Siyuan Han,Professor

2067 Malott Hall
TEL: (785) 864-5831
FAX: (785) 864-5262
Email: han@ku.edu

Professional Background:

2003-Present: Professor, Physics & Astronomy, University of Kansas
2000-2003: Associate Professor (tenured), Physics & Astronomy, University of Kansas
1997-2000: Associate Professor (tenure track), Physics & Astronomy, University of Kansas
1997-2000: Assistant Professor, Physics & Astronomy, University of Kansas

Education:

1986: Ph.D., Experimental Condensed Matter Physics, Iowa State University
1982: B.S., Physics, University of Science and Technology of China

Honors Awards:

Guomoruo Award in Physics, USTC, China, 1981
Member, American Physics Society (APS)
Member, American Association for the Advancement of Science (AAAS)

Research Interests:

Micro- and nano-scale device physics and applications
· Quantum properties of SQUIDs and Josephson junctions and their application to quantum computing.
· Quantum mechanics of macroscopic objects (e.g., Schrodinger's Cat) using superconducting quantum interference devices (SQUIDs).
· Physics and application of Coulomb blockade in nano-devices.
· Stochastic nonlinear dynamic systems.

The goal of our quantum computing project is to develop basic building blocks of a solid state quantum computer using superconducting quantum bits (qubits). In our case, a qubit is essentially a small ring of superconductor containing a Josephson junction. Electrical current in the ring flows without resistance (hence is called supercurrent) and in contrast to one's intuition the circulating current in the ring can flow in two opposite directions simultaneously - a direct consequence of quantum mechanics and one of the cornerstones of quantum computation. However, to maintain a qubit in such a quantum coherent state long enough for useful quantum computation is extremely difficult since interaction between a qubit and its electromagnetic environment can quickly destroy quantum coherence. Our aim is to identify and understand major decoherence mechanisms in superconducting qubits and increase coherence time by optimizing qubit design, quantum gate implementation, control and readout circuits, material properties, and fabrication processes.

Selected Publication:

1. Yang Yu, Shiliang Zhu, Guozhu Sun, Xueda Wen, Ning Dong, Jian Cheng, Peiheng Wu, and Siyuan Han , Quantum Jumps between Macroscopic Quantum States of Superconducting Qubit Coupled to a Microscopic Two-Level Syatem , Phys. Rev. Lett. , 101, 151001 (October 2008).

2. R. Harris, M. W. Johnson, Siyuan Han, A. J. Berkley, J. Johannsson, P. Bunyk, S. Govorkov, M. C. Thom, S. Uchaikin, B. Bumble, A. Fung, A. Kaul, A. Kleinsasser, C.J.S. Truncik, M.H.S. Amin, and D. V. Averin, Probe temperature dependent noise in flux qubits via macroscopic resonant tunneling, Phys. Rev. Lett, 101, 117003 (Sept. 2008).

3. Sun Guozhu, Wang Yiwen, Cao Junyu, Chen Jian, Ji Zhengming, Kang Lin, Xu Weiwei, Yu Yang, Siyuan Han, and Wu Peiheng, Microwave-induced phase escape in a Josephson tunnel junction , Phys. Rev. B77, 104531 (March 2008).

4. Zhongyuan Zhou, Shih-I Chu, and Siyuan Han, Relaxation and decoherence in a resonantly driven qubit , J. Phys. B: At. Mol, Opt. Phys. 41, 045506 (Feb. 2008).

5. Shao-Xiong Li, Wei Qiu, Siyuan Han, Y.F. Wei, X.B. Zhu, C.Z. Gu, S.P. Zhao, and H.B. Wang, Observation of Macroscopic Quantum Tunneling in a Single Bi-2212 Surface Intrinsic Josephson Junction, Phys. Rev. Lett , 99, 037002 (July 2007).

6. Chui-Ping Yang and Siyuan Han, Local measurement for a set of n-qubit maximally entangled states in cavity QED, Phys. Rev. A, 75, 052315 (2007).

7. Chui-Ping Yang and Siyuan Han, Rotation gate for a three-level superconducting quantum interference device qubit with resonant interaction, Phys. Rev. A, 74, 044302 (2006).

