Research

Our group builds and probes hybrid quantum devices where superconductors meet semiconductors. The central questions we pursue are how to engineer, identify, and ultimately control topological states of matter in these platforms, with Majorana zero modes and Kitaev chains as the most prominent targets.

A guiding conviction of our work is that the scaling of quantum technology will ultimately be leveraged through semiconductor manufacturing - the same industrial foundation that enabled classical computing. Every experiment, every fabrication choice, and every materials platform we pursue is weighed against that long horizon.

Minimal Kitaev chains and Majorana physics

A major thread of my research has focused on coupled quantum dot arrays as a platform for realizing Kitaev chains. Early work demonstrated singlet and triplet Cooper pair splitting in hybrid superconducting nanowires (Nature, 2022) - establishing the crossed Andreev reflection and elastic cotunneling processes that are the key ingredient to realize the coupling terms of the Kitaev Hamiltonian. This led to the first experimental realization of a minimal two-site Kitaev chain in coupled quantum dots (Nature, 2023), where the ability to electrically control these processes can be tuned to produce localized Majorana states, when the system is fine-tuned.

The most recent highlight of our program is the three-site Kitaev chain. In Enhanced Majorana stability in a three-site Kitaev chain (Nature Nanotechnology, 2025) we realized a three-site chain in an InSb/Al quantum dot array and directly compared two- and three-site configurations in the same device. A three-site chain is the shortest chain in which no single-parameter perturbation can couple the two edge Majorana modes on its own — the central dot acts as a rudimentary "bulk" protecting the edges. Experimentally, zero-bias peaks persist against electrochemical potential and tunnel-coupling variations that would immediately split the modes of a two-site chain. Estimated coherence times scale from ~10 ns for a two-site chain to ~1 μs for a three-site chain, with ~1 ms projected for a five-site chain.

Complementary work extends this picture: phase-controlled three-site chains probed with an additional quantum dot for direct Majorana localization spectroscopy (Nature Communications, 2026), sign-ordered chains without magnetic flux control (Physical Review Research, 2025), robust poor man's Majorana modes built from Yu–Shiba–Rusinov states (Nature Communications, 2024), and careful analysis of how Andreev bound states within the leads influence spectroscopic signatures (Physical Review X, 2025).

Proximity effect — and beyond nanowires

Building working hybrid quantum devices depends fundamentally on understanding — and engineering — the superconducting proximity effect at semiconductor–superconductor interfaces. Our earlier work on InSb/Al nanowires established much of the physical and fabrication toolkit now used across the field: electrostatic control of the proximity effect in the bulk of hybrids (Nature Communications, 2023), tunable crossed Andreev reflection and elastic cotunneling (Physical Review X, 2023), spin-mixing enhanced proximity in Al-based hybrids (Advanced Materials, 2022), and shadow-wall and single-shot fabrication techniques for ballistic hybrid devices (Nature Communications, 2021; Advanced Functional Materials, 2021).

Looking forward, a central goal of the group is to move this physics onto platforms that are intrinsically more scalable than nanowires. Two-dimensional electron gases in InAs and InSb offer planar geometries compatible with standard top-down lithography, top-gated architectures, and the kind of yield and uniformity that is difficult to achieve with bottom-up grown wires. In parallel, Ge and SiGe heterostructures provide a route directly compatible with industrial silicon processing - a prerequisite, in our view, for any quantum platform that aspires to fault-tolerant scale. Each of these material systems brings its own interface physics, dielectric requirements, and superconductor compatibility questions; resolving these is a core experimental agenda of the group.

On novel proximity effects we work in close collaboration with the Palmstrøm lab at UCSB, whose expertise in epitaxial superconductor–semiconductor growth is central to exploring new material combinations and pushing interface quality beyond what is possible with ex-situ deposition.

Towards novel qubits

Beyond characterizing and controlling non-Abelian modes, a central ambition of the group is to use these building blocks to realize new types of qubits that could reshape the quantum computing landscape. Kitaev-chain-based qubits - encoding information non-locally in Majorana parity - offer a route to intrinsic protection against local noise that conventional superconducting and spin qubits lack.

Our three-site chain results already show the kind of exponential suppression of error with chain length that makes this approach compelling: extrapolation from our measured parameters suggests a five-site chain would reach target coherence times of ~1 ms. Realizing such qubits requires not only demonstrating the underlying physics but also engineering devices at a level of reproducibility and uniformity that only semiconductor processing can provide. Our efforts therefore span from fundamental spectroscopy of minimal chains, through materials and interface engineering, to the design of readout and control schemes compatible with scalable fabrication.

Superconducting electronics and new functionalities

We also explore how hybrid materials can realize new device functionalities beyond qubits, including a gate-tunable Josephson diode (Physical Review Applied, 2024) and an experimental realization of de Gennes' absolute superconducting switch with a heavy-metal interface (Nature Communications, 2025). These are small steps toward a future in which hybrid superconductor–semiconductor devices form the building blocks of cryogenic control electronics sitting alongside quantum processors.

This effort is carried out in longstanding collaboration with Jason Robinson's group at the University of Cambridge, whose expertise in superconducting spintronics and proximity-coupled ferromagnet–superconductor systems has been central to translating new interface physics into working cryogenic devices.

Current directions at UCSB

Since joining UC Santa Barbara in late 2025, my group has been building out a program on Ge/SiGe-based quantum devices, with an emphasis on gate-dielectric engineering and MOS stack optimization as the foundation for future qubit platforms. We combine nanofabrication at the UCSB nanofab with low-temperature transport and spectroscopy to develop materials and device architectures for scalable quantum hardware.