Quantum walks: a comprehensive review

Quantum walks, the quantum mechanical counterpart of classical random walks, is an advanced tool for building quantum algorithms that has been recently shown to constitute a universal model of quantum computation. Quantum walks is now a solid field of research of quantum computation full of exciting open problems for physicists, computer scientists, mathematicians and engineers. In this paper we review theoretical advances on the foundations of both discrete- and continuous-time quantum walks, together with the role that randomness plays in quantum walks, the connections between the mathematical models of coined discrete quantum walks and continuous quantum walks, the quantumness of quantum walks, a summary of papers published on discrete quantum walks and entanglement as well as a succinct review of experimental proposals and realizations of discrete-time quantum walks. Furthermore, we have reviewed several algorithms based on both discrete- and continuous-time quantum walks as well as a most important result: the computational universality of both continuous- and discrete- time quantum walks.Comment: Paper accepted for publication in Quantum Information Processing Journa

Comparison of the timed inspiratory effort index with the T-piece trial as a decision-making tool for extubation: a randomized controlled non-inferiority trial

The “timed inspiratory effort” (TIE) index, a new predictor of weaning outcome, normalizes the maximal inspiratory pressure with the time required to reach this value up to 60 s, incorporating the time domain into the assessment of inspiratory muscle function. The objective of this study was to determine whether the TIE predicts successful extubation at a similar rate as the T-piece trial with less time required. A non-inferiority randomized controlled trial was performed with ICU subjects eligible for weaning. The participants were allocated to the TIE or the T-piece groups. The primary outcome was successful weaning, and the main secondary outcome was ICU mortality. Eighty participants of each group were included in the final analysis. Time from the start of a successful test to effective extubation was significantly lower in the TIE group than in the T-piece group, 15 (10 to 24) vs 55 (40 to 75) min, P<0.001. In the Kaplan-Meier analysis, no significant differences were found in successful weaning (79.5 vs 82.5%, P=0.268) or survival rate (62.9 vs 53.8%, P=0.210) between the TIE and T-piece groups at the 30th day. In this preliminary study, the TIE index was not inferior to the T-piece trial as a decision-making tool for extubation and allowed a reduction in the decision time

Exciton G Factor Of Type-ii Inp Gaas Single Quantum Dots

We investigated the magneto-optical properties of type-II InP GaAs quantum dots using single-dot spectroscopy. The emission energy from individual dots presents a quadratic diamagnetic shift and a linear Zeeman splitting as a function of magnetic fields up to 10 T, as previously observed for type-I systems. We analyzed the in-plane localization of the carriers using the diamagnetic shift results. The values for the exciton g factor obtained for a large number of a InP GaAs dots are mainly constant, independent of the emission energy, and therefore, of the quantum dot dimensions. The result is attributed to the weak confinement of the holes in type-II InP GaAs quantum dots. © 2006 The American Physical Society.733Toda, Y., Shinomori, S., Suzuki, K., Arakawa, Y., (1998) Appl. Phys. Lett., 73, p. 517. , APPLAB 0003-6951 10.1063/1.121919Bayer, M., Kuther, A., Schäfer, F., Reithmaier, J.P., Forchel, A., (1999) Phys. Rev. B, 60, p. 8481. , PRBMDO. 0163-1829. 10.1103/PhysRevB.60.R8481Sugisaki, M., Ren, H.-W., Nishi, K., Sugou, S., Okuno, T., Masumoto, Y., (1998) Physica B, 256-258, p. 169. , PHYBE3 0921-4526Kotlyar, R., Reinecke, T.L., Bayer, M., Forchel, A., (2001) Phys. Rev. B, 63, p. 085310. , PRBMDO 0163-1829 10.1103/PhysRevB.63.085310Ribeiro, E., Govorov, A.O., Carvalho Jr., W., Medeiros-Ribeiro, G., (2004) Phys. Rev. Lett., 92, p. 126402. , PRLTAO 0031-9007 10.1103/PhysRevLett.92.126402Janssens, K.L., Partoens, B., Peeters, F.M., (2002) Phys. Rev. B, 66, p. 075314. , PRBMDO 0163-1829 10.1103/PhysRevB.66.075314Kalameitsev, A.B., Kovalev, V.M., Govorov, A.O., (1989) JETP Lett., 68, p. 669. , JTPLA2 0021-3640 10.1134/1.567926Sugisaki, M., Ren, H.W., Nair, S.V., Nishi, K., Masumoto, Y., (2002) Phys. Rev. B, 66, p. 235309. , PRBMDO 0163-1829 10.1103/PhysRevB.66.235309Godoy, M.P.F., Nakaema, M.K.K., Iikawa, F., Carvalho Jr., W., Ribeiro, E., Gobby, A.L., (2004) Rev. Sci. Instrum., 75, p. 1947. , RSINAK 0034-6748 10.1063/1.1753090Walck, S.N., Reinecke, T.L., (1998) Phys. Rev. B, 57, p. 9088. , PRBMDO 0163-1829 10.1103/PhysRevB.57.9088Laheld, U.E.H., Pedersen, F.B., Hemmer, P.C., (1993) Phys. Rev. B, 48, p. 4659. , PRBMDO 0163-1829 10.1103/PhysRevB.48.4659Bastard, G., Mendez, E.E., Chang, L.L., Esaki, L., (1982) Phys. Rev. B, 26, p. 1974. , PRBMDO 0163-1829 10.1103/PhysRevB.26.1974Nakaoka, T., Saito, T., Tatebayashi, J., Arakawa, Y., (2004) Phys. Rev. B, 70, p. 235337. , PRBMDO 0163-1829 10.1103/PhysRevB.70.235337Yugova, I.A., Ya. Gerlovin, I., Davydov, V.G., Ignatiev, I.V., Kozin, I.E., Ren, H.W., Sugisaki, M., Masumoto, Y., (2002) Phys. Rev. B, 66, p. 235309. , PRBMDO 0163-1829 10.1103/PhysRevB.66.235309Willmann, F., Suga, S., Dreybrodt, W., Cho, K., (1974) Solid State Commun., 14, p. 783. , SSCOA4 0038-1098Landi, S.M., Tribuzy, C.V.B., Souza, P.L., Butendeich, R., Bittencourt, A.C., Marques, G.E., (2003) Phys. Rev. B, 67, p. 085304. , PRBMDO 0163-1829 10.1103/PhysRevB.67.08530

