Principles, fundamentals, and applications of programmable integrated photonics

[EN] Programmable integrated photonics is an emerging new paradigm that aims at designing common integrated optical hardware resource configurations, capable of implementing an unconstrained variety of functionalities by suitable programming, following a parallel but not identical path to that of integrated electronics in the past two decades of the last century. Programmable integrated photonics is raising considerable interest, as it is driven by the surge of a considerable number of new applications in the fields of telecommunications, quantum information processing, sensing, and neurophotonics, calling for flexible, reconfigurable, low-cost, compact, and low-power-consuming devices that can cooperate with integrated electronic devices to overcome the limitation expected by the demise of Moore¿s Law. Integrated photonic devices exploiting full programmability are expected to scale from application-specific photonic chips (featuring a relatively low number of functionalities) up to very complex application-agnostic complex subsystems much in the same way as field programmable gate arrays and microprocessors operate in electronics. Two main differences need to be considered. First, as opposed to integrated electronics, programmable integrated photonics will carry analog operations over the signals to be processed. Second, the scale of integration density will be several orders of magnitude smaller due to the physical limitations imposed by the wavelength ratio of electrons and light wave photons. The success of programmable integrated photonics will depend on leveraging the properties of integrated photonic devices and, in particular, on research into suitable interconnection hardware architectures that can offer a very high spatial regularity as well as the possibility of independently setting (with a very low power consumption) the interconnection state of each connecting element. Integrated multiport interferometers and waveguide meshes provide regular and periodic geometries, formed by replicating unit elements and cells, respectively. In the case of waveguide meshes, the cells can take the form of a square, hexagon, or triangle, among other configurations. Each side of the cell is formed by two integrated waveguides connected by means of a Mach¿Zehnder interferometer or a tunable directional coupler that can be operated by means of an output control signal as a crossbar switch or as a variable coupler with independent power division ratio and phase shift. In this paper, we provide the basic foundations and principles behind the construction of these complex programmable circuits. We also review some practical aspects that limit the programming and scalability of programmable integrated photonics and provide an overview of some of the most salient applications demonstrated so far.European Research Council; Conselleria d'Educació, Investigació, Cultura i Esport; Ministerio de Ciencia, Innovación y Universidades; European Cooperation in Science and Technology; Horizon 2020 Framework Programme.Pérez-López, D.; Gasulla Mestre, I.; Dasmahapatra, P.; Capmany Francoy, J. (2020). Principles, fundamentals, and applications of programmable integrated photonics. Advances in Optics and Photonics. 12(3):709-786. https://doi.org/10.1364/AOP.387155709786123Lyke, J. C., Christodoulou, C. G., Vera, G. A., & Edwards, A. H. (2015). An Introduction to Reconfigurable Systems. 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Quantum sensing has become a mature and broad field. It is generally related with the idea of using quantum resources to boost the performance of a number of practical tasks, including the radar-like detection of faint objects, the readout of information from optical memories or fragile physical systems, and the optical resolution of extremely close point-like sources. Here we first focus on the basic tools behind quantum sensing, discussing the most recent and general formulations for the problems of quantum parameter estimation and hypothesis testing. With this basic background in our hands, we then review emerging applications of quantum sensing in the photonic regime both from a theoretical and experimental point of view. Besides the state-of-the-art, we also discuss open problems and potential next steps.Comment: Review in press on Nature Photonics. This is a preliminary version to be updated after publication. Both manuscript and reference list will be expande

