Published: June 29, 2015
Zhenda Xie, Tian Zhong, Sajan Shrestha, XinAn Xu, Junlin Liang, Yan-Xiao Gong, Allessandro Restelli, Jeffrey Shapiro, Franco N. Wong, Chee Wei Wong, Joshua C. Bienfang
Quantum entanglement is the fundamental resource for quantum information processing and communications, including secure data rates with higher capacities and better error resilience [1-9]. In dense-coded quantum communication channels, it is desirable to encode more information per pair of entangled photons and thus hyperentanglement [1,4,6,7] and high- dimensional states [10-15] has been proposed as a platform for doing so. Here we combine both approaches based on a phase-coherent mode-locked two-photon state in the infrared communications wavelengths. High-dimensional hyperentanglement is achieved with frequency-bin entanglement in d-dimensions and simultaneously polarization entanglement for coding up to 5 qubits per photon. The high-dimensional mode-locked state exhibits the long-postulated revival of the Hong-Ou-Mandel quantum interference, first predicted theoretically by the authors, up to 19 time-bins and with visibilities up to 96.5%. Frequency correlations and anti-correlations of the d-dimensional quantum state are observed. We further witness the high-dimensional frequency- bin entanglement through Franson interference. Entanglement revivals of the non-local interference at discrete time-bins are first observed in a Franson interferometer,  with up to 97.8% visibility. Stabilized hyperentanglement is further observed in the polarization and high-dimensional energy-time bases, with simultaneous Bell violations up to 10.95 and 8.34 standard deviations in the polarization and frequency-bin subspaces respectively. The Clauser-Horne-Shimony-Holt S parameter is determined at different time-bins under the polarization basis with a maximum value of 2.76.
Citation: Nature Physics
Pub Type: Journals
Quantum optics, Entanglement, Quantum Communications, Single-photon detector
Created June 29, 2015, Updated November 10, 2018