispersion regime provides a complementary approach to bridge the nonlinear dynamical studies, including the possibility of square pulse formation with flat-top plateaus, or platicons. Here we report observations of square pulse formation in chip-scale frequency combs, through stimulated pumping at one free-spectral-range and in silicon nitride rings with +55 fs2/mm normal group velocity dispersion. Tuning of the platicon frequency comb via a varied sideband modulation frequency is examined in both spectral and temporal measurements. Determined by second-harmonic auto-correlation and cross-correlation, we observe bright square platicon pulse of 17 ps pulsewidth on a 19 GHz flat frequency comb. With auxiliary-laser-assisted thermal stabilization, we surpass the thermal bistable dragging and extend the mode-locking access to narrower 2 ps platicon pulse states, supported by nonlinear dynamical modeling and boundary limit discussions.

physics.optics↗

arXiv2021

Highly Accurate, Reliable and Non-Contaminating Two-Dimensional Material Transfer System

The exotic properties of two-dimensional (2D) materials and 2D heterostructures, built by forming heterogeneous multi-layered stacks, have been widely explored across a number of subject matters following the goal to invent, design, and improve applications enabled by 2D materials. To successfully harvest these unique properties effectively and increase the yield of manufacturing 2D material-based devices for achieving reliable and repeatable results is the current challenge. The scientific community has introduced various experimental transfer systems explained in detail for exfoliated 2D materials, however, the field lacks statistical analysis and the capability of producing a transfer technique enabling; i) high transfer precision and yield, ii) cross-contamination free transfer, iii) multi-substrate transfer, and iv) rapid prototyping without wet chemistry. Here we introduce a novel 2D material deterministic transfer system and experimentally show its high accuracy, reliability, repeatability, and non-contaminating transfer features by demonstrating fabrication of 2D material-based optoelectronic devices featuring novel device physics and unique functionality. Such rapid and material-near prototyping capability can accelerate not only layered material science in discovery but also engineering innovations.

cond-mat.mes-hall↗

arXiv2021

Phonon modes and Raman signatures of MnBi2nTe3n+1 (n=1,2,3,4) magnetic topological heterostructures

An intrinsic antiferromagnetic topological insulator $\mathrm{MnBi_2Te_4}$ can be realized by intercalating Mn-Te bilayer chain in a topological insulator, $\mathrm{Bi_2Te_3}$. $\mathrm{MnBi_2Te_4}$ provides not only a stable platform to demonstrate exotic physical phenomena, but also easy tunability of the physical properties. For example, inserting more $\mathrm{Bi_2Te_3}$ layers in between two adjacent $\mathrm{MnBi_2Te_4}$ weakens the interlayer magnetic interactions between the $\mathrm{MnBi_2Te_4}$ layers. Here we present the first observations on the inter- and intra-layer phonon modes of $\mathrm{MnBi_{2n}Te_{3n+1}}$ (n=1,2,3,4) using cryogenic low-frequency Raman spectroscopy. We experimentally and theoretically distinguish the Raman vibrational modes using various polarization configurations. The two peaks at 66 cm$^{-1}$ and 112 cm$^{-1}$ show an abnormal perturbation in the Raman linewidths below the magnetic transition temperature due to spin-phonon coupling. In $\mathrm{MnBi_4Te_7}$, the $\mathrm{Bi_2Te_3}$ layers induce Davydov splitting of the A$_{1g}$ mode around 137 cm$^{-1}$ at 5 K. Using the linear chain model, we estimate the out-of-plane interlayer force constant to be $(3.98 \pm 0.14) \times 10^{19}$ N/m$^3$ at 5 K, three times weaker than that of $\mathrm{Bi_2Te_3}$. Our work discovers the dynamics of phonon modes of the $\mathrm{MnBi_2Te_4}$ and the effect of the additional $\mathrm{Bi_2Te_3}$ layers, providing the first-principles guidance to tailor the physical properties of layered heterostructures.

cond-mat.mtrl-sci↗

arXiv2021

Exciton-photon complexes and dynamics in the concurrent strong-weak coupling regime of singular site-controlled cavity quantum electrodynamics

We investigate the exciton complexes photoluminescence, dynamics and photon statistics in the concurrent strong weak coupling regime in our unique site controlled singular inverted pyramidal InGaAs/GaAs quantum dots photonic crystal cavities platform. Different from a clear boundary between strong and weak QD cavity coupling, we demonstrate the strong and weak coupling can coexist dynamically, as a form of intermediate regime mediated by phonon scattering. The detuning dependent microphotoluminescence spectrum reveals concurrence of exciton cavity polariton mode avoided crossing, as a signature of Rabi doublet of the strong coupled system, the blue shifting of coupled exciton cavity mode energy near zero detuning ascribed to the formation of collective states mediated by phonon assisted coupling, and their partial out of synchronization linewidth narrowing linked to their mixed behavior. By detailing the optical features of strongly confined exciton-photon complexes and the quantum statistics of coupled cavity photons, we reveal the dynamics and antibunching/bunching photon statistical signatures of the concurrent strong weak intermediate coupled system at near zero-detuning. This study suggests our device has potential for new and subtle cavity quantum electrodynamical phenomena, cavity enhanced indistinguishable single photon generation, and cluster state generation via the exciton-photon complexes for quantum networks.

