This PDF file contains the front matter associated with SPIE Proceedings Volume 11471, including the Title Page, Copyright information, and Table of Contents.

Weakly interacting atomic gases at ultra low temperatures are superfluid. Owing to the high degree of control they offer, these quantum gases give access to a wonderful playground to explore superfluid dynamics. In particular, quantum gases flowing inside waveguides can mimick the behavior of electrons in superconducting circuits, opening the new field of `atomtronics’. The elementary circuit is the ring, where the atomic circulation is expected to be quantized. I will discuss two opposite limits: the production and decay of a small current of a few quanta, and the fast rotation regime where the velocity exceeds the speed of sound.

Fiber-based quantum networks require on-demand sources of entangled photons in the telecom C-band for long distance information transfer. Historically, the field of in-fiber entanglement distribution has been dominated by photons provided via spontaneous processes. In recent years, semiconductor quantum dots have emerged as strong competitors in terms of generating single and entangled photons due to their promise of deterministic qubit generation in the NIR wavelength region. Here, we show the on-demand generation of polarization entangled photons in the telecom C-band based on InAs/GaAs quantum dots grown via metal-organic vapor-phase epitaxy. By employing a robust phonon-assisted two-photon excitation scheme, we are able to generate pairs of entangled photons with a concurrence of 91.4 ± 3.8 % and a maximum fidelity to the Bell state Φ+ of 95.2 ± 1.1 %.

We investigate the indistinguishability of single photons generated from strain-free GaAs/AlGaAs quantum dots using pulsed resonance fluorescence techniques. In pulsed two-photon interference measurements we observe a single photon indistinguishability with a raw visibility of 95%. This can be traced back to the short intrinsic lifetime of excitons and trions confined in the GaAs quantum dots and demonstrates that for this material system the generation of single photons is possible with near-unity indistinguishability even without Purcell enhancement.

In recent years, two-dimensional semiconductor quantum emitters have gotten substantial attention from the solid-state quantum photonics community. Their potential for on-chip integration in silicon-based photonics makes them an ideal candidate to realize large-scale hybrid quantum photonic circuits. Given the strain-induced quantum emitter formation in two-dimensional WSe2, coupling of such quantum emitters into a SiN photonic waveguides is very promising. However, demonstration of single-photon emission into a waveguide has been elusive so far. Here, we show single-photon emission of strain-induced quantum emitters in a 2D flake integrated into a SiN waveguide. We take advantage of the waveguide edges as nucleation sites for quantum emitters. We observe single-photon emission coupled into the waveguide with a g(2)(0) = 0.15±0.09. This result opens up the way towards large-scale 2D emitter integration in on-chip quantum photonic circuits.

Single photon emitters (SPEs) in hexagonal boron nitride (hBN) have emerged as robust sources of quantum light due to bright and high purity emission at room temperature. Progress in the fabrication, tuning, and integration of the emitters is discussed. Additionally, after years of debate over the structural origin of the emission, we present new experiments identifying the source of visible SPE emission in hBN, and the recent confirmation of spin selective transitions from multiple defect species.

Crystalline metallic thin films comprised of only a few atomic monolayers support high-quality plasmon resonances sought in nanophotonics applications. Here we employ a rigorous quantum-mechanical description of electrons in such films that accounts for the dominant features of their electronic band structure, including surface and quantum well states, to simulate the associated optical response. We demonstrate that quantum-mechanical features manifest in the linear and nonlinear optical response, with the latter enhanced both by propagating plasmons and reductions in film thickness. Our findings support explorations of atomically-thin nonlinear plasmonic devices based on crystalline metal films offering lower loss than their amorphous counterparts.

We study propagating plasmons in 1-D graphene nanoribbons through rigorous quantum-mechanical simulations that account for nonlocal, quantum finite-size, and edge-termination effects in the optical response. Our simulations reveal a strong dependence on such phenomena under excitation by fields carrying high optical momenta components along the direction of transverse symmetry in both the linear and nonlinear optical response, where in the latter case second-order nonlinear phenomena manifest with high efficiency due to the breaking of inversion symmetry. These findings motivate the application of graphene nanostructures towards actively-tunable nonlinear plasmonic conduits in nanophotonic circuitry.

This talk will focus on the development of material platforms and physical mechanisms for high-fidelity control, storage, and transmission of quantum information. In particular, emerging quantum materials - novel diamond impurities - featuring long-lived, optically addressable quantum states are promising candidates fulfilling most of these requirements. We will discuss possible mechanisms for efficient interfacing of these novel solid-state qubits, in particular allowing for high-fidelity quantum-state transduction to superconducting qubits or to the long-lived nuclear spins. Finally, the physical phenomena enabling local quantum control in these materials, including strain-mediated or optically mediated state-transfer and two-qubit gates, will be discussed.

