This thesis is concerned with finding technologically useful quantum phenomena that are robust against real world imperfections. We examine three different areas covering techniques for spin measurement, photon preparation and error correction. The first research chapter presents a robust spin-measurement procedure, using an amplification approach: the state of the spin is propagated over a two-dimensional array to a point where it can be measured using standard macroscopic state mea- surement techniques. Even in the presence of decoherence, our two-dimensional scheme allows a linear growth in the total spin polarisation - an important increase over the √t obtainable in one-dimension. The work is an example of how simple propagation rules can lead to predictable macroscopic behaviour and the techniques should be applicable in other state propagation schemes. The next chapter is concerned with strategies for obtaining a robust and reliable single photon source. Using a microscopic model of electron-phonon interactions and a quantum master equation, we examine phonon-induced decoherence and assess its impact on the rate of production, and indistinguishability, of single photons emitted from an optically driven quantum dot system. We find that, above a certain threshold of desired indistinguishability, it is possible to mitigate the deleterious effects of phonons by exploiting a three-level Raman process for photon production. We introduce a master equation technique for quantum jump situations that should have wide application in other situations. The final chapter focusses on toric error correcting codes. Toric codes form part of the class of surface codes that have attracted a lot of attention due to their ability to tolerate a high level of errors, using only local operations. We investigate the power of small scale toric codes and determine the minimum size of code necessary for a first experimental demonstration of toric coding power.

Recently, developments in novel and high-purity materials allow for the presence of a single, solitary crystalline defect to define the electronic, magnetic, and optical functionality of a device. The discrete nature of the active dopant, whose properties are defined by a quantum mechanical description of its structure, enables radically new quantum investigations and applications in these arenas. Finally,there has been significant development in large-scale device engineering due to mature semiconductor manufacturing techniques. The diverse set of photonic device architectures offering light confinement, guiding, and extraction is a prime example. These three paradigms – solitary dopant photonics and optoelectronics (solotronics), quantum science and technology, and device engineering – merge in the development of novel quantum photonic devices for the next generation of information processing systems. We present in this thesis a series of investigations of optical nanostructures for single optically active spins in single crystal diamond. Chapter 1 introduces the Nitrogen-Vacancy (NV) color center, summarizes its applications, and motivates the need for their integration into photonic structures. Chapter 2 describes two prototype nanobeam photonic crystal cavities for generating strong light-matter interactions with NV centers. The first device consists of a silicon nitride photonic crystal nanobeam cavity with high quality factor \(Q \sim 10^5\) and small mode volume \(V \sim 0.5*(\lambda/n)^3\). The second device consists of a monolithic diamond nanobeam cavity fabricated with the focused ion beam (FIB) directly in a single crystal diamond sample. Chapter 3 presents a high-efficiency source of single photons consisting of a single NV center in a photonic diamond nanowire. Early FIB prototypes are described, as is the first successful realization of the device achieved via reactive ion etching nanowires in a single crystal diamond containing NV centers, and finally a variation of this approach based on incorporation of NV centers in pure diamond via ion implantation. In chapter 4 we consider the optimal design of photonic devices offering both collection efficiency and cavity-enhancements and extend the model of the NV center to include photonic effects. In chapter 5 we briefly introduce a novel optically active spin discovered in a diamond nanowire. Finally, in chapter 6 we conclude with several proposals to extend this research program. / Engineering and Applied Sciences

