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- [1] Quantum computation capability verification protocol for noisy intermediate-scale quantum devices with the dihedral coset problem[J]. PHYSICAL REVIEW A, 2022, 106 (01)论文数: 引用数: h-index:机构:Wen, Weiqiang论文数: 0 引用数: 0 h-index: 0机构: Inst Polytech Paris, Telecom Paris, LTCL, Paris, France Technol Innovat Inst, Abu Dhabi, U Arab Emirates
- [2] Noisy intermediate-scale quantum algorithms[J]. REVIEWS OF MODERN PHYSICS, 2022, 94 (01)Bharti, Kishor论文数: 0 引用数: 0 h-index: 0机构: Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, Singapore Univ Maryland, NIST, Joint Ctr Quantum Informat & Comp Sci, College Pk, MD 20742 USA Univ Maryland, NIST, Joint Quantum Inst, College Pk, MD 20742 USA Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, SingaporeCervera-Lierta, Alba论文数: 0 引用数: 0 h-index: 0机构: Univ Toronto, Dept Comp Sci, Toronto, ON M5S 2E4, Canada Univ Toronto, Dept Chem, Chem Phys Theory Grp, Toronto, ON M5G 1Z8, Canada Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, Singapore论文数: 引用数: h-index:机构:Haug, Tobias论文数: 0 引用数: 0 h-index: 0机构: Imperial Coll London, Blackett Lab, QOLS, London SW7 2AZ, England Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, Singapore论文数: 引用数: h-index:机构:论文数: 引用数: h-index:机构:Degroote, Matthias论文数: 0 引用数: 0 h-index: 0机构: Univ Toronto, Dept Comp Sci, Toronto, ON M5S 2E4, Canada Univ Toronto, Dept Chem, Chem Phys Theory Grp, Toronto, ON M5G 1Z8, Canada Boehringer Ingelheim GmbH & Co KG, Quantum Lab, D-55218 Ingelheim, Germany Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, SingaporeHeimonen, Hermanni论文数: 0 引用数: 0 h-index: 0机构: Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, Singapore Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, SingaporeKottmann, Jakob S.论文数: 0 引用数: 0 h-index: 0机构: Univ Toronto, Dept Comp Sci, Toronto, ON M5S 2E4, Canada Univ Toronto, Dept Chem, Chem Phys Theory Grp, Toronto, ON M5G 1Z8, Canada Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, SingaporeMenke, Tim论文数: 0 引用数: 0 h-index: 0机构: Harvard Univ, Dept Phys, Cambridge, MA 02138 USA MIT, Res Lab Elect, 77 Massachusetts Ave, Cambridge, MA 02139 USA MIT, Dept Phys, Cambridge, MA 02139 USA Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, SingaporeMok, Wai-Keong论文数: 0 引用数: 0 h-index: 0机构: Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, Singapore Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, SingaporeSim, Sukin论文数: 0 引用数: 0 h-index: 0机构: Harvard Univ, Dept Chem & Chem Biol, Cambridge, MA 02138 USA Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, SingaporeKwek, Leong-Chuan论文数: 0 引用数: 0 h-index: 0机构: Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, Singapore CNRS UNS NUS NTU Int Joint Res Unit UMI 3654, MajuLab, Singapore, Singapore Nanyang Technol Univ, Natl Inst Educ, Singapore 637616, Singapore Nanyang Technol Univ, Inst Adv Studies, Singapore 637616, Singapore Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, SingaporeAspuru-Guzik, Alan论文数: 0 引用数: 0 h-index: 0机构: Univ Toronto, Dept Comp Sci, Toronto, ON M5S 2E4, Canada Univ Toronto, Dept Chem, Chem Phys Theory Grp, Toronto, ON M5G 1Z8, Canada Vector Inst Artificial Intelligence, Toronto, ON M5S 1M1, Canada Canadian Inst Forthat Adv Res, Toronto, ON M5G 1Z8, Canada Natl Univ Singapore, Ctr Quantum Technol, Singapore 117543, Singapore
