报告题目（Title）：Controlling interacting few-body systems
报告人（speaker）: Prof. Thomas Busch
摘要（Abstract）:Understanding the properties and dynamics of interacting quantum few-body system and developing methods for coherent control over them is one of the important tasks for extending quantum technologies into ever larger Hilbert spaces. Cold atoms are a well-understood and highly flexible system to explore new questions and tools, and regularly function as the proof-of-principle system for new ideas.
In this presentation I will discuss how the few-body states of multi-component and interacting cold atom systems can be efficiently described and engineered. In particular we consider how an initially non-interacting system can be driven into the strong interactions regime by ramping up a Feshbach resonance, without the creation of out-of-equilibrium excitations. For this we use a variational shortcut-to-adiabaticity approach and quantify it by analyzing the thermodynamic property of the irreversible work created in the system. We also base the fidelity on the reduced density matrix of each subsystem in order to account for all correlations correctly.
报告题目（Title）：Readout and control for a superconducting quantum computer
报告人（speaker）: Mikko Möttönen
摘要（Abstract）:Superconducting circuits provide a promising basis to build a large-scale quantum computer. All three key ingredients - readout, reset, and gates - need to be carried out much faster than the natural decoherence time of the qubits in order to run possibly useful noisy intermediate-scale quantum algorithms, and especially for the implementation of fault-tolerant logical qubits. To this end, we discuss the recent progress at the Quantum Computing and Devices (QCD) Labs at Aalto University in collaboration with VTT Technical Research Centre of Finland. Namely, we present schemes and experiments on the fast initialization of quantum circuits based, for example, on our recently invented quantum-circuit refrigerator. We also introduce a novel method for reading out qubits referred to as multi channel readout. Finally, we discuss how these efforts gave rise to a spinout company IQM.
报告题目（Title）：Treasure hunt for computational problems that can be solved faster by quantum annealing
报告人（speaker）: Prof. Barry Sanders
摘要（Abstract）: "Much current quantum computing research focuses on building quantum annealers, which are analogous to purpose-built simulated annealing machines but enhanced by quantum properties. However, quantum annealing is not yet shown to provide a quantum speed-up for any computational problem thus far. On the other hand, optimism is rife that a computational speedup will be found for the right problem. We explain this search for quantum-enhanced computational problems as a treasure hunt for potential benefits of quantum annealing. This treasure hunt could have many buried treasures of similar types or be of quite different types, or perhaps no buried treasure exists at all.
报告题目（Title）：Emergent Quantum Simulators
报告人（speaker）: Prof. Jörg Schmiedmayer
报告题目（Title）：Machine Learning Enabled Automated Quantum Algorithm Design
报告人（speaker）: Xiaopeng Li (李晓鹏)
Fudan University（复旦大学）
摘要（Abstract）:Quantum algorithm design lies in the hallmark of applications of quantum computation and simulation. In this talk, I will present a deep reinforcement-learning (RL) architecture for automated algorithm design in the framework of quantum-adiabatic-algorithm. Our approach is applicable to a class of problems with solution hard-to-find but easy-to-verify, e.g., searching, factorization, and NP-complete problems. We benchmark this approach in Grover-search and 3-SAT problems, and find that the adiabatic-algorithm obtained by our RL approach leads to significant improvement in the success probability and computing speedups for both moderate and large number of qubits compared to conventional algorithms. The RL-designed algorithm is found to be qualitatively distinct from the linear-algorithm in the resultant distribution of success probability. We show that the RL approach is able to produce algorithms with improved computation-complexity scaling automatically, and that the algorithm by this approach has emergent transferability. These findings imply a huge potential for reinforcement learning application to automated quantum adiabatic algorithm design. Further considering the established complexity-equivalence of circuit and adiabatic quantum algorithms, we expect the RL-designed adiabatic algorithm to inspire novel circuit algorithms as well. Our approach is potentially applicable to different quantum hardwares from trapped-ions and optical-lattices to superconducting-qubit devices.
报告题目（Title）：Application of reinforcement learning to quantum control problems
报告人（speaker）: Xin Wang (王欣)
City University of Hong Kong（香港城市大学）
摘要（Abstract）:In this talk, I will present results from our recent attempts to apply reinforcement learning techniques to quantum control problems. I will discuss how reinforcement learning can be used to generate controlling pulse sequences that prepare a desired quantum state, and its efficiency is compared to two other non-machine-learning methods, namely the stochastic gradient descent and Krotov methods [1]. We have found that reinforcement learning has a particular advantage: it can adaptively optimize the sequences so that the simplest and most optimal ones are found. Moreover, reinforcement learning is also suitable for problems in which controls are discrete, while the Krotov method strongly favors continuous problems. I will also discuss our recent work to apply a version of reinforcement learning to quantum parameter estimation [2]. We have shown that the control generated by our method is more transferrable than traditional methods such as GRAPE, namely the pulse sequences generated by the trained neuron network can be easily used to measure parameters having a range of values with reasonable precision. Our work shows that reinforcement learning can be a judicious numerical method when optimal quantum control is desired.