Cette thèse a été consacrée à l'étude théorique et expérimentale du couplage contrôlé de la source de photon unique (SPS) aux structures photoniques multidimensionnelles, par l'utilisation de la méthode dite écriture directe par laser (DLW) par absorption ultra-faible à un photon (LOPA). La thèse est constitutée de trois parties principales suivantes:La première partie concerne le caractérisation et l'optimisation des dots quantiques (QD) colloïdaux CdSe/CdS. La dépendance de la longeur d'onde d'excitation a été étudiée. En utilisant une excitation à 532 nm, seul le core est excité et l’effet d'Auger est donc supprimé. Cette approche permet donc d'obtenir avec la suppression de la commutation intermittente et une source de photon unique très stable à température ambiante. Afin d’obtenir une meilleure performance des QDs sur une longue période, nous avons ensuite étudié l'influence du milieu dans lequel les QDs sont logés sur leurs propriétés optiques. En intégrant les QDs dans les matrices de polymère SU-8, nous avons montré que l'environnement polymérique permet non seulement de conserver de bonnes caractéristiques des QDs CdSe/CdS avec une photostabilité élevée, mais également de nous offrir une excellente accessibilité à la fabrication des structures en polymère contenant une particule unique.Dans la deuxième partie, la technique LOPA DLW est utilisée pour le couplage des QDs uniques dans diverses structures photoniques. Deux dispositifs, l’antenne du type ''pilier diélectrique'' sous-lambda et la membrane de réseau circulaire (cavité du type ''bulleye''), ont été étudiés théoriquement et expérimentalement pour améliorer l’émission du QD couplé en termes de l'émission spatiale et de l’émission radiative spontanée de l’émetteur.Dans la troisième partie, la manipulation de la SPS est démontrée en couplant le QD unique à des structures magnéto-photoniques multidimensionnelles. À l'aide d'un champ magnétique externe, le mouvement contrôlable d'un seul QD a été démontré dans un environnement fluidique. En contrôlant l'amplitude et l'orientation du champ magnétique externe, la position et l'orientation de la SPS à base d'un QD ont été manipulées à la demande. Les propriétés optiques, magnétiques et mécaniques des dispositifs magnéto-photoniques hybrides ont été étudiées pour montrer les capacités multifonctionnelles de telles structures. / The thesis has been devoted to study the controlled coupling of a colloidal quantum dot (QD) based single photon source (SPS) into multidimensional polymeric photonic structures by using low-one photon absorption (LOPA) direct laser writing (DLW) technique. The thesis consists of three main parts:The first part addresses the characteristic optimization of the CdSe/CdS based SPS. The excitation wavelength dependence of the QDs was investigated. By using 532 nm, only the core of the QD is excited with the suppression of the Auger effects. Thus, this approach allows for obtaining the suppression of fluorescence intermittency and a stable single-photon emission at ambient conditions. In order to obtain the long-term high fluorescence quality of the QDs, we then studied the influence of the local dielectric medium on the optical properties of the QDs. By incorporating the QDs into a photoresist (SU-8), we demonstrated that the polymeric environment not only enables the long-term preservation of the QD with high photostability but also provides us excellent accessibility to fabricate polymeric structures containing SPS.In the second part, the LOPA-based DLW is employed for the coupling of single QD into various photonic structures. Two devices including submicropillar dielectric antenna and 3D membrane bulleye cavity are theoretically and experimentally investigated to enhance the fluorescence emission of the single QD in terms of far-field angular radiation pattern and the spontaneous radiative emission of the emitter.In the third part, the manipulation of SPS is demonstrated by coupling the single QD into multidimensional magneto-photonic structures. With the aid of an external magnetic field, the controllable movement of the coupled QD was performed in the fluidic environment. The position and orientation of the SPS coupled in the structure were manipulated on demand. The mechanical, magnetic and optical properties of the device are investigated showing the multifunctional capabilities of magneto-photonic structures.

Single photons - discrete wavepackets of light - are one of the most fundamental entities in physics. In recent years, the ability to consistently create and manipulate both single photons and pairs of photons has facilitated everything from tests of quantum theory to the implementation of quantum-enhanced precision measurements. These activities all fall within the scope of the rapidly-growing field of quantum information - the exploitation of the properties of quantum states (and specifically their capability to exist in superpositions) to accomplish tasks that would not be possible with classical objects. One stated goal of research in quantum information is to build a device consisting of a network of quantum logic gates that can evaluate quantum algorithms. The photonic implementation of individual logic gates has already been demonstrated. However, partly due to standard methods of preparing single photons, current schemes have severe limitations in terms of scaling up from a single logic gate to multiple concatenated operations. Until now it has not been proven that single photons can be generated in pure and indistinguishable quantum states, something upon which the successful operation of optical quantum logic gates relies. This thesis presents an experimental demonstration of simultaneous generation of almost identical single photons in highly pure states from two independent sources based on parametric downconversion. This is a process of photon pair generation during the passage of a light beam through a nonlinear crystal; one photon from the resulting pair is detected to herald the other. The work herein describes, refines, and implements a technique that minimises the strong quantum correlations usually present within each pair by spectral engineering of the source. This allows the heralded single photons to be in pure states, a property that is confirmed by observing a high-visibility two-photon interference effect without spectral filtering.

