Frequency Bin Entangled Photons

A monochromatic laser pumping a parametric down conversion crystal generates frequency entangled photon pairs. We study this experimentally by addressing such frequency entangled photons at telecommunication wavelengths (around 1550 nm) with fiber optics components such as electro-optic phase modulators and narrow band frequency filters. The theory underlying our approach is developed by introducing the notion of frequency bin entanglement. Our results show that the phase modulators address coherently up to eleven frequency bins, leading to an interference pattern which can violate a Bell inequality adapted to our setup by more than five standard deviations.Comment: 10 pages, 4 figures (extended version

Linear Optical Quantum Computing in a Single Spatial Mode

We present a scheme for linear optical quantum computing using time-bin encoded qubits in a single spatial mode. We show methods for single-qubit operations and heralded controlled phase (CPhase) gates, providing a sufficient set of operations for universal quantum computing with the Knill-Laflamme-Milburn scheme. Our scheme is suited to available photonic devices and ideally allows arbitrary numbers of qubits to be encoded in the same spatial mode, demonstrating the potential for time-frequency modes to dramatically increase the quantum information capacity of fixed spatial resources. As a test of our scheme, we demonstrate the first entirely single spatial mode implementation of a two-qubit quantum gate and show its operation with an average fidelity of 0.84+-0.07.Comment: 5 pages, 4 figures. Updated to be consistent with the published versio

Engineered optical nonlinearity for a quantum light source

Single-photon pairs created in the nonlinear process of spontaneous parametric downconversion form the backbone of fundamental and applied experimental quantum information science. Many applications benefit from careful spectral shaping of the single-photon wave-packets. In this paper we tailor the joint spectral wave-function of downconverted photons by modulating the nonlinearity of a poled crystal without affecting the phase-matching conditions. We designed a crystal with a Gaussian nonlinearity profile and confirmed successful wave-packet shaping by two-photon interference experiments. We numerically show how our method can be applied for attaining one of the currently most important goals of single-photon quantum optics, the creation of pure single photons without spectral correlations.Comment: 7 pages (4 pages + appendices), 5 figures. Minor formatting changes. Fixed typos. Some additional reference

Implementing two-photon interference in the frequency domain with electro-optic phase modulators

Frequency-entangled photons can be readily produced using parametric down-conversion. We have recently shown how such entanglement could be manipulated and measured using electro-optic phase modulators and narrow-band frequency filters, thereby leading to two-photon interference patterns in the frequency domain. Here we introduce new theoretical and experimental developments showing that this method is potentially a competitive platform for the realization of quantum communication protocols in standard telecommunication fibres. We derive a simple theoretical expression for the coincidence probabilities and use it to optimize a Bell inequality. Furthermore, we establish an equivalence between the entangled- photon scheme and a classical interference scheme. Our measurements of two-photon interference in the frequency domain yield raw visibilities in excess of 99%. We use our high quality setup to experimentally validate the theoretical predictions, and in particular we report a violation of the CH74 inequality by more than 18 standard deviations.Comment: 19 pages, 3 figure

Generation of a wave packet tailored to efficient free space excitation of a single atom

We demonstrate the generation of an optical dipole wave suitable for the process of efficiently coupling single quanta of light and matter in free space. We employ a parabolic mirror for the conversion of a transverse beam mode to a focused dipole wave and show the required spatial and temporal shaping of the mode incident onto the mirror. The results include a proof of principle correction of the parabolic mirror's aberrations. For the application of exciting an atom with a single photon pulse we demonstrate the creation of a suitable temporal pulse envelope. We infer coupling strengths of 89% and success probabilities of up to 87% for the application of exciting a single atom for the current experimental parameters.Comment: to be published in Europ. Phys. J.

