arXiv subjects

Linsen Li

Publications and source records attributed to Linsen Li.

17 recordsLinked to original sources

arXiv2026

Using Text-Based Causal Inference to Disentangle Factors Influencing Online Review Ratings

Online reviews provide valuable insights into the perceived quality of facets of a product or service. While aspect-based sentiment analysis has focused on extracting these facets from reviews, there is less work understanding the impact of each aspect on overall perception. This is particularly challenging given correlations among aspects, making it difficult to isolate the effects of each. This paper introduces a methodology based on recent advances in text-based causal analysis, specifically CausalBERT, to disentangle the effect of each factor on overall review ratings. We enhance CausalBERT with three key improvements: temperature scaling for better calibrated treatment assignment estimates; hyperparameter optimization to reduce confound overadjustment; and interpretability methods to characterize discovered confounds. In this work, we treat the textual mentions in reviews as proxies for real-world attributes. We validate our approach on real and semi-synthetic data from over 600K reviews of U.S. K-12 schools. We find that the proposed enhancements result in more reliable estimates, and that perception of school administration and performance on benchmarks are significant drivers of overall school ratings.

cs.CL↗

arXiv2026

Foundry-Enabled Patterning of Diamond Quantum Microchiplets for Scalable Quantum Photonics

Quantum technologies promise secure communication networks and powerful new forms of information processing, but building these systems at scale remains a major challenge. Diamond is an especially attractive material for quantum devices because it can host atomic-scale defects that emit single photons and store quantum information with exceptional stability. However, fabricating the optical structures needed to control light in diamond typically relies on slow, bespoke processes that are difficult to scale. In this work, we introduce a manufacturing approach that brings diamond quantum photonics closer to industrial production. Instead of sequentially defining each device by lithography written directly on diamond, we fabricate high-precision silicon masks using commercial semiconductor foundries and transfer them onto diamond via microtransfer printing. These masks define large arrays of nanoscale optical structures, shifting the most demanding pattern-definition steps away from the diamond substrate, improving uniformity, yield, and throughput. Using this method, we demonstrate hundreds of diamond "quantum microchiplets" with improved optical performance and controlled interaction with quantum emitters. The chiplet format allows defective devices to be replaced and enables integration with existing photonic and electronic circuits. Our results show that high-quality diamond quantum devices can be produced using scalable, foundry-compatible techniques. This approach provides a practical pathway toward large-scale quantum photonic systems and hybrid quantum-classical technologies built on established semiconductor manufacturing infrastructure.

quant-ph↗

arXiv2024

Dynamic Inhomogeneous Quantum Resource Scheduling with Reinforcement Learning

A central challenge in quantum information science and technology is achieving real-time estimation and feedforward control of quantum systems. This challenge is compounded by the inherent inhomogeneity of quantum resources, such as qubit properties and controls, and their intrinsically probabilistic nature. This leads to stochastic challenges in error detection and probabilistic outcomes in processes such as heralded remote entanglement. Given these complexities, optimizing the construction of quantum resource states is an NP-hard problem. In this paper, we address the quantum resource scheduling issue by formulating the problem and simulating it within a digitized environment, allowing the exploration and development of agent-based optimization strategies. We employ reinforcement learning agents within this probabilistic setting and introduce a new framework utilizing a Transformer model that emphasizes self-attention mechanisms for pairs of qubits. This approach facilitates dynamic scheduling by providing real-time, next-step guidance. Our method significantly improves the performance of quantum systems, achieving more than a 3$\times$ improvement over rule-based agents, and establishes an innovative framework that improves the joint design of physical and control systems for quantum applications in communication, networking, and computing.

