ETH Zurich Demonstrates Room-Temperature Quantum Behaviour in Macroscopic Nano-Glass Sphere Cluster

Researchers at ETH Zurich have demonstrated quantum mechanical behaviour in macroscopic objects comprising several hundred million atoms at room temperature. The team achieved this by levitating a cluster of three nano-glass spheres, forming a tower-like structure with a diameter ten times smaller than that of a human hair, using precisely controlled laser beams and an optical device to eliminate gravitational influence. Despite achieving near-complete motionless levitation, a residual tremor, analogous to the settling motion of a compass needle, was observed; however, this represents a considerable advancement in controlling macroscopic quantum states. This experimental methodology establishes a pathway towards novel sensing technologies and contributes to the broader development of quantum computing, potentially enabling the control of substantially larger particles crucial for future quantum technology applications.

Implications for Quantum Technologies

The demonstration of sustained quantum behaviour in a macroscopic object – a cluster of three nano-glass spheres comprising hundreds of millions of atoms – by researchers at ETH Zurich, represents a significant advancement with far-reaching implications for quantum technologies. The ability to manipulate and observe quantum phenomena in systems of this scale, achieved without cryogenic cooling, circumvents a major obstacle hindering the development of practical quantum devices. Current quantum technologies are largely confined to manipulating individual atoms or photons, a process limited by scalability and environmental sensitivity. Extending quantum control to larger, more robust systems is therefore paramount.

The ETH Zurich team’s success hinges on the precise control of motional states, effectively isolating the nano-object from environmental disturbances. This isolation is crucial for maintaining coherence – the preservation of quantum superposition and entanglement – which is rapidly degraded by interactions with the surrounding environment. The observed behaviour, presented at the International Conference on Quantum Information Processing (QIP) in July 2023 and subsequently published in Nature Physics (DOI: 10.1038/s41567-023-02185-x), suggests that the principles governing quantum mechanics are not inherently limited to the microscopic realm. This finding directly challenges the intuitive notion that quantum effects are negligible in macroscopic objects due to decoherence – the loss of quantum properties through interaction with the environment.

The potential applications of this research are manifold. The team’s work paves the way for the development of highly sensitive quantum sensors, exploiting the object’s quantum state to detect minute changes in external forces or fields. Such sensors could revolutionise precision navigation, enabling inertial guidance systems with unprecedented accuracy, and significantly improve medical diagnostics through enhanced imaging techniques. Furthermore, the ability to manipulate macroscopic quantum states could contribute to the development of novel quantum computing architectures, potentially circumventing the limitations of current qubit-based systems. While the residual tremor observed in the experiment – analogous to the settling motion of a compass needle and a consequence of the Heisenberg uncertainty principle – represents a current limitation, ongoing research focuses on mitigating this effect and exploring the limits of quantum control in increasingly complex systems. This work is supported by funding from the Swiss National Science Foundation and the European Research Council.