The first detection of gravitational waves by ground-based detectors in the 10Hz – 10 kHz frequency band is expected after advanced gravitational wave detectors now being installed and commissioned reach their full sensitivity, between 2016-2020. Signals from the known population of binary neutron stars are expected, as well as signals from other sources such as binary black holes. In addition to ground-based detectors, space based detectors for the millihertz band are under active development, pulsar timing observatories are searching for gravitational waves in the nanohertz band, and studies of the cosmic microwave background are searching for evidence for gravitational waves at ~10-16 Hz. The need for an expanded array of ground-based detectors is well understood. Expansion of the array and particularly the addition of a southern hemisphere detector will greatly improve angular resolution, array duty cycle, source galaxy identification, and source parameter estimation. The expanded array should be designed to maximise the science outcomes of gravitational wave astronomy in regard to both the fundamental testing of general relativity and astrophysical observations.

New approaches and new technologies for ground based gravitational wave detectors have been under development for a number of years. Proposed designs for future detectors were considered by the Einstein Telescope collaboration and by LIGO Scientific Collaboration “colour groups” in 2010-2012.

This KITPC Program will bring leading experts in gravitational wave astrophysics, gravitational wave detector science and engineering, quantum opto-mechanics, precision optics, fine mechanics and materials science together in a 5 week program focused on designing the next ground based detectors, and special sessions and workshops on the optimum design for space based detectors.

Future detector designs depend crucially on key enabling technologies in which there has been intense theoretical and experimental research over recent years. These include

– theory of acoustic noise and development of optical materials that combine ultralow acoustic noise and optical losses,
– theory and technology for Newtonian gravitational noise reduction,
– theory and implementation of macroscopic quantum measurement techniques.

Considerations for evaluating different detector arrays include: a) knowledge and modelling of signal sources; b) modelling of detector array performance in relation to source parameter extraction and signal to noise ratio; c) methods of data analysis; d) capabilities and performance of multi-messenger astronomy techniques.

Finally, design choices for the next ground based detectors will depend on practical considerations that include the time scale for achieving performance requirements, understanding of the risks associated with design choices, and cost trade-offs versus funding opportunities.

Week 1 will focus on the entire gravitational wave spectrum including regions targeted by pulsar timing, space laser interferometers, atom interferometers and ground based detectors. It will review the current knowledge of sources, detectors and data analysis, and identify critical areas of research in the physics of sources, gravitational wave detector science and multimessenger astronomy.

Week 2 will include the Third Beijing Workshop on Gravitational Waves (held at Tsinghua University, Beijing). The program of this workshop is centered on the following themes:

– Detection of gravitational waves: instruments, signal analysis, data analysis,…
– Gravitational wave sources: neutron star binaries, black hole binaries,…
– Multi-messenger astrophysics: optical, X-ray, or gamma ray counterparts, neutrinos,…
– Other gravitational-wave related themes (supporting computing architecture,…)

Weeks 3-4 will explore the possibilities for realistic designs for the next ground based detectors, plus workshop to explore space detector designs and their synergy with ground based detectors. Sessions will include:

– Quantum measurement technologies based on optical squeezing and optical spring effects;
– Core technologies including laser wavelength, test mass material, optical coatings, detector configurations, vacuum and cryogenics, and control systems.
– Broadening the sensitivity bandwidth (<10Hz, >3kHz) and multimessenger astronomy.
– Interferometer arm length: vacuum and cost/sensitivity trade-offs. Space detector workshop topics will include:
– Technology: high-power space qualified lasers, ultra-stable oscillators, pointing, sensors, UV discharging, time delay interferometry.
– Mission design: layout, armlength, orbit.
– Sources, data analysis and multimessenger astronomy: galaxy and black hole evolution, optical counterparts, EMRI templates, TeV signatures and dark energy.

Week 5 will focus on the programme outcomes: completion of the science case and conceptual design for the next ground based detectors. Publication: The outcomes will be published as a special issue of a refereed journal containing a single multi-authored design paper on the next ground based detector, a multi-authored review on space detectors and short individual contributions. Week 5 will also organize an international conference on gravitation and cosmology jointed with the 4th Galileo-Xu Guangxi meeting, to celebrate GR 100

About 50 international participants and 100 participants from China are expected to attend the KITP Program, which will take place on the Campus of the CAS-KITP in Beijing. The program will include formal presentations, workshops and informal working groups along the lines of Aspen workshops. The draft program below will be modified according to advice from the IAC and Coordinating Committee and availability of participants. Funding details for participants will be given in the second announcement.

International Organizing Committee
David Blair, Junwei Cao, Zhoujian Cao, Yanbei Chen, Yun-song Piao, Wen Zhao, Zong-Hong Zhu