Optical interface created by laser-cooled atoms trapped in the evanescent field surrounding an optical nanofiber (0912.1179v2)

Abstract: Trapping and optically interfacing laser-cooled neutral atoms is an essential requirement for their use in advanced quantum technologies. Here we simultaneously realize both of these tasks with cesium atoms interacting with a multi-color evanescent field surrounding an optical nanofiber. The atoms are localized in a one-dimensional optical lattice about 200 nm above the nanofiber surface and can be efficiently interrogated with a resonant light field sent through the nanofiber. Our technique opens the route towards the direct integration of laser-cooled atomic ensembles within fiber networks, an important prerequisite for large scale quantum communication schemes. Moreover, it is ideally suited to the realization of hybrid quantum systems that combine atoms with, e.g., solid state quantum devices.

• The paper presents a dual-color optical dipole trap that uses red- and blue-detuned lasers to confine cesium atoms near a nanofiber.
• It achieves an optical depth of 13 with a 0.7% per-atom absorption across roughly 2000 trapped atoms, indicating strong atom-light coupling.
• This setup bridges atomic and solid-state quantum systems, advancing prospects for scalable, fiber-integrated quantum networks.

Optical Interface Created by Laser-Cooled Atoms Trapped in the Evanescent Field Surrounding an Optical Nanofiber

The paper presents an advancement in quantum technology through the integration of laser-cooled cesium atoms with optical nanofibers. This work bridges the gap between atomic and solid-state quantum systems, which is a crucial step towards effective hybrid quantum systems and extensive quantum communication networks.

Experimental Design and Methodology

The research leverages a multi-color evanescent field created around an optical nanofiber to trap and interface laser-cooled atoms. The nanofiber approach avoids the constraints associated with hollow core fibers, which are less compatible with fiber networks. The technique involves the use of a 500-nm diameter nanofiber waist that guides the fundamental HE$_{11}$ mode at both red- and blue-detuned wavelengths. The atoms are trapped in a one-dimensional optical lattice approximately 200 nm from the fiber surface, thereby enabling strong interaction with light transmitted through the fiber.

Key to the setup is a two-color optical dipole trap that uses a combination of red-detuned (1064 nm) and blue-detuned (780 nm) laser fields to create a potential well, exploiting the difference in decay lengths of the fields to achieve confinement. The team generated axial and azimuthal confinement by utilizing a standing wave from red-detuned counter-propagating lasers, supplemented with orthogonal linear polarization for optimal azimuthal potential confinement.

Results and Observations

The experimental configuration, consisting of a tapered optical fiber, effectively trapped cesium atoms, producing a notable optical depth (OD) of 13, which corresponded to a significant absorption of the guided probe light. The measured absorbance was about 0.7% per atom for approximately 2000 trapped atoms. The coherence time for the system was estimated at 50 ms, with a trap lifetime potential extending to 100 s, facilitated by large detunings to minimize scattering rates.

Quantitatively, the trapping frequencies realized were 200 kHz radially, 315 kHz axially, and 140 kHz azimuthally. The system demonstrated the feasibility of efficient atom-light coupling in proximity to the nanofiber, with conduction and thermal effects on decoherence being minor due to the low conductivity of the glass fiber and minimal surface interaction.

Implications and Future Prospects

This research potentially advances the field of quantum networking by paving the way for the integration of fiber-coupled atomic systems with solid-state nanostructures. Such integration is envisaged to enhance quantum optic applications, including non-linear optics. Furthermore, these findings suggest the possibility of exploring collective atomic states and manipulating spontaneous emission properties.

The immediate future of this research could focus on detailed studies of atom-photon interactions, especially in hybrid configurations. Furthermore, enhancing atom detection sensitivity and lifetime stability will likely drive the practical deployment of hybrid systems in real-world quantum technologies. There is also an opportunity to explore fiber-mediated interactions in high-density atom chains, which would further expand the utility of such systems in quantum simulation and computation.

Conclusion

The integration of an optical nanofiber with laser-trapped cesium atoms offers a promising pathway for the development of hybrid quantum technologies. The demonstrated methodology provides an effective means of atom trapping and interfacing, essential for future advancements in large-scale quantum networks and communication systems. As research progresses, these systems could become crucial components in quantum information processing and quantum communication architectures.