Recent results on quantum optics
Achieving strong radiative interactions between single atoms and the fields of nanoscopic optical waveguides or resonators has been a long quest in quantum information science . Strong atom-photon interactions also present new opportunities in atomic based quantum simulators as photon mediated interactions lead to novel quantum spin dynamics and transport phenomena. For this purpose, we have designed a one-dimensional (1D) photonic crystals that support a waveguide mode suitable for far-off resonant optical trap (FORT) for neutral atoms within a unit cell, as well as a second probe mode that accommodates strong atom-photon interactions. Moreover, we have investigated and analyzed a new hybrid trap that combines optical and Casimir-Polder forces to achieve realistic and stable trapping near dielectric nanostructures. By band structure engineering, the atom-photon coupling rate into the probe mode can exceed the rate into all other modes by more than tenfold , enabling diverse investigations of photon-mediated interactions for 1D and 2D atomic lattices and waveguide QED [3, 4]. We have implemented this theoretical framework in the following experiments:
Atom-light interaction in 1D photonic crystals
We designed and fabricated 1D Silicon-Nitrite dielectric waveguides , and studied atom-light interactions using laser-cooled cesium atoms . By using a guided mode as a FORT, we observed that single atoms can be efficiently guided into the nano-waveguide. We measured a large coupling rate to the waveguide mode, about 0.4 times (now up to 3 times) the freespace decay rate, and achieved ~30% (now 75%) single-atom reflectivity of the probe mode. Our result exceeds state-of-the-art nanofiber experiments by ten-fold, entering a regime that collective light transport along a 1D chain of atoms can be excited.
For more details, see A. Goban, C.-L. Hung, S.-P. Yu, J. D. Hood, J. A. Muniz et al. Nature Comm. 5, 3808 (2014) .
See also: Kimble group and Painter group at Caltech.
 H. J. Kimble, The quantum internet. Nature 453, 1023 (2008).
 C.-L. Hung, S. M. Meenehan, D. E. Chang, O. Painter and H. J. Kimble, Trapped Atoms in One-Dimensional Photonic Crystals. New J. Phys. 15, 083026 (2013).
 J. S. Douglas, H. Habibian, C.-L. Hung , A. V. Gorshkov, H. J. Kimble and D. E. Chang, Photonic crystal cavities created by single atoms enable tunable long-range interactions. accepted by Nature Photonics (2015).
 A. González-Tudela, C.-L. Hung , D. E. Chang, H. J. Kimble and I. Cirac, Subwavelength vacuum lattices and photon-mediated atomic interactions in photonic crystals. arXiv:1407.7336 (2014).
 S.-P. Yu, J. D. Hood, J. A. Muniz, M. J. Martin, R. Norte, C.-L. Hung , S. M. Meenehan, J. D. Cohen, O. Painter and H. J. Kimble, Nanowire photonic crystal waveguides for single-atom trapping and strong light-matter interactions. Appl. Phys. Lett. 104, 111103 (2014).
 A. Goban, C.-L. Hung, S.-P. Yu, J. D. Hood, J. A. Muniz, J. H. Lee, M. J. Martin, A. C. McClung, K. S. Choi, D. E. Chang, O. Painter and H. J. Kimble, Atom-Light Interactions in Photonic Crystals. Nature Comm. 5, 3808 (2014).