cs.LG↗

arXiv2024

A scalable cavity-based spin-photon interface in a photonic integrated circuit

A central challenge in quantum networking is transferring quantum states between different physical modalities, such as between flying photonic qubits and stationary quantum memories. One implementation entails using spin-photon interfaces that combine solid-state spin qubits, such as color centers in diamond, with photonic nanostructures. However, while high-fidelity spin-photon interactions have been demonstrated on isolated devices, building practical quantum repeaters requires scaling to large numbers of interfaces yet to be realized. Here, we demonstrate integration of nanophotonic cavities containing tin-vacancy (SnV) centers in a photonic integrated circuit (PIC). Out of a six-channel quantum micro-chiplet (QMC), we find four coupled SnV-cavity devices with an average Purcell factor of ~7. Based on system analyses and numerical simulations, we find with near-term improvements this multiplexed architecture can enable high-fidelity quantum state transfer, paving the way towards building large-scale quantum repeaters.

quant-ph↗

arXiv2023

Heterogeneous integration of spin-photon interfaces with a scalable CMOS platform

Color centers in diamonds have emerged as a leading solid-state platform for advancing quantum technologies, satisfying the DiVincenzo criteria and recently achieving a quantum advantage in secret key distribution. Recent theoretical works estimate that general-purpose quantum computing using local quantum communication networks will require millions of physical qubits to encode thousands of logical qubits, which presents a substantial challenge to the hardware architecture at this scale. To address the unanswered scaling problem, in this work, we first introduce a scalable hardware modular architecture "Quantum System-on-Chip" (QSoC) that features compact two-dimensional arrays "quantum microchiplets" (QMCs) containing tin-vacancy (SnV-) spin qubits integrated on a cryogenic application-specific integrated circuit (ASIC). We demonstrate crucial architectural subcomponents, including (1) QSoC fabrication via a lock-and-release method for large-scale heterogeneous integration; (2) a high-throughput calibration of the QSoC for spin qubit spectral inhomogenous registration; (3) spin qubit spectral tuning functionality for inhomogenous compensation; (4) efficient spin-state preparation and measurement for improved spin and optical properties. QSoC architecture supports full connectivity for quantum memory arrays in a set of different resonant frequencies and offers the possibility for further scaling the number of solid-state physical qubits via larger and denser QMC arrays and optical frequency multiplexing networking.

quant-ph↗

arXiv2023

Closed-Loop Electron-Beam-Induced Spectroscopy and Nanofabrication Around Individual Quantum Emitters

Color centers in diamond play a central role in the development of quantum photonic technologies, and their importance is only expected to grow in the near future. For many quantum applications, high collection efficiency from individual emitters is required, but the refractive index mismatch between diamond and air limits the optimal collection efficiency with conventional diamond device geometries. While different out-coupling methods with near-unity efficiency exist, many have yet to be realized due to current limitations in nanofabrication methods, especially for mechanically hard materials like diamond. Here, we leverage electron-beam-induced etching to modify Sn-implanted diamond quantum microchiplets containing integrated waveguides with width and thickness of 280 nm and 200 nm, respectively. This approach allows for simultaneous high-resolution imaging and modification of the host matrix with an open geometry and direct writing. When coupled with the cathodoluminescence signal generated from the electron-emitter interactions, we can monitor the enhancement of the quantum emitters in real-time with nanoscale spatial resolution. The operando measurement and manipulation of single photon emitters demonstrated here provides a new foundation for the control of emitter-cavity interactions in integrated quantum photonics.

physics.optics↗

arXiv2023

Electrical Tuning of Neutral and Charged Excitons with 1-nm Gate

Electrical control of individual spins and photons in solids is key for quantum technologies, but scaling down to small, static systems remains challenging. Here, we demonstrate nanoscale electrical tuning of neutral and charged excitons in monolayer WSe2 using 1-nm carbon nanotube gates. Electrostatic simulations reveal a confinement radius below 15 nm, reaching the exciton Bohr radius limit for few-layer dielectric spacing. In situ photoluminescence spectroscopy shows gate-controlled conversion between neutral excitons, negatively charged trions, and biexcitons at 4 K. Important for quantum information processing applications, our measurements indicate gating of a local 2D electron gas in the WSe2 layer, coupled to photons via trion transitions with binding energies exceeding 20 meV. The ability to deterministically tune and address quantum emitters using nanoscale gates provides a pathway towards large-scale quantum optoelectronic circuits and spin-photon interfaces for quantum networking.

