Quantum Leap: Entangling Macroscopic Sound Waves Paves teh Way for Scalable Quantum Computing
February 10, 2024 - A groundbreaking study from the University of Chicago‘s Pritzker School of Molecular engineering (UChicago PME) has demonstrated high-fidelity entanglement between two macroscopic acoustic wave resonators, marking a significant step forward in the pursuit of scalable quantum computing. Published Friday in Nature Communications, the research challenges conventional understanding of quantum mechanics and opens new avenues for building powerful quantum processors.
For years, quantum entanglement – the phenomenon where two or more particles become linked and share the same fate, no matter how far apart – has been confined to the realm of microscopic particles like electrons and photons. This new work, led by Professor Andrew cleland, extends this essential principle to considerably larger, “massive” objects, representing a pivotal shift in quantum technology.
Beyond Single Particles: Entangling Collective Motion
“A lot of research groups have successfully entangled very small things, down to the single electron,” explains Ming-Han Chou, co-first author of the study and now at the amazon Web Services Center of Quantum Computing. “But we’ve demonstrated entanglement between two massive objects,and importantly,shown that our platform is scalable – a crucial element for building a large quantum processor.”
The entanglement isn’t occurring within the atoms or molecules comprising the resonators themselves, but rather within the “phonons” they contain. Phonons are, in essence, quantum particles of sound – nanoscale mechanical vibrations. Imagine, if you could, hearing the resonators; the entanglement is happening within that sound.
“A phonon isn’t an elementary particle,” clarifies co-first author Hong Qiao, a postdoctoral researcher in Cleland’s lab. “It’s the collective motion of quadrillions of particles behaving together. This is macroscopic compared to entangling single electrons, single atoms, or single photons.” This collective behavior is key to the potential scalability of the approach.
A History of Phonon Innovation
Professor Cleland’s lab has been at the forefront of phonon research for years. they were the first to successfully create and detect single phonons, and previously demonstrated entanglement between two phonons.This latest breakthrough builds upon that foundation, achieving entanglement wiht significantly higher fidelity and demonstrating the potential for complex entangled states.
This pioneering work has garnered significant recognition, including a 2024 Vannevar Bush Faculty Fellowship from the Department of Defense, awarded to cleland to further pursue phonon-based quantum computing.
Bridging the quantum-classical Divide
The implications of this research extend beyond the technical advancements. “The conventional wisdom has been that quantum mechanics governs the smallest scales, while classical physics rules the human scale,” says Cleland. “Our ability to entangle massive objects through their collective motion pushes that boundary. The realm where Schrödinger’s cat exists gets bigger with each advance.” This refers to the famous thought experiment illustrating the counterintuitive nature of quantum superposition.
How the System Works: Qubits and Acoustic Resonators
The team’s device consists of two surface acoustic wave resonators, each housed on a separate chip with dedicated mechanical support. Each resonator is connected to a superconducting qubit, wich acts as the interface for generating and detecting the entangled phonon states. The researchers successfully demonstrated high-fidelity entanglement between these large resonators, both while physically separated and during operation.
“Previously, entanglement has been demonstrated, but with limited fidelity,” explains Qiao. “We’ve shown we can go a step further, preparing more complicated entangled states, possibly even encoding logical information.” This ability to create more complex states is vital for performing complex quantum computations.
The Path Forward: Extending Coherence Time
While a significant achievement, the research team acknowledges the next critical challenge: extending the coherence time of the resonators. Coherence time refers to how long the entanglement can be maintained before it degrades. Currently, the resonators maintain entanglement for approximately 300 nanoseconds. Increasing this to over 100 microseconds is crucial for enabling more powerful dialogue and distributed quantum computing – key components of future quantum networks.
“Our mechanical resonator has a relatively short lifetime, which limits performance,” says chou. “The next step is clear: we will improve the mechanical resonator lifetime.” Fortunately, several established techniques in quantum acoustics can achieve this significant betterment, and the team plans to implement them in future iterations of the device.
implications for the Future of Quantum technology
This research represents a major leap forward in the field of quantum computing. By demonstrating entanglement in macroscopic objects and showcasing a scalable platform,the University of Chicago team has opened up exciting new possibilities for building robust and powerful quantum processors.The ability to manipulate and entangle sound-like vibrations at this scale promises to unlock new avenues for quantum communication, distributed quantum