On-chip generation of high-dimensional entangled quantum states and their coherent control

Optical quantum states based on entangled photons are essential for solving questions in fundamental physics and are at the heart of quantum information science1. Specifically, the realization of high-dimensional states (D-level quantum systems, that is, qudits, with D > 2) and their control are necessary for fundamental investigations of quantum mechanics2, for increasing the sensitivity of quantum imaging schemes3, for improving the robustness and key rate of quantum communication protocols4, for enabling a richer variety of quantum simulations5, and for achieving more efficient and error-tolerant quantum computation6. Integrated photonics has recently become a leading platform for the compact, cost-efficient, and stable generation and processing of non-classical optical states7. However, so far, integrated entangled quantum sources have been limited to qubits (D = 2)8, 9, 10, 11. Here we demonstrate on-chip generation of entangled qudit states, where the photons are created in a coherent superposition of multiple high-purity frequency modes. In particular, we confirm the realization of a quantum system with at least one hundred dimensions, formed by two entangled qudits with D = 10. Furthermore, using state-of-the-art, yet off-the-shelf telecommunications components, we introduce a coherent manipulation platform with which to control frequency-entangled states, capable of performing deterministic high-dimensional gate operations. We validate this platform by measuring Bell inequality violations and performing quantum state tomography. Our work enables the generation and processing of high-dimensional quantum states in a single spatial mode

Micro-combs: a novel generation of optical sources

The quest towards the integration of ultra-fast, high-precision optical clocks is reflected in the large number of high-impact papers on the topic published in the last few years. This interest has been catalysed by the impact that high-precision optical frequency combs (OFCs) have had on metrology and spectroscopy in the last decade [1–5]. OFCs are often referred to as optical rulers: their spectra consist of a precise sequence of discrete and equally-spaced spectral lines that represent precise marks in frequency. Their importance was recognised worldwide with the 2005 Nobel Prize being awarded to T.W. Hänsch and J. Hall for their breakthrough in OFC science [5]. They demonstrated that a coherent OFC source with a large spectrum – covering at least one octave – can be stabilised with a self-referenced approach, where the frequency and the phase do not vary and are completely determined by the source physical parameters. These fully stabilised OFCs solved the challenge of directly measuring optical frequencies and are now exploited as the most accurate time references available, ready to replace the current standard for time. Very recent advancements in the fabrication technology of optical micro-cavities [6] are contributing to the development of OFC sources. These efforts may open up the way to realise ultra-fast and stable optical clocks and pulsed sources with extremely high repetition-rates, in the form of compact and integrated devices. Indeed, the fabrication of high-quality factor (high-Q) micro-resonators, capable of dramatically amplifying the optical field, can be considered a photonics breakthrough that has boosted not only the scientific investigation of OFC sources [7–13] but also of optical sensors and compact light modulators [6,14]

Manipulation de photons intriqués en fréquence

Les pères fondateurs de la mécanique quantique exploraient les implications de leur théorie avec des "expériences de pensée". Les améliorations continuelles en matière de manipulation de systèmes quantiques individuels ont ouvert la voie à des recherches théoriques et expérimentales. C'est la base de l'information quantique: quand un contenu informationnel est associé à des transformations et mesures sur des systèmes quantiques, cela offre un nouveau paradigme à la théorie de l'information. Une des promesses de l'information quantique est la réalisation d'un internet quantique: des liaisons quantiques permettraient de partager des états quantiques entre les noeuds du réseau. Le contexte de notre travail est l'optique quantique expérimentale dans des fibres optiques aux longueurs d'onde des télécommunications, avec comme perspective des applications en communication quantique. Nous démontrons une nouvelle méthode pour manipuler des photons intriqués en énergie-temps, en utilisant des composants fibrés et optoélectroniques standard. Les photons produits par paires par une source de conversion paramétrique sont envoyés dans des modulateurs de phase électro-optiques indépendants, qui agissent comme des diviseurs de faisceau en fréquence. Nous utilisons ensuite des filtres fréquentiels et des détecteurs de photons uniques pour discriminer les fréquences des photons. Nos résultats expérimentaux incluent l'obtention d'interférences à deux photons robustes, à haute visibilité et à haute dimension, qui permettent la violation d'inégalités de Bell. Cela montre qu'une telle "intrication en bins fréquentiels" est une plate-forme intéressante pour la communication Quantique.The founding fathers of quantum mechanics explored the implications of their theory with "gedanken experiments". Continuous improvement of the experimental manipulation of individual quantum systems has opened the way to exciting research, both on blackboards and in laboratories. lt is the basis for quantum information processing : when an information content is associated with transformations and measurements of quantum systems, it offers a new paradigm, full of potentialities, to information theory. One of the promises of quantum information is the realization of a quantum internet: quantum communication links would allow to share quantum states between the nodes of the network.Our work lies in the context of experimental quantum optics in optical fibers at telecommunication wavelengths, in view of quantum communication applications. We demonstrate a new method for manipulating photons entangled in their energy-time degree of freedom, by using standard fiber-optic and optoelectronic components. The photon pairs produced by a parametric down-conversion source are sent through independent electro­optic phase modulators, which act as high-dimensional frequency beam splitters. We then use frequency filters and single-photon detectors to discriminate the frequencies of the photons. Our experimental results include robust, high-visibility and high-dimensional two­photon interference patterns allowing Bell inequality violations. This shows that such a "frequency -bin entanglement" provides an interesting platform for quantum communication

