摘要：Measurements at the quantum (single-photon or single-spin) limit at GHz frequencies are difficult and cumbersome. Traditionally, they have required either superconducting circuits operating at mK temperatures deep inside dilution refrigerators or else clouds of cold atoms/molecules held within ultra-high vacuum chambers. Towards overcoming these limitations, we report on the design and performance of an optically-pumped maser amplifier, operating on a lab bench at room temperature, whose spin-temperature drops temporarily to a few tens of mK. Though only capable of operating in pulsed mode, we measure the maser’s lowest noise temperature when configured as an amplifier to be 8 K, equivalent to a noise figure (NF) of 0.1 dB, which agrees with our theoretical model. The limitations, advantages, and potential applications of the technology will be discussed.
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简历：Mark Oxborrow builds instruments and devices. He is an Oxford graduate, earnt a PhD (theoretical physics) from Cornell University, USA, and spent 14 years as a metrologist improving the performance of optical and microwave clocks at the UK’s equivalent of NIST. He has constructed lasers with linewidths below 1 Hz, and cryogenic microwave oscillators with fractional frequency instabilities below 10-14 over several minutes. In 2011, he demonstrated the world’s first solid-state maser capable of operating at room temperature.
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