effect of a timebase mismatch in two way optical frequency transfer

Two-way frequency transfer on optical fibers is a powerful technique for the comparison of distant clocks over long and ultra-long hauls. In contrast to traditional Doppler noise cancellation, it is capable of sustaining higher link attenuation, mitigating the need of optical amplification and regeneration and thus reducing the setup complexity. We investigate the ultimate limitations of the two-way approach on a 300 km multiplexed fiber haul, considering fully independent setups and acquisition systems at the two link ends. We derive a theoretical model to predict the performance deterioration due to a bad synchronisation of the measurements, which is confirmed by experimental results. This study demonstrates that two-way optical frequency transfer is a reliable and performing technique, capable of sustaining remote clocks comparisons at the resolution, and is relevant for the development of a fiber network of continental scale for frequency metrology in Europe

Development of impedance spectroscopy based in-situ, self-calibrating, on-board wireless sensor with inbuilt metamaterial inspired small antenna for constituent detection in multi-phase mixtures like soil

Real time and accurate measurement of sub-surface soil moisture and nutrients is critical for agricultural and environmental studies. This work presents a novel on-board solution for a robust, accurate and self-calibrating soil moisture and nutrient sensor with inbuilt wireless transmission and reception capability that makes it ideally suited to act as a node in a network spread over a large area. The sensor works on the principle of soil impedance measurement by comparing the amplitude and phase of signals incident on and reflected from the soil in proximity of the sensor. The permittivity of the soil dielectric mixture which is calculated from these impedance measurements is used as input parameter to the dielectric mixing models which are used to estimate the ionic concentration in soil. The inbuilt wireless transceiver system is connected to a specially designed metamaterial inspired small antenna in order to reduce the sensor size while keeping the path losses to a minimum by using a low frequency. This composite right-left handed (CRLH) antenna for wireless transmission at 433 MHz doubles up as an underground, sensing element (external capacitor) and integrates with the on-board sensor for soil moisture and nutrient determination. The input impedance of the CRLH sensor, surrounded by the soil containing moisture and nutrient and other ions, is measured at multiple frequencies. It is shown that the change in moisture and ioinic-concentration can be successfully detected using the sensor. The inbuilt self-calibrating mechanism makes the sensor reliable at different environmental conditions and also useful for remote, underground and hand-held applications. A multi-power mode transceiver system has been designed to support the implementation of an energy efficient medium-access-control

Electronic Photonic Integrated Circuits and Control Systems

Photonic systems can operate at frequencies several orders of magnitude higher than electronics, whereas electronics offers extremely high density and easily built memories. Integrated photonic-electronic systems promise to combine advantage of both, leading to advantages in accuracy, reconfigurability and energy efficiency. This work concerns of hybrid and monolithic electronic-photonic system design. First, a high resolution voltage supply to control the thermooptic photonic chip for time-bin entanglement is described, in which the electronics system controller can be scaled with more number of power channels and the ability to daisy-chain the devices. Second, a system identification technique embedded with feedback control for wavelength stabilization and control model in silicon nitride photonic integrated circuits is proposed. Using the system, the wavelength in thermooptic device can be stabilized in dynamic environment. Third, the generation of more deterministic photon sources with temporal multiplexing established using field programmable gate arrays (FPGAs) as controller photonic device is demonstrated for the first time. The result shows an enhancement to the single photon output probability without introducing additional multi-photon noise. Fourth, multiple-input and multiple-output (MIMO) control of a silicon nitride thermooptic photonic circuits incorporating Mach Zehnder interferometers (MZIs) is demonstrated for the first time using a dual proportional integral reference tracking technique. The system exhibits improved performance in term of control accuracy by reducing wavelength peak drift due to internal and external disturbances. Finally, a monolithically integrated complementary metal oxide semiconductor (CMOS) nanophotonic segmented transmitter is characterized. With segmented design, the monolithic Mach Zehnder modulator (MZM) shows a low link sensitivity and low insertion loss with driver flexibility

Current advances in~information quantum technologies - critical issues

This article reviews chosen topics related to the development of Information Quantum Technologies in the major areas of measurements, communications, and computing. These fields start to build their ecosystems which in the future will probably coalesce into a homogeneous quantum information layer consisting of such interconnected components as quantum internet, full size quantum computers with efficient error corrections and ultrasensitive quantum metrology nodes stationary and mobile. Today, however, the skepticism expressing many doubts about the realizability of this optimistic view fights with a cheap optimism pouring out of some popular press releases. Where is the truth? Financing of the IQT by key players in research, development and markets substantially strengthens the optimistic side. Keeping the bright side with some reservations, we concentrate on showing the FAST pace of IQT developments in such areas as biological sciences, quantum evolutionary computations, quantum internet and some of its components

Current advances in~information quantum technologies - critical issues

This article reviews chosen topics related to the development of Information Quantum Technologies in the major areas of measurements, communications, and computing. These fields start to build their ecosystems which in the future will probably coalesce into a homogeneous quantum information layer consisting of such interconnected components as quantum internet, full size quantum computers with efficient error corrections and ultrasensitive quantum metrology nodes stationary and mobile. Today, however, the skepticism expressing many doubts about the realizability of this optimistic view fights with a cheap optimism pouring out of some popular press releases. Where is the truth? Financing of the IQT by key players in research, development and markets substantially strengthens the optimistic side. Keeping the bright side with some reservations, we concentrate on showing the FAST pace of IQT developments in such areas as biological sciences, quantum evolutionary computations, quantum internet and some of its components

