A major breakthrough in the quest to unlock the universe's secrets has been achieved by UK scientists, who have successfully demonstrated the effectiveness of a revolutionary new quantum sensor under realistic conditions. This pioneering work paves the way for more precise measurements of gravitational waves and dark matter.
The study, published in Nature, showcases how comparing two atom interferometers operating along a shared baseline enables the effective cancellation of significant experimental noise. This game-changing approach ensures that crucial signals can be recovered even when individual measurements are overwhelmed by background interference. Funded by UKRI’s Quantum Technologies for Fundamental Physics scheme and managed by the Science and Technology Facilities Council (STFC), this research was conducted by scientists at Imperial College London, as part of the Atom Interferometer Observatory and Network (AION) collaboration.
Atom interferometers use lasers to create a quantum superposition, forcing atoms to exist in two places simultaneously before being brought back together. This ultra-precise measurement process can detect minute changes in their motion, potentially indicating hidden signals like dark matter fields. However, the phase noise generated by the control lasers typically far exceeds the signals scientists aim to measure. The new differential approach addresses this critical challenge, comparing two interferometers to cancel out shared noise – a method previously unproven under real-world conditions.
To rigorously test this method, researchers at the Imperial Ultracold Strontium Laboratory built a tabletop prototype using two macroscopically separated clouds of ultracold strontium-87 atoms interrogated by a single ultra-stable clock laser. They deliberately introduced substantial amounts of additional phase noise into the system to simulate challenging conditions, mimicking what would be expected in long-baseline detectors. While individual interferometers became unusable due to noise, the comparative analysis successfully recovered a clear signal operating at the fundamental limit dictated by quantum physics. Further experiments demonstrated that signals akin to passing gravitational waves or dark matter fields could still be detected clearly, even when individual interferometer data was unusable.
This breakthrough paves the way for the AION experiment, which aims to use quantum interference techniques to search for ultralight dark matter and detect gravitational waves in a frequency range currently inaccessible to existing observatories. The AION-10 detector, a 10-metre baseline device, is set to play a crucial role in this endeavour.