Single-photon sources are essential building blocks in quantum photonic networks, where quantum-mechanical properties of photons are utilised to achieve quantum technologies such as quantum cryptography and quantum computing. In this thesis, a single-photon source driven by a surface acoustic wave (SAW) is developed and characterised. This single-photon source is based on a SAW-driven lateral n-i-p junction in a GaAs quantum-well structure. On this device, the lateral n-i-p junction is formed by gate-induced electrons and holes in two adjacent regions. The SAW potential minima create dynamic quantum dots in a 1D channel between these two regions, and are able to transport single electrons to the region of holes along the channel. Single-photon emission can therefore be generated as these electrons consecutively recombine with holes. After characterisation and optimisation in four batches of devices, clear SAW-driven charge transport and the corresponding electroluminescence (EL) can be observed on an optimised SAW-driven n-i-p junction. Time-resolved measurements have been carried out to study the dynamics of SAW-driven electrons. Time-resolved EL signals indicate that a packet of electrons is transported to the region of holes in each SAW minimum. In addition, the carrier lifetime of SAW-driven electrons in the region of holes is shown to be $\sim 100$ ps, which is much shorter than the SAW period of $860$ ps. Hence, it is promising to observe single-photon emission in the optimised device. In order to test single-photon emission, a Hanbury Brown-Twiss experimental setup has been employed to record an autocorrelation histogram of the SAW-driven EL signal at the single-electron regime. Suppression of autocorrelation coincidences at time delay $\Delta t = 0$ is evidence of photon antibunching. By fitting theoretical functions describing the SAW-driven EL signal, it is found that the second-order correlation function shows $g^{(2)}(0) = 0.39 \pm 0.05$, which is lower than the common criterion for a single-photon source $g^{(2)}(0) < 0.5$. Moreover, theoretical calculation and simulation suggest that, if a constant background signal can be filtered out, $\sim 80 \%$ of the SAW-driven EL is single-photon emission.

Photonics has consistently played an important role in the investigation of quantum-enhanced technologies and the corresponding study of fundamental quantum phenomena. The majority of these experiments have relied on the free space propagation of light between bulk optical components. This relatively simple and flexible approach often provides the fastest route to small proof-of-principle demonstrations. Unfortunately, such experiments occupy significant space, are not inherently phase stable, and can exhibit significant scattering loss which severely limits their use. Integrated photonics offers a scalable route to building larger quantum states of light by surmounting these barriers. In the first half of this thesis, we describe the operation of on-chip heralded sources of single photons. Loss plays a critical role in determining whether many quantum technologies have any hope of outperforming their classical analogues. Minimizing loss leads us to choose Spontaneous Four-Wave Mixing (SFWM) in a silica waveguide for our source design; silica exhibits extremely low scattering loss and emission can be efficiently coupled to the silica chips and fibers that are widely used in quantum optics experiments. We show there is a straightforward route to maximizing heralded photon purity by minimizing the spectral correlations between emitted photon pairs. Fabrication of identical sources on a large scale is demonstrated by a series of high-visibility interference experiments. This architecture offers a promising route to the construction of nonclassical states of higher photon number by operating many on-chip SFWM sources in parallel. In the second half, we detail one of the first proof-of-principle demonstrations of a new intermediate model of quantum computation called boson sampling. While likely less powerful than a universal quantum computer, boson sampling machines appear significantly easier to build and may allow the first convincing demonstration of a quantum-enhanced computation in the not-distant future. Boson sampling requires a large interferometric network which are challenging to build with bulk optics, we therefore perform our experiment on-chip. We model the effect of loss on our postselected experiment and implement a circuit characterization technique that accounts for this loss. Experimental imperfections, including higher-order emission from our photon pair sources and photon distinguishability, are modeled and found to explain the sampling error observed in our experiment.

