J Low Temp Phys (2008) 151: 1043–1048 DOI 10.1007/s10909-008-9786-6 Practical Design for Improving the Sensitivity to Search for Dark Matter Axions with Rydberg Atoms M. Shibata · T. Arai · A. Fukuda · H. Funahashi · T. Haseyama · S. Ikeda · K. Imai · Y. Isozumi · T. Kato · Y. Kido · A. Matsubara · S. Matsuki · T. Mizusaki · R. Nakanishi · T. Nishimura · D. Ohsawa · A. Sawada · Y. Takahashi · M. Tosaki · S. Yamada · K. Yamamoto Received: 23 July 2007 / Accepted: 10 October 2007 / Published online: 15 January 2008 © Springer Science+Business Media, LLC 2008 Abstract A microwave single-photon detector was developed with highly-excited alkaline Rydberg-atoms in a cooled resonant cavity to search for dark matter axions. This detector belongs to a microwave single-photon counter, thus being free from M. Shibata KEK, Tsukuba 305-0801, Japan T. Arai · A. Fukuda · A. Matsubara · T. Mizusaki · A. Sawada Research Center for Low Temperature and Materials Sciences, Kyoto University, Kyoto 606-8502, Japan H. Funahashi Osaka Electro-Communication University, Osaka 572-8530, Japan T. Haseyama Japan Laser Corporation, Co. Ltd, Shinjuku, Tokyo 169-0051, Japan S. Ikeda · K. Imai · R. Nakanishi · Y. Takahashi Department of Physics, Kyoto University, Kyoto 606-8502, Japan Y. Isozumi · T. Kato · D. Ohsawa · M. Tosaki Radioisotope Research Center, Kyoto University, Kyoto 606-8501, Japan Y. Kido · T. Nishimura Department of Physics, Ritsumeikan University, Shiga 525-8577, Japan S. Matsuki ( ) Research Organization of Science and Engineering, Ritsumeikan University, Shiga 525-8577, Japan e-mail: smatsuki@zpost.plala.or.jp S. Yamada Kamioka Observatory, ICRR, University of Tokyo, Kamioka 506-1025, Japan K. Yamamoto Department of Nuclear Engineering, Kyoto University, Kyoto 606-8501, Japan