Quantum Noise in Gravitational-Wave Detectors and Applied Squeezed States

Abstract

The development of low-frequency squeezed states is motivated by gravitational-wave detectors being limited by quantum noise. This chapter presents a background to the quantum noise limits in these detectors, along with the enhancements possible with squeezed state injection. The calculations presented are heavily based on the derivations from the works of Kimble et al. (Phys Rev D 65:022002, 2002, [1]) and Buonanno and Chen (Phys Rev D 64:042006, 2001; Phys Rev D 69:102004, 2004, [2, 3]). Cited frequently throughout this chapter, these works use estimated experiment parameters for LIGO and Advanced LIGO detectors. Section 4.1 provides an introduction of the influence of quantum noise in measurement, followed by a brief discussion in the main source of quantum noise in gravitational-wave detection (Sect. 4.2). Subsequently, the quantum noise of three Michelson configurations are explored: a simple Michelson interferometer (Sect. 4.3), a power-recycled Michelson with Fabry-Perot arm cavities (Sect. 4.4), and a Dual-recycled Michelson with Fabry-Perot arm cavities (Sect. 4.5). In each of the configurations, the effect of injected squeezed states is also explored. Section 4.6 concludes the chapter, discussing some of the assumptions used in calculations of quantum noise, as well as implications of injected squeezing towards strain sensitivity.