Quantum computing, like regular computing, requires a way to store the information it uses and processes. Just as the computer you’re currently using stores photos, reminders, and text, quantum computing is still figuring out how and where to store quantum information.
In a recently published paper in Nature Physics, Mohammad Mirhosseini, an assistant professor of electrical engineering and applied physics, presents a new method developed by his lab that efficiently translates electrical quantum states into sound and vice versa. This method could potentially be used to store quantum information generated by future quantum computers, which are likely to be made from electrical circuits.
The technique relies on phonons, which are the sound equivalents of particles of light called photons. In the field of quantum mechanics, waves and particles are interchangeable. The research explores the use of phonons to store quantum information because it is relatively easy to build small devices capable of storing these mechanical waves.
To grasp how sound waves can store information, imagine being in a room with strong echoes. If you need to remember your grocery list, you open the door, shout your items, and close the door. An hour later, when you open the door again, you can hear your own voice echoing the grocery items. This demonstrates how sound waves can store information.
However, in reality, such an echo would not last long, and the sound might become distorted, making it difficult to understand. Additionally, using an entire room to store a small amount of data would be impractical. The research team’s solution is a small device consisting of flexible plates that vibrate at extremely high frequencies when exposed to sound waves. By placing an electric charge on these plates, they can interact with electrical signals carrying quantum information. This enables the information to be stored in the device and retrieved later, similar to opening and closing the door to the room where you shouted earlier.
According to Mohammad Mirhosseini, previous studies had examined piezoelectric materials for converting mechanical energy to electrical energy in quantum applications. However, these materials tend to cause energy loss for both electrical and sound waves, which is problematic in the quantum realm. In contrast, Mirhosseini’s team has developed a new method that is independent of specific material properties, making it compatible with established quantum devices based on microwaves.
Creating efficient storage devices with small footprints has been a practical challenge for researchers in quantum applications. Alkim Bozkurt, a graduate student in Mirhosseini’s group and the lead author of the paper, explains that their method enables the storage of quantum information from electrical circuits for much longer durations than other compact mechanical devices.
The paper describing this work, titled “A quantum electromechanical interface for long-lived phonons,” is featured in the June 22 issue of Nature Physics. The co-authors of the paper include Chaitali Joshi and Han Zhao, both postdoctoral scholars in electrical engineering and applied physics, as well as Peter Day and Henry LeDuc, scientists at the Jet Propulsion Laboratory managed by Caltech for NASA.
