ExpandQISE: Track 1: Development of Er-doped Semiconductor Nanophotonics to realize Optoelectronic Capabilities for Quantum Information Applications at Telecom Wavelengths

Non-technical Abstract: Classical information technologies use optical interconnects to relay information between different media platforms. This is typically done by fiber optics, relaying digital ones and zeros as pulses with light on and off, respectively. For classical technologies, it is not necessary to precisely control how many photons are emitted or detected, only to be able to distinguish bright from dark.

Quantum information technologies require quantum interconnects that can transmit single pairs of entangled photons, which is much more challenging. In this regard, a compact electrically-activated source of single photons would be an important advance. One approach is to utilize single photons emitted from individual Erbium (Er) atoms at standard telecommunication wavelengths.

The Er atoms must be embedded into a semiconductor host to enable electrical excitation, and Gallium Arsenide (GaAs) is ideal due to its well-established growth and nanofabrication. However, attaining emission only from the Er atoms, rather than the GaAs host, remains a challenge. One way to improve the rate of photon emission from Er atoms is to embed the atoms into nanocavities.

The primary objective of this project is to investigate the application of Er-doped GaAs nanocavity devices for QISE, with the ultimate aim of developing an on-chip electrically-pumped single-photon device operating at telecom wavelengths. This project brings together an expert in Rare Earth (RE) physics for classical optoelectronic applications from West Chester University (WCU) and experts in scalable quantum photonic technologies from the University of Delaware (UD).

Additionally, this partnership advances a new 3+2 dual degree program where students earn a bachelor's degree in physics from WCU and a master's degree in QISE from UD in five years. This accelerated educational track is designed to support low-income and underrepresented students, promoting diversity in the QISE workforce while expediting its growth.

Technical Abstract: Creating scalable and reliable QISE technologies requires material and device platforms that preserve quantum coherence and provide suitable interactions to produce and control entanglement. Defect-based quantum emitters in wide bandgap semiconductors have emerged as leading candidates for future QISE applications due to their potential for scalability and integration.

Rare Earth-doped insulators have been extensively studied because the embedded RE ions have sharp, stable optical transitions and long lifetimes that facilitate high-fidelity quantum control. RE-doped semiconductors, however, have not previously received similar attention for QISE due to the limited availability of samples and challenges associated with competing native defects and background spins.

If these challenges can be overcome, the RE-doped semiconductor platform could fill a significant gap for quantum technologies by providing a spectrally-stable electrically-pumped single-photon source, quantum memory, or element of a quantum repeater operating in the telecom C-band. In this approach, single Er ions are coupled to photonic device components, allowing the characterization of Er-doped GaAs as a single-photon source via anti-bunching experiments.

These new devices will be achieved through controlled dilute doping and by enhancing the radiative rates of the Er ions using nanophotonic structures. As part of this effort, the growth of Er-doped GaAs at UD and the design and fabrication of new nanophotonic devices incorporating waveguiding and out-coupling schemes for enhanced light-collection efficiency are established.

This project is jointly funded by the Office of Multidisciplinary Activities (MPS/OMA), and the Technology Frontiers Program (TIP/TF).

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.