Strongly interacting photons in hollow-core waveguides

TL;DR

This paper investigates how cold atoms in hollow-core photonic waveguides can enable strong photon-photon interactions, leading to potential applications in quantum information processing such as deterministic phase gates and nondemolition measurements.

Contribution

It demonstrates the use of Rydberg-mediated interactions in hollow-core waveguides to achieve significant nonlinear effects at the single-photon level.

Findings

Achieved a conditional phase shift of pi for two single-photon pulses.

Proposed a method for quantum nondemolition measurement of photon number.

Showed potential for deterministic photonic quantum gates.

Abstract

Hollow-core photonic-crystal waveguides filled with cold atoms can support giant optical nonlinearities through nondispersive propagation of light tightly confined in the transverse direction. Here we explore electromagnetically induced transparency is such structures, considering a pair of counter-propagating weak quantum fields in the medium of coherently driven atoms in the ladder configuration. Strong dipole--dipole interactions between optically excited, polarized Rydberg states of the atoms translate into a large dispersive interaction between the two fields. This can be used to attain a spatially-homogeneous conditional phase shift of pi for two single-photon pulses, realizing a deterministic photonic phase gate, or to implement a quantum nondemolition measurement of the photon number in the signal pulse by a coherent probe, thereby achieving a heralded source of single or few photon pulses.