Subradiance in a Large Cloud of Cold Atoms

Area of Science:

• Atomic physics
• Quantum optics
• Condensed matter physics

Background:

• Superradiance in atomic ensembles has been extensively studied since Dicke's work.
• Subradiance, a contrasting phenomenon, has remained elusive due to weak environmental coupling and decoherence.

Purpose of the Study:

• To experimentally observe and characterize subradiance in a large, dilute cold-atom sample.
• To investigate the decay dynamics of subradiant states and their dependence on system parameters.

Main Methods:

• Utilized a far-detuned laser to minimize multiple scattering in a cold-atom sample.
• Observed temporal fluorescence decay after a sudden laser switch-off.
• Measured decay time constants and their scaling with the cooperativity parameter.

Main Results:

• Detected a distinct, very slow fluorescence decay after the initial fast decay.
• Observed subradiant decay time constants up to 100 times the natural lifetime of individual atoms.
• Found that the subradiant time constant scales linearly with the cooperativity parameter (optical depth).

Conclusions:

• Successfully demonstrated experimental observation of subradiance in an extended cold-atom system.
• The observed subradiant behavior aligns with predictions from coupled-dipole models.
• This work opens avenues for exploring subradiance and its applications in quantum technologies.