Intercontinental Comparison of Lattice Clocks Using a Broadband VLBI Technique

• Published in: 2019 Joint Conference of the IEEE International Frequency Control Symposium and European Frequency and Time Forum (EFTF/IFC) pp. 1 - 2
• Main Authors: Ido, T., Hachisu, H., Nemitz, N., Takefuji, K., Ujihara, H., Kawai, E., Ishijima, H., Tsusumi, M., Ichikawa, R., Sekido, M., Pizzocaro, M., Bregolin, F., Barbieri, P., Levi, F., Mura, A., Clivati, C., Cerretto, G., Calonico, D., Perini, F., Maccaferri, G., Roma, M., Bortolotti, C., Negusini, M., Ricci, R.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01-04-2019
• Subjects: Broadband antennas; Broadband communication; Clocks; Delays; Frequency measurement; Frequency transfer; Lattices; Masers; optical clock; VLBI
• ISSN: 2327-1949
• DOI: 10.1109/FCS.2019.8856129

We performed a frequency comparison of lattice clocks in Tokyo and Torino for the first time using broadband VLBI technique. Two portable antennas with 2.4 m diameters were installed at NICT Koganei headquarters and INAF Medicina Radio Observatory, close to Bologna, Italy, realizing a VLBI network together with Kashima large-aperture antenna of 34 m diameter. The clock signal at INAF was evaluated by INRIM using an optical fiber link between Medicina and Torino. The fractional frequency difference that VLBI evaluated was consistent with the difference between two HM frequencies which were separately calibrated by a Sr lattice clock at NICT and a Yb lattice clock at INRIM.