| Project Detail |
Turning down quantum noise in gravitational wave detectors
Gravitational wave detectors have opened a new window to our understanding of the universe, but they are ultimately limited by quantum fluctuations generated by light reflecting off mirrors. This quantum back action (typically below 100 Hz) and the uncertainty in the photon count (shot noise typically present in higher frequencies) limit the detector sensitivity. Funded by the Marie Sklodowska-Curie Actions programme, the QNOIWA project proposes an alternative solution to simultaneously tackle both shot noise and quantum back action. The technique relies on entangling the gravitational wave detector and an atomic spin ensemble that behaves as a negative-mass oscillator. The planned proof-of-principle system will serve as a prototype in existing large-scale gravitational wave detectors and in the upcoming Einstein Telescope.
Worldwide efforts are undertaken today towards improving the detection of gravitational waves (GW). The detection of these waves allows to deepen our understanding of the Universe, its composition, and its creation. Today, environmental or technical sources of noise of GW detectors are well controlled. As a result, the strain sensitivity of most GW detectors is fundamentally limited by quantum noise throughout most of their detection bandwidth. In particular, one effect called the quantum back action (QBA) is dominant typically below 100Hz, while shot noise dominates at higher frequencies. One common solution to beat the fundamental quantum limit is to use squeezed light, but this technique is only effective within a relatively narrow frequency band. For broadband detection, it is necessary to impose a frequency-dependent tailoring of the squeezed light source, an expensive solution which requires the construction of large scale (hundreds of meters) Fabry-Pero cavities. In this research project, we propose the experimental investigation of an alternative solution for beating both shot noise (high frequency) and QBA (low frequency) simultaneously. The technique relies on the macroscopic entanglement of the GW detector and an atomic spin ensemble which behaves as a negative-mass oscillator. By probing both systems using a non-degenerate entangled source of light, it becomes possible to beat the quantum limit over a large spectral bandwidth. We intend to build a compact proof-of-principle setup which would serve as a prototype for applications in existing large scale GW detection systems, as well as in the upcoming Einstein Telescope due in 2035. We believe it is competitive with state-of-the-art techniques currently implemented on GW detectors, with nevertheless a great advantage in price, compactness and versatility of integration. If successful, our project could significantly contribute to the next generation of GW detectors. |
