This PDF file contains the front matter associated with SPIE Proceedings Volume 10358, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Properties of quantum light represent a tool for overcoming limits of classical optics. Several experiments have demonstrated this advantage ranging from quantum enhanced imaging to quantum illumination. In this work, experimental demonstration of quantum-enhanced resolution in confocal fluorescence microscopy will be presented. This is achieved by exploiting the non-classical photon statistics of fluorescence emission of single nitrogen-vacancy (NV) color centers in diamond. By developing a general model of super-resolution based on the direct sampling of the kth-order autocorrelation function of the photoluminescence signal, we show the possibility to resolve, in principle, arbitrarily close emitting centers. Finally, possible applications of NV-based fluorescent nanodiamonds in biosensing and future developments will be presented.

We prepare single photons with a temporal envelope with rising exponential shape, resembling the time-reversed version of photons from the spontaneous decay process using a parametric conversion process in a cold atomic vapor. The mechanism is based on correlated photon pair preparation and heralding of one photon by the other one after engineering the temporal envelope of the herald.¹ Such a temporal single photon profile is ideal for absorption by a two level system.^{2, 3} We demonstrate this in an experiment showcasing the absorption by a single Rubidium atom.⁴

The centrosymmetric crystalline structure of Silicon inhibits second order nonlinear optical processes in this material. We report here that, by breaking the silicon symmetry with a stressing silicon nitride over-layer, Second Harmonic Generation (SHG) is obtained in suitably designed waveguides where multi-modal phase-matching is achieved. The modeling of the generated signal provides an effective strain-induced second order nonlinear coefficient of χ⁽²⁾ = (0.30 ± 0.02) pm/V. Our work opens also interesting perspectives on the reverse process, the Spontaneous Parametric Down Conversion (SPDC), through which it is possible to generate mid-infrared entangled photon pairs.

Nanowires offer new opportunities for nanoscale quantum optics; the quantum dot geometry in semiconducting nanowires as well as the material composition and environment can be engineered with unprecedented freedom to improve the light extraction efficiency. Quantum dots in nanowires are shown to be efficient single photon sources, in addition because of the very small fine structure splitting, we demonstrate the generation of entangled pairs of photons from a nanowire. Another type of nanowire under study in our group is superconducting nanowires for single photon detection, reaching efficiencies, time resolution and dark counts beyond currently available detectors. We will discuss our first attempts at combining semiconducting nanowire based single photon emitters and superconducting nanowire single photon detectors on a chip to realize integrated quantum circuits.

Superconducting detectors are now well-established tools for low-light optics, and in particular quantum optics, boasting high-eciency, fast response and low noise. Similarly, lithium niobate is an important platform for integrated optics given its high second-order nonlinearity, used for high-speed electro-optic modulation and polarization conversion, as well as frequency conversion and sources of quantum light. Combining these technologies addresses the requirements for a single platform capable of generating, manipulating and measuring quantum light in many degrees of freedom, in a compact and potentially scalable manner. We will report on progress integrating tungsten transition-edge sensors (TESs) and amorphous tungsten silicide superconducting nanowire single-photon detectors (SNSPDs) on titanium in-di‚used lithium niobate waveguides. ‘e travelling-wave design couples the evanescent €eld from the waveguides into the superconducting absorber. We will report on simulations and measurements of the absorption, which we can characterize at room temperature prior to cooling down the devices. Independently, we show how the detectors respond to ƒood illumination, normally incident on the devices, demonstrating their functionality.

