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23 April 2024 |
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Low-Loss High-Fidelity Frequency-Mode Hadamard Gates Based on Electromagnetically Induced Transparency | | Kao-Fang Chang
; Ta-Pang Wang
; Chun-Yi Chen
; Yi-Hsin Chen
; Yu-Sheng Wang
; Yong-Fan Chen
; Ying-Cheng Chen
; Ite A. Yu
; | | Date: |
8 Jul 2019 | | Abstract: | Frequency-encoded photonic qubits are not only more stable over long
transmission distances but also more robust against birefringent materials. A
50/50 frequency beam splitter (FBS) is the Hadamard gate in quantum logic
operation, which coherently converts a photon in one frequency or wavelength
mode to another photon in the superposition of two different modes. Previous
works revealed that the Hadamard gates or FBS’s operating at the single-photon
level had overall efficiencies or output-to-input ratios less than 50%. Here,
our FBS is made with the four-wave mixing (FWM) process based on the
dual-$Lambda$ electromagnetically induced transparency (EIT) scheme. We
achieved an overall efficiency of 90$pm$4% with coherent-state single photons,
which is the best up-to-date record for 50/50 FBS. In addition, we utilized
this EIT-based scheme to perform wavelength conversion with light pulses of
photon number less than one. We obtained an output-to-input ratio of 84$pm$4%,
which is not only the highest record currently achieved, but also the first
experimental demonstration of preservation of the quantum state in the
dual-$Lambda$ EIT scheme. This demonstration was revealed by the fidelity of
our Hadamard gate. To measure the fidelity, we propose a novel method using
Hong-Ou-Mandel interference (HOMI) for quantum process tomography. The fidelity
of our Hadamard gate indicated by the HOMI’s $g^{(2)}$ measurement is
0.99$pm$0.01. This low-loss high-fidelity Hadamard gate or wavelength
converter based on the dual-$Lambda$ EIT scheme can lead to useful operations
or devices, such as entanglement swapping, multiplexer, etc., in long-distance
quantum communication. | | Source: | arXiv, 1907.3393 | | Services: | Forum | Review | PDF | Favorites | |
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