About

Kerry Fang is an Associate Professor of Urban and Regional Planning at the University of Illinois Urbana-Champaign, where she is also a Tschangho John Kim Scholar in Urban and Regional Systems. Her work focuses on economic development and land use, exploring questions such as why some regions are rich while others are poor, and what policy tools can help create jobs and boost innovation. She examines the consequences of economic development, including encroachment into agricultural areas, sprawling development patterns, and pollution. Her research is interdisciplinary and international, adopting methods from economics, statistics, geography, sociology, and computer science, and she has studied countries including the United States, China, Australia, and Russia.

Research topics

• Quantum mechanics
• Physics
• Optoelectronics
• Condensed matter physics
• Nanotechnology
• Materials science

Selected publications

• Observation of phonon trapping in the continuum with topological charges

  Nature Communications · 31 citations

  Senior authorCorresponding
  • Physics
  • Quantum mechanics

  Abstract Phonon trapping has an immense impact in many areas of science and technology, from the antennas of interferometric gravitational wave detectors to chip-scale quantum micro- and nano-mechanical oscillators. It usually relies on the mechanical suspension—an approach, while isolating selected vibrational modes, leads to serious drawbacks for interrogation of the trapped phonons, including limited heat capacity and excess noises via measurements. To circumvent these constraints, we realize a paradigm of phonon trapping using mechanical bound states in the continuum (BICs) with topological features and conducted an in-depth characterization of the mechanical losses both at room and cryogenic temperatures. Our findings of mechanical BICs combining the microwave frequency and macroscopic size unveil a unique platform for realizing mechanical oscillators in both classical and quantum regimes. The paradigm of mechanical BICs might lead to unprecedented sensing modalities for applications such as rare-event searches and the exploration of the foundations of quantum mechanics in unreached parameter spaces.

  DOI

• Nanophotonic nonlinear Bell-state measurement for enhanced quantum networking

  2026-03-05

  article1st authorCorresponding
  PublisherDOI

• Efficient bidirectional quantum frequency conversion between telecom and visible bands using adaptively phase-matched III-V nanophotonic waveguides

  Nature Communications · 2026-04-08

  articleOpen accessSenior author

  counts per second per hertz at signal-pump detuning of 20 nm. These results mark a significant advance in integrated nonlinear photonics for high-performance QFC, facilitating the development of versatile and scalable quantum networks.

  PublisherDOI

• MMFair: Fair Learning via Min-Min Optimization

  2025-11-08

  article1st authorCorresponding

  Ensuring group fairness is crucial in applications like facial recognition, medical image analysis, and online comment toxicity classification. A key challenge to achieving group fairness arises from spurious correlations in datasets, where features used by models for predictions are unrelated to the true labels. The widespread use of large-scale pre-trained models as feature extractors, followed by fine-tuning for downstream tasks, can exacerbate this issue. In particular, improper fine-tuning on limited data often leads to overfitting, reinforcing spurious correlations and further undermining group fairness. To address this, we propose MMFair, an algorithm that optimizes perturbations through a min-min optimization approach. These perturbations are applied to the deep embeddings, preventing the model from associating irrelevant features with true labels, thus improving group fairness. Notably, since simple linear classifiers are prone to spurious correlations, we use a linear head in the initial stage to generate perturbations. After optimizing the perturbations in the latent space, we incorporate them into the original embeddings and then train a multi-layer perceptron (MLP) as the final classification head. This two-stage approach helps mitigate the bias problem of linear head, while leveraging the more powerful feature-learning capabilities of MLPs, leading to more stable and accurate classification results. We evaluate MMFair on the Waterbirds, CelebA, and ISIC datasets. The results show that MMFair improves the accuracy of the worst-performing group efficiently.

  PublisherDOI

• III-V nanophotonic devices for quantum frequency conversion and quantum teleportation

  2025-09-15

  article1st authorCorresponding

  We present an emerging III-V integrated nonlinear photonics platform based on indium gallium phosphide (InGaP) combining its large second-order susceptibility (220 pm/V) and low optical losses. Utilizing InGaP nanophotonic devices, we show quantum frequency conversion with unprecedented performances and nonlinear-optical quantum teleportation, which have significant implications for quantum information and networking.

