Determination of Low Loss in Isotopically Pure Single Crystal 28Si at Low Temperatures and Single Microwave Photon Energy

Abstract

The low dielectric losses of an isotopically pure single crystal 28Si sample were determined at a temperature of 20 mK and at powers equivalent to that of a single photon. Whispering Gallery Mode (WGM) analysis revealed large Quality Factors of order 2 × 106 (dielectric loss ~5 × 10−7) at high powers, degrading to 7 × 10−5 (dielectric loss ~1.4 × 10−6 at single photon energy. A very low-loss narrow line width paramagnetic spin flip transition was detected with extreme sensitivity in 28Si, with very small concentration below 1010 cm−3 (less than 10 parts per trillion) and g-factor of 1.995 ± 0.008. Such determination was only possible due to the low dielectric photonic losses combined with the long lifetime of the spin transition (low magnetic loss), which enhances the magnetic AC susceptibility. Such low photonic loss at single photon energy combined with the narrow line width of the spin ensemble, indicate that single crystal 28Si could be an important crystal for future cavity QED experiments.

Piezoelectric tunable microwave superconducting cavity

“…Measurements were undertaken at 10 mK with an input power of -127 dBm; such conditions combined with a Q-factor of 10 5 implicates that we achieved approximately 35 microwave photons on average stored within the cavity, just 15 dB from the single photon level. This level of photons has been shown to be sufficient for cavity characterization for quantum applications 17,18 .…”

Low-Temperature Properties of Whispering-Gallery Modes in Isotopically Pure Silicon-28

“…Previously, a very low-loss paramagnetic spin ensemble was detected in enriched silicon with a narrow linewidth of less than 7 kHz for a 10 parts per trillion concentration of impurity ions [10]. This was only possible by virtue of the low dielectric photonic losses combined with the long lifetime of the spin transition (low magnetic loss), which enhanced the AC magnetic susceptibility.…”

Loss channels affecting lithium niobate phononic crystal resonators at cryogenic temperature

“…The complete phononic bandgap induced by the crystal's periodic patterning not only tightly localizes mechanical motion, but also offers protection against spurious acoustic radiation of the superconducting circuit. In contrast to approaches based on bulk acoustic or surface acoustic waves 17 , the phononic bandgap suppresses scattering loss due to inevitable fabrication disorder, such as surface or electrode roughness or isotopic impurities 18 . It is also straightforward to precisely engineer the frequency and coupling strength of these resa) Electronic mail: ewollack@stanford.edu b) Present address:…”