The development of silicon-organic hybrid (SOH) and plasmonic-organic hybrid (POH) electro-optic modulators in the 2010s has enabled the large electro-optic (EO) performance of organic chromophores to be leveraged for high-performance photonic components capable of integration with CMOS electronics. However, hybrid devices also present unique design considerations for maximizing material performance, including electrode-chromophore interactions, minimization of leak-through current, and maintaining material performance through all important processing and packaging steps. We report materials with an uncompromising combination of EO performance and thermal stability, as well as development of a new generation of materials and advances in processing techniques required to implement them for classical and quantum computing and networking applications.

Strong quantum-mechanical coupling between single emitters and cavity modes enables quantum transduction between photons and excitations in the solid state. However, previous experiments have been limited to cryogenic temperatures. By coupling single colloidal quantum dots to plasmonic nanocavities, we have demonstrated strong coupling at room temperature for single solid-state emitters.

Integration of fluorescent nanoparticles into photonic resonators is crucial for on-chip integration and applications in nanophotonics and quantum technologies. In this work we demonstrate a cavity design with a pocket at its center to host fluorescent nanoparticles. Simulations show that filling the pocket with a particle drastically reduces the mode volume to ~ 0.015 (λ/n)3 and strongly increases the field overlap of the fluorescent material with the cavity mode thus achieving more efficient coupling. We then demonstrate a method to fabricate dielectric cavities that naturally form a nano-pocket during the processing steps. Finally, the functionality of devices with and without particle in the pocket are directly compared. We show a PL enhancement by a factor of 20 and 2.5-fold lifetime reduction at room temperature versus 3.5 PL enhancement and 1.7 lifetime reduction for cavities with particle in a pocket and particle outside a pocket, respectively.

Blinking of Purcell-enhanced gold luminescence in plasmonic nanojunctions

2D materials offer a wide range of perspectives for hosting highly localized 0D states, e.g. vacancy defects, that offer great potential for integrated quantum photonic applications. Here, we create individual defects that act as our single-photon emitters by highly local He-ion irradiation in a monolayer MoS2 van der Waals heterostructure. The defects show anti-bunched light emission at a characteristic energy of ~ 1.75 eV. The emission is highly homogeneous and background free due to the hBN encapsulation with a creation yield of > 70%. Spectroscopic investigation of individual single-photon emitters reveals a strongly asymmetric line shape resembling interaction with acoustic phonons in excellent agreement with an independent boson model. Moreover, emitters are spatially integrated and electrically controlled in field-switchable van der Waals devices. Our work firmly establishes 2D materials as a highly scalable material platform for integrated quantum photonics.

Scanning probe microscopy (SPM) traditionally employs a sharp tip as a sensor. This geometry is a problem for many modern near-field probes, such as NV centers in diamond, which cannot easily be placed on a tip. Here we present a novel, tipless approach - a technique to scan a planar probe parallel to a planar sample at a distance of few tens of nanometers. The core of our scheme are optical far-field techniques to measure both distance and tilt between the probe and the sample with sub-nm and sub-mrad precision. These measurements are employed as a feedback signal for positioning. Using this scheme, we demonstrate scanning near-field optical microscopy (SNOM) of plasmonic modes in silver nanowires using shallow NV centers in a bulk diamond. We will equally present ongoing experiments to implement a scanning nanogap cavity. S. Ernst et al., ACS Photonics 6, 327 (2019)

Recent experiments with the Aharonov-Bohm geometry have shown that in addition to an electron-interference fringe shift, there is also a lateral displacement of the electron diffraction envelope. In this paper, we derive an electron displacement force based on a second-order expansion of the magnetic vector potential. The analysis illustrates the conservation of canonical angular momentum, where the mechanical angular momentum and field angular momentum sum to a constant of the motion; the azimuthal force required to change the mechanical momentum is thus supplied by changes in field momentum associated with the second-order vector potential term. Our results are consistent with all known Aharonov-Bohm experiments, including interference fringe shifts, lateral displacements, and the absence of longitudinal time delays.

Grating-based structures have recently been used as components of magneto-optical traps (MOT) to simplify the setup for trapping Rb atoms. Here, we design diffractive chips to trap more than one atom species. Our full-wave simulations show that a two-dimensional (2D) grating chip can simultaneously have high force-balancing efficiency for a wavelength of 780 nm for trapping Rb atoms and a wavelength of 852 nm for Cs atoms. We fabricated and characterized a mm-scale grating chip using electron-beam lithography, and are in the process of trapping experiments. Our work opens the door to compact multi-species MOTs.

Quantum frequency comb is a useful resource for the preparation of multi-dimensional photonic quantum states and frequency multiplexed photon pairs. Recently, based on a quadratic nonlinear optical waveguide inside a cavity, we demonstrated an efficient and wide-range generation of the quantum frequency comb. Due to the singly resonant configuration, the frequency comb is observed continuously over 80 nm at the telecom band, apart from the conventional multiple resonant configurations. We will present our recent progress on the quantum frequency comb generation.