  PublisherDOI

• Observation of merging mechanical bound states in the continuum in phononic crystals

  2025-03-19

  articleSenior author
  PublisherDOI

• Faithful Quantum Teleportation via a Nanophotonic Nonlinear Bell State Analyzer

  Physical Review Letters · 2025-04-22 · 14 citations

  articleOpen accessSenior author

  Quantum networking protocols, including quantum teleportation and entanglement swapping, use linear-optical Bell state measurements for heralding the distribution and transfer of quantum information. However, a linear-optical Bell state measurement requires identical photons and is susceptible to errors caused by multiphoton emission, fundamentally limiting the efficiency and fidelity of quantum networking protocols. Here we show a nonlinear Bell state analyzer for time-bin encoded photons based on a nanophotonic cavity with a sum-frequency generation efficiency of 4×10^{-5} to filter multiphoton emissions, and utilize it for faithful quantum teleportation involving spectrally distinct photons with fidelities ≥94% down to the single-photon level. Our result demonstrates that nonlinear-optical entangling operations, empowered by our efficient nanophotonics platform, can realize faithful quantum information protocols without requiring identical photons and without the fundamental limit on the fidelity of a Bell state measurement imposed by linear optics, which facilitates the realization of practical quantum networks.

  PublisherOA PDFDOI

• Efficient bidirectional quantum frequency conversion between telecom and visible bands using programmable III-V nanophotonic waveguides

  ArXiv.org · 2025-10-19

  preprintOpen accessSenior author

  Quantum frequency conversion (QFC) is essential for interfacing quantum systems operating at different wavelengths and for realizing scalable quantum networks. Despite extensive progress, achieving QFC with simultaneous high efficiency, low pump power, minimal noise, broad bandwidth, and pump-wavelength flexibility remains challenging. Here, we demonstrate efficient, low-noise, and bidirectional QFC between the telecom (1550-nm) and visible (780-nm) bands using unpoled indium gallium phosphide (InGaP) $χ^{(2)}$ nanophotonic waveguides, eliminating the need for a long-wavelength pump. Leveraging the large nonlinear susceptibility of InGaP together with programmable modal-phase-matching control, we obtain record-low pump power (20 mW) -- an order of magnitude lower than that in previous demonstrations using integrated thin-film waveguides -- and record-high loss-inclusive normalized conversion efficiency among non-resonant QFC implementations. The platform maintains quantum coherence and entanglement of input photons with noise well below the single-photon level. These results mark a significant advance in integrated nonlinear photonics for high-performance QFC, facilitating the development of versatile and scalable quantum networks.

  PublisherOA PDFDOI

• Quantum-coherent optical isolation and circulation using frequency conversion on a chip

  arXiv (Cornell University) · 2025-11-01

  preprintOpen accessSenior author

  Breaking optical reciprocity enables new regimes of light--matter interaction with broad implications for fundamental physics and emerging quantum technologies. Although various approaches have been explored to achieve optical nonreciprocity, realizing it at the single-photon level has remained a major challenge. Here, we demonstrate nonmagnetic optical nonreciprocity -- including both isolation and circulation -- in the quantum regime, enabled by efficient and noiseless all-optical frequency conversion on an integrated III-V photonic chip. Our device preserves the quantum coherence and entanglement of the input photons while delivering exceptional performance parameters, including a high extinction ratio of 34 dB, low insertion loss of 0.8 dB, broad bandwidth of 44 GHz, high operational fidelity of 97%, and widely tunable operation wavelength. This realization of quantum optical nonreciprocity in a scalable photonic platform opens a pathway toward directional quantum communication and noise-resilient quantum networks.

  PublisherOA PDFDOI

• InGaP χ(2) integrated quantum photonics platform for broadband, ultra-efficient nonlinear conversion and entangled photon generation

  2025-01-01

  articleSenior author

  We report an indium gallium phosphide (InGaP) integrated photonics platform achieving one to two orders of magnitude improvement in efficiency over state of the art for nonlinear wavelength conversion and entangled photon generation.

  PublisherDOI

Recent grants

• ECCS/EPMD: Single-photon quantum information processing with nonlinear photonic integrated circuits

  NSF · $399k · 2022–2026

• CAREER: Cavity-less optomechanics with macroscopic resonances

  NSF · $500k · 2020–2025

• Cavity-Electro-Optomechanical Circuits with Broken Time-Reversal Symmetry

  NSF · $360k · 2018–2021

Frequent coauthors

• Shanhui Fan

  Stanford University

  22 shared

• Zongfu Yu

  University of Wisconsin–Madison

  11 shared

• Mengdi Zhao

  Suzhou University of Science and Technology

  11 shared

• P. Nussenzveig

  Universidade de São Paulo

  6 shared

• Matthew H. Matheny

  Amazon (United States)

  6 shared

• Shiyu Du

  Taiyuan University of Technology

  6 shared

• Shengyan Liu

  Gansu Agricultural University

  5 shared

• Oskar Painter

  California Institute of Technology

  5 shared

Labs

• Department of Urban & Regional PlanningPI