Electron Spin Resonance Spectroscopy of Bismuth donors in Silicon using a Parametric Amplifier

Bismuth donor spins in Silicon are well suited to implement a quantum memory for superconducting qubits [1], owing to their long coherence times and large hyperfine interaction leading to a zero-field splitting of 7.35GHz [2]. We report low-field electron-spin resonance spectroscopies of ensembles of Bismuth spins with a concentration of 5 10$^{16}$cm$^{-3}$ in an isotopically purified $^{28}$Si sample at 10 mK, at which the electronic spin is expected to be fully polarized. The spectrometer consists of a planar aluminium superconducting resonator patterned on top of the substrate, with a quality factor of 10$^{5}$. The signal coming from the spins is amplified using a Josephson Parametric Amplifier [3]. Hahn-echo coherence times up to 10 ms are observed. \\[4pt] [1] B. Julsgaard, C. Grezes, P. Bertet, K. Moelmer, Phys. Rev. Lett. 110, 250503 (2013).\\[0pt][2] G. Wolfowicz et al., Nature nanotechnology 8, 561 (2013).\\[0pt][3] X. Zhou et al., Phys. Rev. B 89, 214517 (2014).