Nonlinearity in Single Photon Detection: Modeling and Quantum Tomography

Single Photon Detectors are integral to quantum optics and quantum information. Superconducting Nanowire based detectors exhibit new levels of performance, but have no accepted quantum optical model that is valid for multiple input photons. By performing Detector Tomography, we improve the recently proposed model [M.K. Akhlaghi and A.H. Majedi, IEEE Trans. Appl. Supercond. 19, 361 (2009)] and also investigate the manner in which these detectors respond nonlinearly to light, a valuable feature for some applications. We develop a device independent model for Single Photon Detectors that incorporates this nonlinearity

Phenolic resin aerogels: The significance of inserting an oxidative ring-fusion aromatization step at the early stages of pyrolytic carbonization, and the application of these materials in CO₂ storage and separation

Phenolic aerogels, prepared via polycondensation of phenolic monomers and formaldehyde, were converted to carbon aerogels at 800 ⁰C/Ar followed by reactive etching under flowing CO2. Previously, it was found that a lower-temperature air-oxidation of polybenzoxazine aerogels was necessary in order to obtain highly porous, isomorphic carbon aerogels with high carbonization yields. Using those findings as the point of departure, phenolic aerogels were oxidized at 240 ⁰C/air prior to carbonization. During that air-oxidation step, phenolic aerogels based on phloroglucinol (1,3,5- trihydroxybenzene) undergo fusion of their aromatic rings, yielding 6-membered heteroaromatic pyryliums with pendant phenoxide ions. The resulting carbon aerogels have higher surface areas than other carbon aerogels not subjected to aromatization. Subsequently, carbon aerogels were studied for their CO2 adsorption capacity at 273 K up to 1 bar, relevant to post-combustion separation of CO2 from N2. Carbon aerogels from phenolic resins were compared to carbon aerogels from Ishida\u27s polybenzoxazine, and from a random copolymer of polyamide, polyurea, and polyimide. The results show that phenolic resin-derived carbons (containing phenoxide) adsorb more CO2 than the latter, which contain N in addition to oxygen. Interestingly, resorcinol-formaldehyde-derived carbon aerogels uptook 14.8 ± 3.9 mmol g-1 CO2, which is much higher than the values reported in the literature for other microporous materials. Opening of closed micropores and enlargement of micropore size, resulted in a multilayer coverage of micropore walls with CO2. The high capacity for CO2 was attributed to an energy-neutral reaction between surface phenoxides and CO2 --Abstract, page iv

Stimulated quantum phase slips from weak electromagnetic radiations in superconducting nanowires

We study the rate of quantum phase slips in an ultranarrow superconducting nanowire exposed to weak electromagnetic radiations. The superconductor is in the dirty limit close to the superconducting-insulating transition, where fluxoids move in strong dissipation. We use a semiclassical approach and show that external radiation stimulates a significant enhancement in the probability of quantum phase slips. This can help to outline a new type of detector for microwave to submillimetre radiations based on stimulated quantum phase slip phenomenon.Comment: 10 pages, 9 figure

Quantum Key Distribution over Probabilistic Quantum Repeaters

A feasible route towards implementing long-distance quantum key distribution (QKD) systems relies on probabilistic schemes for entanglement distribution and swapping as proposed in the work of Duan, Lukin, Cirac, and Zoller (DLCZ) [Nature 414, 413 (2001)]. Here, we calculate the conditional throughput and fidelity of entanglement for DLCZ quantum repeaters, by accounting for the DLCZ self-purification property, in the presence of multiple excitations in the ensemble memories as well as loss and other sources of inefficiency in the channel and measurement modules. We then use our results to find the generation rate of secure key bits for QKD systems that rely on DLCZ quantum repeaters. We compare the key generation rate per logical memory employed in the two cases of with and without a repeater node. We find the cross-over distance beyond which the repeater system outperforms the non-repeater one. That provides us with the optimum inter-node distancing in quantum repeater systems. We also find the optimal excitation probability at which the QKD rate peaks. Such an optimum probability, in most regimes of interest, is insensitive to the total distance.Comment: 12 pages, 6 figures; Fig. 5(a) is replace

Karakteristik Bio-Oil Hasil Pirolisis Limbah Brem Dengan Variasi Temperatur

AbstrakPeningkatan teknologi otomotif dan jumlah kendaraan yang meningkat menyebabkan penggunaan bahan bakar fosil semakin meningkat. Maka  dibutuhkan bakan bakar alternatif sebagai pengganti atau campuran bahan bakar, untuk menjaga agar tidak terjadi krisis bahan bakar. Bio-oil merupakan salah satu produk hasil pirolisis yang dapat digunakan sebagai campuran bahan bakar solar. Bio-oil diperoleh dari limbah brem yang diproses dengan cara  pirolisis. Pirolisis merupakan proses pembakaran suatu bahan pada suhu tinggi tanpa oksigen. Pada penelitian ini menggunakan variasi temperatur 250oC, 350oC, 450oC dan 550oC dengan waktu 3 jam dan massa 500 gram. Bio-oil hasil pirolisis divariasikan dengan solar dan diuji untuk mengetahui karakteristiknya. Pengujian pertama dilakukan untuk mendapatkan volume hasil pirolisis dari tiap temperatur. Pengujian kedua menggunakan metode ASTM D 445-12 untuk mendapatkan viskositas pada suhu 40oC dan metode ASTM D 93-12 untuk mendapatkan titik nyala. Hasil pengujian menunjukkan volume tertinggi diperoleh dari temperatur 5500C menghasilkan bio-oil sebanyak 254 ml. Hasil pengujian variasi campuran 5% bio-oil dari tiap temperatur diperoleh hasil yang terbaik yaitu dari temperatur 4500C, sedangkan persentase campuran yang optimal bio-oil dengan solar diperoleh viskositas tertinggi pada campuran 15% bio-oil dengan 85% solar sebesar 4,779 mm2/s dan titik nyala tertinggi diperoleh dari campuran 5% bio-oil dengan 95% solar sebesar 61oC Kata Kunci: Bio-oil, Pirolisis, Titik nyala,  Viskosita

Quantum Optomagnetics in Graphene

Graphene can be magnetized through nonlinear response of its orbital angular momentum to an intense circularly polarized light. This optomagnetic effect can be well exemplified by the Inverse Faraday Effect (IFE) where an optically-generated DC magnetization leads to graphene's optical activity. We provide a single-particle quantum mechanical model of an IFE in graphene by solving Schr\"odinger's equation in the presence of a renormalized Hamiltonian near a Dirac point in the presence of circularly polarized monochromatic light. We derive an analytical expression for DC magnetization based on non-perturbative and dressed states of quasi-electrons where their energy spectrum is isotropically gapped by the circularly polarized light. Optical rotatory power is then computed through the gyroelectric birefringence where a measurable polarization rotation angle under moderate and intense optical radiations is predicted.Comment: 7 pages, 7 figures; general typos corrected, 1 typo in equation correct, 2 typos in notation corrected, introduction extended, original magnetization expression integrated over k, figure added for comparison, figures slightly changed and plotted in lower intensity range