Final Report Summary - SAGNACSPEEDMETER (Interferometry beyond the Standard Quantum Limit using a Velocity Sensitive Sagnac Interferometer)
On the 14th September 2015 the two advanced LIGO observatories picked up the tiny but unmistakable signature of two black holes merging 1.4 billion years ago. This first ever direct observation of a black hole binary merger event was not only the first direct observation of GW or a black hole, but moreover it allowed us to determine the existence of a new class of heavy stellar-mass black holes and additionally created unprecedented possibilities to study compact objects in the highly non-linear strong-field gravity regime.
This discovery often described as one of the scientific break-throughs of the century, was not only rewarded with the physics Nobel prize in 2017, but even topped in attention by the discovery of the signal from a binary neutron star in August 2017, leading to the biggest ever concerted astronomical observation campaign. All of this heralded the new era of GW astronomy, fand over the next decades we anticipate GW observations will revolutionise our view of the Universe, providing new insights into astrophysics, cosmology, the nature of gravitation and fundamental physics.
The focus of this project was to establish a new interferometer typology to further improve the already mind-boggling sensitivity of current GW detectors. In particular improvements at the low-frequency end of the observation band are crucial, because that is the frequency range where most of the signal-to-noise ratio is picked up for many of the targeted gravitational wave sources. In addition, the low frequencies become more and more important the deeper we probe into the cosmos, due to increased redshift of the signals.
All current GW detectors, such as Advanced LIGO, are built on the Michelson interferometer configuration. At design sensitivity, Advanced LIGO will be limited over its entire detection band by quantum noise, a combination of sensing noise, i.e. shot noise at the readout photodiodes at high frequencies and back-action noise, i.e. quantum radiation pressure acting on the suspended interferometer test masses at low frequencies. This quantum noise arises for the reason that continuous position measurements of the test masses do not commute, i.e. there is a Heisenberg limit. In contrast, quantum mechanics allows for continuous measurements of momentum (or loosely-speaking speed, and hence the term ‘speedmeter’) of the test masses being carried out without being limited by Heisenberg Uncertainty.
Over the period of this project we have developed the speedmeter from a simple idea to a valid alternative to the state-of-the-art Michelson interferometer. Achievements of the project include the i) Deepening our understanding of speedmeters; ii) Solving a variety of experimental challenges related to speedmeters; iii) Inventing new and beneficial speedmeter concepts that can be implemented in future gravitational wave detectors at lower cost and with less risk than the original speedmeter concept.
I believe it is fair to say that the work of my team has allowed us to establish the speedmeter concept within the GW community (See for instance the Instrument White-Paper of the LIGO Scientific Collaboration). We have now mostly caught up with 40 years worth of intensive development of gravitational wave detection based on Michelson interferometers and we have build the solid baseline for the speedmeter concept to superseed the Michelson interferometer as state-of-the-art gravitational wave detector.
Detailed outputs of the project can be found at the project webpage: www.speed-meter.eu
This discovery often described as one of the scientific break-throughs of the century, was not only rewarded with the physics Nobel prize in 2017, but even topped in attention by the discovery of the signal from a binary neutron star in August 2017, leading to the biggest ever concerted astronomical observation campaign. All of this heralded the new era of GW astronomy, fand over the next decades we anticipate GW observations will revolutionise our view of the Universe, providing new insights into astrophysics, cosmology, the nature of gravitation and fundamental physics.
The focus of this project was to establish a new interferometer typology to further improve the already mind-boggling sensitivity of current GW detectors. In particular improvements at the low-frequency end of the observation band are crucial, because that is the frequency range where most of the signal-to-noise ratio is picked up for many of the targeted gravitational wave sources. In addition, the low frequencies become more and more important the deeper we probe into the cosmos, due to increased redshift of the signals.
All current GW detectors, such as Advanced LIGO, are built on the Michelson interferometer configuration. At design sensitivity, Advanced LIGO will be limited over its entire detection band by quantum noise, a combination of sensing noise, i.e. shot noise at the readout photodiodes at high frequencies and back-action noise, i.e. quantum radiation pressure acting on the suspended interferometer test masses at low frequencies. This quantum noise arises for the reason that continuous position measurements of the test masses do not commute, i.e. there is a Heisenberg limit. In contrast, quantum mechanics allows for continuous measurements of momentum (or loosely-speaking speed, and hence the term ‘speedmeter’) of the test masses being carried out without being limited by Heisenberg Uncertainty.
Over the period of this project we have developed the speedmeter from a simple idea to a valid alternative to the state-of-the-art Michelson interferometer. Achievements of the project include the i) Deepening our understanding of speedmeters; ii) Solving a variety of experimental challenges related to speedmeters; iii) Inventing new and beneficial speedmeter concepts that can be implemented in future gravitational wave detectors at lower cost and with less risk than the original speedmeter concept.
I believe it is fair to say that the work of my team has allowed us to establish the speedmeter concept within the GW community (See for instance the Instrument White-Paper of the LIGO Scientific Collaboration). We have now mostly caught up with 40 years worth of intensive development of gravitational wave detection based on Michelson interferometers and we have build the solid baseline for the speedmeter concept to superseed the Michelson interferometer as state-of-the-art gravitational wave detector.
Detailed outputs of the project can be found at the project webpage: www.speed-meter.eu