Scientists from University College London (UCL), along with researchers from the University of Southampton and the Bose Institute in Kolkata, India, is proposing an experiment that could potentially challenge the conventional limits of quantum mechanics. Quantum theory, renowned for its accuracy in describing the behavior of particles at minuscule scales, has yet to manifest observable effects in objects larger than approximately 10^-20 grams.
Published in Physical Review Letters, the experiment seeks to explore the quantum nature of relatively massive objects. The core principle it exploits is rooted in quantum mechanics – the notion that the act of measuring an object can fundamentally alter its nature. This includes any interaction with a probing element, such as exposure to light.
The proposed experiment revolves around a pendulum-like object resembling a ball on a string. A series of light exposures provide information about the object's location during its oscillation. If the object behaves quantum mechanically, the initial measurement disrupts its trajectory due to measurement-induced collapse, a distinctive feature of quantum mechanics. This disturbance alters the probabilities of the object's location at subsequent measurements. In contrast, if the object follows classical physics, observation should have no impact on its motion.
Lead author Dr. Debarshi Das emphasizes the peculiarities of quantum mechanics, stating, “A crowd at a football match cannot affect the result of the game simply by staring strongly. But with quantum mechanics, the act of observation or measurement itself changes the system.” The experiment aims to discern whether an act of observation can induce changes in the motion of an object, thereby distinguishing between classical and quantum behavior.
The researchers suggest that this experiment could be conducted using current technologies, employing nanocrystals or even mirrors at the Laser Interferometer Gravitational-Wave Observatory (LIGO) in the United States. LIGO's mirrors, collectively vibrating like a single 10kg object, have already been cooled to near absolute zero, a requisite state for experiments seeking to detect quantum behavior.
Senior author Professor Sougato Bose explains the broader implications of the proposed experiment, stating, “Our scheme has wide conceptual implications. It could test whether relatively large objects have definite properties, i.e., their properties are real, even when we are not measuring them.” If successful, this experiment could extend the applicability of quantum mechanics beyond the traditionally accepted scales.
Quantum mechanics posits that objects lack definite properties until observed or interacting with their environment, existing in a state of superposition. While seemingly counterintuitive, these principles have underpinned technological advancements such as computers, smartphones, and medical imaging.
While most physicists believe in the validity of quantum mechanics at larger scales, the challenge lies in observing these effects, requiring meticulous isolation to preserve a quantum state. The proposed experiment builds upon a previous quantum test from 2018, with an ongoing project led by the University of Southampton already exploring the quantum nature of a nanocrystal composed of a billion atoms. This new scheme could potentially push the boundaries further, examining objects with trillions of atoms using existing technologies. If successful, it could deepen our understanding of the relationship between quantum theory and the reality we experience.
Source: University College London