cond-mat.mes-hall↗

arXiv2023

Nanoelectromechanical control of spin-photon interfaces in a hybrid quantum system on chip

Atom-like defects or color centers (CC's) in nanostructured diamond are a leading platform for optically linked quantum technologies, with recent advances including memory-enhanced quantum communication, multi-node quantum networks, and spin-mediated generation of photonic cluster states. Scaling to practically useful applications motivates architectures meeting the following criteria: C1 individual optical addressing of spin qubits; C2 frequency tuning of CC spin-dependent optical transitions; C3 coherent spin control in CC ground states; C4 active photon routing; C5 scalable manufacturability; and C6 low on-chip power dissipation for cryogenic operations. However, no architecture meeting C1-C6 has thus far been demonstrated. Here, we introduce a hybrid quantum system-on-chip (HQ-SoC) architecture that simultaneously achieves C1-C6. Key to this advance is the realization of piezoelectric strain control of diamond waveguide-coupled tin vacancy centers to meet C2 and C3, with ultra-low power dissipation necessary for C6. The DC response of our device allows emitter transition tuning by over 20 GHz, while the large frequency range (exceeding 2 GHz) enables low-power AC control. We show acoustic manipulation of integrated tin vacancy spins and estimate single-phonon coupling rates over 1 kHz in the resolved sideband regime. Combined with high-speed optical routing with negligible static hold power, this HQ-SoC platform opens the path to scalable single-qubit control with optically mediated entangling gates.

quant-ph↗

arXiv2023

A fully packaged multi-channel cryogenic module for optical quantum memories

Realizing a quantum network will require long-lived quantum memories with optical interfaces incorporated into a scalable architecture. Color centers quantum emitters in diamond have emerged as a promising memory modality due to their optical properties and compatibility with scalable integration. However, developing a scalable color center emitter module requires significant advances in the areas of heterogeneous integration and cryogenically compatible packaging. Here we report on a cryogenically stable and network compatible quantum-emitter module for memory use. This quantum-emitter module is a significant development towards advanced quantum networking applications such as distributed sensing and processing.

quant-ph↗

arXiv2023

Multiplexed control of spin quantum memories in a photonic circuit

A central goal in many quantum information processing applications is a network of quantum memories that can be entangled with each other while being individually controlled and measured with high fidelity. This goal has motivated the development of programmable photonic integrated circuits (PICs) with integrated spin quantum memories using diamond color center spin-photon interfaces. However, this approach introduces a challenge in the microwave control of individual spins within closely packed registers. Here, we present a quantum-memory-integrated photonics platform capable of (i) the integration of multiple diamond color center spins into a cryogenically compatible, high-speed programmable PIC platform; (ii) selective manipulation of individual spin qubits addressed via tunable magnetic field gradients; and (iii) simultaneous control of multiple qubits using numerically optimized microwave pulse shaping. The combination of localized optical control, enabled by the PIC platform, together with selective spin manipulation opens the path to scalable quantum networks on intra-chip and inter-chip platforms.

quant-ph↗

arXiv2023

Modular chip-integrated photonic control of artificial atoms in diamond nanostructures