Nanophotonic components allow the control of the flow of light in integrated optical environments. Thereby, the light’s strong confinement leads to an inherent link between its local polarization and propagation direction which fundamentally alters the physics of light-matter interaction and gives rise to phenomena such as directional emission and direction-dependent coupling strengths [1]. I will present the underlying principles of this chiral light-matter interaction and its consequences for integrated applications [1]. In particular, I will show how we employ this effect to control the direction of spontaneous emission [2] and to realize low-loss nonreciprocal transmission at the single-photon level through a silica nanofiber [3]. We use two different approaches where either an ensemble of spin-polarized atoms is weakly coupled to a nanofiber or a single atom is strongly coupled to the nanofiber via a whispering-gallery-mode resonator. The resulting optical isolators show a strong imbalance between the transmissions in forward and reverse direction and, at the same time, a forward transmissions exceeding 70%. We extended this system to a 4-port device, where a single atom routes photons nonreciprocally from one fiber port to the next. This realizes a quantum optical circulator [4] which can even be prepared in a superposition of its operational modes. The demonstrated systems exemplify a new class of (quantum) nanophotonic devices that are ideally suited for photonic quantum information processing and quantum simulation. [1] Nature 541, 473, (2017). [2] Science 346, 67 (2014). [3] Phys. Rev. X 5, 041036 (2015). [4] Science 354, 1577 (2016).

Efficient quantum light sources and non-linear optical elements at the few photon level are the basic ingredients for most applications in nano and quantum technologies. On the other hand, a scalable platform for quantum ICT typically requires reliable light matter interfaces and on-chip integration. In this work we demonstrate the potential of a novel hybrid technology which combines single organic molecules as quantum emitters and dielectric chips [1]. Dibenzoterrylene molecules in anthracene crystals (DBT:Ac) are particularly suitable quantum systems for this task, since they exhibit long-term photostability in thin samples [2], easy fabrication methods and life-time limited emission at cryogenic temperatures [3]. We demonstrate at room temperature the emission of single photons from DBT molecules into ridge waveguides with a branching ratio up to 40%. The overall single-photon source efficiency, including emission into the guided mode, propagation losses, and emission into a quasi-gaussian mode in free space, is estimated around 16%. These results are competitive with state-of-the-art single photon emission into propagating guided modes from solid state systems [4], while offering a novel platform with unprecedented versatility. References [1] P. Lombardi et al., Arxiv: 1701.00459v1 (2017). [2] C. Toninelli et al., Opt. Express 18, 6577 (2010). [3] A. A. L. Nicolet et al., ChemPhysChem 8, 1929 (2007). [4] I. Zadeh et al., Nano Lett. 16, 2289 (2016); R. S. Daveau et al., Arxiv: 1610.08670v1 (2016). [5] J. Hwang et. al., New J. Phys. 13, 085009 (2011); H.-W. Lee et al., Phys. Rev. A 63, 012305 (2000).

Atomic-superconducting hybrid systems are of particular interest as they are combining the long coherence times of ultracold atoms and fast gate operation times of superconducting circuits. Here we discuss an experimental realization of an interface between cold Rydberg atoms and a transmon circuit embedded in a microwave cavity. We present numerical calculations showing a significant coupling of Rydberg atoms to a transmon. Here we place the atoms in the vicinity of the transmon shunting capacitor. Exciting them to the Rydberg states alters the dielectric constant of the medium inside the capacitor. This results in a dispersive shift of the transmon resonance frequency. Using the protocols developed in Ref. 1, 2 will allow the coherent transfer of quantum states between these two systems.

Optically active rare-earth Neodymium (Nd) ions are integrated in Niobium (Nb) thin films forming a new quantum memory device (Nd:Nb) targeting long-lived coherence times and multi-functionality enabled by both spin and photon storage properties. Nb is implanted with Nd spanning 10-60 keV energy and 10¹³-10¹⁴ cm^-2 dose producing a 1- 3% Nd:Nb concentration as confirmed by energy-dispersive X-ray spectroscopy. Scanning confocal photoluminescence (PL) at 785 nm excitation are made and sharp emission peaks from the 4F_3/2 -< 4I_11/2 Nd³⁺ transition at 1064-1070 nm are examined. In contrast, un-implanted Nb is void of any peaks. Line-shapes at room temperature are fit with Lorentzian profiles with line-widths of 4-5 nm and 1.3 THz bandwidth and the impacts of hyperfine splitting via the metallic crystal potential are apparent and the co-contribution of implant induced defects. With increasing Nd from 1% to 3%, there is a 0.3 nm red shift and increased broadening to a 4.8 nm linewidth. Nd:Nb is photoconductive and responds strongly to applied fields. Furthermore, optically detected magnetic resonance (ODMR) measurements are presented spanning near-infrared telecom band. The modulation of the emission intensity with magnetic field and microwave power by integration of these magnetic Kramer type Nd ions is quantified along with spin echoes under pulsed microwave π-π/2 excitation. A hybrid system architecture is proposed using spin and photon quantum information storage with the nuclear and electron states of the Nd³⁺ and neighboring Nb atoms that can couple qubit states to hyperfine 7/2 spin states of Nd:Nb and onto NIR optical levels excitable with entangled single photons, thus enabling implementation of computing and networking/internet protocols in a single platform.

