About

Alex High is an associate professor of molecular engineering at the University of Chicago Pritzker School of Molecular Engineering. His research focuses on quantum and optical science, exploring new physics and technologies that emerge when quantum systems are engineered at the nanoscale level. His lab investigates methods to craft interactions between photons and solid-state systems, aiming to fundamentally modify materials by breaking time-reversal symmetry or inducing long-range coherence, and to create deterministic, coherent interactions between single photons and quantum states. High's work involves developing optical quantum circuits and realizing new technologies based on engineered light/matter interactions. He received his BA in physics from the University of Pennsylvania and his PhD in physics from the University of California, San Diego. His research contributions include studies on microwave-based quantum control and coherence protection of tin-vacancy spin qubits in strain-tuned diamond-membrane heterostructures, as well as the development of direct-bonded diamond membranes for heterogeneous quantum and electronic technologies. His work also encompasses the creation of tunable and transferable diamond membranes for integrated quantum technologies and the fabrication of high-Q nanophotonic resonators on diamond membranes using templated atomic layer deposition of TiO2.

Research topics

• Physics
• Quantum mechanics
• Chemistry
• Optics
• Chemical physics
• Condensed matter physics
• Nanotechnology
• Materials science

Selected publications

• Heterogeneously Integrated Diamond-on-Lithium Niobate Quantum Photonic Platform

  ArXiv.org · 2026-03-09

  articleOpen access

  Diamond photonics has enabled efficient interfaces for quantum memories and is predicted to be a critical component of quantum networks. However, scalable network architectures require spatial, temporal, and spectral control of photons, which relies on nonlinear and electro-optic functionalities that diamond alone cannot provide. Here, we demonstrate heterogeneous integration of a thin-film lithium niobate (TFLN) platform, which has strong chi-2 nonlinearity and electro-optic effects, with thin diamond films. We demonstrate high-Q diamond photonic crystal cavities (Q factors exceeding 5x10^4 at 735 nm) that are lithographically aligned with TFLN photonic backbone and critically coupled to it. This allows us to realize low-loss diamond-TFLN "escalators" (loss ~1 dB/coupler) that support efficient light transfer between them. At cryogenic temperatures (5K), we can collect photons emitted from silicon vacancies (SiVs) embedded within the diamond structure via the TFLN photonic circuit. This approach establishes a scalable route toward integrated photonic circuits for practical quantum networking and other technologies.

  PublisherOA PDF

• Heterogeneously Integrated Diamond-on-Lithium Niobate Quantum Photonic Platform

  Open MIND · 2026-03-09

  preprint

  Diamond photonics has enabled efficient interfaces for quantum memories and is predicted to be a critical component of quantum networks. However, scalable network architectures require spatial, temporal, and spectral control of photons, which relies on nonlinear and electro-optic functionalities that diamond alone cannot provide. Here, we demonstrate heterogeneous integration of a thin-film lithium niobate (TFLN) platform, which has strong chi-2 nonlinearity and electro-optic effects, with thin diamond films. We demonstrate high-Q diamond photonic crystal cavities (Q factors exceeding 5x10^4 at 735 nm) that are lithographically aligned with TFLN photonic backbone and critically coupled to it. This allows us to realize low-loss diamond-TFLN "escalators" (loss ~1 dB/coupler) that support efficient light transfer between them. At cryogenic temperatures (5K), we can collect photons emitted from silicon vacancies (SiVs) embedded within the diamond structure via the TFLN photonic circuit. This approach establishes a scalable route toward integrated photonic circuits for practical quantum networking and other technologies.

  DOI

• Molecular Optomechanics with Atomic Antennas

  ACS Photonics · 2025-05-29

  article

  A typical surface-enhanced Raman scattering (SERS) system relies on deeply subwavelength field localization in nanoscale plasmonic cavities to enhance both the excitation and emission of Raman-active molecules. Here, we demonstrate that a germanium-vacancy (GeV) defect in a diamond can efficiently mediate the excitation process, by acting as a bright atomic antenna. At low temperatures, the GeV’s low dissipation allows it to be efficiently populated by the incident field, resulting in a thousand-fold increase in the efficiency of Raman scattering. We show that atomic antenna-enhanced Raman scattering can be distinguished from conventional SERS by tracing the dependence of Stokes intensity on input power.

