The year of 2016 ends up with being a year of condensed matter physics---in particular of topological orders. This conference did not expect to but happens to celebrate this year's victory of topological orders. The emergent phenomena in topological orders not only play a fundamental role in condensed matter physics but also point to a new way of thinking about spacetime, namely as an emergent entity of more fundamental discrete degrees of freedom. On the other hand, the anyonic excitations in topological orders also lead to topological quantum computation---a quantum computing scheme robust again local errors.
This conference aims to assemble the leading theorists and experimentalists of topological orders, quantum information and computation, and emergent spacetime for active exchange of ideas and collaborations, with an eye on potential realization and applications.
Panelists:
In alphabetical order：
Dapeng Yu —— Southern University Of Science And Technology & Peking University
David G. Cory —— University of Waterloo
Dieter Suter —— University Dortmund
Fernando Brandao —— California Institute of Technology
Jiangfeng Du —— University of Science and Technology of China
Qian Niu —— University of Texas
Qikun Xue —— Tsinghua University
Other speakers:
In alphabetical order：
Adrian Lupascu —— University of Waterloo
Akira Oiwa —— Osaka University
Alexey Gorshkov —— University of Maryland
Barry Sanders —— University of Calgary
Beni Yoshida —— Perimeter Institute
Duanlu Zhou —— Institute of Physics, Chinese Academy of Sciences
Guilu Long —— Tsinghua University
Guoxing Miao —— University of Waterloo
Haidong Yuan —— The Chinese University of Hong Kong
Haixing Miao —— University of Birmingham
Haohua Wang —— Zhejiang University
Huan Yang —— Princeton
Hui Zhai —— Tsinghua University
Jianqiang You —— Beijing Computational Science Research Center
Ke He —— Tsinghua University
Lei Zhou —— Fudan University
Liang Jiang —— Yale University
Mang Feng —— Wuhan Institute Of Physics and Mathematics, Chinese Academy of Sciences
Matteo Mariantoni —— University of Waterloo & IQC
Mikio Nakahara —— Kinki University
Nengkun Yu —— University of Technology Sydney
Renbao Liu —— The Chinese University of Hong Kong
Seigo Tarucha —— University of Tokyo
Steven Flammia —— University of Sydney
Supeng Kou —— Beijing Normal University
Tong Zhang —— Fudan University
Xi Chen —— Shanghai University
Xi Chen —— Tsinghua University
Xiangang Wan —— Nanjing University
Xiaosong Ma —— Nanjing University
Xie Chen —— California Institute of Technology
Xin Wan —— Zhejiang University
Yan Chen —— Fudan University
Yi Ling —— Institute of High Energy Physics
Ying Ran —— Boston College
Yu Shi —— Fudan University
Yuao Chen —— University of Science and Technology of China
Zhengfeng Ji —— University Of Technology Sydney
Zhengwei Zhou —— University of Science and Technology of China
Zhiming wang —— University Of Electronic Science and Technology Of China
Zidan Wang —— The University of Hong Kong
Conference Room
Date 12.19: Lecture Hall of Yifu science and technology building.
逸夫楼科技报告厅.
Date 12.20-12.23: Guang-hua East “assistant” building room 103 (on the ground floor).
光华东辅楼103室
Dining: Danyuan restaurant, second floor.