Le siècle dernier a vu l'accomplissement de la mécanique quantique, du traitement de l'information etde l'optique intégrée. Aujourd'hui, ces trois domaines se rencontrent pour donner naissance à l'optiqueintégrée pour les communications quantiques. Un des enjeux aujourd'hui dans ce domaine est ledéveloppement de sources de photons unique aux longueurs d’onde des télécommunications fibrés.Durant ce travail de thèse les émetteurs étudiés sont des boîtes quantiques d’InAsP épitaxiés parEPVOM (Epitaxie en Phase Vapeur aux OrganoMétalliques). On démontrera que ces objets uniquessont capables d’émettre des états quantiques de la lumière grâce à une expérience de dégroupement dephotons. De plus la spectroscopie de ces objets sera déduite des études résolues en temps. Lapossibilité d’intégrer ces objets au sein de nanocavité de taille ultime permet de modifier leur tauxd’émission spontanée, ainsi les résultats obtenus grâce aux cavités métalliques permettent d’observerune accélération de l’émission spontanée sur une large bande spectrale. Finalement il a été mis enévidence une forte modification de l’émission d’un ensemble de boîtes quantiques entre 4K et 300K,en utilisant une technique originale basé sur l’effet laser. / The last century saw the advent of quantum mechanics, information processing and integrated optics.These fields lead to the integrated optics for quantum communication. One of the challenges is thedevelopment of single photon sources operating at fiber’s telecommunication wavelength. In this workwe use quantum dots growth by MOVPE (MetalOrganic Vapour Phase Epitaxy). We demonstratethese emitters can generate some quantum state of light thanks to the antibunching experiment.Moreover the spectroscopy of these objects will be deducted by the time resolved spectroscopy. Thepossibility to integrate these sources in ultimate’s size cavity permits to modify the spontaneous rateemission, so the result obtain with metallic cavity permit to observe an acceleration of the spontaneousemission on a wide spectral band. Finally a strong emission modification of the quantum dot’sensemble between 4K and 300K will be presented by using an original way based on the laser effect.

Dans ce travail de thèse, on s’intéresse aux applications des concepts d’antenne pour la manipulation de la lumière. Aux fréquences optiques, les antennes métalliques font intervenir des modes de surfaces dit plasmoniques permettant une forte interaction lumière/matière dans des volumes hautement confinés. Pour tirer partie de cette propriété, on s’intéressera à trois applications des antennes plasmoniques. D’abord dans le cadre des sources de photons uniques, on présentera une étude théorique et expérimentale des performances d’émetteurs uniques en présence d’une antenne planaire métallique. Nous proposerons ensuite une stratégie pour améliorer les performances de l’antenne. Puis dans le cadre de la génération électrique de lumière par effet tunnel inélastique, on analysera la modification des propriétés de rayonnement en présence d’un petit cylindre métallique. Cette analyse ouvre la voie à la conception de sources électriques intégrées de plasmons de surface. Enfin dans le cadre de la détection de molécules en faible quantité, on étudiera théoriquement l’interaction d’un faisceau infrarouge avec une couche de molécules résonnantes déposées sur un miroir métallique nanostructuré. / The work of this thesis has been devoted to a few applications of antenna concepts for the manipulation of light. In the optical range, surface modes called surface plasmon polaritons take place in the vicinity of metallic antennas, enabling a strong light/matter interaction within highly confined volumes. In order to take advantage of this property, three applications of plasmonic antennas will be investigated. First, in the case of single-photon sources, both theoretical and experimental studies of single-emitters performance when coupled to a planar metallic antenna will be presented. A strategy to enhance its performance will be studied theoretically. Then, in the case of electrical generation of light by inelastic electron tunneling, we will analyse the modification of radiation properties close to a metallic nano-rod. This analysis paves the way towards the design of integrated, compact electrical sources of surface plasmons. Finally, in the case of detecting a weak quantity of molecules, the interaction between an infrared light beam and a sub-nanometric layer of resonant molecules deposited on a nanostructured metallic mirror will be studied.

