This paper gives an overview of potential upgrades of second-generation gravitational wave detectors and the required key technologies to improve the limiting noise sources. In addition, the baseline ...design of the Einstein telescope, a European third-generation gravitational wave observatory, is briefly discussed.
Crystallization in Ising quantum magnets Schauß, P.; Zeiher, J.; Fukuhara, T. ...
Science (American Association for the Advancement of Science),
03/2015, Letnik:
347, Številka:
6229
Journal Article
Recenzirano
Odprti dostop
Dominating finite-range interactions in many-body systems can lead to intriguing self-ordered phases of matter. For quantum magnets, Ising models with power-law interactions are among the most ...elementary systems that support such phases. These models can be implemented by laser coupling ensembles of ultracold atoms to Rydberg states. Here, we report on the experimental preparation of crystalline ground states of such spin systems. We observe a magnetization staircase as a function of the system size and show directly the emergence of crystalline states with vanishing susceptibility. Our results demonstrate the precise control of Rydberg many-body systems and may enable future studies of phase transitions and quantum correlations in interacting quantum magnets.
The German-British laser-interferometric gravitational wave detector GEO 600 is in its 14th year of operation since its first lock in 2001. After GEO 600 participated in science runs with other ...first-generation detectors, a program known as GEO-HF began in 2009. The goal was to improve the detector sensitivity at high frequencies, around 1 kHz and above,with technologically advanced yet minimally invasive upgrades. Simultaneously, the detector would record science quality data in between commissioning activities. As of early 2014, all of the planned upgrades have been carried out and sensitivity improvements of up to a factor of four at the high-frequency end of the observation band have been achieved. Besides science data collection, an experimental program is ongoing with the goal to further improve the sensitivity and evaluate future detector technologies. We summarize the results of the GEO-HF program to date and discuss its successes and challenges.
Quantum technologies will ultimately require manipulating many-body quantum systems with high precision. Cold atom experiments represent a stepping stone in that direction: a high degree of control ...has been achieved on systems of increasing complexity. However, this control is still sub-optimal. In many scenarios, achieving a fast transformation is crucial to fight against decoherence and imperfection effects. Optimal control theory is believed to be the ideal candidate to bridge the gap between early stage proof-of-principle demonstrations and experimental protocols suitable for practical applications. Indeed, it can engineer protocols at the quantum speed limit - the fastest achievable timescale of the transformation. Here, we demonstrate such potential by computing theoretically and verifying experimentally the optimal transformations in two very different interacting systems: the coherent manipulation of motional states of an atomic Bose-Einstein condensate and the crossing of a quantum phase transition in small systems of cold atoms in optical lattices. We also show that such processes are robust with respect to perturbations, including temperature and atom number fluctuations.
Achieving the demanding sensitivity and bandwidth, envisaged for third-generation gravitational wave (GW) observatories, is extremely challenging with a single broadband interferometer. Very high ...optical powers (megawatts) are required to reduce the quantum noise contribution at high frequencies, while the interferometer mirrors have to be cooled to cryogenic temperatures in order to reduce thermal noise sources at low frequencies. To resolve this potential conflict of cryogenic test masses with high thermal load, we present a conceptual design for a 2-band xylophone configuration for a third-generation GW observatory, composed of a high-power, high-frequency interferometer and a cryogenic low-power, low-frequency instrument. Featuring inspiral ranges of 3200 Mpc and 38 000 Mpc for binary neutron stars and binary black holes coalesences, respectively, we find that the potential sensitivity of xylophone configurations can be significantly wider and better than what is possible in a single broadband interferometer.
By numerical simulation, we compare the performance of four speedmeter interferometer configurations with potential application in future gravitational wave detectors. In the absence of optical loss, ...all four configurations can be adjusted to yield the same sensitivity in a fair comparison. Once we introduce a degree of practicality in the form of lossy optics and mode mismatch, however, the situation changes: the sloshing Sagnac and the speedmeter of Purdue and Chen have almost identical performance showing smaller degradation from the ideal than the speedmeter of Freise and the speedmeter of Miao. In a further step, we show that there is a similar hierarchy in the degree of improvement obtained through the application of 10 dB squeezing to the lossy speedmeters. In this case, the sensitivity of each speedmeter improves, but it is greatest for the sloshing Sagnac and the speedmeter of Purdue and Chen, in particular in the lower part of the target frequency range.
