Group Delay Controlled by the Decoherence of a Single Artificial Atom

Area of Science:

• Quantum optics
• Solid-state physics
• Quantum information science

Background:

• Controlling light speed at the single-photon level is crucial for quantum technologies.
• Waveguide quantum electrodynamics (QED) offers a platform for manipulating quantum states of light.

Purpose of the Study:

• To demonstrate dynamic control over microwave light velocities using a single artificial atom.
• To explore mechanisms for slowing down and speeding up light pulses in a waveguide.

Main Methods:

• Utilizing a superconducting artificial atom positioned before a mirror in a waveguide.
• Implementing two distinct methods based on controlling radiative decay and nonradiative decoherence rates.
• Tuning atomic radiative decay via mirror-induced interference effects.
• Modulating atomic nonradiative decoherence through optical pumping.

Main Results:

• Achieved dynamic control over microwave light velocities.
• Observed positive group delay when radiative decay dominates over decoherence.
• Observed negative group delay when nonradiative decoherence dominates.
• Demonstrated the influence of atomic decay rates on light propagation speed.

Conclusions:

• The study presents novel methods for manipulating light speed at the quantum level.
• These techniques advance signal processing capabilities within waveguide QED systems.
• The findings have potential applications in quantum information processing and quantum technologies.