Atom interferometry with ultracold atoms for inertial sensing

In light pulse atom interferometry wave packets are spatially separated and recombined in a coherent manner by interacting with laser pulses. Typically, two photon transitions are used to perform Rabi oscillations between two internal or/and external states to construct atom-optical elements, like beam splitters or mirrors. The phase difference accumulated between two atomictrajectories can be used to measure quantities such as accelerations or rotations. The velocity distribution and size of the employed atomic sources can significantly limit the efficiency of the atom-light interactions and thus the performance of the interferometer. To overcome this limitation, ensembles with momentum distributions far below the recoil of a photon are used, such as collimated Bose-Einstein condensates (BEC). Exploiting the properties of a BEC opens up a wide range of possibilities for new techniques and concepts, especially for increasing the sensitivity of measurements performed in small volumes. This work presents some of these novelties. The technique of an innovative (re-)launch mechanism helps to effectively increase the available interferometry time in compact gravimeter setups. A symmetric large momentum transfer in the form of a twin-lattice enables the enclosure of large space-time areas suitable for rotation measurements with high sensitivities. The exploitation of a BEC in combination with momentum transfer by double Bragg diffraction contributed to the development of a new concept. Using a single BEC, it is possible to create two simultaneous interferometers, which are employed to differentiate between rotations and accelerations. Its symmetry allows this geometry to be extended to form the basis of a six-axis quantum inertial measurement unit. Last but not least, the (re-)launch in combination with the symmetric splitting also provides the basis for a multi-loop atom interferometer. With this concept, an area can be enclosed that offers unique scalability for rotational sensors. Each atom interferometer is affected by the quality of its interrogating light fields. Therefore specific detrimental effects are pointed out in this work and possible mitigation strategies are presented subsequently. One way to reduce the susceptibility of light beams to distortions at apertures is to change their profile from the commonly used Gaussian profile to a more locally limited intensity distribution. For this purpose, the application of flat-top beam profiles is investigated. This brings the added benefit of a uniform power distribution, which helps to increase the beam area in which the ensemble of atoms can be manipulated with the same properties. Imperfections can also lead to position-dependent dipole forces that have a parasitic effect on the output of an interferometer. Especially for large momentum transfer techniques this has proven to be a limitation which can necessitate a compensation mechanism. To this end, a laser system is constructed that achieves the required high laser powers and includes additional frequency components. Many of the interferometry methods and concepts introduced are well suited for compact or transportable systems. For this purpose, a laser system based on telecommunication fiber components is presented, which represents an all-in-one solution for the generation, preparation and subsequent beam splitting of ultracold atoms. Inspired by all of the above, the future vision of a quantum sensor for inertial navigation applications is discussed

Programmable multifunctional integrated nanophotonics

[EN] Programmable multifunctional integrated nanophotonics (PMIN) is a new paradigm that aims at designing common integrated optical hardware configurations, which by suitable programming can implement a variety of functionalities that can be elaborated for basic or more complex operations in many application fields. The interest in PMIN is driven by the surge of a considerable number of emerging applications in the fields of telecommunications, quantum information processing, sensing and neurophotonics that will be calling for flexible, reconfigurable, low-cost, compact and low-power-consuming devices, much in the same way as how field programmable gate array (FPGA) devices operate in electronics. The success of PMIN relies on the research into suitable interconnection hardware architectures that can offer a very high spatial regularity as well as the possibility of independently setting (with a very low power consumption) the interconnection state of each connecting element. Integrated waveguide meshes provide regular and periodic geometries, formed by replicating a unit cell, which can take the form of a square, hexagon or triangle, among other configurations. Each side of the cell is formed by two integrated waveguides connected by means of a Mach-Zehnder interferometer (MZI) or a tunable directional coupler that can be operated by means of an output control signal as a crossbar switch or as a variable coupler with independent power division ratio and phase shift. In this paper, we review the recent advances reported in the field of PMIN and, especially, in those based on integrated photonic waveguide meshes, both from the theoretical as well as from the experimental point of view. We pay special attention to outlining the design principles, material platforms, synthesis algorithms and practical constraints of these structures and discuss their applicability to different fields.Pérez-López, D.; Gasulla Mestre, I.; Capmany Francoy, J. (2018). Programmable multifunctional integrated nanophotonics. Nanophotonics (Online). 7(8):1351-1371. https://doi.org/10.1515/nanoph-2018-0051135113717

Processes and diagrams: an integrated and multidisciplinary approach for the education of quantum information science