Advanced techniques in GEO 600 Affeldt, C; Danzmann, K; Dooley, K L ...
Classical and quantum gravity,
11/2014, Letnik:
31, Številka:
22
Journal Article
Recenzirano
Odprti dostop
For almost 20 years, advanced techniques have been developed and tested at the GEO 600 laser-interferometric gravitational wave detector. Many of these innovations have improved the sensitivity of ...GEO 600 and could be shown to be consistent with stable and reliable operation of gravitational wave detectors. We review the performance of these techniques and show how they have influenced the upgrades of other detectors worldwide. In the second half of the paper, we consider how GEO 600 continues to pioneer new techniques for future gravitational wave detectors. We describe some of the new methods in detail and present new results on how they improve the sensitivity and/or the stability of GEO 600 and possibly of future detectors.
The speed meter concept has been identified as a technique that can potentially provide laser-interferometric measurements at a sensitivity level which surpasses the standard quantum limit (SQL) over ...a broad frequency range. As with other sub-SQL measurement techniques, losses play a central role in speed meter interferometers and they ultimately determine the quantum noise limited sensitivity that can be achieved. So far in the literature, the quantum noise limited sensitivity has only been derived for lossless or lossy cases using certain approximations (for instance that the arm cavity round trip loss is small compared to the arm cavity mirror transmission). In this article we present a generalized, analytical treatment of losses in speed meters that allows accurate calculation of the quantum noise limited sensitivity of Sagnac speed meters with arm cavities. In addition, our analysis allows us to take into account potential imperfections in the interferometer such as an asymmetric beam splitter or differences of the reflectivities of the two arm cavity input mirrors. Finally, we use the examples of the proof-of-concept Sagnac speed meter currently under construction in Glasgow and a potential implementation of a Sagnac speed meter in the Einstein Telescope to illustrate how our findings affect Sagnac speed meters with metre- and kilometre-long baselines.
Abstract
To achieve the expected level of sensitivity of third-generation gravitational-wave (GW) observatories, more accurate and sensitive instruments than those of the second generation must be ...used to reduce all sources of noises. Amongst them, one of the most relevant is seismic noise, which will require the development of a better isolation system, especially at low frequencies (below 10 Hz), the operation of large cryogenic silicon mirrors, and the improvement of optical wavelength readouts. In this framework, this article presents the activities of the E-TEST (Einstein Telescope Euregio Meuse-Rhine Site & Technology) to develop and test new key technologies for the next generation of GW observatories. A compact isolator system for a large silicon mirror (100 kg) at low frequency (
<
10 Hz) is proposed. The design of the isolator allows the overall height of the isolation system to be significantly compact and also suppresses seismic noise at low frequencies. To minimize the effect of thermal noise, the isolation system is provided with a 100 kg silicon mirror which is suspended in a vacuum chamber at cryogenic temperature (25–40 K). To achieve this temperature without inducing vibrations to the mirror, a radiation-based cooling strategy is employed. In addition, cryogenic sensors and electronics are being developed as part of the E-TEST to detect vibrational motion in the penultimate cryogenic stage. Since the commonly used silicon material is not transparent below the wavelengths typically used in the 1
µ
m range for GW detectors, new optical components and lasers must be developed in the range above 1500 nm to reduce absorption and scattering losses. Therefore, solid-state and fiber lasers with a wavelength of 2090 nm, matching high-efficiency photodiodes, and low-noise crystalline coatings are being developed. Accordingly, the key technologies provided by E-TEST serve crucially to reduce the limitations of the current generation of GW observatories and to determine the technical design for the next generation.
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