Efficient interaction of light and matter at the ultimate limit of single photons and single emitters is of great interest from a fundamental point of view and for emerging applications in quantum engineering. However, the difficulty of generating single-photon streams with specific wavelengths, bandwidths, and power as well as the weak interaction probability of a single photon with an optical emitter pose a formidable challenge toward this goal. Here, we demonstrate a general approach based on the creation of single photons from a single emitter and their use for performing spectroscopy on a second emitter situated at a distance. While this first proof of principle realization uses organic molecules as emitters, the scheme is readily extendable to quantum dots and color centers. Our work ushers in a new line of experiments that provide access to the coherent and nonlinear couplings of few emitters and few propagating photons.
Efficient interaction of light and matter at the ultimate limit of single photons and single emitters is of great interest from a fundamental point of view and for emerging applications in quantum engineering. However, the difficulty of generating single-photon streams with specific wavelengths, bandwidths, and power as well as the weak interaction probability of a single photon with an optical emitter pose a formidable challenge toward this goal. Here, we demonstrate a general approach based on the creation of single photons from a single emitter and their use for performing spectroscopy on a second emitter situated at a distance. While this first proof of principle realization uses organic molecules as emitters, the scheme is readily extendable to quantum dots and color centers. Our work ushers in a new line of experiments that provide access to the coherent and nonlinear couplings of few emitters and few propagating photons.
At the quantum limit of nonlinear optics, where single photons interact with individual emitters, new phenomena are found. One-dimensional, subwavelength waveguides have recently emerged as a promising quantum optical platform capable of both guiding and confining photons, leading to efficient light-matter interactions and enhancing quantum optical nonlinearities. We explore this regime using both single organic molecules and epitaxially grown quantum dots coupled to nanoscale waveguides. In the first case, two-color experiments allow us to observe distinctly quantum nonlinearities such as Stark shifts of the molecular resonances or amplification without population inversion, although we are limited by relatively weak molecule-waveguide coupling. In contrast, quantum dots can be nearly perfectly coupled to waveguides, allowing us to demonstrate optical nonlinearities at the true single photon level. These, as we discuss, can be used as a basis for novel on-chip quantum technologies.
Many interesting proposals in quantum optics and light-matter interaction rely on having multiple quantum emitters well-coupled to a single mode of light. Of particular interest are cases where several identical emitters couple to a one-dimensional (1D) photonic medium. Recently, we presented such a system by evanescent coupling of organic dye molecules to the same guided mode of an on-chip subwavelength waveguide [1]. While this coupling allowed us to demonstrate up to 7.5% transmission extinction of the propagating light by a single molecule, it is still not sufficient for achieving higher-order effects such as photon-mediated interaction of multiple emitters coupled to the same waveguide.
Experiments with single quantum systems are at the frontier of modern physics. Probing single molecules allows for very precise control of light-matter interaction and for quantum optical studies. Moreover, a single guest molecule in a solid host matrix is a very sensitive probe of local dynamics in its nano-environment. Fluorescence excitation spectroscopy on single molecules is a powerful tool for spectroscopic characterizations at highest resolution, as information can be revealed that is not accessible in experiments on ensembles of molecules. The detection of the fluorescence signal of a single absorber is achieved by exploiting the high spectral selectivity given by the ratio (10 10) of homogeneous to inhomogeneous linewidths of optical transitions at cryogenic temperatures (zero-phonon transitions). Two-photon fluorescence excitation, a fundamental nonlinear optical process, was observed on a single quantum system [1]. Single diphenyl-octatetraene molecules trapped in an n-tetradecane matrix were excited from the 1Ag ground to the lowest excited singlet state by simultaneous absorption of two photons using a single-mode cw laser. Excited molecules were observed through weak one-photon emission resulting from a symmetry breaking induced by the crystal field. The fundamental principles and the experimental technique of single molecule spectroscopy will be introduced briefly and some particular single molecule experiments presented. This work was done in collaboration with T. Plakhotnik, A. Renn and U.P. Wild
The development of single-photon sources has been nothing but rapid in recent years, with quantum emitter-based systems showing especially impressive progress. In this article, we give an overview of the developments in single-photon sources based on single molecules. We will introduce polycyclic hydrocarbons as the most commonly used emitter systems for the realization of an organic solid-state single-photon source. At cryogenic temperatures this special class of fluorescent molecules demonstrates remarkable optical properties such as negligible dephasing, indefinite photostability, and high photon rates, which make them attractive as fundamental building blocks in emerging quantum technologies. To better understand the general properties and limitations of these molecules, we discuss sample preparation and relevant emitter parameters such as absorption and emission spectra, lifetime, and dephasing. We will also give an overview of light extraction strategies as a crucial part of a single-photon source. Finally, we conclude with a look into the future, displaying current challenges and possible solutions.
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.
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.