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We present the first results from a rotating Michelson-Morley experiment that uses two orthogonally orientated cryogenic sapphire resonator oscillators operating in whispering gallery modes near 10 GHz. The experiment is used to test for violations of Lorentz invariance in the framework of the photon sector of the standard model extension (SME), as well as the isotropy term of the Robertson-Mansouri-Sexl (RMS) framework. In the SME we set a new bound on the previously unmeasured kappa(ZZ)(e-) component of 2.1(5.7) x 10(-14), and set more stringent bounds by up to a factor of 7 on seven other components. In the RMS a more stringent bound of -0.9(2.0) x 10(-10) on the isotropy parameter, P(MM) = delta-beta + 1 / 2 is set, which is more than a factor of 7 improvement.

Thermal Nyquist noise fluctuations of high-Q Bulk Acoustic Wave (BAW) cavities have been observed at cryogenic temperatures with a DC Superconducting Quantum Interference Device (SQUID) amplifier. High Q modes with bandwidths of few tens of milliHz produce thermal fluctuations with a Signal-To-Noise ratio of up to 23dB. The estimated effective temperature from the Nyquist noise is in good agreement with the physical temperature of the device, confirming the validity of the equivalent circuit model and the non-existence of any excess resonator self-noise. The measurements also confirm that the quality factor remains extremely high (Q > 10 8 at low order overtones) for very weak (thermal) system motion at low temperatures, when compared to values measured with relatively strong external excitation. This result represents an enabling step towards operating such a high-Q acoustic device at the standard quantum limit.Phonon-trapping Bulk Acoustic Wave (BAW) cavity resonator technology shows great potential for use in applications that require precision control, measurement and sensing at the quantum limit [1]. This is mainly due to the relatively high mechanical frequencies and extremely high Q-factors achievable in such devices at cryogenic temperatures (Q > 10 9 ), which potentially lead to extraordinarily large coherence times [2][3][4] beyond the capability of any other competing technology compared in [5]. This uniqueness has been perfected for decades for precision room temperature oscillators and related devices [6,7], culminating in Q × f -products as high as 2 · 10 13 Hz [8]. Interestingly, it is no longer the deficiency of the Q-factor, which halts further progress in the reduction of phase fluctuations, but rather the intrinsic fluctuations of the BAW resonator itself [9,10]. In particular, it has been concluded that further improvement of BAW based frequency sources could only be achieved by reducing the resonator flicker phase self-noise, since this is the dominant noise source of ultra-stable BAW oscillators both at cryogenic and room temperature [9,11].The origin of the flicker frequency noise is still poorly understood despite its significant influence on many systems [12,13] ranging from biological substances[14] to superconducting electronics [15,16]. The influence on the frequency stability of high-performance quartz oscillators on time scales of order 1-10 seconds is welldocumented [10,17,18] with several attempts to understand its origins [19][20][21]. It is also important for other mechanical resonators such as High Overtone [22] and Thin Film[23] BAW devices. On the other hand, coherence times of ultra-high Q quartz BAW cavities are predicted * maxim.goryachev@uwa.edu.au to exceed 10 seconds. Thus, the question of the influence of low Fourier frequency noise has never been raised with respect to these types of measurements due to the relatively low Q factors of the mechanical resonators utilised so far [24][25][26]. So, this type of noise can be another limiting factor on the coherence times of...

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The cryogenic resonant-mass gravitational radiation antenna at the University of Western Australia (UWA) has obtained a noise temperature of <2 mK using a zero order predictor filter. This corresponds to aIms burst strain sensitivity of 7x 10-19 . The antenna has been in continuous operation since August 1993. The antenna operates at about 5 K and consists of a 1· 5 tonne niobium bar with a 710 Hz fundamental frequency, and a closely tuned secondary mass of 0·45 kg effective mass. The vibrational state of the secondary mass is continuously monitored by a 9·5 GHz superconducting parametric transducer. This paper presents the current design and operation of the detector. From a two-mode model we show how we calibrate, characterise and theoretically determine the sensitivity of our detector. Experimental results confirm the theory.