8. Zhongyuan Zhou, Shih-I Chu, and Siyuan Han, A unified approach to realize universal quantum gates in a coupled two-qubit system with fixed always-on coupling, Phys. Rev. B, 73, 104521 (2006).

9. Chui-Ping Yang and Siyuan Han, Realization of an n-qubit controlled-U gate with superconducting quantum interference devices or atoms in cavity QED, Phys. Rev. A, 73, 032317 (2006).

10. Chui-Ping Yang and Siyuan Han, An n-qubit controlled phase gate with superconducting quantum interference devices coupled to a resonator, Phys. Rev. A, 72, 032311 (2005).

11. Zhongyuan Zhou, Shih-I Chu, and Siyuan Han, Rapid optimization of working parameters of microwave-driven multi-level qubits for minimal gate leakage, Phys. Rev. Lett. 95, 120501 (2005).

12. Chui-Ping Yang and Siyuan Han, Extracting an arbitrary relative phase from a multiqubit two-component entangled state, Phys. Rev. A, 72, 014306 (2005).

13. Chui-Ping Yang and Siyuan Han, A scheme for the teleportation of multiqubit quantum information via the control of many agents in a network, submitted to Phys. Lett. A, 343, 267-273 (2005).

14. J. Mannik, S. Li, W. Qiu, W. Chen, V. Patel, S. Han, and J. E. Lukens, Crossover from Kramers to phase-diffusion switching in hysteretic DC-SQUIDs, Phys. Rev. B 71, 220509(R) (2005).

15. Chui-Ping Yang and Siyuan Han, Generation of Greenberger-Horne-Zeilinger entangled states with three SQUID qubits: a scheme with tolerance to non-uniform device parameters, Physica A 347, 253-267 (2005).

16. Chui-Ping Yang and Siyuan Han, Preparation of Greenberger-Horne-Zeilinger entangled states with multiple superconducting quantum interference device qubits/atoms in cavity QED, Physical Review A 70, 062323-1 - 7 (2004)

17. Zhongyuan Zhou, Shih-I Chu, and Siyuan Han, Suppression of energy-relaxation-induced decoherence in L-type three-level SQUID flux qubits: A dark-state approach, Physical Review B 70, 094513-1 - 5 (2004)

18. Chui-Ping Yang, Shih-I Chu, and Siyuan Han, Efficient many party controlled teleportation of multiqubit quantum information via entanglement, Physical Review A 70, 022329-1 - 8 (2004)

19. Chui-Ping Yang, Shih-I Chu, and Siyuan Han, Quantum information transfer and entanglement with SQUID qubits in cavity QED: A dark-state scheme with tolerance to non-uniform device parameters, Physical Review Letters 92, 117902 (2004)

20. Yang Yu and Siyuan Han, Resonant Activation over an Oscillating Barrier in Under-damped Josephson Tunnel Junction, Physical Review Letters 91, 127003 (2003)

21. Zhongyuan Zhou, Shih-I Chu, and Siyuan Han, Quantum computing with superconducting device: A three-level SQUID qubit, Physical Review B 66, 054527 (2002)

22. Shaoxiong Li, Yang Yu, Yu Zhang, Wei Qiu, Siyuan Han, and Zhen Wang, Quantitative study of macroscopic quantum tunneling in a dc SQUID - A system with two degrees of freedom, Physical Review Letters 89, 098301 (2002)

23. Yang Yu, Siyuan Han, Xi Chu, Shih-I Chu, and Zhen Wang, Coherent temporal oscillations of macroscopic quantum states in a Josephson junction, Science 296, 889-892 (2002)

24 . Siyuan Han, Yang Yu, Xi Chu, Shih-I Chu, and Zhen Wang, Time resolved measurement of disspation-induced decoherence in a josephson junction, Science 293, 1457 (2001)

25 . Siyuan Han, R. Rouse, and J. E. Lukens. Observation of cascade two-photon-induced transitions between fluxoid states of a SQUID, Physical Review Letters 84, 1300-1303 (2000)

Click on Pictures below for more information on Dr. Han's Research