A key requirement for many applications in solid-state quantum sciences is a high fluence of indistinguishable photons. The spontaneous emission of these photons is governed by the coupling of an excited quantum system to electromagnetic vacuum fluctuations. In our experiment, we enhance this coupling by engineering a tunable Fabry-Perot microcavity. The quantum system we study is the nitrogen-vacancy (NV) center in diamond, a workhorse for quantum science and engineering, due to its optical transitions and the coherent electron spin system it hosts. Our device consists of a high-quality, nano-fabricated, single-crystalline diamond membrane bonded to a planar mirror; the cavity is completed by a second, concave mirror. Using piezo positioners, we achieve full spectral and spatial tunability and freedom in selecting NVs with favorable emission properties in our low-temperature (4 Kelvin) experiments. Upon tuning of the cavity into resonance, we find significant enhancement of the 637 nm zero phonon line for several individual NVs which is accompanied by a strong reduction of the overall photoluminescence (PL) lifetime. We infer a 30-fold enhancement of the zero-phonon transition rate at best. The fraction of the PL emission associated to this resonant transition is thereby increased from 3% to 46%. Our results constitute a significant leap on the route towards the implementation of fast long-distance quantum networks, which are currently limited by the photon emission rate in their nodes. Furthermore, our versatile design is readily applicable to other solid-state quantum emitters like color centers in silicon carbide.

Defect qubits in silicon carbide are an emerging system for quantum information science and technology. It is important to passivate and protect the surface to preserve the particular defect configurations as well as to provide means to tune the opto-electronic properties via electronic or opto-electronic gating. In this work, we construct defect qubit device structures that integrate Indium-Tin-Oxide (ITO) electrodes and a thin atomic layer deposited (ALD) siliconoxide surface passivation. The devices are formed via 12C ion implantation and high temperature annealing of 4H and 6H silicon carbide. The process involves the integration of optically transparent indium tin oxide electrodes and a surface passivation film of silicon-oxide by atomic layer deposition. We find good contact is formed between ITO and SiC, and after complete processing, the measured broad-band photoluminescence (PL) with excitation at 785 nm in a scanning PL system is consistent with the formation of silicon vacancies. We find minimal change in the room temperature emission in regions beneath the ITO electrodes and the SiOx-SiC passivated surface. We evaluate the ability of an electric field to tune the optically detected magnetic resonance (ODMR) response of the qubit system by simulations of the spectrum with a modified spin Hamiltonian that considers the Stark Effect. We quantify the simulated strength of the electric-field tuning of the energy levels and ODMR response for the various identified spin 3/2 transitions of the silicon vacancy.

In this work, we describe a simple module that could be ubiquitous for quantum information based applications. The basic modules comprises a single NV^- center in diamond embedded in an optical cavity, where the cavity mediates interactions between photons and the electron spin (enabling entanglement distribution and efficient readout), while the nuclear spins constitutes a long-lived quantum memories capable of storing and processing quantum information. We discuss how a network of connected modules can be used for distributed metrology, communication and computation applications. Finally, we investigate the possible use of alternative diamond centers (SiV/GeV) within the module and illustrate potential advantages.