- [3] Noisy intermediate-scale quantum computers[J]. FRONTIERS OF PHYSICS, 2023, 18 (02)Cheng, Bin论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaDeng, Xiu-Hao论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaGu, Xiu论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China论文数: 引用数: h-index:机构:Hu, Guangchong论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaHuang, Peihao论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaLi, Jun论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaLin, Ben-Chuan论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaLu, Dawei论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Dept Phys, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaLu, Yao论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaQiu, Chudan论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Dept Phys, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaWang, Hui论文数: 0 引用数: 0 h-index: 0机构: Univ Sci & Technol China, Hefei Natl Res Ctr Phys Sci Microscale, Hefei 230026, Peoples R China Univ Sci & Technol China, Sch Phys Sci, Hefei 230026, Peoples R China Univ Sci & Technol China, CAS Ctr Excellence Quantum Informat & Quantum Phys, Hefei 230026, Peoples R China Univ Sci & Technol China, Hefei Natl Lab, Hefei 230088, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaXin, Tao论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China论文数: 引用数: h-index:机构:Yung, Man-Hong论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaZeng, Junkai论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaZhang, Song论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaZhong, Youpeng论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaPeng, Xinhua论文数: 0 引用数: 0 h-index: 0机构: Univ Sci & Technol China, Sch Phys Sci, Hefei 230026, Peoples R China Univ Sci & Technol China, CAS Ctr Excellence Quantum Informat & Quantum Phys, Hefei 230026, Peoples R China Univ Sci & Technol China, Hefei Natl Lab, Hefei 230088, Peoples R China Univ Sci & Technol China, CAS Key Lab Microscale Magnet Resonance, Hefei 230026, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaNori, Franco论文数: 0 引用数: 0 h-index: 0机构: RIKEN, Quantum Comp Ctr, Wako, Saitama 3510198, Japan Univ Michigan, Phys Dept, Ann Arbor, MI 48109 USA Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R ChinaYu, Dapeng论文数: 0 引用数: 0 h-index: 0机构: Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China Int Quantum Acad, Shenzhen 518048, Peoples R China Southern Univ Sci & Technol, Guangdong Prov Key Lab Quantum Sci & Engn, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Dept Phys, Shenzhen 518055, Peoples R China Southern Univ Sci & Technol, Shenzhen Inst Quantum Sci & Engn, Shenzhen 518055, Peoples R China