A photonic CMOS field effect transistor includes a built-in laser in the drain region, and multiple photon sensors in the well region. The MOSFET, laser, and photon sensors are fabricated as one integral transistor. When the MOSFET is on, the laser can also be turned on. When the MOSFET is off, the laser is off. The photonic CMOS can be a light emitting device. Traditional CMOS transistors are not. Various types of lasers may be fabricated in a photonic MOSFET: quantum well lasers, quantum dots lasers, tunnel LED, VCSEL, quantum cascade lasers. VF (laser diode forward voltage) = 0V has been reported with very low series resistance. There are advantages of using photonic CMOS to replace a laser diode used in the DPSSL: better thermal stability, higher power efficiency, improved capability for Q-Switching and Phase-Locking, and potentially better laser beam quality and lifetime. Nonlinear optical films can be integrated in the photonic CMOSFETs. Photonic CMOS pumped solid state laser (CPSSL) may replace DPSSL in the future.

Dissipation was traditionally considered as a destructive effect for quantum phenomena such as quantum light interference. In spite of this, correctly designed dissipation may provide an additional degree of freedom for quantum light control. Here we investigate, both theoretically and experimentally, different aspects of coherent quantum light interaction with lossy beamsplitters. Applications of dissipative interference for quantum technology are discussed.

Quantum optical nonlinearities have received growing interest for their key role in quantum information science, quantum simulations, and other quantum technologies. Unfortunately, most materials exhibit very weak optical nonlinearities, virtually non-existent at the single photon level. Nano-scale optical resonators can store light for a long period of time in cubic-wavelength scale volume, and thus present a unique opportunity to enhance the light-matter interaction. Additionally, breakthroughs in materials science allow us to engineer inherently strong nonlinear materials. In this talk, I will present our theoretical and experimental efforts in nonlinear nanophotonics, integrated with atomically thin 2D materials, specifically transition metal dichalcogenides and solution-processed quantum dots. By confining both light and matter in the wavelength scale, we aim to reach the nonlinear regime, where single photons start repelling each other. I will also elaborate on the possibility of scaling this platform to multiple single photon quantum nodes with the possibility of creating a correlated quantum fluid of light.

Perovskite quantum dots have shown to be promising bright, tunable, high oscillator strength quantum emitters with potential in quantum optical applications. However, they suffer from intermittency. While superficially similar to other quantum dots, we show that the mechanisms behind intermittency must be fundamentally different, and the models commonly used to describe quantum dot intermittency are insufficient for these systems.

We study the effect of charge state conversion of nitrogen vacancy (NV) centers on the local density of states (LDOS) induced modifications in emission lifetime. The pump-dependent decay rates reveal two power regimes according to the dominance of photoionization of NV centers or the effect of LDOS. The extent of lifetime modification is achieved at low pump power, whereby the emission rate of zero phonon line is enhanced and the rate of phonon sideband emission is suppressed. At high pump power, the effect of modified emission rate is demeaned due to increased photoionization of NV centers.

Two dimensional (2-D) atomic layers have several advantages such as flexibility in choosing substrates, easy fabrication, large package area, minimum change of components, enhanced expiration date, and reduced defects by oxygen blocking structure for smart sensor. The sensors with excellent flexibility and stretchability are crucial components that can provide health monitoring systems with the capability of continuously tracking physiological signals of human body without conspicuous uncomfortableness and invasiveness. The signals acquired by these sensors, such as body motion, heart rate, breath, skin temperature and metabolism parameter, are closely associated with personal health conditions.

Currently, perovskite containing organometal halides have issues for limited color range and low photoluminescence (PL). In this regard, we designed split-ligand mediated re-precipitation (Split-LMRP) as a unique synthesis method for improved stability and PL by separating octylamine and oleic acid (OA), compared to a conventional method. [Accepted manuscript] Octylamine adjusted the size of the nucleus as main ligand, while OA acted only as a stabilizer. Especially, the QDs based on Split-LMRP remained PL intensity after 5 days with strong PL emission and a high PL quantum yield (PLQY) of 91.5% due to the removal of most polar solvents during re-precipitation. In addition, the size of the QDs was adjusted constantly in the range of 2-5 nm depending on the concentration of octylamine. When the perovskite QDs were used as the intermediate layer of the perovskite solar cell, performance and reproducibility of the PSC were improved by forming stable phases.

Quantum key distribution introduces a new way of key exchange through a public quantum channel between two communicating nodes. However, the first introduced BB84 protocol was theoretically verifying security based on single photon sources. At this time, it was hard to achieve such device. Therefore, it was a challenging aspect to prove the security of QKD system using coherent light sources or “multi emitting photon source”, which introduces Photon number splitting attacks. We are interested to simulate and investigate the QKD system using coherent laser sources and study the PNS attack. The idea involves that; Eve can crash a beam of light, absorbing some photons using QND measurement and transmit the others. Such attack can make Eve dominant to the situation and gain much information of the key without the fear of getting exposed to the communicating parties. Herein, this paper discusses some useful solution to detect such attack and proves the security of QKD even with weak laser sources.