Feedback cooling of the normal modes of a massive electromechanical system to submillikelvin temperature

Authors :: Vinante, A.
Bignotto, M.
Bonaldi, M.
Cerdonio, M.
Conti, L.
Falferi, P.
Liguori, N.
Longo, S.
Mezzena, R.
Ortolan, A.
Prodi, G. A.
Salemi, F.
Taffarello, L.
Vedovato, G.
Vitale, S.
Zendri, J. -P.
Source :: Phys. Rev. Lett. 101, 033601 (2008)
Publication Year :: 2008
Abstract: We apply a feedback cooling technique to simultaneously cool the three electromechanical normal modes of the ton-scale resonant-bar gravitational wave detector AURIGA. The measuring system is based on a dc Superconducting Quantum Interference Device (SQUID) amplifier, and the feedback cooling is applied electronically to the input circuit of the SQUID. Starting from a bath temperature of 4.2 K, we achieve a minimum temperature of 0.17 mK for the coolest normal mode. The same technique, implemented in a dedicated experiment at subkelvin bath temperature and with a quantum limited SQUID, could allow to approach the quantum ground state of a kilogram-scale mechanical resonator.<br />Comment: 4 pages, 4 figures

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