Showing papers by "Tim Duty published in 2011"
TL;DR: The dynamical Casimir effect is observed in a superconducting circuit consisting of a coplanar transmission line with a tunable electrical length and two-mode squeezing in the emitted radiation is detected, which is a signature of the quantum character of the generation process.
Abstract: One of the most surprising predictions of modern quantum theory is that the vacuum of space is not empty. In fact, quantum theory predicts that it teems with virtual particles flitting in and out of existence. Although initially a curiosity, it was quickly realized that these vacuum fluctuations had measurable consequences-for instance, producing the Lamb shift of atomic spectra and modifying the magnetic moment of the electron. This type of renormalization due to vacuum fluctuations is now central to our understanding of nature. However, these effects provide indirect evidence for the existence of vacuum fluctuations. From early on, it was discussed whether it might be possible to more directly observe the virtual particles that compose the quantum vacuum. Forty years ago, it was suggested that a mirror undergoing relativistic motion could convert virtual photons into directly observable real photons. The phenomenon, later termed the dynamical Casimir effect, has not been demonstrated previously. Here we observe the dynamical Casimir effect in a superconducting circuit consisting of a coplanar transmission line with a tunable electrical length. The rate of change of the electrical length can be made very fast (a substantial fraction of the speed of light) by modulating the inductance of a superconducting quantum interference device at high frequencies (>10 gigahertz). In addition to observing the creation of real photons, we detect two-mode squeezing in the emitted radiation, which is a signature of the quantum character of the generation process.
864 citations
TL;DR: In this paper, the microwave properties of a crystalline sapphire dielectric whispering gallery mode resonator have been measured at very low excitation strength (E/ℏω≈1) and low temperatures (T≈30 mK).
Abstract: The microwave properties of a crystalline sapphire dielectric whispering gallery mode resonator have been measured at very low excitation strength (E/ℏω≈1) and low temperatures (T≈30 mK). The measurements were sensitive enough to observe saturation due to a highly detuned electron spin resonance, which limited the loss tangent of the material to about 2×10−8 measured at 13.868 and 13.259 GHz. Small power dependent frequency shifts were also measured which correspond to an added magnetic susceptibility of order 10−9. This work shows that quantum limited microwave resonators with Q-factors >108 are possible with the implementation of a sapphire whispering gallery mode system.
81 citations
TL;DR: In this paper, the microwave properties of a crystalline sapphire dielectric whispering gallery mode resonator have been measured at very low excitation strength (E/hf=1) and low temperatures (T = 30 mK).
Abstract: The microwave properties of a crystalline sapphire dielectric whispering gallery mode resonator have been measured at very low excitation strength (E/hf=1) and low temperatures (T = 30 mK). The measurements were sensitive enough to observe saturation due to a highly detuned electron spin resonance, which limited the loss tangent of the material to about 2e-8 measured at 13.868 and 13.259 GHz. Small power dependent frequency shifts were also measured which correspond to an added magnetic susceptibility of order 1e-9. This work shows that quantum limited microwave resonators with Q-factors > 1e8 are possible with the implementation of a sapphire whispering gallery mode system.
43 citations
Proceedings Article•
01 Jan 2011
TL;DR: The Frequency Standards and Metrology Research Group at the University of Western Australia have been developing some of the world's most ultra-precise measurements at microwave frequencies since the 1990s as discussed by the authors.
Abstract: The Frequency Standards and Metrology Research Group at the University of Western Australia have been developing some of the world's most ultra-precise measurements at microwave frequencies since the 1990s. This paper reviews past and intended future work with applications to low temperatures where quantum effects become important.
3 citations
28 Aug 2011
TL;DR: In this paper, the authors reported the first cooling of a bulk sapphire sample below super fluid liquid helium temperature (1.6K) to as low as 25mK.
Abstract: Single crystal sapphire exhibits extremely high electrical and mechanical Q-factors (∼109 at 4K), which are important characteristics for electromechanical experiments at the quantum limit. We report the first cool down of a bulk sapphire sample below super fluid liquid helium temperature (1.6K) to as low as 25mK. The electromagnetic properties were characterized at microwave frequencies over a broad range of excitation powers. At high powers we report the observation of thermal bistability in millikelvin sapphire due to the material properties such as the T3 dependence on thermal conductivity and the ultra-low dielectric loss tangent of the material. We identify "magic temperatures" between 80 to 2100 mK, the lowest ever measured, at which the onset of bistability is suppressed. At very low excitation strength (E/ ω∼1) measurements were sensitive enough to measure saturation effects due to a highly detuned electron spin resonance, which limited the loss tangent of the material to about 2> 108 are possible by implementing sapphire whispering gallery modes. These phenomena at low temperatures make sapphire suitable for a host of quantum metrology applications.
Proceedings Article•
01 Jan 2011
TL;DR: The Frequency Standards and Metrology Research Group at the University of Western Australia have been developing some of the world's most ultra-precise measurements at microwave frequencies since the 1990s as discussed by the authors.
Abstract: The Frequency Standards and Metrology Research Group at the University of Western Australia have been developing some of the world's most ultra-precise measurements at microwave frequencies since the 1990s This paper reviews past and intended future work with applications to low temperatures where quantum effects become important