A new search algorithm could be a quantum leap in detecting gravitational waves


A new method of identifying gravitational wave signals using quantum computing could provide a valuable new tool for future astrophysicists.

A team from the University of Glasgow‘s School of Physics & Astronomy has developed a quantum algorithm to drastically reduce the time it takes to match gravitational wave signals to a large database of patterns.

This process, known as matched filtering, is part of the methodology behind some of the findings of gravitational wave signals from detectors such as the Laser Interferometer Gravitational Observatory (LIGO) in America and Virgo in Italy.

These detectors, the most sensitive sensors ever created, pick up the faint ripples in spacetime caused by massive astronomical events like black hole collisions and mergers.

Matched filtering allows computers to remove gravitational wave signals from the noise of the data collected by the detector. It works by sifting through the data, looking for a signal that matches one of hundreds of trillions of potential patterns – pre-created pieces of data that are likely to correlate with a real gravitational wave signal.

Although the process has made many gravitational wave detections since LIGO picked up its first signal in September 2015, it is time-consuming and resource-intensive.

In a new article published in the journal Physical examination researchthe team describes how the process could be greatly sped up by a quantum computing technique called Grover’s algorithm.

Grover’s algorithm, developed by computer scientist Lov Grover in 1996, exploits the unusual capabilities and applications of quantum theory to make the process of searching through databases much faster.

While quantum computers capable of processing data using Grover’s algorithm are still a developing technology, conventional computers are able to model their behavior, allowing researchers to develop techniques that can be adopted when the technology has matured and quantum computers are readily available.

The Glasgow team is the first to adapt Grover’s algorithm for the purpose of searching for gravitational waves. In the paper, they demonstrate how they applied it to gravitational wave research through software they developed using the Python programming language and Qiskit, a quantum computing process simulation tool.

The system developed by the team is able to speed up the number of operations proportionally to the square root of the number of models. Current quantum processors are much slower to perform basic operations than classical computers, but as the technology develops their performance should improve. This reduction in the number of calculations would result in an acceleration over time. In the best-case scenario, this means that, for example, if a search using classical computing would take a year, the same search could take as little as a week with their quantum algorithm.

Dr Scarlett Gao, from the University’s School of Physics and Astronomy, is one of the lead authors of the paper. Dr Gao said: ‘Adaptive filtering is a problem that Grover’s algorithm seems well placed to help solve, and we have been able to develop a system which shows that quantum computing could have valuable applications in gravitational wave astronomy.

“My co-author and I were PhD students when we started this work, and we are fortunate to have had access to support from some of the UK’s leading quantum computing and gravitational wave researchers during the development process of this software.

“Although we have focused on one type of search in this article, it is possible that it could also be adapted to other processes which, like this one, do not require the database to be loaded into a quantum random access memory.

Fergus Hayes, a doctoral student in the School of Physics and Astronomy, is co-lead author of the paper. He added: “Researchers here in Glasgow have been working on the physics of gravitational waves for over 50 years, and work at our Institute for Gravitational Research has helped underpin the development and data analysis aspects of LIGO.

“The interdisciplinary work that Dr. Gao and I conducted demonstrated the potential of quantum computing in matched filtering. As quantum computers develop in the coming years, it is possible that such processes could be used in future gravitational wave detectors. It’s an exciting prospect, and we look forward to developing this first proof of concept in the future.

Reference: “A quantum algorithm for the adaptive filtering of gravitational waves” by Sijia Gao, Fergus Hayes, Sarah Croke, Chris Messenger and John Veitch, Physical examination research.

The article was co-authored by Dr Sarah Croke, Dr Christopher Messenger and Dr John Veitch, all from the School of Physics and Astronomy at the University of Glasgow.

The team’s paper, titled “A quantum algorithm for adaptive filtering of gravitational waves”, is published in Physical examination research. The research was supported by funding from the Science and Technology Facilities Council (STFC) and the Leverhulme Trust.


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