Zhe-Xian KoongGuillem Ballesteros-GarciaRaphaël ProuxDan DalacuPhilip J. PooleBrian D. Gerardot , Multiplexed Single Photons from Deterministically Positioned Nanowire Quantum Dots,  https://arxiv.org/abs/2005.05361


Abstract

Solid-state quantum emitters are excellent sources of on-demand indistinguishable or entangled photons and can host long-lived spin memories, crucial resources for photonic quantum information applications. However, their scalability remains an outstanding challenge. Here we present a scalable technique to multiplex streams of photons from multiple independent quantum dots, on-chip, into a fiber network for use off-chip. Multiplexing is achieved by incorporating a multi-core fiber into a confocal microscope and spatially matching the multiple foci, seven in this case, to quantum dots in an array of deterministically positioned nanowires. First, we report the coherent control of the emission of biexciton-exciton cascade from a single nanowire quantum dot under resonant two-photon excitation. Then, as a proof-of-principle demonstration, we perform parallel spectroscopy on the nanowire array to identify two nearly identical quantum dots at different positions which are subsequently tuned into resonance with an external magnetic field. Multiplexing of background-free single photons from these two quantum dots is then achieved. Our approach, applicable to all types of quantum emitters, can readily be scaled up to multiplex > 100  quantum light sources, providing a breakthrough in hardware for photonic based quantum technologies. Immediate applications include quantum communication, quantum simulation, and quantum computation.

H. Baek, M. Brotons-Gisbert, ZX Koong, A. Campbell, M. Rambach, K. Watanabe, T. Takashi, and BD Gerardot,  Highly tunable quantum light from moiré trapped excitons,  https://arxiv.org/ abs / 2001.04305 . 

Mauro Brotons-Gisbert, Hyeonjun Baek, Aidan Campbell, Kenji Watanabe, Takashi Taniguchi, and Brian D. Gerardot, Moiré-Trapped Interlayer Trions in a Charge-Tunable WSe2/MoSe2 Heterobilayer, https://journals.aps.org/prx/abstract/10.1103/PhysRevX.11.031033

Abstract

Transition-metal dichalcogenide heterobilayers offer attractive opportunities to realize lattices of interacting bosons with several degrees of freedom. Such heterobilayers can feature moiré patterns that modulate their electronic band structure, leading to spatial confinement of single interlayer excitons (IXs) that act as quantum emitters with C3 symmetry. However, the narrow emission linewidths of the quantum emitters contrast with a broad ensemble IX emission observed in nominally identical heterobilayers, opening a debate regarding the origin of IX emission. Here we report the continuous evolution from a few trapped IXs to an ensemble of IXs with both triplet- and singlet-spin configurations in a gate-tunable 2HMoSe2/WSe2 heterobilayer. We observe signatures of dipolar interactions in the IX ensemble regime which, when combined with magneto-optical spectroscopy, reveal that the narrow quantum-dot-like and broad ensemble emission originate from IXs trapped in moiré potentials with the same atomic registry. Finally, electron doping leads to the formation of three different species of localized negative trions with contrasting spin-valley configurations, among which we observe both intervalley and intravalley IX trions with spin-triplet optical transitions. Our results identify the origin of IX emission in MoSe2/WSe2 heterobilayers and highlight the important role of exciton-exciton interactions and Fermi-level control in these highly tunable quantum materials.

Daniel Andres-Penares, Mauro Brotons-GisbertCristian BonatoJuan F. Sánchez-RoyoBrian D. Gerardot, Optical and dielectric properties of MoO3 nanosheets for van der Waals heterostructures, https://aip.scitation.org/doi/10.1063/5.0066219


Abstract

Two-dimensional (2D) insulators are a key element in the design and fabrication of van der Waals heterostructures. They are vital as transparent dielectric spacers whose thickness can influence the photonic, electronic, and optoelectronic properties of 2D devices. Simultaneously, they provide the protection of active layers in the heterostructure. For these critical roles, hexagonal boron nitride (hBN) is the dominant choice due to its large bandgap, atomic flatness, low defect density, and encapsulation properties. However, the broad catalogue of 2D insulators offers exciting opportunities to replace hBN in certain applications that require transparent thin layers with additional optical degrees of freedom. Here, we investigate the potential of single-crystalline molybdenum oxide (MoO3) as an alternative 2D insulator for the design of nanodevices that require precise adjustment of the light polarization at the nanometer scale. First, we measure wavelength-dependent refractive indices of MoO3 along its three main crystal axes and determine the in-plane and out-of-plane anisotropy of its optical properties. We find that the birefringence in MoO3 nanosheets compares favorably with other 2D materials that exhibit strong birefringence, such as black phosphorus, ReS2, or ReSe2, in particular in the visible spectral range, where MoO3 has the unique advantage of transparency. Finally, we demonstrate the suitability of MoO3 for dielectric encapsulation by reporting linewidth narrowing and reduced inhomogeneous broadening of 2D excitons and optically active quantum emitters, respectively, in a prototypical monolayer transition-metal dichalcogenide semiconductor. These results show the potential of MoO3 as a 2D dielectric layer for manipulation of the light polarization in vertical 2D heterostructures.

Emanuele Pelucchi, Giorgos Fagas, Igor Aharonovich, Dirk Englund, Eden Figueroa, Qihuang Gong, Hübel Hannes, Jin Liu, Chao-Yang Lu, Nobuyuki Matsuda, Jian-Wei Pan, Florian Schreck, Fabio Sciarrino, Christine Silberhorn, Jianwei Wang, Klaus D. Jöns, The potential and global outlook of integrated photonics for quantum technologies, https://www.nature.com/articles/s41467-021-21624-3


Abstract

Integrated quantum photonics uses classical integrated photonic technologies and devices for quantum applications. As in classical photonics, chip-scale integration has become critical for scaling up and translating laboratory demonstrators to real-life technologies. Integrated quantum photonics efforts are centred around the development of quantum photonic integrated circuits, which can be monolithically, hybrid or heterogeneously integrated. In this Roadmap, we argue, through specific examples, for the value that integrated photonics brings to quantum technologies and discuss what applications may become possible in the future by overcoming the current roadblocks. We provide an overview of the research landscape and discuss the innovation and market potential. Our aim is to stimulate further research by outlining not only the scientific challenges of materials, devices and components associated with integrated photonics for quantum technologies but also those related to the development of the necessary manufacturing infrastructure and supply chains for delivering these technologies to the market.