  PublisherDOI

• Metalens formed by structured arrays of atomic emitters

  Nanophotonics · 2025-01-30

  articleOpen access

  Abstract Arrays of atomic emitters have proven to be a promising platform to manipulate and engineer optical properties, due to their efficient cooperative response to near‐resonant light. Here, we theoretically investigate their use as an efficient metalens. We show that, by spatially tailoring the (subwavelength) lattice constants of three consecutive two‐dimensional arrays of identical atomic emitters, one can realize a large transmission coefficient with arbitrary position‐dependent phase shift, whose robustness against losses is enhanced by the collective response. To characterize the efficiency of this atomic metalens, we perform large‐scale numerical simulations involving a substantial number of atoms ( N ∼ 5 × 10 5 ) that is considerably larger than comparable works. Our results suggest that low‐loss, robust optical devices with complex functionalities, ranging from metasurfaces to computer‐generated holograms, could be potentially assembled from properly engineered arrays of atomic emitters.

  PublisherOA PDFDOI

• Donor-Acceptor Pairs near Silicon Carbide surfaces

  ArXiv.org · 2025-04-14

  preprintOpen access

  Donor-acceptor pairs (DAPs) in wide-bandgap semiconductors are promising platforms for the realization of quantum technologies, due to their optically controllable, long-range dipolar interactions. Specifically, Al-N DAPs in bulk silicon carbide (SiC) have been predicted to enable coherent coupling over distances exceeding 10 nm. However, their practical implementations require an understanding of the properties of these pairs near surfaces and interfaces. Here, using first principles calculations we investigate how the presence of surfaces influence the stability and optical properties of Al-N DAPs in SiC, and we show that they retain favorable optical properties comparable to their bulk counterparts, despite a slight increase in electron-phonon coupling. Furthermore, we introduce the concept of surface-defect pairs (SDPs), where an electron-hole pair is generated between a near-surface defect and an occupied surface state located in the bandgap of the material. We show that vanadium-based SDPs near OH-terminated 4H-SiC surfaces exhibit dipoles naturally aligned perpendicular to the surface, greatly enhancing dipole-dipole coupling between SDPs. Our results also reveal significant polarization-dependent modulation in the stimulated emission and photoionization cross sections of V-based SDPs, which are tunable by two orders of magnitude via the polarization angle of the incident laser light. The near-surface defects investigated here provide novel possibilities for the development of hybrid quantum-classical interfaces, as they can be used to mediate information transfer between quantum nodes and integrated photonic circuits.

  PublisherOA PDFDOI

• Purcell-Enhanced Emissions from Diamond Color Centers in Slow Light Photonic Crystal Waveguides

  Nano Letters · 2025-07-31 · 5 citations

  articleCorresponding

  Diamond color centers are promising candidates for optically addressable quantum memories, which motivates the development of efficient photonic interfaces, often using nanophotonic cavities with narrow spectral line widths and small mode volumes. However, they require perfect spectral and spatial overlap between the cavity mode and quantum emitter, which is challenging. This is especially true for solid-state quantum emitters that are often randomly positioned and suffer from inhomogeneous broadening. Another approach to enhance light-matter interaction across large optical bandwidths and areas is using slow light waveguides. Here, we demonstrate diamond slow light photonic crystal (PhC) waveguides optically coupled to embedded silicon-vacancy (SiV) color centers. We use the recently developed thin-film diamond approach to fabricate fully suspended two-dimensional PhC waveguides. We demonstrate waveguide modes with high group indices up to 70 and observe Purcell-enhanced emissions of the SiVs. Our approach represents a practical diamond platform for robust spin-photon interfaces with color centers.

  PublisherDOI

• Purcell enhancement of diamond color centers coupled to slow light photonic crystal waveguides

  2025-01-01

  article

  We fabricate PhC slow light waveguide on thin film diamond and observe Purcell enhancement of spontaneous emissions from SiV centers coupled to the slow light mode of the device.

