Researchers at Swansea University have made a significant discovery in the field of quantum noise reduction, which could have implications for quantum experiments and sensor technology. Published in Physical Review Research, the study explores how the act of measuring nanoparticles disturbs them due to "backaction," a phenomenon where light particles, or photons, perturb the tiny particles they encounter.
The research, led by PhD student Rafal Gajewski, demonstrates that creating conditions where measurement is impossible eliminates this disturbance. "Our work has shown that if you can create conditions where measurement becomes impossible, the disturbance disappears too," said Gajewski. By positioning a particle at the center of a hemispherical mirror, the researchers found that specific conditions make the particle indistinguishable from its mirror image. Consequently, no position information can be extracted from the scattered light, and quantum backaction is nullified.
The implications of this discovery are broad, with potential applications including creating quantum states for larger objects than atoms, testing fundamental quantum physics, and developing ultra-sensitive sensors. Such advancements could be instrumental for projects like the proposed space mission MAQRO (Macroscopic Quantum Resonators), which aims to test quantum physics with larger objects.
Dr. James Bateman, who supervised the study, noted: "This work reveals something fundamental about the relationship between information and disturbance in quantum mechanics. What's particularly surprising is that the backaction disappears precisely when light scattering is maximised – the opposite of what intuition might suggest."
The team's research falls within the realm of "levitated optomechanics," where lasers suspend and control tiny particles in a vacuum. Advances in this field have allowed for particles to be cooled to their quantum ground state, illustrating the level of control scientists can achieve.
The breakthrough opens new avenues for experimentation and suggests that by manipulating the environment around a quantum object, it is possible to control the quantum noise experienced, leading to potentially more sensitive measurements. The team is pursuing experimental demonstrations and practical applications for these findings.