The background to this thesis is the παιδέια , the education. To educate is a dialecti- cal process that moves from an abstract line of thought, through scientifically designed techniques, into concrete action; and vice versa. We believe that educating today means enabling teachers first and their students second, to be able to read and interpret the complexity of phenomena, to teach them a model for observing this complexity, describing it, analyzing it and, finally, making it their own. In this thesis, we attempt to make sense of these needs by describing an integrated and multidisciplinary pathway, whose diagram- matic language pushes towards the search for a universal approach to science. An initial educational contribution is thus made to the understanding of the dialectic between disciplines: theoretical physics, experimental physics, computer science, mathe- matics and mathematical logic are presented in their mutual influence, in an attempt to clarify the informational viewpoint on modern physics. The search for this dialectic for educational purposes is, in our opinion, the most significant contribution of the present work. To address this issue, we sought to build a community of practice on the topics of the second quantum revolution. Guided by the Model of Educational Reconstruction (MER), we built a first course for teacher professional development that would enable teachers to be introduced to quantum computation and quantum communication. The emergence and development of quantum technologies provides the impetus for a deep conceptual change: “a paradigm shift from quantum theory as a theory of microscopic matter to quantum theory as a framework for technological applications and information processing”. This shift is supported, theoretically, by the informational interpretation of the postulates of quantum mechanics: preparation, transformation and measurement are reinterpreted com- putationally as the encoding, processing and decoding of information; and vice versa. In this interpretation, what changes between classical and quantum theory? From a logical point of view, the transition from bit to qubit, from a physical point of view, the laws of composition of systems. We therefore present monoidal categories as a natural theoretical framework for the description of physical systems and processes for quantum and non- quantum computation and communication, demonstrating how this language is suitable for an integrated and multidisciplinary approach. The cultural impact of the proposal, the fruitful interaction between researchers in physics education and those in the area of theoretical research, and the passion of some teachers made it possible to start a collaboration to build an educational sequence for students. The result of this collaboration is a teaching leaning sequence on quantum technologies for students, led by the MER and based on inquiry-based learning and the modelling- based teaching. Supported by these methodological frameworks, we produced lessons and worksheets all along the way that had the dual task of supporting teachers’ work and students’ learning. They also made it possible to experimentally verify the positive and critical effects of the proposal. The instructional materials constructed, the data analysis and the constant monitoring with the teachers involved, determined the development of a second course for teacher professional development, inspired by the first, based entirely on research. We hope that this attempt at integrated and multidisciplinary approach for the education of quantum information science, based on the concept of compositionality and the diagrammatic model, can be increased and provide inspiration for future educational paths in other disciplines as well

Design of Ultrafast All-Optical Pseudo Binary Random Sequence Generator, 4-bit Multiplier and Divider using 2 x 2 Silicon Micro-ring Resonators

All-optical devices are essential for next generation ultrafast, ultralow-power and ultrahigh bandwidth information processing systems. Silicon microring resonators (SiMRR) provide a versatile platform for all-optical switching and CMOS-compatible computing, with added advantages of high Q-factor, tunability, compactness, cascadability and scalability. A detailed theoretical analysis of ultrafast all-optical switching 2 x 2 SiMRRs has been carried out incorporating the effects of two photon absorption induced free-carrier injection and thermo optic effect. The results have been used to design simple and compact all-optical 3-bit and 4-bit pseudo-random binary sequence generators and the first reported designs of all-optical 4 x 4-bit multiplier and divider. The designs have been optimized for low-power, ultrafast operation with high modulation depth, enabling logic operations at 45 Gbps.Comment: 13 pages, 4 figures. Submitted at Journal (Optik) for publicatio

Adiabatic technique based low power synchronous counter design

The performance of integrated circuits is evaluated by their design architecture, which ensures high reliability and optimizes energy. The majority of the system-level architectures consist of sequential circuits. Counters are fundamental blocks in numerous very large-scale integration (VLSI) applications. The T-flip-flop is an important block in synchronous counters, and its high-power consumption impacts the overall effectiveness of the system. This paper calculates the power dissipation (PD), power delay product (PDP), and latency of the presented T flip-flop. To create a 2-bit synchronous counter based on the novel T flip-flops, a performance matrix such as PD, latency, and PDP is analyzed. The analysis is carried out at 100 and 10 MHz frequencies with varying temperatures and operating voltages. It is observed that the presented counter design has a lesser power requirement and PDP compared to the existing counter architectures. The proposed T-flip-flop design at the 45 nm technology node shows an improvement of 30%, 76%, and 85% in latency, PD, and PDP respectively to the 180 nm node at 10 MHz frequency. Similarly, the proposed counter at the 45 nm technology node shows 96% and 97% improvement in power dissipation, delay, and PDP respectively compared to the 180 nm at 10 MHz frequency