Locations:
Poster session is held during each tea break and on Wednsday before the banquet
Panel discussionÃÂÃÂ¯ÃÂÃÂ¼ÃÂÃÂquantum matter sciences: roads ahead and international collaborations
Schedule of conference
Date | Time | Speaker |
Dec. 19th, 2016 | 8:00 - 9:15 | Registration |
9:15 - 9:45 | Opening remarks: Ningsheng Xu, Jian Shen | |
9:45 - 10:15 | Tea break | |
10:15 - 11:30 | Keynote speech: David G. Cory | |
Lunch till 14:00 | ||
14:00 - 15:00 | Panel discussion part I | |
15:00 - 15:30 | Tea break | |
15:30 -16:30 | Panel discussion part II | |
Dec. 20th, 2016 | Session chair: Yi Ling | |
9:00 - 10:00 | Keynote speech: Qian Niu | |
10:05 - 10:35 | Hui Zhai | |
10:35 - 11:05 | Tea break | |
Session chair: Guoxing Miao | ||
11:05 - 11:35 | Steven T. Flammia | |
11:40 -12:10 | Xiangang Wan | |
Lunch till 14:00 | ||
Session chair: Mikio Nakahara | ||
14:00 - 14:30 | Guilu Long | |
14:35 -15:05 | Supeng Kou | |
15:05 -15:35 | Tea break | |
Session chair: Xie chen | ||
15:35 - 16:05 | Zhiming Wang | |
16:10 - 16:40 | Haohua Wang | |
16:40 - 17:10 | Xiaopeng Li | |
Dec. 21st, 2016 | Session chair: Muxin Han | |
9:00 - 9:30 | Barry Sanders | |
9:35 - 10:05 | Alexey Gorshkov | |
10:05 - 10:35 | Tea break | |
Session chair: Mang Feng | ||
10:35 - 11:05 | Xin Wan | |
11:10 - 11:40 | Renbao Liu | |
Lunch till 14:00 | ||
Session chair: Zhengfeng Ji | ||
14:00 - 14:30 | Zidan Wang | |
14:35 - 15:05 | Akira Oiwa | |
15:05 - 15:35 | Tea break | |
Session chair: Huan Yang | ||
15:35 - 16:05 | Adrian Lupascu | |
16:10 - 16:40 | Xi Chen (Shanghai University) | |
Banquet | ||
Dec. 22nd, 2016 | Session chair: Beni Yoshida | |
9:00 - 9:30 | Xi Chen (Tsinghua University) | |
9:35 - 10:05 | Matteo Mariantoni | |
10:05 - 10:35 | Tea break | |
Session chair: Nengkun Yu | ||
10:35 - 11:05 | Dieter Suter | |
11:10 - 11:40 | Liang Jiang | |
Lunch till 14:00 | ||
Session chair: Xinhua Peng | ||
14:00 - 14:30 | Seigo Tarucha | |
14:35 - 15:05 | Zhengwei Zhou | |
15:05 - 15:35 | Tea break | |
Session chair: Beni Yoshida | ||
15:35 -16:05 | Ying Ran | |
16:10 - 16:40 | Ke He | |
Dec. 23rd, 2016 | Session chair: Duanlu Zhou | |
9:00 - 9:30 | Jianqiang You | |
9:35 - 10:05 | Haidong Yuan | |
10:05 -10:35 | Tea break | |
Session chair: Ling-Yan Hung | ||
10:35 - 11:05 | Xiaosong Ma | |
11:10 - 11:40 | Yu shi | |
Lunch till 14:00 | ||
Session chair: Guoxing Miao | ||
14:00 -14:30 | Yan Chen | |
14:35 - 15:05 | Lei Zhou | |
15:05 - 15:35 | Tea break | |
Session chair: Yidun Wan | ||
15:35 - 16:05 | Tong Zhang | |
皇冠假日酒店
Crown Plaza Hotel：
Address: No. 199 Handan Road, Yangpu District, Shanghai, China
Official website: http://www.crowneplazafudan.com/
Elong reservation connection：http://hotel.elong.com/shanghai/50201067/
复宣酒店
Fuxuan Hotel:
Address: No. 400 Guoding Road, Yangpu District, Shanghai, China
Official website: http://www.fuxuanhotels.com/
Elong reservation connection: http://hotel.elong.com/shanghai/60201219/
卿云宾馆
Qingyun Hotel:
Address: No. 220 Handan Road, Yangpu District, Shanghai, China (on campus)
燕园宾馆
Yanyuan Hotel:
Address: No. 270 Zhengtong Road, Yangpu District, Shanghai, China
Official website: http://11311.hotel.cthy.com/
Elong reservation connection: http://hotel.elong.com/shanghai/10201164/
Locations:
Quantum Materials, Characterization and Devices
David G. Cory
I will introduce the new Canada First Research Excellence Fund program in Transformative Quantum Technologies at the University of Waterloo. The program aims to develop impactful quantum devices in collaboration with industry and a team of early adopters. It focuses on three grand challenges:
Develop quantum processors with devices that have a complexity beyond the capacity of classical simulators. The systems should be useful as testbeds for verification/validation/error correction, as well as for quantum simulation.
Develop quantum sensors with applications, for example to biochemistry, medicine, environment, materials characterization, navigation, etc.