Integrated photonic transmitters for secure space quantum communication

An important issue in today's information society is the security of data transmission against potential intruders, which always put at risk the confidentiality. Current methods to increase security require that the two parties wishing to transmit information, exchange or share one or more security keys. Once the key has been identified, the information can be transferred in a provable secure way using a one-time pad, i. e. the key length is as long as the plaintext. Therefore, the security of the information transmission is based exclusively on the security of the key exchange. Quantum cryptography, or more precisely quantum key distribution (QKD), guarantees absolutely secure key distribution based on the principles of quantum physics, according to which it is not possible to measure or reproduce a state (e.g. polarization or phase of a photon) without being detected. The key is generated out from the measurement of the information encoded into specific quantum states of a photon, named qubits. For example, a qubit can be created using properties such as the polarization or the phase of a photon. Achieved goals of this thesis are the development of a new class of high speed integrated photonic sources for applications in quantum key distribution systems, capable of producing unprecedented qubit rates (100 Mbps - 1 Gbps) and transmitting those over larger distances than those achieved so far (>200 km). More specifically the work has been focused on developing faint pulse sources which can be used in very demanding environmental conditions, such as those in Space. For the development of these sources, apart from the optical design, essential is the opto-mechanical engineering as well as the integration with the electronics. One of the objectives was to achieve very high level of integration and power efficiency, e.g. volumes and power consumption between 10 and 100 times smaller than those typical of a laboratory experiment. Moreover, work in related parts of a whole QKD transmission system has been carried out. In particular, a new scheme for a compact, fast and simple random number generator has been demonstrated successfully achieving a random number generation rate of 1.1 Gbps. Also, during the course of this thesis, the development and engineering of a free-space QKD optical link has been initiated. This thesis makes use of novel ideas to alternatively demonstrate proof-of-concept experiments, which could then further develop into commercial products. To this end, close collaborations with world-wide leading companies in the field have been established. The Optoelectronics Group at ICFO has been involved in current European Space Agency (ESA) projects to develop a small footprint and low power consumption quantum transceiver and a high-flux entangled photon source.En l’actual societat del coneixement és important la seguretat en la transmissió de dades contra potencial intrusos, els quals sempre posen en risc la confidencialitat. Mètodes actuals per incrementar la seguretat requereixen que les dos parts que volen transmetre informació, intercanviïn o comparteixin una o més claus. Una vegada la clau ha estat identificada, la informació pot ser transferida de forma provadament segura utilitzant ”‘one-time pad”’. Per tant, la seguretat en la transmissió de la informació es basa exclusivament en la seguretat en l’intercanvi de la clau. La criptografia quàntica, o més precisament distribució de clau quàntica (QKD), garanteix absolutament la seguretat de la distribució de la clau basant-se en els principis de la física quàntica, segons la qual no és possible mesurar o reproduir un estat (p. e. la polarització o fase d’un fotó) sense ser detectat. La clau es genera a partir de les mesures de la informació codificada en estat quàntics del fotó, anomenats qubits. Per exemple, un qubit pot ser creat utilitzant propietats com la polarització o fase d’un fotó. Els objectius aconseguits d’aquesta tesis són el desenvolupament d’una nova classe d’emissors fotònics d’alta velocitat per a aplicacions en sistemes de distribució de clau quàntica, capaç¸os de produir velocitats de qubit sense precedents (100 Mbps - 1 Gbps) i transmetre’ls a través de distàncies més llunyanes que les aconseguides fins ara (> 200 Km). Més en concret el treball s’ha centrat en el desenvolupament de fonts de pulsos atenuats que poden ser usades en condicions ambientals molt extremes, com les presents a l’Espai. Per al desenvolupament d’aquestes fonts, apart del disseny òptic, importantíssim es l’enginyeria optomecànica com també la integració amb la electrònica. Un dels objectius ha estat aconseguir un molt alt nivell de integració i eficiència de potència, p. e. volums i consums de potència entre 10 i 100 vegades més petits que els típics en experiments de laboratori. Ademés, s’ha realitzat treball en altres parts relacionades amb un sistema de transmissió QKD. En particular, un nou esquema per a un generador de números aleatori compacte, ràpid i simple ha estat positivament demostrat aconseguint velocitats de generació de números aleatoris de 1:1 Gbps. També, el desenvolupament i enginyeria d’un enllaç òptic per a QKD en espai lliure ha estat iniciat durant aquesta tesis. Aquesta tesis utilitza idees novedoses per a demostrar experiments de prova de concepte, els quals poden esdevenir en productes comercials. Per a aquest fi, s’han establert col•laboracions amb empreses internacionals líders del sector. A més a més, el Grup d’Optoelectrònica de ICFO ha estat involucrat en projectes de la Agència Espacial Europea (ESA) per a desenvolupar un transceptor quàntic de tamany reduït i baix consum de potència, el qual també conté una font de fotons entrellaçts d’alt flux

On the genesis and evolution of Integrated Quantum Optics

International audienceApplications of Integrated Optics to quantum sources, detectors, interfaces, memories and linear optical quantum computing are described in this review. By their inherent compactness, efficiencies, and interconnectability, many of the demonstrated individual devices can clearly serve as building blocks for more complex quantum systems, that could also profit from the incorporation of other guided wave technologies