Scientists at Harvard’s School of Engineering and Applied Sciences have developed a technique for preserving quantum information using mechanical vibrations, or phonons, which could advance the creation of smaller quantum networks integrated directly onto chips and support hybrid systems combining different types of quantum bits.
The research, led by Marko Lončar’s laboratory and published in Nature Physics, explores an approach that uses the electron spin in diamond impurities to store quantum data, with phonons serving as carriers to transport information between qubit nodes. Phonons offer potential advantages over light in quantum communication because they possess shorter wavelengths at equivalent frequencies, enabling researchers to construct smaller components and arrange them more densely. Additionally, phonons interact effectively with both solid-state spins and electromagnetic fields, making them particularly suitable for hybrid quantum systems that integrate multiple qubit types.
A central challenge in phonon-based quantum computing has been maintaining quantum coherence—the ability of qubits to retain their quantum state long enough to perform useful computations while resisting environmental disturbances. Traditional protection methods using microwave pulses prove ineffective for qubits positioned within phononic cavities, creating a conflict between achieving strong phonon interactions and maintaining long-lasting quantum memory.
The Harvard team resolved this issue by implementing what they term “all-mechanical coherence protection” for silicon-vacancy spins in diamond. Rather than employing conventional microwave pulses, researchers applied a continuous mechanical driving field composed of phonons, transforming the qubit into a “dressed” state in which it effectively wears an acoustic field. This configuration reduces vulnerability to low-frequency environmental noise. The protective mechanism operates within phononic cavity structures, enabling phonons to simultaneously transport information and shield it from environmental interference.
The experiments demonstrated that this approach extended the coherence time of silicon-vacancy spins by approximately threefold, indicating that continuous mechanical noise suppression can enhance quantum coherence in practical devices. The findings suggest that microscopic sound waves could become instrumental in developing more dependable and compact quantum computing systems. The Harvard Office of Technology Development is pursuing patent protection and commercialization possibilities for the research outcomes.
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