Researchers at EPFL have developed a breakthrough superconductor circuit platform that shows record-low quantum decoherence alongside high-fidelity quantum control. Their “vacuum-gap drumhead capacitor” achieved the longest-ever quantum state lifetime in a mechanical oscillator, opening new possibilities in quantum computing and sensing.
Efficiently generating quantum effects like entanglement or squeezing in macroscopic objects has proven tremendously difficult due to disruptive decoherence from the environment. But researchers at EPFL have now reported major strides in minimizing decoherence and manipulating optomechanical systems quantumly through an innovative superconductor capacitor design.
Their low-loss capacitor architecture yielded unprecedented coherence times for a mechanical oscillator, overcoming a pivotal roadblock in harnessing the promise of quantum optomechanics. This breakthrough demonstrates a newfound command of quantum control and mitigation of noise sources, with significant implications.
Quantum optomechanical systems link mechanical oscillators and optical fields to manifest photonic-esque quantum properties in larger-scale solid objects. However, ambient interference rapidly degrades fragile quantum states through energy exchange and phase fluctuations before useful operations can occur.
Researchers must balance thoroughly isolating systems from the environment to prevent decoherence while retaining enough tunable coupling to exert control and exchange information. This requirement has hampered practical applications.
But the EPFL team implemented a damping-optimized “drumhead” capacitor design with an aluminum vibrating membrane suspended over a silicon trench. This novel architecture slashed mechanical losses by orders of magnitude compared to previous optomechanical demonstrators.
As a result, they achieved record-breaking coherence times for a quantum optomechanical system – exceeding 7 milliseconds. This represents a 100-fold gain over prior state-of-the-art. With quantum states persisting dramatically longer, the door cracks open to advanced techniques like error correction.
The researchers also employed this low-noise platform to demonstrate quantum ground state cooling of the mechanical mode using sideband extraction – an optomechanical staple – with exceptional 93% fidelity. Additional quantum control was illustrated through generation of motion squeezing below the standard quantum limit.
The unprecedented qubit-like coherence proves out the drumhead capacitor as an ideal oscillator for actualizing quantum optomechanics milestones intractable previously. Optimized further, such architectures could enable tests of quantum theory at mesoscopic scales and pave the way for technologies like quantum transducers or optical routers.
Moreover, the results provide a blueprint for combating decoherence across quantum platforms. The drumhead’s combination of record coherence and high optomechanical coupling quality represents a pivotal step toward controlled, sustained quantum states in mass-manufacturable mechanical objects.
In summary, through ingenious capacitor engineering, the EPFL researchers managed to tip the delicate balance of environmental isolation and control in quantum superconductor optomechanics – producing more quantum behavior with less noise. Their breakthrough resonator design moves photonic-like quantum effects in macroscopic systems significantly closer to practicality.
Read more here: “A squeezed mechanical oscillator with millisecond quantum decoherence” by Amir Youssefi, Shingo Kono, Mahdi Chegnizadeh and Tobias J. Kippenberg, 10 August 2023, Nature Physics.