Atomic, Optical and Quantum Physics Group

People

Research Activities

The group is focused on strongly interacting Fermi gases, synthetic spin-orbit couplings in atomic gases; quantum cryptographic protocols; implementation of quantum computation and quantum simulation in cold atom and solid-state systems.

Prof. Chau focuses on the theoretical study of quantum information theory and quantum computation. The aim is to prove the security of various quantum cryptographic protocols as well as getting a better understanding of how to manipulate quantum information by quantum error-correction codes. In collaboration with researchers in HP Labs, Bristol, our group has recently proven that certain quantum key distribution scheme is unconditionally secure as well as obtained a U.S. patent on certain quantum key distribution protocols.

Prof. Yang conducts both theoretical and experimental research in nanophotonics, free electron optics, and topological photonics. In particular, he is interested in the extreme light-matter interaction between photons and material electrons, free electrons, and synthetic gauge fields. His recent research includes a general electromagnetic framework at the extreme nanoscale, a fundamental upper limit to spontaneous free-electron radiation, the observation of strong interaction between free electrons and photonic flat bands, and the realization of the long-sought non-Abelian Aharonov-Bohm effect.

Prof. Wang investigates theoretically quantum information physics, and explores implementation of quantum computation and quantum simulation in physical systems, including superconducting quantum circuits and cold atoms as well as trapped ions. Current research interests extend to include topological quantum computing and quantum machine learning. Recently, his group has established a hybrid theory for realizing quantum machine learning tasks, taking the both advantages of discrete and continuous quantum variables.

Prof. Zhang studies ultra-cold atomic gases, which have emerged as a multi-disciplinary subject and is at the interface of modern atomic and molecular physics, quantum optics and condensed matter physics. It proves to be an excellent laboratory for investigating strongly interacting quantum many-body systems and in particular correlated quantum phases and phase transitions. Current topics of interest include strongly interacting two-component Fermi gases and BEC-BCS crossover, synthetic gauge fields and spin-orbit couplings in atomic gases, novel mixtures of bosons and fermions.

Prof. Luu’s research focuses on studying electronic processes in their native time scale, which requires tools that are extremely fast, i.e. as fast as hundreds of atto-second (1as = 10-18 s). By combining high power laser pulses and strong-field physics, creation of attosecond pulses was made possible. The tools, either extreme ultraviolet or optical attosecond pulses, play a crucial role in time-resolved spectroscopy where the extreme temporal resolution allows one to initiate, follow, and control electronic processes in matters with the highest possible fidelity. Furthermore, they additionally enable studies of electronic properties of matters in a novel approach.

Some Representative Publications

Prof. H.F. Chau

1. "Decoy-State Quantum Key Distribution With More Than Three Types Of Photon Intensity Pulses", H. F. Chau, Physical Review A (Rapid Communications), 97, 040301(R) (2018).
2. "Quantum Key Distribution Using Qudits That Each Encode One Bit Of Raw Key", H.F. Chau, Physical Review A, 92, 062324 (2015).
3. "Metrics on Unitary Matrices and their Application to Quantifying the Degree of Non-commutativity between Unitary Matrices", H.F. Chau, Quantum Information and Computation, 11, 721-740 (2011).
4. "Unconditionally Secure Key Distribution in Higher Dimensions by Depolarization", H.F. Chau, IEEE Transactions on Information Theory, 51, 1451-1468 (2005).
5. "Practical scheme to share a secret key through a quantum channel with a 27.6% Bit Error Rate", H. F. Chau, Physical Review A, 66, 060302(R): 1-4 (2002).
6. "Unconditional Security of Quantum Key Distribution over Arbitrarily Long Distances", H.K. Lo and H.F. Chau, Science, 283, 2050-2056 (1999).
7. "Is Quantum Bit Commitment Really Possible?", H.K. Lo and H.F. Chau, Physical Review Letters, 78, 3410-3413 (1997).