A central goal in creating long-distance quantum networks and distributed quantum computing is the development of interconnected and individually controlled qubit nodes. Atom-like emitters in diamond have emerged as a leading system for optically networked quantum memories, motivating the development of visible-spectrum, multi-channel photonic integrated circuit (PIC) systems for scalable atom control. However, it has remained an open challenge to realize optical programmability with a qubit layer that can achieve high optical detection probability over many optical channels. Here, we address this problem by introducing a modular architecture of piezoelectrically-actuated atom-control PICs (APICs) and artificial atoms embedded in diamond nanostructures designed for high-efficiency free-space collection. The high-speed 4-channel APIC is based on a splitting tree mesh with triple-phase shifter Mach-Zehnder interferometers. This design simultaneously achieves optically broadband operation at visible wavelengths, high-fidelity switching ($> 40$ dB) at low voltages, sub-$μ$s modulation timescales ($> 30$ MHz), and minimal channel-to-channel crosstalk for repeatable optical pulse carving. Via a reconfigurable free-space interconnect, we use the APIC to address single silicon vacancy color centers in individual diamond waveguides with inverse tapered couplers, achieving efficient single photon detection probabilities (15$\%$) and second-order autocorrelation measurements $g^{(2)}(0) < 0.14$ for all channels. The modularity of this distributed APIC - quantum memory system simplifies the quantum control problem, potentially enabling further scaling to 1000s of channels.

quant-ph↗

arXiv2022

Photonic indistinguishability of the tin-vacancy center in nanostructured diamond

Tin-vacancy centers in diamond are promising spin-photon interfaces owing to their high quantum-efficiency, large Debye-Waller factor, and compatibility with photonic nanostructuring. Benchmarking their single-photon indistinguishability is a key challenge for future applications. Here, we report the generation of single photons with $99.7^{+0.3}_{-2.5}\%$ purity and $63(9)\%$ indistinguishability from a resonantly excited tin-vacancy center in a single-mode waveguide. We obtain quantum control of the optical transition with $1.71(1)$-ns-long $π$-pulses of $77.1(8)\%$ fidelity. A modest Purcell enhancement factor of 12 would enhance the indistinguishability to $95$\%. The greater than $100$ ms spectral stability shown would then enable strings of up to $10^6$ identical photons to be generated.

quant-ph↗

arXiv2022

Surface engineering for ultrathin metal anodes enabling high-performance Zn-ion batteries

Zn metal battery has been considered a promising alternative energy storage technology in renewable energy storage and grid storage. It is well-known that the surface orientation of a Zn metal anode is vital to the reversibility of a Zn metal battery. Herein, the (101)-oriented thin Zn metal anode (down to 2 μm) is electrodeposited on a Cu surface by adding dimethyl sulfoxide (DMSO) electrolyte additive in ZnSO4 aqueous solution. Scanning electron microscope (SEM) observation indicates the formation of flat terrace-like compact (101)-oriented surfaces. Insitu optical observation confirms that the (101)-oriented surfaces can be reversibly plated and stripped. DFT calculations reveal two mechanisms for the nucleation and growth of the Zn-(101) surface: (1) formation of Zn(101)//Cu(001) could lower the interface energy as compared to Zn(002)//Cu(001); (2) large reconstruction of the Zn (101) surface with DMSO and H2O absorption. Raman, XPS, and ToF-SIMS characterizations indicate that adding DMSO in ZnCl2 could facilitate the formation of ZnO-based SEI on Zn metal surface, while OH- and S-based SEI can be obtained with DMSO in ZnSO4. The electrochemical testings are performed, which demonstrates a higher cyclability for the (101)-oriented Zn in the half cell as well as a lower charge transfer barrier with respect to the (002)-dominated surface of the same electrode thickness. Zn||V2O5 full cells are further assembled, showing better capacity retention for the (101)-Zn as compared to the (002)-Zn with the same thickness (5 μm, 3 μm, and 2 μm). We hope this study to spur further interest in the control of Zn metal surface crystallographic orientation towards ultrathin Zn metal anodes.

cond-mat.mtrl-sci↗

arXiv2021

Upcycling Low-Nickel Polycrystalline Cathodes from Retired Electric Vehicle Batteries into Single-Crystal Nickel-Rich Cathodes