- [4] Quantum solvability of noisy linear problems by divide-and-conquer strategy[J]. QUANTUM SCIENCE AND TECHNOLOGY, 2022, 7 (02)Song, Wooyeong论文数: 0 引用数: 0 h-index: 0机构: Korea Inst Sci & Technol, Ctr Quantum Informat, Seoul 02792, South Korea Hanyang Univ, Dept Phys, Seoul 04763, South Korea Korea Inst Sci & Technol, Ctr Quantum Informat, Seoul 02792, South KoreaLim, Youngrong论文数: 0 引用数: 0 h-index: 0机构: Korea Inst Adv Study, Sch Computat Sci, Seoul 02455, South Korea Korea Inst Sci & Technol, Ctr Quantum Informat, Seoul 02792, South KoreaJeong, Kabgyun论文数: 0 引用数: 0 h-index: 0机构: Korea Inst Adv Study, Sch Computat Sci, Seoul 02455, South Korea Seoul Natl Univ, Res Inst Math, Seoul 08826, South Korea Korea Inst Sci & Technol, Ctr Quantum Informat, Seoul 02792, South KoreaJi, Yun-Seong论文数: 0 引用数: 0 h-index: 0机构: Seoul Natl Univ, Res Inst Math, Seoul 08826, South Korea Korea Inst Sci & Technol, Ctr Quantum Informat, Seoul 02792, South Korea论文数: 引用数: h-index:机构:Kim, Jaewan论文数: 0 引用数: 0 h-index: 0机构: Korea Inst Adv Study, Sch Computat Sci, Seoul 02455, South Korea Korea Inst Sci & Technol, Ctr Quantum Informat, Seoul 02792, South KoreaKim, M. S.论文数: 0 引用数: 0 h-index: 0机构: Korea Inst Adv Study, Sch Computat Sci, Seoul 02455, South Korea Imperial Coll London, Blackett Lab, QOLS, London SW7 2AZ, England Korea Inst Sci & Technol, Ctr Quantum Informat, Seoul 02792, South KoreaBang, Jeongho论文数: 0 引用数: 0 h-index: 0机构: Elect & Telecommun Res Inst, Daejeon 34129, South Korea Korea Inst Sci & Technol, Ctr Quantum Informat, Seoul 02792, South Korea
- [5] Quantum search on noisy intermediate-scale quantum devices[J]. EPL, 2022, 140 (01)Zhang, K.论文数: 0 引用数: 0 h-index: 0机构: SUNY Stony Brook, Dept Chem, Stony Brook, NY 11794 USA SUNY Stony Brook, Dept Chem, Stony Brook, NY 11794 USAYu, K.论文数: 0 引用数: 0 h-index: 0机构: Brookhaven Natl Lab Upton, Comp Sci Initiat, Upton, NY 11973 USA SUNY Stony Brook, Dept Chem, Stony Brook, NY 11794 USAKorepin, V.论文数: 0 引用数: 0 h-index: 0机构: Stony Brook Univ Stony Brook, CN Yang Inst Theoret Phys, Stony Brook, NY 11794 USA SUNY Stony Brook, Dept Chem, Stony Brook, NY 11794 USA
- [6] Quantum Metrology in the Noisy Intermediate-Scale Quantum Era[J]. ADVANCED QUANTUM TECHNOLOGIES, 2023,Jiao, Lin论文数: 0 引用数: 0 h-index: 0机构: Lanzhou Univ, Lanzhou Ctr Theoret Phys, Key Lab Quantum Theory & Applicat MoE, Lanzhou 730000, Peoples R China Lanzhou Univ, Lanzhou Ctr Theoret Phys, Key Lab Quantum Theory & Applicat MoE, Lanzhou 730000, Peoples R ChinaWu, Wei论文数: 0 引用数: 0 h-index: 0机构: Lanzhou Univ, Lanzhou Ctr Theoret Phys, Key Lab Quantum Theory & Applicat MoE, Lanzhou 730000, Peoples R China Lanzhou Univ, Lanzhou Ctr Theoret Phys, Key Lab Quantum Theory & Applicat MoE, Lanzhou 730000, Peoples R China论文数: 引用数: h-index:机构:论文数: 引用数: h-index:机构:
- [7] Parallel quantum chemistry on noisy intermediate-scale quantum computers[J]. PHYSICAL REVIEW RESEARCH, 2022, 4 (03):Schade, Robert论文数: 0 引用数: 0 h-index: 0机构: Paderborn Univ, Paderborn Ctr Parallel Comp, D-33098 Paderborn, Germany Paderborn Univ, Paderborn Ctr Parallel Comp, D-33098 Paderborn, GermanyBauer, Carsten论文数: 0 引用数: 0 h-index: 0机构: Paderborn Univ, Paderborn Ctr Parallel Comp, D-33098 Paderborn, Germany Paderborn Univ, Paderborn Ctr Parallel Comp, D-33098 Paderborn, GermanyTamoev, Konstantin论文数: 0 引用数: 0 h-index: 0机构: Paderborn Univ, Dynam Condensed Matter, Chair Theoret Chem, D-33098 Paderborn, Germany Paderborn Univ, Inst Sustainable Syst Design, Chair Theoret Chem, D-33098 Paderborn, Germany Paderborn Univ, Paderborn Ctr Parallel Comp, D-33098 Paderborn, Germany论文数: 引用数: h-index:机构:Plessl, Christian论文数: 0 引用数: 0 h-index: 0机构: Paderborn Univ, Paderborn Ctr Parallel Comp, D-33098 Paderborn, Germany Paderborn Univ, Dept Comp Sci, D-33098 Paderborn, Germany Paderborn Univ, Paderborn Ctr Parallel Comp, D-33098 Paderborn, GermanyKuehne, Thomas D.