Reconfigurable frequency coding of triggered single photons in the telecom C--band

In this work, we demonstrate reconfigurable frequency manipulation of quantum states of light in the telecom C-band. Triggered single photons are encoded in a superposition state of three channels using sidebands up to 53 GHz created by an off-the-shelf phase modulator. The single photons are emitted by an InAs/GaAs quantum dot grown by metal-organic vapor-phase epitaxy within the transparency window of the backbone fiber optical network. A cross-correlation measurement of the sidebands demonstrates the preservation of the single photon nature; an important prerequisite for future quantum technology applications using the existing telecommunication fiber network.Comment: Samuel Gyger and Katharina D. Zeuner contributed equall

Single-Mode Squeezed Light Generation and Tomography with an Integrated Optical Parametric Oscillator

Quantum optical technologies promise advances in sensing, computing, and communication. A key resource is squeezed light, where quantum noise is redistributed between optical quadratures. We introduce a monolithic, chip-scale platform that exploits the $\chi^{(2)}$ nonlinearity of a thin-film lithium niobate (TFLN) resonator device to efficiently generate squeezed states of light. Our system integrates all essential components -- except for the laser and two detectors -- on a single chip with an area of one square centimeter, significantly reducing the size, operational complexity, and power consumption associated with conventional setups. Our work addresses challenges that have limited previous integrated nonlinear photonic implementations that rely on either $\chi^{(3)}$ nonlinear resonators or on integrated waveguide $\chi^{(2)}$ parametric amplifiers. Using the balanced homodyne measurement subsystem that we implemented on the same chip, we measure a squeezing of 0.55 dB and an anti-squeezing of 1.55 dB. We use 20 mW of input power to generate the parametric oscillator pump field by employing second harmonic generation on the same chip. Our work represents a substantial step toward compact and efficient quantum optical systems posed to leverage the rapid advances in integrated nonlinear and quantum photonics.Comment: 21 pages; 4 figures in main body, 8 supplementary figure

Resonance fluorescence from waveguide-coupled strain-localized two-dimensional quantum emitters

Efficient on-chip integration of single-photon emitters imposes a major bottleneck for applications of photonic integrated circuits in quantum technologies. Resonantly excited solid-state emitters are emerging as near-optimal quantum light sources, if not for the lack of scalability of current devices. Current integration approaches rely on cost-inefficient individual emitter placement in photonic integrated circuits, rendering applications impossible. A promising scalable platform is based on two-dimensional (2D) semiconductors. However, resonant excitation and single-photon emission of waveguide-coupled 2D emitters have proven to be elusive. Here, we show a scalable approach using a silicon nitride photonic waveguide to simultaneously strain-localize single-photon emitters from a tungsten diselenide (WSe2) monolayer and to couple them into a waveguide mode. We demonstrate the guiding of single photons in the photonic circuit by measuring second-order autocorrelation of g$^{(2)}(0)=0.150\pm0.093$ and perform on-chip resonant excitation yielding a g$^{(2)}(0)=0.377\pm0.081$. Our results are an important step to enable coherent control of quantum states and multiplexing of high-quality single photons in a scalable photonic quantum circuit

Resonance fluorescence from waveguide-coupled strain-localized two-dimensional quantum emitters

Efficient on-chip integration of single-photon emitters imposes a major bottleneck for applications of photonic integrated circuits in quantum technologies. Resonantly excited solid-state emitters are emerging as near-optimal quantum light sources, if not for the lack of scalability of current devices. Current integration approaches rely on cost-inefficient individual emitter placement in photonic integrated circuits, rendering applications impossible. A promising scalable platform is based on two-dimensional (2D) semiconductors. However, resonant excitation and single-photon emission of waveguide-coupled 2D emitters have proven to be elusive. Here, we show a scalable approach using a silicon nitride photonic waveguide to simultaneously strain-localize single-photon emitters from a tungsten diselenide (WSe2) monolayer and to couple them into a waveguide mode. We demonstrate the guiding of single photons in the photonic circuit by measuring second-order autocorrelation of g$^{(2)}(0)=0.150\pm0.093$ and perform on-chip resonant excitation yielding a g$^{(2)}(0)=0.377\pm0.081$. Our results are an important step to enable coherent control of quantum states and multiplexing of high-quality single photons in a scalable photonic quantum circuit