Explore long distance entanglement and the means of generating and controlling it. Develop quantum repeaters.
I will describe an approach to a hybrid quantum processor based on electron spin actuators of nuclear spin qubits, all controlled by microwave superconducting electronics. This will include a description of how new materials and control methods enable node-based processors.
I will also describe the development of neutron based quantum sensors for characterizing materials with applications to imaging and characterizing helicity of materials including quantum materials.
Ultrafast Growth of Graphene Single Crystal
Dapeng Yu
Graphene single crystal has become as a promising material for next generation electronics and optoelectronics. Unfortunately we can’t grow 12-inch graphene single-crystal wafer as we can do in silicon industry. One of the main hamper is that we nowadays grow graphene single crystal very slow. In this talk I will introduce why we need to grow graphene faster and how fast we can achieve in our recently developed new technology [1].
Reference:
[1] Xiaozhi Xu, Zhihong Zhang, Dapeng Yu, Enge Wang, Feng Ding*, Hailin Peng*, Kaihui Liu*, et al. “Ultrafast Growth of Single-crystal Graphene Assisted by a Continuous Oxygen Supply”, Nature Nanotechnology 2016, in press.
Out-of-Time-Ordered Correlation and Entanglement Entropy
Hui Zhai
The out-of-time order correlation (OTOC) has recently emerged as a quantity that brings together interests from several different fields, which diagnoses chaotic behavior in the condensed matter systems, saturates an upper bound for systems with holographic duality to a black hole in the gravity physics and relates to information scrambling in the quantum information context. In this talk, we will first present a Quantum Critical Point (QCP) conjecture that the Lyapunov exponent defined from the OTOC displays a peak at the quantum critical regime, and we will present numerical evidence in the Bose-Hubbard model to support this conjecture. Then, we will consider the OTOC for a many-body localization (MBL) system and we will show that the OTOC can distinguish MBL from thermalized phase and the Anderson localized phase. Most importantly, we will present an OTOC-EE theorem that discovers a general relation between the OTOC in an equilibrium system and the entanglement entropy (EE) in a quenched system. Finally, we should present the first experimental measurement of OTOC using NMR quantum simulator.
Ref:
[1] Huitao Shen, Pengfei Zhang, Ruihua Fan and Hui Zhai, arXiv: 1608.02438
[2] Ruihua Fam, Pengfei Zhang, Huitao Shen and Hui Zhai, arXiv: 1608.01914
[3] Jun Li, Ruihua Fan, Hengyan Wang, Bingtian Ye, Bei Zeng, Hui Zhai, Xinhua Peng and Jiangfeng Du, arXiv: 1609.01246
Steven T. Flammia: TBC
Realization of Massive Relativistic Spin-3/2 Rarita Schwinger Quasiparticle in Condensed Matter Systems
Xiangang Wan
Very recently, there has been significant progress in realizing high-energy particles in condensed-matter (CM). Described by Rarita-Schwinger (RS) equation, spin-3/2 relativistic fermion has been known in quantum field theory, but has not been observed until now. We build a Hamiltonian which contains RS modes. Based on ab initio calculations, we also explore the real materials which host this exotic excitation close to the Fermi level.
Guilu Long: TBC
Majorana Fermions: polygon sign rules, quantum simulation and universal topological quantum computation
Supeng Kou
Recently, Majorana fermions (MFs) have attracted intensive attention due to their exotic statistics and possible applications in topological quantum computation. In this talk, firstly we show that Majorana fermions in different topological systems obey different types of polygon sign rules: vortex-induced Majorana fermions obey topological polygon sign rule and line-defect-induced Majorana fermions obey normal polygon sign rule. Secondly, we numerically study the non-Abelian statistics of the zero-energy Majorana fermions on the end of Majorana chain and show its application to quantum computing by mapping it to a spin model with special symmetry. Numerical evidence and comparison in both Majorana-representation and spin-representation are presented. Thirdly, based on a topological superfluid on a Peierls lattice, we find Majorana zero modes on fractionalized flux that gives a realistic proposal to realize the universal topological quantum computation.