Manipulation de photons intriqués en fréquence

The founding fathers of quantum mechanics explored the implications of their theory with "gedanken experiments". Continuous improvement of the experimental manipulation of individual quantum systems has opened the way to exciting research, both on blackboards and in laboratories. lt is the basis for quantum information processing : when an information content is associated with transformations and measurements of quantum systems, it offers a new paradigm, full of potentialities, to information theory. One of the promises of quantum information is the realization of a quantum internet: quantum communication links would allow to share quantum states between the nodes of the network.Our work lies in the context of experimental quantum optics in optical fibers at telecommunication wavelengths, in view of quantum communication applications. We demonstrate a new method for manipulating photons entangled in their energy-time degree of freedom, by using standard fiber-optic and optoelectronic components. The photon pairs produced by a parametric down-conversion source are sent through independent electro­optic phase modulators, which act as high-dimensional frequency beam splitters. We then use frequency filters and single-photon detectors to discriminate the frequencies of the photons. Our experimental results include robust, high-visibility and high-dimensional two­photon interference patterns allowing Bell inequality violations. This shows that such a "frequency -bin entanglement" provides an interesting platform for quantum communication.Les pères fondateurs de la mécanique quantique exploraient les implications de leur théorie avec des "expériences de pensée". Les améliorations continuelles en matière de manipulation de systèmes quantiques individuels ont ouvert la voie à des recherches théoriques et expérimentales. C'est la base de l'information quantique: quand un contenu informationnel est associé à des transformations et mesures sur des systèmes quantiques, cela offre un nouveau paradigme à la théorie de l'information. Une des promesses de l'information quantique est la réalisation d'un internet quantique: des liaisons quantiques permettraient de partager des états quantiques entre les noeuds du réseau. Le contexte de notre travail est l'optique quantique expérimentale dans des fibres optiques aux longueurs d'onde des télécommunications, avec comme perspective des applications en communication quantique. Nous démontrons une nouvelle méthode pour manipuler des photons intriqués en énergie-temps, en utilisant des composants fibrés et optoélectroniques standard. Les photons produits par paires par une source de conversion paramétrique sont envoyés dans des modulateurs de phase électro-optiques indépendants, qui agissent comme des diviseurs de faisceau en fréquence. Nous utilisons ensuite des filtres fréquentiels et des détecteurs de photons uniques pour discriminer les fréquences des photons. Nos résultats expérimentaux incluent l'obtention d'interférences à deux photons robustes, à haute visibilité et à haute dimension, qui permettent la violation d'inégalités de Bell. Cela montre qu'une telle "intrication en bins fréquentiels" est une plate-forme intéressante pour la communication Quantique