Annual Report 2009–10

47 研 究 Research 社會科學院 Faculty of Social Science 理學院 Faculty of Science 以最優動力學解耦保存固體中量子自旋的相干性 Preservation of Spin Coherence in Solids by Optimal Dynamical Decoupling 物理系劉仁保教授與中國科學技術大學的研究人員合作，提高了量子在室溫固體中自 旋可保持相干狀態的時間，大大提升了穩定性。現實環境對量子系統發生耦合干擾，使 量子相干性隨時間衰減，稱為量子的消相干效應，一直是量子電腦發展的障礙。理論 上，透過最優動力學解耦可以減低量子的消相干性，然而實際上尚未驗證。 劉教授的研究團隊透過最優動力學解耦，以微波脈衝把一種名為丙二酸的材料內的電 子自旋相干時間，在絕對溫度五十度至室溫中延長。該研究為在室溫中固體量子自旋 相干的發展奠定了基礎，已於國際權威學術期刊《自然》發表。 Prof. Liu Renbao (Department of Physics), in collaboration with researchers from the University of Science and Technology of China, demonstrated how electron spin coherence could be preserved in solids at room temperature. Spin decoherence, the tendency of electrons to couple to their noisy environment, has long been an obstacle to the development of quantum computing. It had been demonstrated theoretically that spin decoherence could be combated by dynamical decoupling, which uses stroboscopic spin flips to give an average coupling to an environment that is effectively zero, but this technique had yet to be realised experimentally. Professor Liu and his collaborators used pulsed electron paramagnetic resonance to demonstrate experimentally optimal dynamical decoupling for preserving electron spin coherence in irradiated malonic acid crystals at temperatures from 50K to room temperature. His results, which lay the foundation for quantum coherence of spins in solids at room temperature, were published in the prestigious scientific journal Nature . 傳播與強迫遷移 Communication and Forced Migration 尋求庇護人士常在全球化討論中被邊緣化，新聞與傳播學院賽詩雅教授的研究，目的 是分析全球化、傳播、空間及強迫遷移的相互關係，建立一套理論來深入探討尋求庇 護者的人口流動性，提出獨特見解。研究獲優配研究金資助。 賽詩雅教授的研究數據主要源於德國，指出尋求庇護人士的社會流動及人身活動能力 處處受限：一、他們被安置到收容中心等指定地區生活；二、他們被媒體輿論為威脅社 會、文化及經濟發展的一群；三、他們在接觸主流語言社區及新式通訊技術時，受到諸 多制肘。研究於《傳播學刊》刊登，把這課題提升至學術研究的層次，並使在香港尋求 庇護者更受關注。 Prof. Saskia Witteborn (School of Journalism and Communication) has been conducting an important GRF project on the topic ‘Communication and Forced Migration: Seeking Asylum in a Globalized World’. Her project seeks to theorize the interrelations between globalization, communication, space and forced migration and to provide insights into the mobility of asylum seekers, a group often overlooked in discussions of globalization. Professor Witteborn’s data, which have been mainly collected in Germany, demonstrate that asylum seekers are restricted in social and physical mobility by (1) being assigned to designated living areas like asylum shelters, (2) media discourses that construct the forced migrant as a location of risk to the social, cultural, and economic prosperity of the nation, and (3) limited access to the majority language community and new communication technologies. Professor Witteborn has published an article on forced migration in the prestigious Journal of Communication . Her studies have helped to raise the academic profile of this issue, and have also drawn attention to the plight of asylum seekers in Hong Kong.