A Simple Twist of Atom-Thin Crystals Gives Scientists New Control Over Quantum Light

Researchers have found that twisting layered sheets of hexagonal boron nitride can dramatically change the light produced by quantum emitters embedded within the material, handing scientists an unexpected new dial for controlling the single particles of light that future quantum technologies will rely on. The technique offers a level of control over these components that strain-based methods have struggled to match.

Quantum emitters are tiny defects in a crystal that release light one photon at a time — the basic currency of quantum communication and many quantum-computing schemes. The challenge has always been tuning them: making an emitter produce light at exactly the wavelength a device needs, and doing so reliably and repeatedly. The new work shows that simply rotating one atom-thin layer relative to another can shift that wavelength on demand.

A team from the University of Technology Sydney, working with the University of Minnesota and Kyung Hee University, demonstrated in situ tuning of the embedded emitters by mechanically twisting the top hexagonal boron nitride layer. They achieved a tuning range of more than 30 nanometers — equivalent to roughly 100 milli-electron volts — surpassing what strain-based approaches had previously delivered for the same class of materials.

Crucially, the process is reversible and repeatable. The researchers were able to lift, rotate and restack the material again and again, continuously modifying its optical properties rather than locking in a single setting. That kind of adjustable, mechanical control is rare in quantum hardware, where small fabrication differences often leave each emitter slightly different from its neighbors.

Because the approach works without the extreme cooling or elaborate equipment some quantum systems require, it could prove practical for building the photonic components of quantum computers, secure communication links and ultra-sensitive sensors. Being able to bring many emitters into alignment — tuning each to the same wavelength — is a long-standing obstacle that this twist-based method could help overcome.

The findings, published in the journal Science Advances, add to a fast-growing body of research exploiting the strange behavior that emerges when atom-thick materials are stacked and rotated. By showing that a mechanical twist can finely steer quantum light, the team has pointed toward a simpler, more flexible path for scaling up the delicate building blocks on which quantum technology depends.