Strongly interacting and highly entangled photons in asymmetric quantum   well with resonant tunneling
  We propose an asymmetric quantum well structure to realize strong interaction between two slow optical pulses. The linear optical properties and nonlinear optical responses associated with cross-Kerr nonlinearity are analyzed. Combining the resonant tunneling and the advantages of inverted-Y type scheme, giant cross-Kerr nonlinearity can be achieved with vanishing absorptions. Based on the unique feature, we demonstrate that highly entangled photons can be produced and photonic controlled phase gate can be constructed. In this construction, the scheme is symmetric for the probe and signal pulses. Consequently, the condition of group velocity matching can be fulfilled by adjusting the initial electron distribution. 
Shuangli Fan, Hui Sun, Xun-Li Feng, Chunfeng Wu, Shangqing Gong,   Guoxiang Huang, and C. H. Oh
physics.optics