Observing two-photon subwavelength interference of broadband chaotic light in polarization-selective Michelson interferometer

Demonstration of a squeezed light enhanced power- and signal-recycled Michelson interferometer

We report on the experimental combination of three advanced interferometer techniques for gravitational wave detection, namely power-recycling, detuned signal-recycling and squeezed field injection. For the first time we experimentally prove the compatibility of especially the latter two. To achieve a broadband non-classical sensitivity improvement we applied a filter cavity for compensation of quadrature rotation. Signal to noise ratio was improved by up to 2.8 dB beyond the coherent state's shot noise. The complete set-up was stably locked for arbitrary times and characterized by injected si…

Broadband detuned Sagnac interferometer for future generation gravitational wave astronomy

Broadband suppression of quantum noise below the Standard Quantum Limit (SQL) becomes a top-priority problem for the future generation of large-scale terrestrial detectors of gravitational waves, as the interferometers of the Advanced LIGO project, predesigned to be quantum-noise-limited in the almost entire detection band, are phased in. To this end, among various proposed methods of quantum noise suppression or signal amplification, the most elaborate approach implies a so-called *xylophone* configuration of two Michelson interferometers, each optimised for its own frequency band, with a com…

为桌面干涉仪设计的宽带压缩光源

A Broadband Squeezed Light Source for Table-Top Interferometry

本文报道了为量子增强时空（QUEST）实验开发的宽带压缩光源的表征，利用平衡锁相检测。该实验采用共址桌面功率回收迈克尔逊干涉仪，旨在探测静态时空波动，通过压缩光降低射频噪声。

Enhancing the sensitivity of the LIGO gravitational wave detector by using squeezed states of light

Nearly a century after Einstein first predicted the existence of gravitational waves, a global network of earth-based gravitational wave observatories is seeking to directly detect this faint radiation using precision laser interferometry. Photon shot noise, due to the quantum nature of light, imposes a fundamental limit on the attometer level sensitivity of the kilometer-scale Michelson interferometers deployed for this task. Here we inject squeezed states to improve the performance of one of the detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) beyond the quantum no…

Direct observation of photon bunching in thermal light in quantum Fourier transform spectroscopy

In quantum mechanics, photons are bosons -- there is no restriction on the number of them that occupy the same quantum state, so many of them can bunch together, and this is well known as photon bunching effect. However, photon bunching and multiphoton interference of bunched photons have never been directly observed from a broadband thermal chaotic light source. Nevertheless, it has been known that the interference intensity of a number N of bunched photons oscillates with a wavelength of N times shorter than the wavelength of the constituent single photons, which should be observable in Four…

Multi-user distribution of polarization entangled photon pairs

We experimentally demonstrate multi-user distribution of polarization entanglement using commercial tele- com wavelength division demultiplexers. The entangled photon pairs are generated from a broadband source based on spontaneous parametric down conversion in a periodically poled lithium niobate crystal using a double path setup employing a Michelson interferometer and active phase stabilisation. We test and compare demultiplexers based on various technologies and analyze the effect of their characteristics, such as losses and polarization dependence, on the quality of the distributed entang…

频率依赖压缩在Einstein Telescope低频探测器中的方法

Approaches of frequency-dependent squeezing for the low frequency detector of Einstein Telescope

本文研究了在Einstein Telescope低频探测器中用耦合腔或EPR压缩替代滤波腔的可行性，发现EPR压缩可消除一个滤波腔并有望提升探测器灵敏度。