论文数: 0 引用数: 0 h-index: 0机构: Paderborn Univ, Dynam Condensed Matter, Chair Theoret Chem, D-33098 Paderborn, Germany Paderborn Univ, Inst Sustainable Syst Design, Chair Theoret Chem, D-33098 Paderborn, Germany Paderborn Univ, Paderborn Ctr Parallel Comp, D-33098 Paderborn, Germany
- [8] Noisy intermediate-scale quantum algorithm for semidefinite programming[J]. PHYSICAL REVIEW A, 2022, 105 (05)Bharti, Kishor论文数: 0 引用数: 0 h-index: 0机构: Natl Univ Singapore, Ctr Quantum Technol, 3 Sci Dr 2, Singapore 117543, Singapore Natl Univ Singapore, Ctr Quantum Technol, 3 Sci Dr 2, Singapore 117543, SingaporeHaug, Tobias论文数: 0 引用数: 0 h-index: 0机构: Imperial Coll London, Blackett Lab, QOLS, London SW7 2AZ, England Natl Univ Singapore, Ctr Quantum Technol, 3 Sci Dr 2, Singapore 117543, SingaporeVedral, Vlatko论文数: 0 引用数: 0 h-index: 0机构: Natl Univ Singapore, Ctr Quantum Technol, 3 Sci Dr 2, Singapore 117543, Singapore Univ Oxford, Clarendon Lab, Parks Rd, Oxford OX1 3PU, England Natl Univ Singapore, Ctr Quantum Technol, 3 Sci Dr 2, Singapore 117543, SingaporeKwek, Leong-Chuan论文数: 0 引用数: 0 h-index: 0机构: Natl Univ Singapore, Ctr Quantum Technol, 3 Sci Dr 2, Singapore 117543, Singapore CNRS UNS NUS NTU Int Joint Res Unit, MajuLab, UMI 3654, Singapore, Singapore Nanyang Technol Univ, Natl Inst Educ, 1 Nanyang Walk, Singapore 637616, Singapore Sch Elect & Elect Engn, Block S2-1,50 Nanyang Ave, Singapore 639798, Singapore Natl Univ Singapore, Ctr Quantum Technol, 3 Sci Dr 2, Singapore 117543, Singapore
- [9] Continuous Monitoring for Noisy Intermediate-Scale Quantum Processors[J]. PHYSICAL REVIEW APPLIED, 2023, 19 (01)Zolotarev, Y. F.论文数: 0 引用数: 0 h-index: 0机构: Russian Quantum Ctr, Moscow 143026, Russia Natl Univ Sci & Technol MISIS, Moscow 119049, Russia Russian Quantum Ctr, Moscow 143026, RussiaLuchnikov, I. A.论文数: 0 引用数: 0 h-index: 0机构: Russian Quantum Ctr, Moscow 143026, Russia Natl Univ Sci & Technol MISIS, Moscow 119049, Russia Russian Quantum Ctr, Moscow 143026, RussiaLopez-Saldivar, J. A.论文数: 0 引用数: 0 h-index: 0机构: Russian Quantum Ctr, Moscow 143026, Russia Natl Univ Sci & Technol MISIS, Moscow 119049, Russia Russian Quantum Ctr, Moscow 143026, RussiaFedorov, A. K.论文数: 0 引用数: 0 h-index: 0机构: Russian Quantum Ctr, Moscow 143026, Russia Natl Univ Sci & Technol MISIS, Moscow 119049, Russia Russian Quantum Ctr, Moscow 143026, RussiaKiktenko, E. O.论文数: 0 引用数: 0 h-index: 0机构: Russian Quantum Ctr, Moscow 143026, Russia Natl Univ Sci & Technol MISIS, Moscow 119049, Russia Russian Quantum Ctr, Moscow 143026, Russia
- [10] Fisher Information in Noisy Intermediate-Scale Quantum Applications[J]. QUANTUM, 2021, 5Meyer, Johannes Jakob论文数: 0 引用数: 0 h-index: 0机构: Free Univ Berlin, Dahlem Ctr Complex Quantum Syst, D-14195 Berlin, Germany Univ Copenhagen, Dept Math Sci, QMATH, DK-2100 Copenhagen O, Denmark Free Univ Berlin, Dahlem Ctr Complex Quantum Syst, D-14195 Berlin, Germany