  PublisherDOI

• Donor–Acceptor Pairs Near Silicon Carbide Surfaces

  The Journal of Physical Chemistry Letters · 2025-09-30 · 2 citations

  article

  Donor–acceptor pairs (DAPs) in wide-bandgap semiconductors are promising platforms for the realization of quantum technologies, due to their optically controllable, long-range dipolar interactions. Specifically, Al–N DAPs in bulk silicon carbide (SiC) have been predicted to enable coherent coupling over distances exceeding 10 nm. However, their practical implementations require an understanding of the properties of these pairs near surfaces and interfaces. Here, using first-principles calculations, we investigate how the presence of surfaces influence the stability and optical properties of Al–N DAPs in SiC, and we show that they retain favorable optical properties comparable to their bulk counterparts, despite a slight increase in electron–phonon coupling. Furthermore, we introduce the concept of surface-defect pairs (SDPs), where an electron–hole pair is generated between a near-surface defect and an occupied surface state located in the bandgap of the material. We show that vanadium-based SDPs near OH-terminated 4H-SiC surfaces exhibit dipoles naturally aligned perpendicular to the surface, greatly enhancing dipole–dipole coupling between SDPs. Our results also reveal significant polarization-dependent modulation in the stimulated emission and photoionization cross sections of V-based SDPs, which are tunable by 2 orders of magnitude via the incident laser’s polarization angle. The near-surface defects investigated here provide novel possibilities for the development of hybrid quantum-classical interfaces, as they can be used to mediate information transfer between quantum nodes and integrated photonic circuits.

  PublisherDOI

• Extending exciton and trion lifetimes in MoSe$_{2}$ with a nanoscale plasmonic cavity

  ArXiv.org · 2025-07-23

  preprintOpen accessSenior author

  Excitons in transition metal dichalcogenides (TMDs) have extremely short, picosecond-scale lifetimes which hinders exciton thermalization, limits the emergence of collective coherence, and reduces exciton transport in optoelectronic devices. In this work, we explore an all-optical pathway to extend exciton lifetimes by placing MoSe$_2$ in a deep-subwavelength Fabry-Perot silver cavity. The cavity structure is designed to suppress radiative recombination from in-plane optical dipoles, such as bright excitons and trions. We observe a consistent decrease in photoluminescence (PL) linewidths of excitons and trions (~1 nm), along with a corresponding lifetime increase (~10 ps). We confirm the experimental observations arise purely from exciton-cavity interactions-etching back the top silver layer returns the PL linewidth and lifetimes return to their original values. Our study offers a pathway to engineer excited state lifetimes in 2D materials which can be utilized for studies of optically dark excitons and have potential applications for novel optoelectronic devices.

  PublisherOA PDFDOI

• Pump Free Microwave-Optical Quantum Transduction

  ArXiv.org · 2025-12-04

  preprintOpen access

  Distributed quantum computing involves superconducting computation nodes operating at microwave frequencies, which are connected by long-distance transmission lines that transmit photons at optical frequencies. Quantum transduction, which coherently converts between microwave and optical (M-O) photons, is a critical component of such an architecture. Current approaches are hindered by the unavoidable problem of device heating due to the optical pump. In this work, we propose a pump-free scheme based on color centers that generates time-bin encoded M-O Bell pairs. Our scheme first creates spin-photon entanglement and then converts the spin state into a time-bin-encoded microwave photon using a strongly coupled Purcell-enhanced resonator. In our protocol, the microwave retrieval is heralded by detecting the microwave signal with a three-level transmon. We have analyzed the resulting Bell state fidelity and generation probability of this protocol. Our simulation shows that by combining a state-of-the-art spin-optical interface with our proposed strongly-coupled spin-microwave design, the pump-free scheme can generate M-O Bell pairs at a heralding rate exceeding one kilohertz with near-unity fidelity, which establishes the scheme as a promising source for M-O Bell pairs.

  PublisherOA PDFDOI

Recent grants

• EAGER: Quantum Manufacturing: Manufacturing Integrated Quantum Sensing and Quantum Photonic Technologies Through Direct Bonding of Diamond Membranes

  NSF · $300k · 2023–2025

Frequent coauthors

• L. V. Butov

  40 shared

• D. D. Awschalom

  36 shared

• A. C. Gossard

  University of California, Santa Barbara

  36 shared

• Nazar Delegan

  University of Chicago

  30 shared

• F. Joseph Heremans

  Argonne National Laboratory

  29 shared

• M. Hanson

  Cardiff University

  29 shared

• Hongkun Park

  Harvard University

  23 shared

• A. T. Hammack

  Lawrence Berkeley National Laboratory

  21 shared

Labs

• Alex High LabPI