Quantum photonic circuits based on nanophotonic components hold promise for overcoming scalability limitations in optical quantum systems. Functional systems will require the co-integration of single photon sources, detectors and tunable photonic components. Waveguide integrated single photon detectors based on superconducting nanowires (SNSPDs) have been shown to fulfill the demanding requirements for on-chip quantum photonics. Because they provide very wide optical detection bandwidth, their use with optically pumped single photon sources poses severe challenges for on-chip filtering. We overcome these challenges by co-integrating electrically driven single photon sources with superconducting detectors. Single photon sources with nanoscale footprint are realized by depositing electrically contacted carbon nanotubes (CNTs) across nanophotonic waveguides. CNTs under electrical current bias are shown to emit non-classical light which is coupled efficiently into the underlying photonic framework. The CNTs are shown to provide high count rates in the MHz range. The statistical characterization of the CNT light source crucially relies on the high timing resolution of the SNSPDs which allows for measuring photon statistics for emitters with sub-100ps lifetime. The combination of top-down nanofabrication with deposition by electrophoresis provides a waferscale approach for realizing non-classical circuits on chip. Such hybrid quantum photonic devices therefore hold promise for realizing complex integrated devices without additional optical input ports.

Photonic integration is an enabling technology for photonic quantum science, offering greater scalability, stability, and functionality than traditional bulk optics. Here, we describe a scalable, heterogeneous III-V/silicon integration platform to produce Si3N4 photonic circuits incorporating GaAs-based nanophotonic devices containing self-assembled InAs/GaAs quantum dots. We demonstrate pure single-photon emission from individual quantum dots in GaAs waveguides and cavities - where strong control of spontaneous emission rate is observed - directly launched into Si3N4 waveguides with > 90 % efficiency through evanescent coupling. To date, InAs/GaAs quantum dots constitute the most promising solid state triggered single-photon sources, offering bright, pure and indistinguishable emission that can be electrically and optically controlled. Si3N4 waveguides offer low-loss propagation, tailorable dispersion and high Kerr nonlinearities, desirable for linear and nonlinear optical signal processing down to the quantum level. We combine these two in an integration platform that will enable a new class of scalable, efficient and versatile integrated quantum photonic devices.

Due to their deterministic nature and efficiency, devices based on quantum dots (QD) are currently replacing traditional single-photon sources in the most complex quantum optics experiments, such as boson sampling protocols. Embedding these emitters into photonic crystal (PhCs) cavities enables the creation of an array of Purcell-enhanced single photons required to build quantum photonic integrated circuits. So far scaling of the number of these cavity-emitters nodes on a single chip has been hampered by practical problems such as the lack of post-fabrication methods to control their relative detuning and the complexity involved with their optical excitation. Here, we present a tuneable single-photon source combining electrical injection and nano-opto-electromechanical cavity tuning. The device consists of a double-membrane electromechanically tuneable PhC structure. A vertical p-i-n junction, hosted in the top membrane, is exploited to inject current in the QD layer and demonstrate a tunable nano LED whose cavity wavelength can be reversibly varied over 15 nanometers by electromechanically varying the distance between membranes. Besides, electroluminescence from single QD lines coupled to PhC cavities is reported for the first time. The measurement of the second-order autocorrelation function from a cavity-enhanced line proves the anti-bunched character of the emitted light. Since electrical injection does not produce stray pump photons, it makes the integration with superconducting single-photon detectors much more feasible. The large-scale integration of such tuneable single-photon sources, passive optics and waveguide detectors may enable the implementation of fully-integrated boson sampling circuits able to manipulate tens of photons.

Quantum communication applications require a scalable approach to integrate bright sources of entangled photon-pairs in complex on-chip quantum circuits. Currently, the most promising sources are based on III/V semiconductor quantum dots. However, complex photonic circuitry is mainly achieved in silicon photonics due to the tremendous technological challenges in circuit fabrication. We take the best of both worlds by developing a new hybrid on-chip nanofabrication approach. We demonstrate for the first time on-chip generation, spectral filtering, and routing of single-photons from selected single and multiple III/V semiconductor nanowire quantum emitters all deterministically integrated in a CMOS compatible silicon nitride photonic circuit.

