用于核退磁低温恒温器中微波光力学的片上温度测量
On-chip thermometry for microwave optomechanics implemented in a nuclear demagnetization cryostat
摘要：
我们的报告上进行的核绝热退磁低温恒温器，其温度是由精确的测温从低于500 $~μ$ K约1 $~$开尔文的微波光力学测量。我们描述了一种用于访问片上温度的方法，建立在蓝失谐参数不稳定性和标准微波设置上。实验装置和开发技术的能力和灵敏度均通过约4 $~$ MHz的极弱耦合氮化硅双钳位光束模式和约6 $~$ GHz的铌片上腔谐振来证明。我们报告一个不稳定的内在驱动力在耦合的微波-机械系统上的力学，出现在通常低于100 $~$ mK。这一现象的起源仍不清楚，值得理论投入。它使我们无法在通常低于10-30 $~$ mK的温度下进行可靠的实验;然而，没有观察到热去耦的证据，我们建议在不同强度水平下，在共享微波技术的所有器件中应存在相同的功能。我们进一步证明经验如何大部分的不稳定功能可以被歼灭，并推测如何机制可以链接到原子尺度的两个级别的系统。所述微波/微开尔文设施是电磁脉冲平台的一部分，将用于毫开尔文范围内和以下的进一步实验。
英文摘要：
We report on microwave optomechanics measurements performed on a nuclear adiabatic demagnetization cryostat, whose temperature is determined by accurate thermometry from below 500$~μ$K to about 1$~$Kelvin. We describe a method for accessing the on-chip temperature, building on the blue-detuned parametric instability and a standard microwave setup. The capabilities and sensitivity of both the experimental arrangement and the developed technique are demonstrated with a very weakly coupled silicon-nitride doubly-clamped beam mode of about 4$~$MHz and a niobium on-chip cavity resonating around 6$~$GHz. We report on an unstable intrinsic driving force in the coupled microwave-mechanical system acting on the mechanics that appears below typically 100$~$mK. The origin of this phenomenon remains unknown, and deserves theoretical input. It prevents us from performing reliable experiments below typically 10-30$~$mK; however no evidence of thermal decoupling is observed, and we propose that the same features should be present in all devices sharing the microwave technology, at different levels of strengths. We further demonstrate empirically how most of the unstable feature can be annihilated, and speculate how the mechanism could be linked to atomic-scale two level systems. The described microwave/microkelvin facility is part of the EMP platform, and shall be used for further experiments within and below the millikelvin range.
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