cond-mat.mes-hall↗

arXiv2021

Robust Preparation of Many-body Ground States in Jaynes-Cummings Lattices

Strongly-correlated polaritons in Jaynes-Cummings (JC) lattices can exhibit quantum phase transitions between the Mott-insulating and superfluid phases at integer fillings. The prerequisite to observe such phase transitions is to pump polariton excitations into a JC lattice and prepare them into appropriate ground states. Despite previous efforts, it is still challenging to generate many-body states with high accuracy. Here we present an approach for the robust preparation of many-body ground states of polaritons in finite-sized JC lattices by optimized nonlinear ramping. We apply a Landau-Zener type of estimation to this finite-sized system and derive the optimal ramping index for selected ramping trajectories, which can greatly improve the fidelity of the prepared states. With numerical simulation, we show that by choosing an appropriate ramping trajectory, the fidelity in this approach can remain close to unity in almost the entire parameter space. This approach can shed light on high-fidelity state preparation in quantum simulators and advance the implementation of quantum simulation with practical devices.

quant-ph↗

arXiv2020

Gain-assisted chiral soliton microcombs

The emerging microresonator-based frequency combs revolutionize a broad range of applications from optical communications to astronomical calibration. Despite of their significant merits, low energy efficiency and the lack of all-optical dynamical control severely hinder the transfer of microcomb system to real-world applications. Here, by introducing active lasing medium into the soliton microcomb, for the first time, we experimentally achieve the chiral soliton with agile on-off switch and tunable dual-comb generation in a packaged microresonator. It is found that such a microresonator enables a soliton slingshot effect, the rapid soliton formation arising from the extra energy accumulation induced by inter-modal couplings. Moreover, tuning the erbium gain can generate versatile multi-soliton states, and extend the soliton operation window to a remarkable range over 18 GHz detuning. Finally, the gain-assisted chirality of counterpropagating soliton is demonstrated, which enables an unprecedented fast on-off switching of soliton microcombs. The non-trivial chiral soliton formation with active controllability inspires new paradigms of miniature optical frequency combs and brings the fast tunable soliton tools within reach.

physics.optics↗

arXiv2020

Nanometric precision distance metrology via chip-scale soliton microcombs

Laser interferometry serves a fundamental role in science and technology, assisting precision metrology and dimensional length measurement. During the past decade, laser frequency combs - a coherent optical-microwave frequency ruler over a broad spectral range with traceability to time-frequency standards - have contributed pivotal roles in laser dimensional metrology with ever-growing demands in measurement precision. Here we report spectrally-resolved laser dimensional metrology via a soliton frequency microcomb, with nanometric-scale precision. Spectral interferometry provides information on the optical time-of-flight signature, and the large free-spectral range and high-coherence of the microcomb enables tooth-resolved and high-visibility interferograms that can be directly readout with optical spectrum instrumentation. We employ a hybrid timing signal from comb-line homodyne interferometry and microcomb spectrally-resolved interferometry - all from the same spectral interferogram. Our combined soliton and homodyne architecture demonstrates a 3-nm repeatability achieved via homodyne interferometry, and over 1,000-seconds stability in the long-term precision metrology at the white noise limits.

physics.ins-det↗

arXiv2020

A chip-scale oscillation-mode optomechanical inertial sensor near the thermodynamical limits

High-precision inertial sensing and gravity sensing are key in navigation, oil exploration, and earthquake prediction. In contrast to prior accelerometers using piezoelectric or electronic capacitance readout techniques, optical readout provides narrow-linewidth high-sensitivity laser detection along with low-noise resonant optomechanical transduction near the thermodynamical limits. Here an optomechanical inertial sensor with 8.2micro-g/Hz^1/2 velocity random walk (VRW) at acquisition rate of 100 Hz and 50.9 micro-g bias instability is demonstrated, suitable for consumer and industrial grade applications, e.g., inertial navigation, inclination sensing, platform stabilization, and/or wearable device motion detection. Driven into optomechanical sustained-oscillation, the slot photonic crystal cavity provides radio-frequency readout of the optically-driven transduction with enhanced 625 microg/Hz sensitivity. Measuring the optomechanically-stiffened oscillation shift, instead of the optical transmission shift, provides a 220x VRW enhancement over pre-oscillation mode detection due to the strong optomechanical transduction. Supported by theory, this inertial sensor operates 2.56x above the thermodynamical limit at small integration times, with 43-dB dynamic range, in a solid-state room-temperature readout architecture.

physics.ins-det↗