ORCID

https://orcid.org/0009-0009-7370-5363

Date of Award

Spring 2026

Embargo Period

4-29-2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School/Department

Department of Nanoscale Science and Engineering

Program

Nanoscale Engineering

First Advisor

Spyros Gallis

Committee Members

Nathaniel Cady, Walid Redjem, Mengbing Huang, Nick Vamivakas

Keywords

quantum information science, erbium, telecom photonics, quantum engineering, materials science

Subject Categories

Nanoscience and Nanotechnology | Physics | Quantum Physics

Abstract

Advancing quantum information science demands solid-state quantum systems that maintain long quantum coherence at elevated temperatures while supporting scalable, CMOS-compatible fabrication and telecom C-band operation. No existing platform has simultaneously achieved these requirements, as state-of-the-art demonstrations of coherent control of erbium ions, with an intrinsic telecom-band optical transition, have been confined to cryogenic temperatures below < 10 K under controlled vacuum conditions. This thesis introduces a new paradigm in which materials science and engineering provides the enabling pathway to quantum coherence.

A foundry-compatible nanofabrication approach, paired with targeted materials engineering, is developed to realize a new class of CMOS-scalable quantum system: arrays of spatially isolated single-erbium-ion qudits (five-level systems) embedded in silicon-based (e.g., silicon carbide (SiC) and SiCxOy) hollow nanopillars (HNPs). Non-lithographically defined nanostructure geometries with ≤ 5 nm critical dimensions, achieved through conformal chemical vapor deposition (CVD) with growth rates of ~0.3 Å/s, impose a geometric confinement that self-aligns and spatially isolates individual Er3+ ions with nanometer-scale placement accuracy. Oxygen co-doping during growth introduces Si–C–O defect centers that mediate efficient energy transfer to Er3+ ions, yielding an effective excitation cross section of ~2 × 10−17 cm2, two to three orders of magnitude larger than in bulk crystalline hosts, enabling room-temperature single-ion optical detection without the use of nanophotonic cavities.

Within these devices, record-long room-temperature optical quantum coherence in the telecom C-band is demonstrated: T2 = 568 µs via photon echo and T2* = 32 µs via Ramsey interferometry, a performance previously limited to vacuum conditions at temperatures over 900 times lower. Coherent Rabi oscillations are observed with >96% contrast, and pulsed photon-correlation measurements confirm single-photon emission (g2(0) = 0.25) from spatially isolated Er3+ ions at ambient conditions. Furthermore, an upconversion-mediated readout protocol accesses the multi-level qudit structure, producing background-free single-photon emission at 518 nm (g2(0) = 0.06) and 980 nm (g2(0) = 0.18) without the use of an optical cavity, the first such demonstration for erbium.

Together, these results establish a materials-driven engineering approach that integrates scalable thin-film growth, nanostructure design, implantation optimization, and quantum-optical characterization, overcoming the fundamental requirement for cryogenic operation in telecom quantum systems. Thus, it establishes a pathway toward revolutionary breakthroughs in cryogenic-free quantum photonic integrated devices for practical, deployable quantum sensing, communication, and networking application

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This work is licensed under the University at Albany Standard Author Agreement.

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