Abstract:
We experimentally demonstrated a frequency beam splitter (FBS) with the tunable split ratio based on slow light, i.e., the effect of electromagnetically induced transparency, in the double-Lambda configuration. This FBS can be utilized as the frequency-mode Hadamard gate (FHG) or quantum frequency converter (QFC). Previous works showed that FGHs and QFCs operating at the single-photon level all had output-to-input ratios or overall efficiencies (including decay due to propagation or insertion loss in media, input coupling efficiency, frequency conversion efficiency, etc.) around 50% or less. Here, we achieved an overall efficiency of 90% with the FGH and that of 84% with the QFC. Both overall efficiencies reported by this work are the best up-to-date records. Furthermore, we utilized the Hong-Ou-Mandel interference (HOMI) to perform quantum process tomography. The measured photon-photon correlation function in the HOMI indicates that the fidelity of our FBS is 0.99. The FBS with the tunable split ratio demonstrated by the FHG and QFC in this work can lead to useful quantum operations or devices, e.g., entanglement swapping, quantum multiplexing, etc. As frequency-encoded photonic qubits are more stable over long transmission distances and more robust against birefringent materials, the low-loss high-fidelity FBS reported by the manuscript can greatly improve the success rate in long-distance quantum communication.
Brief Bio:
Career and Honors
- Chairman of the Department of Physics and Director of the Institute of Astronomy, NTHU (2017/8-now)
- Associate Professor, Professor, Distinguished Professor, & Tsing Hua Chair Professor (1995~now), NTHU
- Fellow of OSA since 2018
- Fellow of the Taiwan Physical Society since 2014
- Outstanding Research Award, Ministry of Science and Technology (2012) & (2016)
- Outstanding Scholar Award, Foundation for the Advancement of Outstanding Scholarship (2013) & (2016)
Research Interests
With cold atoms, my research group has been studying slow/stored light and quantum information manipulation. Slow/stored light not only greatly enhances the interaction time between light and matters to achieve a photon-photon interaction or qubit-qubit operation via media, but also provides a method of coherent transfer of wave functions between photons and atoms to lead to the application of quantum memory. These developments have made great impacts to quantum information manipulation.