The electrification revolution in automobile industry and others demands annual production capacity of batteries at least on the order of 102 gigawatts hours, which presents a twofold challenge to supply of key materials such as cobalt and nickel and to recycling when the batteries retire. Pyrometallurgical and hydrometallurgical recycling are currently used in industry but suffer from complexity, high costs, and secondary pollution. Here we report a direct-recycling method in molten salts (MSDR) that is environmentally benign and value-creating based on a techno-economic analysis using real-world data and price information. We also experimentally demonstrate the feasibility of MSDR by upcycling a low-nickel polycrystalline LiNi0.5Mn0.3Co0.2O2 (NMC) cathode material that is widely used in early-year electric vehicles into Ni-rich (Ni > 65%) single-crystal NMCs with increased energy-density (>10% increase) and outstanding electrochemical performance (>94% capacity retention after 500 cycles in pouch-type full cells). This work opens up new opportunities for closed-loop recycling of electric vehicle batteries and manufacturing of next-generation NMC cathode materials.

physics.app-ph↗

arXiv2021

Field-based Design of a Resonant Dielectric Antenna for Coherent Spin-Photon Interfaces

We propose a field-based design for dielectric antennas to interface diamond color centers with a Gaussian propagating far field. This antenna design enables an efficient spin-photon interface with a Purcell factor exceeding 400 and a 93% mode overlap to a 0.4 numerical aperture far-field Gaussian mode. The antenna design is robust to fabrication imperfections, such as variations in the dimensions of the dielectric perturbations and the emitter dipole location. The field-based dielectric antenna design provides an efficient free-space interface to closely packed arrays of quantum memories for multiplexed quantum repeaters, arrayed quantum sensors, and modular quantum computers.

physics.optics↗

arXiv2019

Design Principles for Self-forming Interfaces Enabling Stable Lithium Metal Anodes

The path toward Li-ion batteries with higher energy-densities will likely involve use of thin lithium metal (Li) anode (<50 $μ$m in thickness), whose cyclability today remains limited by dendrite formation and low Coulombic efficiency. Previous studies have shown that the solid-electrolyte-interface (SEI) of Li metal plays a crucial role in Li electrodeposition and stripping. However, design rules for optimal SEIs on lithium metal are not well-established. Here, using integrated experimental and modeling studies on a series of structurally-similar SEI-modifying compounds as model systems, we reveal the relationship between SEI compositions, Li deposition morphology and coulombic efficiency, and identify two key descriptors (ionicity and compactness) for high performance SEIs through integrated experimental and modeling studies. Using this understanding, we design a highly ionic and compact SEI that shows excellent cycling performance in LiCoO$_2$-Li full cells at practical current densities. Our results provide guidance for the rational selection and optimization of SEI modifiers to further improve Li metal anodes.

physics.app-ph↗

arXiv2016

Origins of Large Voltage Hysteresis in High Energy-Density Metal Fluoride Lithium-Ion Battery Conversion Electrodes

Metal fluoride and oxides can store multiple lithium-ions through conversion chemistry to enable high energy-density lithium-ion batteries. However, their practical applications have been hindered by an unusually large voltage hysteresis between charge and discharge voltage-profiles and the consequent low energy efficiency (< 80%). The physical origins of such hysteresis are rarely studied and poorly understood. Here we employ in situ X-ray absorption spectroscopy (XAS), transmission electron microscopy (TEM), density-functional-theory (DFT) calculations, and galvanostatic intermittent titration technique (GITT) to first correlate the voltage profile of iron fluoride ($FeF_3$), a representative conversion electrode material, with evolution and spatial distribution of intermediate phases in the electrode. The results reveal that, contrary to conventional belief, the phase evolution in the electrode is symmetrical during discharge and charge. However, the spatial evolution of the electrochemically active phases, which is controlled by reaction kinetics, is different. We further propose that the voltage hysteresis in the $FeF_3$ electrode is kinetic in nature. It is the result of Ohmic voltage drop, reaction overpotential, and different spatial distributions of electrochemically-active phases (i.e. compositional inhomogeneity). Therefore, the large hysteresis can be expected to be mitigated by rational design and optimization of material microstructure and electrode architecture to improve the energy efficiency of lithium-ion batteries based on conversion chemistry.

cond-mat.mtrl-sci↗