Prof. Y. Yang

1. "A General Theoretical and Experimental Framework for Nanoscale Electromagnetism", Y. Yang*, D. Zhu*, W. Yan, A. Agarwal, M. Zheng, J. D. Joannopoulos, P. Lalanne, T. Christensen, K. K. Berggren, M. Soljačić, Nature 576, 248 (2019)
2. "Synthesis and Observation of Non-Abelian Gauge Fields in Real Space", Y. Yang, C. Peng, D. Zhu, H. Buljan, J. D. Joannopoulos, B. Zhen, M. Soljačić, Science 365, 1021 (2019)
3. "Maximal Spontaneous Photon Emission and Energy Loss from Free Electrons", Y. Yang, A. Massuda, C. Roques-Carmes, S. E. Kooi, T. Christensen, S. J Johnson, J. D. Joannopoulos, O. D. Miller, I. Kaminer, M. Soljačić, Nature Physics 14, 894 (2018)
4. "Low-loss Plasmonic Dielectric Nanoresonators", Y. Yang, O.D. Miller, T. Christensen, J. D. Joannopoulos, M. Soljačić, Nano Letters 17, 3238 (2017)
5. "All-angle negative refraction of highly squeezed plasmon and phonon polaritons in graphene–boron nitride heterostructures”, Xiao Lin*, Yi Yang*, Nicholas Rivera, Josué J López, Yichen Shen, Ido Kaminer, Hongsheng Chen, Baile Zhang, John D Joannopoulos, Marin Soljačić, PNAS, 114, 6717 (2017)

Prof. Z.D. Wang

1. "Novel Z₂ topological metals and semimetals", Y. X. Zhao and Z. D. Wang, Phys. Rev. Lett. 116, 016401 (2016).
2. "Unified theory of PT and CP invariant topological metals and nodal superconductors", Y. X. Zhao, A. P. Schynder, and Z. D. Wang, Phys. Rev. Lett. 116, 156402 (2016).
3. "Disordered Weyl semimetals and their topological family", Y.X. Zhao and Z.D. Wang, Phys. Rev. Lett., 114, 206602 (2015).
4. "Topological classification and stability of Fermi surfaces", Y.X. Zhao and Z.D. Wang, Phys. Rev. Lett., 110, 240404 (2013).
5. "Unconventional Geometric Quantum Computation", S.L. Zhu and Z.D. Wang, Phys. Rev. Lett., 91, 187902 (2003).
6. "Implementation of Universal Quantum Gates Based on Nonadiabatic Geometric Phases", S.L. Zhu and Z.D. Wang, Phys. Rev. Lett., 89, 097902 (2002).

Prof. S.Z. Zhang

1. "Evidence for Universal Relations Describing a Gas with p-Wave Interactions", C. Luciuk, S. Trotzky, S. Smale, Z. Yu, S. Zhang, and J. H. Thywissen, Nature Physics, 6, 599-605 (2016)
2. "Universal Relations for a Fermi Gas Close to a p-Wave Interaction Resonance", Z.H. Yu, J.H. Thywissen, S.Z. Zhang, Physical Review Letters, 115, 135304:1-5 (2015)
3. “Transverse Demagnetization Dynamics of a Unitary Fermi Gas”, A.B. Bardon, S. Beattie, C. Luciuk, W. Cairncross, D. Fine, N.S. Cheng, G.J.A. Edge, E. Taylor, S.Z. Zhang, S. Trotzky, J.H. Thywissen, Science, 344, 722-724 (2014)
4. “Theory of quantum oscillations in the vortex-liquid state of high-T_c superconductors”,S. Banerjee, S.Z. Zhang, M. Randeria, Nature Communications, 4, 1700:1-7 (2013)
5. "Bose-Einstein condensates with spin-orbit interaction", T.L. Ho and S.Z. Zhang, Physics Review Letter, 107, 150403 (2011)
6. "BEC-BCS crossover induced by a synthetic non-abelian gauge field", J.P. Vyasanakere, S.Z. Zhang and V. Shenoy, Physics Review B, 84, 014512 (2011)
7. "Atom loss maximum in ultracold Fermi gases", S.Z. Zhang and T.L. Ho, New Journal of Physics, 13, 055003 (2011)
8. "Universal properties of the ultracold Fermi gas", S.Z. Zhang and A.J. Leggett, Physics Review A, 79, 023601 (2009)