Passive CPHASE Gate via Cross-Kerr Nonlinearities.

@article{Brod2016PassiveCG,
  title={Passive CPHASE Gate via Cross-Kerr Nonlinearities.},
  author={Daniel Jost Brod and Joshua Combes},
  journal={Physical review letters},
  year={2016},
  volume={117 8},
  pages={
          080502
        }
}
A fundamental and open question is whether cross-Kerr nonlinearities can be used to construct a controlled-phase (cphase) gate. Here we propose a gate constructed from a discrete set of atom-mediated cross-Kerr interaction sites with counterpropagating photons. We show that the average gate fidelity F between a cphase and our proposed gate increases as the number of interaction sites increases and the spectral width of the photon decreases; e.g., with 12 sites we find F>99%. 

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