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Coherence time limit of the biphotons generated in a dense cold atom cloud
Zhiguang Han1, Peng Qian1, L Zhou1
1Quantum Institute for Light and Atoms, State Key Laboratory of Precision Spectroscopy, Department of Physics, East China Normal University, No. 500 Dongchuan Road, Shanghai, 200241, China.
Scientific Reports
|March 18, 2015
Summary
Researchers achieved a record 2.34 μs coherence time for biphotons using spontaneous four-wave mixing in cold atoms. This breakthrough enhances light-atom interactions for quantum technologies.
Area of Science:
- Quantum Optics
- Atomic Physics
- Quantum Information Science
Background:
- Biphotons with long coherence times are crucial for strong light-atom coupling.
- Strong coupling is essential for quantum information processing, storage, and communication.
- Direct manipulation of biphoton wavefunctions requires coherence times over submicroseconds.
Purpose of the Study:
- To generate narrow-band biphotons with an extended coherence time.
- To investigate the factors limiting biphoton coherence time.
- To explore the potential for ultra-long coherence times in quantum applications.
Main Methods:
- Spontaneous four-wave mixing (SFWM) in a dense cold atom cloud.
- Utilizing a narrow electromagnetically-induced transparency (EIT) window for anti-Stokes photons.
- Detailed analysis of factors limiting coherence time.
Main Results:
- Generation of narrow-band biphotons with a coherence time of 2.34 μs.
- Achieved the longest coherence time for paired photons reported to date.
- Identified EIT coherence as a critical factor determining biphoton coherence time.
Conclusions:
- The coherence time of biphotons is fundamentally limited by the EIT dephasing rate.
- Ultra-long biphoton coherence times exceeding ten microseconds are achievable.
- Further improvements in EIT dephasing rate below 100 kHz could unlock new quantum capabilities.
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