Zhiming Wang: TBC
Emulating anyonic fractional statistical behavior in a superconducting quantum circuit
Haohua Wang
In this talk, I will review our recent activities with our collaborators on designing and fabricating various superconducting circuits for scalable quantum information processing. I will show that we are able to manipulate superconducting circuits with moderate complexity, which may integrate up to ten qubits and exhibit decent coherence performance. In particular, I will present an experiment of emulating anyonic fractional statistical behavior in a superconducting circuit that consists of four qubits. In the experiment we create the anyonic excitations by dynamically generating the ground and excited states of the toric code model, i.e., four-qubit Greenberger-Horne-Zeilinger states. The anyonic braiding is implemented via single-qubit rotations: A phase shift of pi related to braiding, the hallmark of Abelian 1/2 anyons, has been observed through a Ramsey-type interference measurement.
Xiaopeng Li: TBC
Qian Niu: TBC
Spacetime replication of continuous-variable quantum information
Barry Sanders
Combining the relativistic speed limit of information transmission with the linearity and unitarity of quantum mechanics leads to a relativistic extension of the no-cloning principle, which we call spacetime replication of quantum information. We introduce continuous-variable spacetime-replication protocols, expressed in a Gaussian-state basis, that build on homologically constructed continuous-variable quantum error correcting codes and show how the relativistic no cloning principle reduces to a quantum secret sharing protocol.
Entanglement renormalization and area law with long-range interactions
Alexey Gorshkov
In many synthetic quantum systems, such as polar molecules, Rydberg atoms, and trapped ions, interactions fall off with distance as a power law. In this talk, we will first show [arXiv:1612.02442] how such long-range interactions can enable fast state transfer and fast preparation of entangled states given by a MERA (multiscale entanglement renormalization ansatz). We will then discuss the stability of the entanglement area law in the presence of long-range interactions.
Striped quantum Hall phase at 5/2 Landau level filling
Xin Wan
Two-dimensional electron systems at half Landau level fillings can be understood as composite-fermion sea subject to various instabilities. At 5/2 filling, the composite fermions are believed to pair into a chiral p-wave superfluid, which supports non-Abelian quasiparticles. According to the bulk-edge correspondence, the edge of a 5/2 droplet has both charged bosonic and neutral fermionic modes. In this talk, we first discuss the edge spectrum in a realistic microscopic setup using a Jack polynomial method. We find that when confining potential becomes weaker, the fermionic edge mode, rather than the bosonic one, becomes soft. This has an interesting consequence that a striped fractional quantum Hall state, which has the particle-hole symmetry in the average sense, can emerge as the global ground state. The resulting state is incompressible and thus a charge insulator in the bulk, but a heat conductor due to the presence of gapless neutral bulk modes.
Renbao Liu: TBC
Realizing and manipulating various topological semimetal bands with superconducting quantum circuits
Zidan Wang
Symmetry and topology, as the two fundamentally important concepts in physics and mathematics, have not only manifested themselves in science, but also provided us with profound understanding of various natural phenomena. Recently, topological gapless systems, including Z2 topological metals/semimetals [1-3], have attarcted significant research interests both theoretically and experimentally. In this talk, we will report experimental realization and manipulation several topological semimetal bands in superconducting quantum circuits as well as the detection of exotic topological characters in these systems [4,5].
This work was done in collaboration with Y. Yu, X. Tan, Y. X. Zhao, Q. Liu, G. Xue, H. Yu, and is partly supported by the GRF of Hong Kong (HKU173055/15P &HKU173309/16P) and the NKRDP of China (Grant No. 2016YFA0301802).
References:
[1]. Y. X. Zhao and Z. D. Wang, Phys. Rev. Lett. 110, 240404 (2013).
[2]. Y. X. Zhao and Z. D. Wang, Phys. Rev. Lett. 116, 016401 (2016).
[3]. Y. X. Zhao, A. P. Schnyder, and Z. D. Wang, Phys. Rev. Lett. 116, 156402 (2016).
[4]. X. Tan et al., to be published (2017).
[5]. X. Tan et al., to be submitted.
Conversion from single photon polarizations to single electron spins using gate-defined GaAs double quantum dots
Akira Oiwa
Quantum state conversion from a photon polarization state described by a Poincaré sphere to an electron spin state described by a Bloch sphere provides an elemental technology indispensable for long distance quantum communication. Electron spins in gate-defined quantum dots (QDs) showing relatively long spin coherence times have been comprehensively studied as suitable candidates of scalable solid-state qubits. The quantum state conversion from photons to electron spins has been proposed and has been experimentally verified by ensemble time-resolved magneto-optical measurements using quantum well (QW) structures [1,2]. To extend this technology for the practical applications to quantum infromation techology, the conversion between single quanta have to be realzied.
