Single photon emitters in 2D and nanoscale materials provide an increasingly promising framework for scalable quantum networking and photonic quantum simulation, but control of the emitter photophysics remains an obstacle to the realization of useful photonic quantum technologies. Here, we use correlative cathodoluminescence, photoluminescence, and atomic force microscopies to probe the effect of nanoscale strain gradients on strain-localized excitons in GaSe. With this understanding in hand, we describe the potential for in situ electron-beam manipulation and optical characterization of emitter photophysics.
Magneto-optical spectroscopies are increasingly powerful probes of spin excitations in quantum materials, but at cryogenic temperatures, the laser excitation can be highly non-perturbative. While balanced photodetection can be used to suppress classical noise sources, the photon shot noise limit fundamentally constrains the measurement sensitivity for a given laser power. Here, we have used a two-mode squeezed light source to suppress noise below the shot noise level for magnetic circular dichroism measurements, thus enabling lower power measurements with reduced photothermal effects. We also describe the fundamental sensitivity limits for quantum enhanced interferometric and intensity-difference magneto-optical Kerr effect and circular dichroism spectroscopies.
Boron vacancy color centers in hBN have drawn substantial interest over the past year because of the potential for quantum sensing in van der Waals heterostructures. Here, we describe strong localized enhancement and redshifting of boron vacancy luminescence at creases in an hBN flake measured with correlative photoluminescence and cathodoluminescence microscopies. These results are consistent with density functional theory calculations showing boron vacancy migration toward regions with uniaxial compressive strain, and they are essential for the development of new quantum devices that leverage the optically accessible spin state in boron vacancy color centers in hBN.
We describe the operation of a free-space confocal optical microscope operated in a dilution refrigerator. The microscope is installed on a cold insertable probe to enable fast sample exchange while the refrigerator is held at low temperatures. A vector magnet provides a 6 T field normal to the sample and 1 T fields at arbitrary angles. A variety of optical microscopies and spectroscopies, including photoluminescence, Raman, magneto-optical Kerr effect, and spin relaxometry measurements are described, and some of the challenges associated with performing these measurements at milliKelvin temperatures are explored.
KEYWORDS: Nanophotonics, Microscopy, Plasmonics, Single photon, Nonlinear optics, Color centers, Structural design, Scanning electron microscopy, Quantum optics, Quantum information processing
Non-linear manipulation of light at the nanoscale is increasingly important for quantum optics and photonics. Plasmonic media provide one important workbench for the manipulation of these nonlinearities.1 The design of plasmonic structures typically involves time-consuming, iterative, computer simulations, nanofabrication and characterization with large suites of independent tools. Hence, in-situ fabrication and characterization along with real time design optimization is an appealing option for the development of hybrid quantum nanophotonic devices. Here, we will describe emerging capabilities for in situ electron beam induced deposition (EBID) and cathodoluminescence (CL) microscopy in an environmental SEM. We outline our work writing and characterizing nanoplasmonic structures that exhibit well-defined field localization and multiple tunable resonances over a broad spectrum as part of the development of new high-efficiency nanophotonic nonlinear media. Developing deter- ministic high-quality single photon emitters is an equally important direction for photonic quantum information processing. Due to the sub-nanometer footprint of such emitters, optical methods are often insufficient for local characterization. We describe our efforts to create, manipulate and characterize color centers in 2D and bulk materials such as hBN. We discuss e-beam induced effects for localized defect creation and EBID based control of color centers to allow emission tuning. Cathodoluminescence lifetime and autocorrelation measurements are utilized for sub-diffraction-limited in-situ assessment of the single photon emission properties.
We present and experimentally show a novel protocol for distributing secret information between two and only two parties in a N-party single-qubit Quantum Secret Sharing (QSS) system. We demonstrate this new algorithm with N = 3 active parties over ~6km of telecom. fiber. Our experimental device is based on the Clavis2 Quantum Key Distribution (QKD) system built by ID Quantique but is generalizable to any implementation. We show that any two out of the N parties can build secret keys based on partial information from each other and with collaboration from the remaining N − 2 parties. This algorithm allows for the creation of two-party secret keys were standard QSS does not and significantly reduces the number of resources needed to implement QKD on a highly connected network such as the electrical grid.
Zinc oxide is a wide bandgap insulator with significant promise for applications in optics, electro-optics and electronics.
However, there are challenges in growing high-quality material, and a prominent visible luminescence channel due to
defect recombination competes with the ultraviolet band-edge exciton decay. Here we demonstrate the possibility of
characterizing a specific defect by means of Purcell enhanced exciton-plasmon dynamics and photoluminescence.
Nanostructured metal-ZnO systems provide an ideal workbench for studying the dynamics of exciton-plasmon coupling.
In order to characterize the interactions, we grew tri-layer structures comprising thin films of ZnO, variable-thickness
spacer layers of MgO, and thin films of Ag or Au. Analysis of the photoluminescence of these structures as a function
of increasing MgO thickness confirms the existence of surface plasmon polariton-exciton coupling through Purcell
enhancement of the excitonic emission for MgO films thinner than 30 nm, and through emission at the SPP resonance
for MgO films thicker than 30 nm. Further, we demonstrate the enhancement of the ZnO impurity photoluminescence
through dipole-dipole scattering with Ag and Au LSPs. Preliminary degenerate band-edge pump-probe measurements
confirm the conclusions developed from photoluminescence measurements. In order to disentangle and further quantify
the interactions seen in these systems, we are lithographically patterning metal nanoparticle arrays and metal hole arrays
on ZnO quantum wells and beginning to perform white-light pump-probe spectroscopy to fully characterize the
dynamics of energy transfer within these systems.
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