Using shallow implantation of ions and molecules with masses centred at 27 atomic mass units(amu) in diamond, a new artificial optical centre with unique properties has been created. The centre shows a linearly polarised fluorescence with a main narrow emission line mostly found at 582 nm, together with a weak vibronic sideband at room temperature. The fluorescence lifetime is∼2 ns and the brightest centres are more than three times brighter than the nitrogen-vacancy centres. A majority of the centres shows stable fluorescence whereas some others present a blinking behaviour, at faster or slower rates. Furthermore, a second kind of optical centre has been simultaneously created in the same diamond sample, within the same ion implantation run. This centre has a narrow zero-phonon line (ZPL) at∼546 nm and a broad phonon sideband at room temperature. Interestingly, optically detected magnetic resonance (ODMR) has been measured on several single 546 nm centres and two resonance peaks are found at 0.99 and 1.27 GHz. In view of their very similar ODMR and optical spectra, the 546 nm centre is likely to coincide with the ST1 centre, reported once (with a ZPL at 550 nm), but of still unknown nature. These new kinds of centres are promising for quantum information processing, sub-diffraction optical imaging or use as single-photon sources.

Die hier vorgelegte Dissertation beschäftigt sich mit Untersuchungen an nanoskopischen Emittern und den Möglichkeiten, deren Fluoreszenzverhalten durch kontrollierte Ankopplung an photonische und plasmonische Strukturen zu beeinflussen. Zum einen werden mit Ytterbium- und Erbium-Ionen kodotierte NaYF4 -Nanokristalle untersucht, die hervorragende Eigenschaften bei der Umwandlung von niederenergetischen Photonen in solche höherer Energie besitzen. Das so entstehende Fluoreszenzlicht einer Ansammlung von Nanokristallen wird auf seine Abhängigkeit von der Anregungsintensität untersucht. Mit der Hilfe eines Rasterkraftmikroskops (AFM) wird eine Abhängigkeit der spektralen Zusammensetzung des Fluoreszenzlichts einzelner Nanokristalle von deren Größe im Bereich von wenigen bis 50 nm aufgezeigt. Durch gezielte Manipulation mit dem AFM werden ebenfalls einzelne Nanokristalle an Goldnanokügelchen gekoppelt und die Mechanismen der beobachteten plasmonischen Verstärkung der Emission durch zeitaufgelöste Messungen analysiert. Einzelne Stickstoff-Fehlstellen-Zentren in Nanodiamanten werden in einem zweiten Themenkomplex als Einzelphotonenquellen eigesetzt. Diese werden durch den Einsatz einer Nahfeld-Sonde auf Mikrokugel-Resonatoren aufgebracht, wodurch die Emission aufgrund der Ankopplung an die Flüstergalerie-Moden der Kugeln die typischen, scharfen Überhöhungen im Spektrum aufweist. Diese Methode lässt sich nicht nur verwenden, um zwei oder mehr Emitter an die selben Resonanzen einer Kugel zu koppeln. Es ist auch möglich, die Kugeln in einem Vorbereitungsschritt zu charakterisieren, und so kann insbesondere eine spektrale Übereinstimmung zwischen einer der Resonanzen und dem Emitter erreicht werden. Desweiterne wird demonstriert, wie durch die Kopplung an eine plasmonische Antenne aus Goldnanokugeln mittels AFM auch die Effizienz der Einzelphotonenquelle gesteigert werden kann. / The topic of the dissertation presented here is the investigation of nanoscopic emitters and the possibilities to influence their fluorescence behavior by controlled coupling to photonic and plasmonic structures. NaYF4 nanocrystals codoped with ytterbium and erbium are investigated since they provide excellent properties in upconverting of low-energetic photons to photons with higher energy. The fluorescence light that is generated in this process of a small cluster of nanocrystals is investigated on its dependence on the excitation intensity. With the help of an atomic force microscope (AFM) a dependence of the spectral composition of the fluorescence light from single nanocrystals on their size ranging between a few to 50 nm is demonstrated. By selective manipulation with the AFM, individual nanocrystals are coupled to gold nanospheres and the mechanisms of the observed plasmonic amplification of the emission is analyzed with time-resolved measurements. Single nitrogen–vacancy centers in nanodiamonds are employed as single-photon sources in a second subject area. A near-field probe is employed to attach these single quantum systems to microspherical resonators, by which their emission features the typical peaks in the spectrum due to the coupling to the whispering gallery modes of the spheres. This method can not only be applied to couple two or more single-photon emitters to the very same modes of a microsphere, but the resonators themselves can be pre-characterized to match one of the modes with the emitter. Furthermore, it will be demonstrated how the efficiency of a single-photon source can be enhanced by coupling the nitrogen-vacancy center to a plasmonic antenna made of gold nanospheres.