We propose a device which enables us to convert coherently between photon polarization states and electron spin states as Poincaré interface. The scheme for trapping and detecting the single electrons generated by a single photon has been developed using a gate-defined quantum dot (QD) [3,4,5]. Moreover, angular momentum conversion from single photons to single electron spins in gate-defined double QDs has been achieved [6]. At present, we aim to realize quantum state conversion and efficient coupling between photons and electron spins in QDs for applications to quantum communication. We discuss the detection of single photoelectron spins generated by single photons and angular momentum conversion using a gate-defined QD and recent progresses on enhancing the coupling between photons and electron spins in QDs.
This work was supported by Grants-in-Aid for Scientific Research A (No. 25246005), S (No.26220710), and Innovative Area "Nano Spin Conversion Science" (No. 26103004), CREST JST.
References
[1] R. Vrijen and E. Yablonovitch, Phys. E 10, 569 (2001).
[2] H. Kosaka et al., Phys. Rev. Lett. 100 096602 (2008).
[3] A. Pioda et al., Phys. Rev. Lett. 106, 146804 (2011).
[4] T. Fujita et al., Phys. Rev. Lett. 110, 266803 (2013).
[5] K. Morimoto et al., Phys. Rev. B 90, 085306 (2014).
[6] T. Fujita et al., arXiv:1504.03696.
Ultrastrong coupling of a single artificial atom to the electromagnetic field
Adrian Lupascu
I will present the results of experiments in which an artificial atom interacts strongly with the electromagnetic field. I will first discuss the observation of ultrastrong interactions between the artificial atom and a one-dimensional quantum field. In this new regime the atomic frequency is comparable to or larger than the atomic frequency. We design a tunable coupling circuit between the atom, a flux qubit, and the transmission line, which allows us to explore the transition from weak to ultrastrong coupling. The experiments rely on coherent measurements of scattering of microwaves by the atom. We observe a linewidth comparable to the atomic frequency, a clear signature of ultra-strong coupling. We also find that the frequency of maximum scattering is systematically smaller than the bare atomic frequency, in agreement with renormalization by the field. Our results open the way to systematic studies of the spin-boson model and development of new quantum devices.
In the second part of the talk, I will discuss the dynamics of the artificial atom interacting with a strong driving field. The field strength, corresponding to the Rabi frequency in the weak driving regime, is largely exceeding the atomic frequency. The dynamics is described in the framework of Floquet theory, and is relevant for the design of high-speed high-fidelity quantum gates.
Enhancement of superconductivity by disorder in monolayer NbSe2
Xi Chen
Conventional s-wave pairing is robust to weak non-magnetic disorder, while strong disorder may suppress superconductivity. However superconductivity enhancement induced by disorder is rare. We grew noncentrosymmetric monolayer NbSe2 on the graphitized SiC(0001) surface. The superconducting gap was measured by using the low temperature scanning tunneling spectroscopy. Disorder was gradually introduced by either adding Si adaptors on the top of NbSe2 monolayer or replacing Se by S. With increasing disorder, the superconducting gap first increases and then decreases gradually, showing a dome structure. The maximum gap and critical temperature are up to three times of those for pure NbSe2. We attribute the enhancement of superconductivity to the localization of electrons or phonons.
Prototyping Scalable Technologies for Superconducting Quantum Computing
Matteo Mariantoni
Quantum computing architectures with ten or more quantum bits (qubits) have been implemented using trapped ions and superconducting devices. The next milestone in the quest for a quantum computer is the realization of quantum error correction codes. Such codes will require a very large number of qubits that must be controlled and measured by means of classical electronics. Two architectural aspects requiring immediate attention are the realization of a suitable interconnect between the quantum and classical hardware as well as the implementation of large substrates that incorporate 100 or more qubits. In this talk, I will introduce the quantum socket, a three-dimensional wiring method for qubits with superior performance as compared to two-dimensional methods based on wire bonding. The quantum socket is based on spring-mounted micro wires – the three-dimensional wires – that connect electrically to a micro-fabricated chip by pushing directly on it. I will present a detailed characterization of the quantum socket and a series of experiments where a socket was used to measure superconducting resonators at a temperature of ~10 mK. I will then show a chip-to-chip bonding technique that we developed in order to mitigate the effects of spurious resonance modes present in large qubit substrates. I will discuss the bonding fabrication process and I will show measurements of the electrical properties of pairs of bonding chips at room temperature and at 10 mK. I will give an outlook demonstrating how the quantum socket and chip-to-chip bonding technique can be used to wire a quantum processor with a 10×10 qubit lattice.
