Benjamin Lienhard

Bright and photostable single-photon emitter in silicon carbide

Single-photon sources are of paramount importance in quantum communication, quantum computation, and quantum metrology. In particular, there is great interest in realizing scalable solid-state platforms that can emit triggered photons on demand to achieve scalable nanophotonic networks. We report on a visible-spectrum single-photon emitter in 4H silicon carbide (SiC). The emitter is photostable at room and low temperatures, enabling photon counts per second in excess of 2×106 from unpatterned bulk SiC. It exists in two orthogonally polarized states, which have parallel absorption and emission dipole orientations. Low-temperature measurements reveal a narrow zero phonon line (linewidth 30% of the total photoluminescence spectrum.

Tunable and high-purity room temperature single-photon emission from atomic defects in hexagonal boron nitride.

Two-dimensional van der Waals materials have emerged as promising platforms for solid-state quantum information processing devices with unusual potential for heterogeneous assembly. Recently, bright and photostable single photon emitters were reported from atomic defects in layered hexagonal boron nitride (hBN), but controlling inhomogeneous spectral distribution and reducing multi-photon emission presented open challenges. Here, we demonstrate that strain control allows spectral tunability of hBN single photon emitters over 6 meV, and material processing sharply improves the single photon purity. We observe high single photon count rates exceeding 7 × 106 counts per second at saturation, after correcting for uncorrelated photon background. Furthermore, these emitters are stable to material transfer to other substrates. High-purity and photostable single photon emission at room temperature, together with spectral tunability and transferability, opens the door to scalable integration of high-quality quantum emitters in photonic quantum technologies.Inhomogeneous spectral distribution and multi-photon emission are currently hindering the use of defects in layered hBN as reliable single photon emitters. Here, the authors demonstrate strain-controlled wavelength tuning and increased single photon purity through suitable material processing.

Efficient Extraction of Light from a Nitrogen-Vacancy Center in a Diamond Parabolic Reflector

Quantum emitters in solids are being developed for a range of quantum technologies, including quantum networks, computing, and sensing. However, a remaining challenge is the poor photon collection due to the high refractive index of most host materials. Here we overcome this limitation by introducing monolithic parabolic reflectors as an efficient geometry for broadband photon extraction from quantum emitter and experimentally demonstrate this device for the nitrogen-vacancy (NV) center in diamond. Simulations indicate a photon collection efficiency exceeding 75% across the visible spectrum and experimental devices, fabricated using a high-throughput gray scale lithography process, demonstrating a photon extraction efficiency of (41 ± 5)%. This device enables a raw experimental detection efficiency of (12 ± 1)% with fluorescence detection rates as high as (4.114 ± 0.003) × 106 counts per second (cps) from a single NV center. Enabled by our deterministic emitter localization and fabrication process, we find a high number of exceptional devices with an average count rate of (3.1 ± 0.9) × 106 cps.

Quantum emission from atomic defects in wide-bandgap semiconductors

Non-classical light sources, such as atoms and atom-like emitters play central roles in many areas of quantum information processing with applications as single photon generators, sources for nonlinearity and quantum memories. Solid-state quantum emitters have attracted growing interest due to the promise of combining remarkable optical properties with the convenience of scalability [1]. In recent years, there has been tremendous progress in developing quantum emitter systems based on crystallographic defects in wide-bandgap semiconductors. Nitrogen vacancies (NV) in diamond were among the first studied systems due to the well-defined optical transitions as well as electronic spin states that can be controlled optically. Quantum spins in diamond are among the most advanced systems in solid state for quantum based technologies such as quantum computing or quantum sensing [2]. Nevertheless, solid-state quantum emitters are not only limited to diamond and efforts to engineer single photon emitters (SPE) based on atom-like defects in scalable system have expanded beyond NV centers in diamond. Similar quantum emitters have been discovered in many other wide-bandgap host materials, including silicon carbide (SiC), III-nitride semiconductors such as gallium nitride (GaN) and aluminum nitride (AlN), and layered materials such as hexagonal boron nitride (hBN) [1]. Here, we will review our recent progress in developing and characterizing new quantum emitters in wide-bandgap semiconductors, and consider their applications as quantum light sources and sensors.

High-purity single photon emitter in aluminum nitride photonic integrated circuit

Efficient, on-demand, and robust single photon emitters (SPEs) are important to a wide varity of applications in quantum information processing [1]. Over the past decade, color centers in solid-state systems have emerged as excellent SPEs [2] and have also been shown to provide optical access to internal spin states at room and cyogenic temperatures. Color centers in diamond [3] and silicon carbide [4] are among the most intensively studied SPEs. Recently, other cost-efficient wide-bandgap materials have become attractive as potential host materials. Theoretical calculations show that aluminum nitride (AlN) with a bandgap of 6.015 eV can serve as a stable environment for well isolated SPEs with optically accessible spin states [5].

Tunable quantum emission from atomic defects in hexagonal boron nitride

We demonstrate that strain control of exfoliated hexagonal boron nitride allows spectral tuning of single photon emitters over 6 meV. We propose a material processing that sharply improves the single-photon purity with g(2)(0) = 0.077, and brightness with emission rate exceeding 107 counts/sec at saturation.