Yale Researchers Cool Sound Vibrations to Quantum Ground State

Researchers at Yale University, led by Professor Peter Rakich, have demonstrated the quantum cooling of acoustic vibrations within a crystalline quartz resonator to its quantum ground state. Using lasers, the team achieved quantum-coherent motion in approximately 100 quadrillion atoms within a 10-microgram object, representing a scale increase of approximately one million times over previous demonstrations of quantum mechanical control. This approach, which focuses on manipulating bulk acoustic waves rather than surface interactions, resulted in increased coherence times – a critical factor in the development of quantum technologies. The findings, published in Nature Physics, suggest a pathway to mitigating decoherence and improving the viability of practical quantum computing.

Yale researchers have demonstrated the ability to cool quantized vibrations of sound within massive objects to their quantum ground state, utilising laser technology. Published in Nature Physics, the research involved a micro-scale resonator constructed from crystalline quartz, enabling control of vibrations at the quantum level within these macroscopic mechanical objects. Professor Peter Rakich notes that, within the quantum realm, ‘massive’ is a relative term; the system employs 10 micrograms of material in acoustic wave motion – a quantity smaller than a grain of sand, yet comprising 100 quadrillion atoms moving in quantum-coherent fashion.

This advance represents a significant improvement over prior methods, which were limited to controlling motion at the quantum level in objects approximately a million times smaller. The increased scale achieved by the Yale team is important because it translates to longer coherence times – the duration for which quantum information can maintain its quantum properties before decaying. Increasing coherence times is a critical challenge for quantum scientists and represents a key barrier to the development of practical quantum computers.

The Rakich laboratory’s approach, utilising light to access sound waves within the bulk of a crystal, reduces surface interactions, thereby protecting the system from unwanted quantum decoherence. Controlling interactions at surfaces is notoriously difficult, and accessing the bulk of the crystal minimises these problematic interactions. Consequently, a smaller proportion of atoms resides at the surface, contributing to the observed longer coherence times and the demonstrated control of quantum mechanical vibrations.