Spin-based quantum simulations
Dieter Suter
As quantum computers become more powerful, one of the earliest motivations for building computers based on quantum mechanics moves back into focus: the simulation of quantum systems on quantum computers. The dynamics of quantum systems is well known to be a computationally hard problem, requiring resources that scale exponentially with the size of the system. Quantum computers or specialized quantum simulators can overcome this obstacle, since the scaling properties of suitable quantum algorithms are qualitatively different from those of algorithms designed for classical computers. A specific example is the problem of localization: While ideal quantum systems often have ground states that are delocalized, random perturbations can cause them to become localized, with a sharp phase transition at a specific value of the perturbation strength. This example was demonstrated in an experimental quantum simulator based on nuclear spin qubits.
Quantum Channels Construction with Circuit Quantum Electrodynamics
Jiang, Liang
Quantum channels can describe all transformations allowed by quantum mechanics. We provide an explicit universal protocol to construct all possible quantum channels, using a single qubit ancilla with quantum non-demolition readout and adaptive control. Our construction is efficient in both physical resources and circuit depth, and can be demonstrated using superconducting circuits and various other physical platforms. There are many applications of quantum channel construction, including system stabilization and quantum error correction, Markovian and exotic channel simulation, implementation of generalized quantum measurements and more general quantum instruments. Efficient construction of arbitrary quantum channels opens up exciting new possibilities for quantum control, quantum sensing and information processing tasks.
Spin dynamics and QND spin measurement with quantum dots
Seigo Tarucha
Various kinds of spin qubits, spin-1/2, singlet-triplet and exchange-only, have been developed to date. Coupling of them can provide efficient quantum gates and more variations of quantum operations. We use a triple GaAs quantum dot to manipulate coupling between a spin-1/2 qubit and a singlet-triplet qubit and apply it for QND readout of the spin-1/2 state and CPHASE operation. We prepare phase-controlled singlet-triplet entanglement in two dots and show the phase evolution frequency is modulated depending on the orientation of the spin-1/2 in the third dot. This frequency modulation can be used for QND measurement of the spin-1/2 state and also for CPHASE operation. In addition, I will discuss quantum dephasing of spin-1/2 states due to the nuclear spin environment. I show that the dephasing is significantly reduced by decreasing the data acquisition time in the non-ergodic condition. Both fast gating and fast measurement are useful to suppress the influence from slowly fluctuating nuclear spin environment and improve the gate fidelity.
Simulating Topological physics by using synthetic dimensions based on optical orbital angular momentum
Zheng-Wei Zhou
Quantum simulation is one of the most important research fields in quantum information science, which not only allows the study of the existed physical systems, but also new physical modes with new phenomena. Currently, there are various experimental platforms used for quantum simulation, such as ultra-cold neutral atom, trapped ion, integrated optical system et al. Orbital angular momentum of light is a fundamental optical degree of freedom. It is characterized by unlimited number of available angular momentum states, and has proved invaluable in diverse recent studies ranging from quantum information to optical communication.
In this talk, we will introduce fully new applications of photon’s orbital angular momentum in quantum simulation of topological physics. The basic idea is to design a degenerate cavity supporting photonic modes carrying different orbital angular momentum (i.e. the Laguerre-Gaussian modes), whose resonance frequencies are the same. By coupling photons in different orbital angular momentum states, a single degenerate cavity is equivalent to a 1D coupled-cavity array. Consequently, 1D coupled degenerate cavity array can be used to simulate 2D physics. We proposed some schemes to realize arbitrary Abelian gauge field, SU(2) non-Abelian gauge field, to detect topological invariants such as edge state and Chern number, and to observe topological quantum phase transition. In contrast to other 2D proposals, this 1D structure greatly reduces the complexity of the simulator, and feasible scale of simulation is also increased[1].