[1] X.-M. Zhang, Z. Wei, R. Asad, X.-C. Yang, and XW, arXiv:1902.02157.
[2] H. Xu, J. Li, L. Liu, Y. Wang, H. Yuan, and XW, arXiv:1904.11298.
报告题目（Title）：Layered Topological Materials
报告人（speaker）: Guoxing Miao (苗国兴)
IQC
摘要（Abstract）:Topologically protected bands are useful toolset to engineer novel devices towards both quantum and classical information processing. We show our efforts on topological insulators and Weyl semimetals, where the protected Dirac band structures serve as the platform to potentially host exotic composite particles for further manipulations. Specifically, in a vertical topological insulator Josephson junction, edge currents show Andreev bound states centered at zero energy signaturing presence of unconventional fermions. On the other hand, planar Hall effects in Weyl semimetals reveal mixed type of the Weyl fermions
报告题目（Title）：Quantum Learning Control –good solutions from “bad”models
报告人（speaker）: Rebing Wu (吴热冰)
Tsinghua University（清华大学）
摘要（Abstract）: In the quest to achieve scalable quantum information processing technologies, gradient-based optimal control algorithms (e.g., GRAPE) are broadly used for implementing high-precision quantum gates, but their performance is often hindered by deterministic or random errors in the system model and the control electronics. In this talk, we show that GRAPE can be taught to be smarter by learning from the data and/or from an imperfect model, and propose a series of gradient-based algorithms, deterministic or stochastic, for designing both robust and high-precision quantum control.
报告题目（Title）：TBD
报告人（speaker）: Yu Zhang (张昱)
University of Science and Technology of China（中国科学技术大学）
报告题目（Title）：Five-qubit quantum error correction in a superconducting system
报告人（speaker）: Xiongfeng Ma (马雄峰)
Tsinghua University（清华大学）
摘要（Abstract）:Universal fault-tolerant quantum computing relies on the implementation of quantum error correction. An essential milestone is the achievement of error-corrected logical qubits that genuinely benefit from error correction, outperforming simple physical qubits. In this talk, I present the recent implementation of the five-qubit quantum error correcting code, which can correct single generic qubit errors, in a superconducting system. This is achieved first by dedicated experimental optimization of our superconducting quantum qubits, enabling us to realize more than a hundred of quantum gates. We theoretically compiled and optimized the encoding process to minimize the number (eight) of nearest-neighbor controlled-phase gates. These experimental and theoretical advances finally enable us to realize the basic ingredients of a fully functional five-qubit error correcting code, involving the encoding of a general logical qubit into an error correcting code, with the subsequent verification of all key features including the identification of an arbitrary physical error, the power for transversal manipulation of the logical state, and state decoding. The work is recently put on arxiv [arXiv:1907.04507].
报告题目（Title）：TBD
报告人（speaker）: Oscar Dahslten
Southern University of Science and Technology（南方科技大学）
报告题目（Title）：Quantum memory of different degrees of freedom
报告人（speaker）: Dongsheng Ding(丁冬生)
University of Science and Technology of China（中国科学技术大学）
摘要（Abstract）:In the field of quantum information, a photon encoded with information in its different degrees of freedom enables quantum networks to carry much more information and increase their channel capacity greatly compared with those of current technology because of the inherent infinite Hilbert spaces. Quantum memories are indispensable to construct quantum networks of communication and computation, in which the distant nodes can be made to demonstrate information processing in time synchronization. Storing different degrees of freedom states has attracted significant attention recently, and many important advances in this direction have been achieved during the past years. I will talk about our works in this field, including polarization and orbital angular momentum qubits quantum memory, orbital angular momentum entangled state storage in two-dimensional and high-dimensional space. All achievements described here are very helpful to study different degrees of freedom quantum information processing and quantum information.
References
1. Dong-Sheng Ding, Wei Zhang, Zhi-Yuan Zhou, Shuai Shi, Bao-Sen Shi, Guang-Can Guo. Raman Quantum Memory of Photonic Polarized Entanglement. Nature Photonics. 9, 332–338 (2015).
2. Dong-Sheng Ding, Zhi-Yuan Zhou, Bao-Sen Shi, Guang-Can Guo. Single-photon-level quantum image memory based on cold atomic ensembles. Nat. Commun. 4. 2527(2013).