Integrerad Fotonik för Kvantoptik

Quantum physics allows us a vision of Nature's forces that bind the world, all its seeds and sources. After decades of primarily scientific research, we've arrived at a stage in time where quantum technology can be applied to practical problems and add value outside the field. Four pillars of quantum technologies are commonly identified: quantum computing, quantum simulation, quantum communication, and quantum sensing. For example, quantum computers will allow us to model quantum systems beyond our current capabilities, and quantum communication allows us to protect information unconditionally based on physics. Quantum sensing will enable us to measure our reality beyond classical limits. Within all of these areas, optical photons play a unique role. In quantum computer implementations (e.g. photonic, trapped ion, or superconducting) photons can serve as a computational resource, for system read-out, or for linking distant hardware nodes. Quantum communication can only be realized via photons, utilizing the low-loss propagation of photons in optical fibers, on photonic devices as well as in free space. In quantum sensing and metrology, squeezed light can be used to go beyond the current limits of sensing methods. Therefore, the quantum technology field crucially relies on precise and efficient methods to generate, steer, manipulate and detect photons. This dissertation discusses work in integrated photonic circuits, self-assembled semiconductor quantum dot devices, and superconducting nanowire single--photon detectors. We integrate multiple materials on a silicon nitride platform, including Cu2O as a platform for solid-state Rydberg physics, WS2 to improve non-linear light-generation within Si3N4, and hBN as an excellent single-photon emitter.We demonstrate optically active quantum dots as single-photon emitters in the telecom C-band and their compatibility with commercial telecom equipment.We strain-control the fine-structure splitting of these devices, which is required for future quantum interference-based protocols. Finally, we study superconducting nanowire single-photon detectors (SNSPD) and combine them with photonic micro-electromechanical systems (MEMS), establishing a cryo-compatible, reconfigurable photonic platform.Kvantfysiken ger oss en möjlighet att skåda naturens krafter som binder världen, alla dess frön och källor. Efter decennier av främst vetenskaplig forskning har vi nått det stadie i tiden där kvantteknologi kan tillämpas på praktiska problem och tillföra värde utanför akademin. Vanligtvis identifieras fyra pelare av kvantteknologier: kvantberäkning, kvantsimulering, kvantkommunikation och kvantsensorer. Till exempel kommer kvantdatorer att tillåta oss att modellera kvantsystem utöver våra nuvarande möjligheter, och kvantkommunikation tillåter oss att skydda information villkorslöst baserat på fysikens lagar samtidigt som kvantavkänning kommer att göra det möjligt för oss att mäta vår verklighet bortom klassiska gränser.  Inom alla dessa områden spelar optiska fotoner en unik roll. I kvantdatorimplementationer (t.ex. fotoniska, fångade joner eller supraledande) kan fotoner fungera som en beräkningsresurs, för systemavläsning eller för att länka avlägsna hårdvaru-noder. Kvantkommunikation kan endast förverkligas via fotoner, på grund av den låga förlusten av fotoner i optiska fibrer, på fotoniska enheter såväl som i fri luft. Inom kvantavkänning och metrologi kan klämt ljus användas för att överskrida de nuvarande gränserna för avkänningsmetoder. Därför förlitar sig kvantteknikområdet på exakta och effektiva metoder för att generera, styra, manipulera och detektera fotoner. Den här avhandlingen diskuterar arbete i integrerade fotoniska kretsar, självmonterade halvledarkvantpricksenheter och supraledande nanotrådsdetektorer för enstaka fotoner. Vi integrerar flera material på en kiselnitridplattform, inklusive Cu2O som en plattform för rydbergs fysik i fast tillstånd, WS2 för att förbättra icke-linjär ljusgenerering inom Si3N4 och hBN som utmärkt singelfoton-sändare. Vi demonstrerar optiskt aktiva kvantprickar som enstaka foton sändare i telekom C-bandet och deras kompatibilitet med kommersiell telekomutrustning. Vi kontrollerar finstruktursdelningen av dessa enheter med hjälp av töjning, vilket krävs för framtida kvantinterferensbaserade protokoll. Slutligen studerar vi supraledande nanotrådsdetektorer för enstaka fotoner och kombinerar dem med fotoniska mikroelektromekaniska system, vilket skapar en kryokompatibel, konfigurerbar fotonisk plattform