Furthermore, we also investigate 1D topological models by using single degenerate cavity. We propose a method to construct a sharp boundary so that the open boundary condition can be implemented for this effective lattice system. In doing so, the topological properties of the system can manifest themselves on the edge states, which can be probed from the spectrum of output cavity field. We demonstrate this with two examples: a static Su-Schrieffer-Heeger chain and a periodically driven Floquet topological insulator[2].
Reference:
[1] Xi-Wang Luo, Xingxiang Zhou, Chuan-Feng Li, Jin-Shi Xu, Guang-Can Guo & Zheng-Wei Zhou, Quantum simulation of 2D topological physics in a 1D array of optical cavities, Nature Communications 6,7704 (2015).
[2] Xiang-Fa Zhou, Xi-Wang Luo, Su Wang, Guang-Can Guo, Xingxiang Zhou, Han Pu, & Zheng-Wei Zhou, Dynamical manipulation of topological edge modes and Floquet topological insulator in a single degenerate optical cavity, submitted.
symmetric tensor-networks and topological phases
Ying Ran
I will describe a theoretical framework to systematically classify and construct generic tensor-network wavefunctions (in d=1,2,3 spatial dimensions) respecting both onsite and spatial symmetries, which turns out to be useful from both conceptual and practical points of view. For example, on the conceptual side, our results show that the bosonic cohomological symmetry protected topological (SPT) phases are classified by H^{d+1}(SG,U(1)) where SG is the full symmetry group which may involves spatial symmetries, and both time-reversal symmetry and mirror reflection symmetries should be treated as anti-unitary. We also identify a generic connection between SPT phases and rather conventional symmetry enriched topological (SET) phases via an anyon condensation mechanism, which may serve as a guideline to search for SPT phases in realistic models. On the practical side, the constructed generic tensor-network wavefunctions are useful for variational numerical simulations, and I will discuss our results on the spin-1/2 Heisenberg model on the kagome lattice.
Searching for high temperature quantum anomalous Hall materials
Ke He
The quantum anomalous Hall (QAH) effect is a quantum Hall effect induced by spontaneous magnetization instead of an external magnetic field. The effect occurs in two-dimensional (2D) insulators with topologically nontrivial electronic band structure characterized by a non-zero Chern number. The experimental observation of the QAH in thin films of magnetically doped topological insulators (TIs) paves the ways for practical applications of dissipationless quantum Hall edge states and for realizations of the novel quantum phenomena, but a temperature as low as 30 mK is required to reach a perfect quantization. Further studies in these directions require magnetic TI materials that can show the QAH effect at higher temperature. We have performed systematic study on the QAH effect in magnetically doped TI films with different thicknesses, magnetic dopants and compositions [2,3]. The results clarify the relations between the QAH effect and the energy band structure, electronic localization and ferromagnetism of a magnetic TI film and provide insights into designing and fabrication of high temperature QAH materials.
[1] C. -Z. Chang et al., Science 340, 167 (2013).
[2] X. Feng et al., Adv. Mater. DOI: 10.1002/adma.201600919 (2016).
[3] Y. Ou et al., APL Mater. DOI: 10.1063/1.4960111 (2016).
Magnon Kerr effect in a cavity quantum electrodynamics system
Jianqiang You
We report the experimental demonstration of the magnon Kerr effect in a cavity quantum electrodynamics system, where magnons in a small yttrium iron garnet (YIG) sphere are strongly but dispersively coupled to the microwave photons in a three-dimensional cavity. When considerable magnons are generated by pumping the YIG sphere, the Kerr effect gives rise to a shift of the cavity central frequency and yields more appreciable shifts of the magnon modes, including the Kittel mode (i.e., the ferromagnetic resonance mode), which holds homogeneous magnetization, and the magnetostatic (MS) modes, which have inhomogeneous magnetization. We derive an analytical relation between the magnon frequency shift and the pumping power for a uniformly magnetized YIG sphere and find that it agrees very well with the experimental results of the Kittel mode. In contrast, the experimental results of MS modes deviate from this relation owing to the spatial variations of the MS modes over the sample. To enhance the magnon Kerr effect, the pumping field is designed to directly drive the YIG sphere and its coupling to the magnons is strengthened using a loop antenna. Moreover, this field is tuned very off-resonance with the cavity mode to avoid producing any appreciable effects on the cavity. Our work is the first convincing study of a cavity QED system with magnon Kerr effect and paves the way to experimentally explore nonlinear effects in the cavity QED system with magnons.
