2021-2022学年高二物理竞赛课件：单原子与电磁场相互作用

1、单原子与电磁场相互作用2单原子与电磁场相互作用薛定谔猫的理论与实验量子退相干Nature 427, 711-714 (2004)4超导量子计算机基于Josephson结的超导量子比特是目前较为成熟且具有广阔发展前景的实用量子比特。利用超导Josephson结固体电路实现可控二能级人造原子（量子比特）5 约瑟夫森效应即超导隧道效应.在玻璃衬板上镀一层超导金属膜,使其上形成厚度很薄的绝缘氧化层,在氧化层上再镀上一层超导金属膜,就得到一个超导-绝缘-超导结,称为约瑟夫森结. 当绝缘层厚度在100nm左右时,由于隧道效应,库柏对穿过势垒后仍保持配对状态因此绝缘层中出现少量超导电子而具有了弱超导电性.

2、1999年,日本NEC基础研究实验室的Nakamra等人在实验中观测到了约瑟夫森结中相干的量子振荡,这是研究人员首次观测到固体中的宏观量子相干.6Cavity-QED(腔量子电动力学)量子比特量子比特数据总线用“数据总线”连接量子比特1cm7Circuit QEDSuperconducting coplanar waveguide transmissoin line resonator replaces cavityCooper pair box as the artificial atomProbing the system with microwaves near the resonato

3、r mode frequency2.5 cm5 mmCooper Pair Box8Cooper Pair BoxVgEJCg9Theoretical Model of Transmission Line ResonatorVRMS1mV10Ion Trap（离子阱）离子阱技术 1980年科学家首次观测到了阱中的单个离子 1986年做到了对离子不同塞曼能级的区分 1996年利用拉比振荡(Rabi flops)实现了单个量子比特的控制,并进一步实现了对离子链中某个离子的选择性操作,利用激光能够以接近于1的成功率测量离子的状态 2003年,奥地利因斯布鲁克大学的Blatt研究小组利用离子阱技术成功

4、地实现了控制非门 同一年同一研究小组利用离子阱技术第一次成功地演示了Deutsch-Jozsa算法11Ion trap4 rod electrodes AC 1kv MHztrap the ionsIons (cold trapped)End-rings Charged to prevent escapingNo AC electric field, spin direction as qubit12A schematic of a trapped ion process13How an Ion Trap Works14+V+V00F00+V+VF+V+V00F00+V+VF+V+V00F00

5、+V+VF+V+V00FInnsbruckMPQ/GarchingOxfordIon Trap（离子阱）15centre of mass (COM)wx“stretch”2 wxIon Motion in Trap:single ion:like a mass on a springmultiple, cold ions:“normal modes” - the string moves as one.N ions:N modes per direction16Cold trapped ions for quantum information processingIdea: I. Cirac

6、and P. Zoller (1995). Experiments: Wineland Boulder, Blatt InnsbruckQubits: Internal states of electron in a cold trapped ion (laser cooled). Interaction: Use coupling of ions with vibrational states of “cristal” (phonons).Operations: Shine lasers on ions to make them interact. 2003: c-not gate betw

7、een two ions17Cirac-Zoller CNOT gateTo create an effective spin-spin coupling, “control” spin state is mapped on to the motional “bus” state, the target spin is flipped according to its motion state, then motion is remapped onto the control qubit.|controltargetCirac and Zoller, Phys. Rev. Lett. 74, 4091 (1995)Raman beams18Ion Traps - initia