Computador quântico em silício: há luz no fim do tunel?
Arquiteturas de computadores quânticos baseadas em silício vêm atraindo atenção
devido às suas perspectivas de escalabilidade, integraçao e utilização dos recursos
já instalados associados à tecnologia do Si. Spins eletrônicos de doadores rasos
(por exemplo fósforo) em Si são candidatos ideais para bits quânticos (qubits) nestas
propostas, devido aos tempos de coerência relativamente longos dos spins em matrizes
de Si. Para estes qubits de spin, a manipulação da carga do elétron do doador por eletrodos
externos é um ingrediente importante para controle e leitura das operações de um-qubit,
enquanto que as portas de troca são frequentemente invocadas para as operações de dois-qubits.
Mais recentemente, qubits de carga baseados no tunelamento do elétron no íon molecular P+2 em
Si foram também propostos. Discutimos aqui as operações elementares envolvidas na computação
quântica baseada em doadores rasos em Si, levando em consideração as peculiaridades do Si.
Mostramos que a interferência quântica entre estados do cristal perfeito devida à presença do
doador não afeta significativamente as operações envolvendo um único doador, mas leva a oscilações
no acoplamento de troca e no acoplamento via tunelamento quando a posição relativa do par é modificada
na escala de distâncias do parâmetro de rede. Nossos estudos ilustram as potencialidades bem
como os enormes desafios envolvidos na implementação de qubits de spin e carga em Si.
Esta palestra acontecerá no dia 22 de Fevereiro de 2018
Horário de início: 14h30
Horário de término: 16h00
Sobre a professora
Belita Koiller is a Professor of Physics at the Instituto de Fisica, Universidade Federal do Rio de Janeiro (UFRJ) , Brazil. Belita Koiller received her PhD in Physics in 1975, at University of California – Berkeley, where she worked in theoretical Condensed Matter Physics under the supervision of Leo Falicov. She returned to Brazil upon completing her Ph.D., starting her professional activities at the Physics Department of the Pontificia Universidade Católica do Rio de Janeiro (PUC/RJ) where, in 1992, she was appointed Full Professor. She left PUC/RJ in 1994 to become Full Professor of the Physics Institute at Universidade Federal do Rio de Janeiro (UFRJ), where she remains to the present.
Both at PUC/RJ and at UFRJ, she is active in teaching, research, academic supervision of students and post-docs, administration and scientific community support. At PUC/RJ, she was Chair of the Physics Department in 1983/1984. She was elected three times as a General Councilor of the Brazilian Physical Society, for the 4-year periods starting in 1993, 1999 and 2005. She participated in, and also organized several national and international scientific events. In 2008 she chaired the 29th International Conference on the Physics of Semiconductors, held in Rio de Janeiro and sponsored by IUPAP.
Belita Koiller is a Condensed Matter Theorist, and has contributed to the understanding of the properties of disordered solids, particularly disordered chains and semiconductor alloys. More recently, she has been interested in quantum control of individual electrons spin and charge in semiconductors, aiming at applications in quantum information and quantum computing.
She has had long-term past and present collaborations with several scientific institutions in Brazil and abroad. Specifically in the United States, with UC Berkeley, Johns Hopkins University and the Condensed Matter Theory Center at the University of Maryland. She promotes visits to Brazilian institutions by distinguished international scientists. She was in the Editorial Board of Applied Physics Letters and Journal of Applied Physics for three years, starting 2006.
Belita Koiller received a Guggenheim Fellowship in 1982, and she has been a research fellow of the Brazilian National Research Council since 1985. In 1995 she was the first woman to be elected a full member to the Brazilian Academy of Sciences in the Physical Sciences division. She was decorated Comendador da Ordem Nacional do Mérito Científico by the Presidency of Brazil in 2002. Belita Koiller is a LOréal UNESCO 2005 Laureate for Women in Physical Sciences (Latin America).
She served for 3 years, starting in 1994, as a member of the ICSU Committee on Capacity Building in Science. Since 2005 she has been a member of the Executive Committee of the International Human Rights Network of Academies and Scholarly Societies, which assists colleagues (scientists and scholars) who suffer repression for having exercised their rights in accordance with the Universal Declaration of Human Rights. In 2008 she became a member of the IUPAP Commission on Semiconductors. She was elected International Councillor of the American Physical Society for the term 2010/2011 and is Associate Editor of Journal of Applied Physics since 2010. (Retirado da página pessoal do pesquisador)