Reducing noise in a Raman quantum memory.

Area of Science:

• Quantum Information Science
• Atomic and Molecular Physics
• Optical Physics

Background:

• Optical quantum memories are crucial for quantum computing and communication.
• Raman schemes offer broad bandwidth for ultrashort optical pulses but suffer from four-wave mixing noise.
• Eliminating noise is essential for practical quantum memory applications.

Purpose of the Study:

• To demonstrate a practical quantum memory using hydrogen molecules at room temperature.
• To overcome the challenge of four-wave mixing noise in Raman-based quantum memories.
• To enable the storage and retrieval of quantum information in ultrashort optical pulses.

Main Methods:

• Utilized the rotational states of hydrogen molecules for quantum memory.
• Employed polarization selection rules to suppress four-wave mixing.
• Stored and retrieved attenuated coherent states with specific photon numbers and pulse durations.

Main Results:

• Achieved quantum memory operation at room temperature using hydrogen.
• Successfully suppressed four-wave mixing noise through polarization selection.
• Stored and retrieved attenuated coherent states (mean photon number 0.9, pulse duration 175 fs).
• Measured a 1/e memory lifetime of 85.5 ps.
• Demonstrated a time-bandwidth product of approximately 480.

Conclusions:

• The developed hydrogen-based quantum memory operates effectively at room temperature.
• Suppression of four-wave mixing noise is achieved, enhancing memory fidelity.
• The memory's performance is suitable for integration with broadband heralded down-conversion and fiber-based photon sources for quantum technologies.