3. Dong-Sheng Ding, Wei Zhang, Zhi-Yuan Zhou, Shuai Shi, Xi-Shi Wang,Yun-Kun Jiang, Bao-Sen Shi. and Guang-Can Guo. Quantum Storage of Orbital Angular Momentum Entanglement in an Atomic Ensemble. Physical Review Letters. 114, 050502 (2015).
4. Wei Zhang, Dong-Sheng Ding†, Shuai Shi, Zhi-Yuan Zhou, Bao-Sen Shi, Guang-Can Guo, Experimental Realization of Memory-Memory Entanglement in Multiple Degrees of Freedom, Nat. Commun. 7. 13514 (2016).
5. Dong-Sheng Ding†, Wei Zhang, Shuai Shi, Zhi-Yuan Zhou, Yan Li, Bao-Sen Shi, and Guang-Can Guo, High-dimensional entanglement between distant atomic-ensemble memories, Light science & applications 5,e16157 (2016).
6. Wei Zhang, Ming-Xin Dong, Dong-Sheng Ding†, Shuai Shi, Kai Wang, Shi-Long Liu, Zhi-Yuan Zhou, Guang-Can Guo, and Bao-Sen Shi. Einstein-Podolsky-Rosen entanglement between separated atomic ensembles. Physical Review A 100, 012347 (2019).
7. Dong-Sheng Ding†, Ming-Xin Dong, Wei Zhang, Shuai Shi,Yi-Chen Yu, Ying-Hao Ye, Guang-Can Guo, and Bao-Sen Shi. Broad Spiral Bandwidth of Orbital Angular Momentum Interface between Photon and Memory. To appear in Communication Physics.
报告题目（Title）：Space-Depth Tradeoff of CNOT Circuits
报告人（speaker）:Xiaoming Sun(孙晓明)
The Institute of Computing Technology of the Chinese Academy of Sciences（中科院计算所）
报告题目（Title）：Quantum simulation by superconducting quantum circuits.
报告人（speaker）: Heng Fan(范桁)
Institute of Physics CAS（中科院物理所）
摘要（Abstract）:Superconducting quantum circuits are promising for quantum simulation of various physical phenomena. Recently, remarkable progresses have been made in this direction. In this talk, I will present our recent results about strongly correlated quantum walks in a 1D array of 12-qubit superconducting quantum processor. The one- and two-particle quantum walks are realized by flip one qubit or two qubits after initialization. For one-particle quantum walks, the propagations of quantum information including entanglement are shown precisely. We can find that the propagations of different physical quantities can be described by Lieb-Robinson bounds which are analogous to light-cone phenomenon. The anti-bunching is shown in two-particle quantum walks due to strongly correlated excitations. Results about simulation of localizations for a Bose-Hubbard ladder model by 20 superconducting qubits, generation of 20-qubit Schrodinger cat states and 18-qubit GHZ state with superconducting qubits will be presented.
References:
[1] C. Song et al., Science 365, 574-577 (2019).
[2] Z. Yan et al., Science 364, 753-756 (2019).
[3] Y. Ye et al., Phys. Rev. Lett. 123, 050502 (2019).
报告题目（Title）：Toward automatic verification of quantum programs
报告人（speaker）:Mingsheng Ying (应明生)
Institute of Software Chinese Academy of Sciences（中科院软件所）
摘要（Abstract）: We will systematically review the results obtained by the speaker and his collaborators in verification of quantum programs in the last 10 years, including quantum Hoare logic, invariant generation and termination analysis for quantum programs. We will also present the automatic tools for verification of quantum programs recently developed by the speaker's team. Some problems for future research will be proposed at the end of the talk.
报告题目（Title）：Hybrid quantum-classical computing: A distributed semi-quantum computing model with application in phase estimation
报告人（speaker）: Daowen Qiu(邱道文) Sun Yat-sen University（中山大学）
摘要（Abstract）: It seems still difficult to design a large universal quantum computer nowadays. Even for some special quantum computers, their cost of manufacture is also very high. So, another way is to consider how to use small size quantum computers to solve some problems with essentially faster than classical computers.
In this talk, I would like to design a distributed semi-quantum algorithm for phase estimation which has a better time complexity even than the conventional quantum algorithm. The basic idea is to use distributed micro quantum computers to process respectively a small quantity of quantum states and then communicate with a given classical computer via classical channel to transport the results. Furthermore, we would mention other hybrid quantum-classical devices: quantum finite automata with classical states; semi-quantum key distribution.
报告题目（Title）：Duality computing in quantum computers
报告人（speaker）: Prof.Guilu Long (龙桂鲁) Tsinghua University（清华大学）