Carrier Dynamics In Stacked Inpgaas Quantum Dots

We investigated two stacked layers of InPGaAs type-II quantum dots by transmission electron microscopy and optical spectroscopy. The results reveal that InP quantum dots formed in two quantum dot layers are more uniform than those from a single layer structure. The thermal activation energies as well as the photoluminescence decays are rather independent of the separation between quantum dot layers and the presence of the second layer. The quantum dot optical emission persists for thermal activation energy larger than the calculated exciton binding energy. The photoluminescence decay is relatively fast for type-II alignment. © 2007 American Institute of Physics.9112Goldstein, L., Glas, F., Marzin, M.J.Y., Charasse, N., Le Roux, G., (1985) Appl. Phys. Lett., 47, p. 1099Xie, Q., Madhkar, A., Chen, P., Kobayashi, N., (1995) Phys. Rev. Lett., 75, p. 2542Ledentsov, N.N., Shchukin, V.A., Grundmann, M., Kirstaedter, N., Böhmer, J., Schmidt, O., Bimberg, D., Heydenreich, J., (1996) Phys. Rev. B, 54, p. 8743Solomon, G.S., Trezza, J.A., Marchall, A.F., Harris Jr., J.S., (1996) Phys. Rev. Lett., 76, p. 952Sugiyama, Y., Nakata, Y., Futatsugi, T., Sugawara, M., Awano, Y., Yokoyama, N., (1996) Jpn. J. Appl. Phys., Part 2, 36, p. 158Schmidt, O.G., Kienzie, O., Hao, Y., Eberl, K., (1999) Appl. Phys. Lett., 74, p. 1272Chang, W.-H., Chen, W.-Y., Chou, A.-T., Hsu, T.-M., Chen, P.-S., Pei, Z., Lai, L.-S., (2003) J. Appl. Phys., 93, p. 4999Susuki, K., Hogg, R.A., Arakawa, Y., (1999) J. Appl. Phys., 85, p. 8349Sun, C.-K., Wang, G., Bowers, J.E., Brar, B., Blank, H.-R., Kroemer, H., Pilkuhn, M.H., (1996) Appl. Phys. Lett., 68, p. 1543Hatami, F., Grundmann, M., Ledentsov, N.N., Heinrichsdorff, F., Heitz, R., Böhrer, J., Bimberg, D., Alferov Zh., I., (1998) Phys. Rev. B, 57, p. 4635De Godoy, M.P.F., Gomes, P.F., Nakaema, M.K.K., Iikawa, F., Brasil, M.J.S.P., Caetano, R.A., Madureira, J.R., Bittencourt, A.C.R., (2006) Phys. Rev. B, 73, p. 033309Wang, B., Chua, S.-J., (2001) Appl. Phys. Lett., 78, p. 628Nakaema, M.K.K., Iikawa, F., Brasil, M.J.S.P., Ribeiro, E., Medeiros-Ribeiro, G., Carvalho Jr., W., Maialle, M.Z., Degani, M.H., (2002) Appl. Phys. Lett., 81, p. 2743Zundel, M.K., Specht, P., Eberl, K., Jin-Phillipp, N.Y., Phillipp, F., (1997) Appl. Phys. Lett., 71, p. 2972Sanguinetti, S., Henini, M., Grassi Alessi, M., Capizzi, M., Frigeri, P., Franchi, S., (1999) Phys. Rev. B, 60, p. 827

Efeito da endogamia na produção de sementes de pepino caipira

Este trabalho teve por objetivo verificar se existe depressão por endogamia para produção de sementes com sucessivas gerações de autofecundações em uma população de pepino caipira, obtida a partir da geração F2 do cruzamento (Safira x Hatem) x Safira. O delineamento experimental utilizado foi em blocos ao acaso, com seis tratamentos (diferentes gerações de autofecundação - S0 a S5), quatro repetições e cinco plantas por parcela. Não houve diferença estatística para todas as características avaliadas (número de frutos por planta, massa de sementes por planta, massa de sementes por fruto, número de sementes por planta, número de sementes por fruto, massa de 100 sementes, teste-padrão de germinação, primeira contagem do teste-padrão de germinação e índice de velocidade de germinação), observando-se que a endogamia não afetou a produção e qualidade das sementes nessa população.The objective of this work was to evaluate the inbreeding depression after successive generations of self-pollination in a cucumber population, generation F2 from the cross (Safira x Hatem) x Safira. Experimental design was randomized blocks with six treatments (different generations of self-pollination - S0 to S5), four replicates and five plants per plot. There was no statistical difference among all evauated characteristics (fruit number per plant, number and weight of seeds per plant and per fruit, germination test, first count of germinated seeds, index of germination a and weight of 100 seeds), showing that inbreeding did not affect seed production and quality in this population