Illinois Quantum Information Science and Technology Center

March 9, 2021

Nature, at the scale of atoms, is governed by quantum mechanics. While we can peek into this realm with powerful microscopes, much of it remains obscured because of heat. Signature quantum features like superposition and entanglement are extremely delicate when it comes to temperature changes — they dissipate like water droplets on a hot summer day. For scientists, this presents a conundrum: devices that harness the elusive world of quantum could revolutionize technology but attempts to reach into that world are riddled with obstacles.

Scientists studying optomechanics, or the interactions between light and mechanical vibrations, live at the edge of the quantum realm. They build chips and structures that are often bigger than the typical quantum platform, which only makes their battle with heat more acute. In such devices the quantum versions of mechanical vibrations, known as phonons, are tiny but prevalent vehicles for heat.

In the October issue of Nature Communications, a team of IQUIST researchers led by Kejie Fang, Assistant Professor in Electric and Computer Engineering, present a new method for efficiently trapping phonons inside a fabricated device. Their design reduces heating by keeping some phonons stuck in place while redirecting others, and the heat they carry, to a completely different part of the device. The researchers also showed that trapped phonons stayed stable for a long time. This work could provide a starting point for the development of new quantum tools that use phonons for storing information, converting mechanical motion into electrical signals, or detecting rare astrophysics events.

In optomechanics, fabricated structures vibrate and produce acoustic waves. These undulations are made up of discrete bundles of energy called phonons. From a quantum perspective, each phonon can be visualized as a tiny spring, rather than a wave spread out across space. And they can be affected by any particle that collides with them — just like a spring reacts to any force that pushes on it.

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