Ultimate precision limit for quantum parameter estimation
Haidong Yuan
Measurement and estimation of parameters are essential for science and engineering, where the main quest is to find out the highest achievable precision with given resources and design schemes to attain it. With recent development of technology, it is now possible to design measurement protocols utilizing quantum mechanical effects, such as entanglement, to attain far better precision than classical schemes. This has found wide applications in quantum phase estimation, quantum imaging, atomic clock synchronization, etc, and created a high demand for better understanding of measurement protocols based on quantum effects. In this talk I will present a framework for quantum metrology which relates the ultimate precision limit directly to the underlying quantum dynamics. This framework provides efficient methods for the identification of the optimal probe states and the corresponding precision limit.
Harnessing single photons in quantum technology
Xiaosong Ma
Quantum technology employs the ‘spooky’ phenomena of quantum physics such as superposition, randomness and entanglement to process information in a novel way. Quantum photonics provides a promising path for both delivering quantum-enhanced technologies, including quantum simulation and quantum communication, as well as exploring fundamental physics, including realizations of delayed-choice experiments and nonlocal quantum erase.
In this talk, I will first present our work on long-distance free-space quantum teleportation. Quantum and classical channels were employed over 143 kilometers between two Canary Islands (La Palma to Tenerife). This demonstration represents a major step towards the realization of quantum communication on a global scale.
It is foreseeable that future technologies will require integrated optics architecture for enhanced performance, miniaturization and scalability. In the second part of my talk, I will cover our recent endeavors along this line. Finally, I will discuss the opportunities and challenges for improving the scalability of photonic quantum systems.
Yu Shi: TBA
Yan Chen: Two-Dimensional Tunable Weyl Semimetal in Non-Abelian Gauge Field
Yuao Chen: TBA
Metamaterials/metasurfaces: An ideal platform to manipulate light
Lei Zhou
Metamaterials are artificial electromagnetic materials composed by man-made functional subwavelength microstructures (meta-atoms) arranged in a specific order, and metasurfaces are the two-dimensional realizations of metamaterials. By tailoring the meta-atoms and their arranging order, many fascinating wave-manipulation effects have been realized, including negative refraction, cloaking, polarization control and the generalized laws of refraction/reflection. In this talk, I will briefly review the recent theoretical/experimental works that we did in this field, with the hope to stimulate collaborations with researchers from other fields.
Application of STM in the study of topological materials
Tong Zhang
Scanning tunneling microscopy (STM) is a powerful tool to study the electron properties at the atomic scale with very high energy resolution. In this talk I will discuss the application of STM in topological materials, mainly based on our previous works on Bi2Se(Te)3 and related materials [1~4]. I will also present our recent STM results on the superconductivity of CuxBi2Se3 under rotational magnetic field.
Refs:
[1]. T. Zhang, et al, Experimental demonstration of the topological surface states protected by the time-reversal symmetry, Physical Review Letters 103, 266803 (2009)
[2]. P. Cheng, et al, Landau Quantization of massless Dirac Fermions in Topological Insulator, Physical Review Letters 105, 076801 (2010)
[3]. T. Zhang, J. Ha, N Levy, Y. Kuk, J. Stroscio*, Electric Field Tuning of the Surface Band Structure of Topological Insulator Sb2Te3 Thin Films, Physical Review Letters 111, 056803 (2013)
[4]. N.Levy, T. Zhang, J. Ha, F. Sharifi, A.-A. Talin, Y. Kuk, J.-A. Stroscio*, Experimental evidence for s-Wave pairing symmetry in superconducting CuxBi2Se3 single crystals using a Scanning Tunneling Microscope, Physical Review Letters 110, 117001 (2013)
The President of Fudan University: Ningsheng Xu （许宁生）
The Dean of Department of Physics, Fudan University: Jian Shen （沈健）
Panel discussion on the theme of "quantum matter sciences: roads ahead and international collaborations":
Group Photo of the Invited Speakers:
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