Length sensing and control strategies for the LCGT interferometer

干涉式引力波探测器中的残余幅度调制

Residual Amplitude Modulation in Interferometric Gravitational Wave Detectors

本文分析残余幅度调制对引力波探测激光干涉仪腔长信号、传感矩阵及噪声扣除的影响，并通过仿真给出Advanced LIGO的RAM要求，证明其不会限制灵敏度。

Control of a velocity-sensitive audio-band quantum non-demolition interferometer

The Sagnac speed meter interferometer topology can potentially provide enhanced sensitivity to gravitational waves in the audio-band compared to equivalent Michelson interferometers. A challenge with the Sagnac speed meter interferometer arises from the intrinsic lack of sensitivity at low frequencies where the velocity-proportional signal is smaller than the noise associated with the sensing of the signal. Using as an example the on-going proof-of-concept Sagnac speed meter experiment in Glasgow, we quantify the problem and present a solution involving the extraction of a small displacement-p…

Development of signal-extraction scheme for Resonant Sideband Extraction

As a future plan, an advanced gravitational-wave detector will employ an optical configuration of resonant sideband extraction (RSE), achieved with an additional mirror at the signal-detection port of the power-recycled Fabry-Perot Michelson interferometer. To control the complex coupled cavity system, one of the most important design issues is how to extract the longitudinal control signals of the cavities. We developed a new signal-extraction scheme which provides an appropriate sensing matrix. The new method uses two sets of sidebands: one of the sideband components satisfies the critical c…

Using an atom interferometer to infer gravitational entanglement generation

If gravitational perturbations are quantized into gravitons in analogy with the electromagnetic field and photons, the resulting graviton interactions should lead to an entangling interaction between massive objects. We suggest a test of this prediction. To do this, we introduce the concept of interactive quantum information sensing. This novel sensing protocol is tailored to provable verification of weak dynamical entanglement generation between a pair of systems. We show that this protocol is highly robust to typical thermal noise sources. The sensitivity can moreover be increased both using…

Angular instability due to radiation pressure in the LIGO gravitational wave detector

We observed the effect of radiation pressure on the angular sensing and control system of the Laser Interferometer Gravitational-Wave Observatory (LIGO) interferometer's core optics at LIGO Hanford Observatory. This is the first measurement of this effect in a complete gravitational wave interferometer. Only one of the two angular modes survives with feedback control, since the other mode is suppressed when the control gain is sufficiently large. We developed a mathematical model to understand the physics of the system. This model matches well the dynamics that we observe.

Enhancing the sensitivity of interferometers with stable phase-insensitive quantum filters

We present a new quantum control strategy for increasing the shot-noise-limited sensitivity of optical interferometers. The strategy utilizes active phase-insensitive quantum filtering of the signal inside the interferometer and does not rely on optical squeezing. On the example of the coupled-cavity resonators, employed in the gravitational-wave detectors, we show that fully causal and stable phase-insensitive filters can improve the interferometer sensitivity by more than an order of magnitude. The role of the phase-insensitive component in such systems is to provide frequency-dependent comp…

位移噪声自由干涉仪的量子精度极限

Quantum precision limits of displacement noise free interferometers

本文推导一般位移噪声自由干涉仪的量子精度极限，提出三角形腔DFI方案，并证明其通过噪声抑制和压缩增益提升测量精度。