A quantum-enhanced prototype gravitational-wave detector

Abstract

The quantum nature of the electromagnetic field imposes a fundamental limit on the sensitivity of optical precision measurements such as spectroscopy, microscopy, and interferometry [1]. The so-called quantum limit is set by the zero-point fluctuations of the electromagnetic field, which constrain the precision with which optical signals can be measured [2,3,4]. In the world of precision measurement, laser-interferometric gravitational wave (GW) detectors [4,5, 7] are the most sensitive position meters ever operated, capable of measuring distance changes on the order of 10 −18 m RMS over kilometer separations caused by GWs from astronomical sources [8]. The sensitivity of currently operational and future GW detectors is limited by quantum optical noise [7]. Here we demonstrate a 44% improvement in displacement sensitivity of a prototype GW detector with suspended quasi-free mirrors at frequencies where the sensitivity is shot-noise-limited, by injection of a squeezed state of light [1,2,3]. This demonstration is a critical step toward implementation of squeezing-enhancement in large-scale GW detectors.

Towards practical quantum metrology with photon counting

“…Photonic quantum metrology 1 promises to surpass the shot-noise limit (SNL, Δϕ $ 1=ON) by using quantum states of light that exhibit entanglement, 2 discord 3 or squeezing 4 to suppress statistical fluctuation in optical-phase estimation. This will ultimately enable greater precision in measuring experimental quantities of interest, such as distance, birefringence, angle or sample concentration.…”

High-sensitivity three-mode optomechanical transducer

“…The sensitivity of this experiment can be improved in a straightforward fashion by increasing the cavity finesse, the ETM transmissivity, and the photodetector's quantum efficiency, as well as to add a suspended mode cleaner to filter out high-order modes before the cavity injection. Figure 7 shows the calculated thermal noise, the shot noise and the radiation-pressure noise of the system with a cavity finesse of 15 000 (achievable with typical commercially available good quality mirrors), ETM transmission of 100 ppm, QPD quantum efficiency of 0.8 [27], input power of 5 W, and the same mechanical parameters as in the current experiment. The three-mode parametric cooling effect is obvious in Fig.…”

A gravitational wave detector operating beyond the quantum shot-noise limit: Squeezed light in application

“…[9]. Important milestones were the controlled generation of squeezed states at audio-band frequencies [19][20][21], the test of compatibility of squeezedlight injection with enhancement cavities [22][23][24][25][26], and the generation of strongly squeezed states of light [27][28][29][30][31][32]. Figure 3 shows a photograph of our squeezed-light laser that was completed in 2010 at the Institute for Gravitational Physics (Albert-Einstein-Institute Hannover) and that is now part of the GEO 600 02002-p.3 Figure 3.…”