{"id":63,"date":"2013-02-16T13:46:27","date_gmt":"2013-02-16T13:46:27","guid":{"rendered":"http:\/\/blog.ufes.br\/luciofassarella\/?p=63"},"modified":"2017-05-22T17:54:00","modified_gmt":"2017-05-22T17:54:00","slug":"controle-de-sistemas-quanticos-o-caminho-para-a-computacao-quantica","status":"publish","type":"post","link":"https:\/\/blog.ufes.br\/luciofassarella\/2013\/02\/16\/controle-de-sistemas-quanticos-o-caminho-para-a-computacao-quantica\/","title":{"rendered":"Controle de Sistemas Qu\u00e2nticos: o caminho para a computa\u00e7\u00e3o qu\u00e2ntica?"},"content":{"rendered":"

O controle de sistemas qu\u00e2nticos (ou controle qu\u00e2ntico)<\/strong> consiste na manipula\u00e7\u00e3o desses sistemas pela a\u00e7\u00e3o de campos e\/ou intera\u00e7\u00e3o com outros sistemas qu\u00e2nticos visando determinar\/delimitar deliberadamente seu comportamento. Tipicamente, o problema consiste em conduzir um dado sistema qu\u00e2ntico de um estado inicial para um estado \u0085nal prestabelecido:<\/p>\n

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“The systems-theoretic concept of controllability is elaborated for quantum-mechanical systems, su\u00a2 cient conditions being sought under which the state vector\u00a0\u00a0 can be guided in time to a chosen point in the Hilbert space H of the system. The Schr\u00f6dinger equation for a quantum object in\u0087uenced by adjustable external \u0085elds provides a state-evolution equation which is linear in\u00a0\u00a0 and linear in the external controls (thus a bilinear control system).\u0094”
\nHuang & Tarn & Clark [1]<\/p>\n<\/blockquote>\n

Especialistas em teoria da informa\u00e7\u00e3o e computa\u00e7\u00e3o qu\u00e2ntica consideram o controle qu\u00e2ntico essencial para o desenvolvimento de tecnologias de informa\u00e7\u00e3o e computa\u00e7\u00e3o qu\u00e2ntica:<\/p>\n

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“\u0093The universality of any quantum computing element can be understood and veri\u0085ed via a precise mathematical criterion which tests for the controllability of an associated quantum control system. This relation between quantum computing and quantum control is deeper in that tools of coherent control of quantum dynamics may be used to arrive at speci\u0085c designs for quantum computing devices\u0094.”<\/p>\n

Ramakrishna & Rabitz [2]<\/p>\n

\u0093”The development of general principles of quantum control theory is an essential task for a future quantum technology.\u0094”<\/p>\n

Dowling & Milburn [3]<\/p>\n

\u0093The integration of quantum physics and engineering methodologies has become one of the most interesting and potentially transformative programs relating to emergent technologies.”\u0094<\/p>\n

Gough & Belavkin [4].<\/p>\n<\/blockquote>\n

A relev\u00e2ncia da teoria do controle de sistemas qu\u00e2nticos<\/strong> pode ser ilustrada pelo Pr\u00eamio Nobel de F\u00edsica do ano 2012. O pr\u00eamio foi concedido a Serge Haroche e David J. Wineland pelo desenvolvimento de t\u00e9cnicas experimentais para mensura\u00e7\u00e3o e manipula\u00e7\u00e3o de sistemas qu\u00e2nticos individuais (especi\u0085ficamente, \u00edons em armadilhas e f\u00f3tons em cavidades) que preservam propriedades qu\u00e2nticas sui generis<\/em>, tais como pureza e emaranhamento. Tais t\u00e9cnicas est\u00e3o baseadas no controle de sistemas qu\u00e2nticos e s\u00e3o especialmente not\u00e1veis porque tornam poss\u00edvel investigar em laborat\u00f3rio fen\u00f4menos qu\u00e2nticos bastante sutis e intrigantes, tais como o chamado Paradoxo do Gato de Schr\u00f6dinger. O artigo da Real Academia Su\u00ed\u00e7a de Ci\u00eancias alusivo \u00e0 premia\u00e7\u00e3o salienta as implica\u00e7\u00f5es te\u00f3ricas e tecnol\u00f3gicas desse trabalho, destacadamente na \u00e1rea da computa\u00e7\u00e3o qu\u00e2ntica:<\/p>\n

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“David Wineland and Serge Haroche have invented and implemented new technologies and methods allowing the measurement and control of individual quantum systems with high accuracy. Their work has enabled the investigation of decoherence through measurements of the evolution of Schr\u00f6dinger\u0092s cat like states, the \u0085rst steps towards the quantum computer, and the development of extremely accurate optical clocks.\u0094” Link<\/a>! (14\/02\/2013)<\/p>\n<\/blockquote>\n

A teoria do controle qu\u00e2ntico \u00e9 uma \u00e1rea em franco desenvolvimento, com amplas perspectivas de avan\u00e7os te\u00f3ricos e em t\u00e9cnicas experimentais:<\/p>\n

“To some extent this an ongoing program [on quantum control] is still speculative as the current state of physical quantum control is strikingly dissimilar to its classical counterpart: one major anomaly is the fact that modern classical control deals almost exclusively with feedback system, whereas this features in only a relatively small fraction of theoretical work on quantum control, and even rarer in experiment. However, we would argue that this is only a temporary situation, and that the future development of the \u0085field will see the powerful insights of classical control theory emerging again in the quantum setting.\u0094”
\nGough & Belavkin [5, p.1399].<\/p><\/blockquote>\n

Pesquisadores brasileiros<\/strong> t\u00eam estudado o controle de sistemas qu\u00e2nticos, alguns com destaque:<\/p>\n