Over the last ten years, there have been significant breakthroughs in generating quantum effects in mechanical systems, a feat considered impossible just fifteen years ago. Scientists have successfully created quantum states in large mechanical objects by coupling them with light photons, forming “optomechanical systems.” This advancement has enabled cooling these systems to their lowest energy level, reducing vibrations, and entangling them. These achievements have promising applications in quantum sensing, compact quantum computing storage, testing quantum gravity, and searching for dark matter.
However, operating optomechanical systems in the quantum realm presents a challenge. Scientists must balance isolating mechanical oscillators to minimize energy loss with coupling them to other systems for control. Achieving this balance involves extending the quantum state lifetime while minimizing “decoherence,” which arises from environmental influences.
A recent breakthrough by the laboratory of Tobias J. Kippenberg at EPFL introduces a superconducting circuit optomechanical platform. This system exhibits remarkably low quantum decoherence, coupled with strong optomechanical coupling, enabling precise quantum control. A “vacuum-gap drumhead capacitor,” comprising a thin aluminum film suspended over a silicon trench, is the key innovation. This capacitor serves as both the vibrating component of the oscillator and a resonant microwave circuit.
Through advanced nanofabrication, the research team reduced mechanical losses in the resonator. This resulted in an unprecedentedly low thermal decoherence rate, equivalent to a quantum state lifetime of 7.7 milliseconds—the longest ever achieved in a mechanical oscillator. The reduced decoherence enabled optomechanical cooling, achieving a 93% fidelity in the quantum state occupation and mechanical squeezing beyond zero-point fluctuation.
The team’s achievement allows for observing extended free evolution of mechanical squeezed states with minimal quantum decoherence. This breakthrough not only enhances quantum control and measurement of mechanical systems but also facilitates interfacing with superconducting qubits and supports tests of quantum gravity. The longer storage time compared to superconducting qubits makes this platform ideal for quantum storage applications.