Nonlinear quantum optics in a waveguide: distinct single photons strongly interacting at the single atom level

Area of Science:

• Quantum electrodynamics
• Photonics
• Atomic physics

Background:

• Strong light-matter interactions are crucial for quantum information processing.
• Waveguide quantum electrodynamics (QED) offers a promising avenue for controlling photon interactions.
• Existing methods often rely on high-quality cavities or dense atomic ensembles.

Purpose of the Study:

• To propose and theoretically investigate a waveguide-QED system for strong photon-photon interactions.
• To demonstrate photon-induced phase shifts and tunneling using a single atom coupled to a waveguide.
• To explore single-photon scattering mediated by a classical control beam.

Main Methods:

• Theoretical modeling of a ladder-type three-level atom coupled to a waveguide.
• Analysis of photon scattering and phase shift phenomena under specific frequency and coupling conditions.
• Investigation of the system's response to both quantum (single photon) and classical control fields.

Main Results:

• A control photon tuned to the upper transition induces a π phase shift on a probe photon.
• The control photon enables tunneling of the probe photon through an otherwise reflective transition.
• The system exhibits single-photon scattering controlled by a classical beam.

Conclusions:

• Waveguide-QED systems with single atoms can achieve strong photon-photon interactions.
• This approach offers an alternative to traditional methods like high-quality cavities.
• The demonstrated control mechanisms are valuable for quantum information processing applications.