Time-frequency domain is a promising platform for optical quantum technologies due to large Hilbert space available for quantum information encoding. Moreover, photons appear as perfect candidates for interface between different quantum systems as they can be transmitted over large distances in a low-loss manner. Obviously mostly desired would be such link at telecommunication wavelengths, because it can be integrated with classical communication schemes. We report on a tunable telecom-wavelength photon pair source based on bulk periodically poled potassium titanyl phosphate (PPKTP) pumped by femtosecond laser pulses. The pairs are produced via type-II spontaneous parametric down conversion (SPDC). The spectra of photons, which lies in telecommunication range, in our source can be affected via both changing the spectrum of pumping laser and changing the phase matching by using crystals of different lengths. By appropriate choice of these parameters either the pair of photons occupy single-mode in frequency and is in a separable state or is multimode and entangled [1]. Here we report on experimental active modification the photon pairs’ spectral properties. We employ fast electro-optic temporal phase modulation to induce a deterministic change of photons’ joint spectral intensity (JSI). Central wavelength of one photon is shifted by up to 0.2 nm. The measurement of the spectrum of single photons is based upon frequency to time mapping, implemented by large group delay dispersion (GDD) in chirped fiber Bragg grating (CFBG) [2]. An unprecedented sub-10 pm resolution of correlated single-photon spectral measurements has been achieved. Further work will be done to modify not only the position, but also the shape of JSI by using techniques based on the time-lens principle [3]. References: [1] P. G. Evans, R. S. Bennink, W. P. Grice, T. S. Humble, Phys. Rev. Lett. 105, 253601 (2010) [2] A. O. C. Davis, P. M. Saulnier, M. Karpinski, B. J. Smith, arXiv:1610.03040 (2016) [3] M. Karpiński, M. Jachura, L. J. Wright, B. J. Smith, Nature Photonics 11, 53–57 (2017)

Metasurfaces made of dielectric resonators exhibit electromagnetic surface modes analogous to surface plasmons. These modes possess a very small group velocity due to the weak coupling between the resonators. These modes can be used to reach the regime of strong coupling with a quantum resonator situated in the vicinity of the metasurface. We develop a full quantum theoretical approach to describe this coupling.

We investigate quantum teleportation of ensembles of coherent states of light with a Gaussian distributed displacement in phase space. Recently, the following general question has been addressed in [P. Liuzzo-Scorpo et al., arXiv:1705.03017]: Given a limited amount of entanglement and mean energy available as resources, what is the maximal fidelity that can be achieved on average in the teleportation of such an alphabet of states? Here, we consider a variation of this question, where Einstein–Podolsky–Rosen steering is used as a resource rather than plain entanglement. We provide a solution by means of an optimisation within the space of Gaussian quantum channels, which allows for an intuitive visualisation of the problem. We first show that not all channels are accessible with a finite degree of steering, and then prove that practical schemes relying on asymmetric two-mode Gaussian states enable one to reach the maximal fidelity at the border with the inaccessible region. Our results provide a rigorous quantitative assessment of steering as a resource for secure quantum teleportation beyond the so-called no-cloning threshold. The schemes we propose can be readily implemented experimentally by a conventional Braunstein–Kimble continuous variable teleportation protocol involving homodyne detections and corrective displacements with an optimally tuned gain. These protocols can be integrated as elementary building blocks in quantum networks, for reliable storage and transmission of quantum optical states.

The realization of tabletop optical analogue experiments of superfluidity relies on the engineering of suitable optical media, with tailored optical properties. This work shows how quantum atomic optical systems can be used to develop highly tunable optical media, with localized control of both linear and nonlinear susceptibility. Introducing the hydrodynamic description of light, the superfluidity of light in these atomic media is investigated through GPU-enhanced numerical simulations, with the numeric observation of the superfluidic signature of suppressed scattering through a defect