Figure 1: Schematic diagram of the system in the study. The yellow spheres indicate bright phonon modes placed inside a bottle, which represents an optomechanical system. The blue spheres at the neck of the bottle represent dark phonon modes. These dark modes act as a gate that confines the phonons, creating a so-called phonon blockade. By manipulating and controlling the dark balls, the gate can be opened to enable controlled phonon transfer. © 2026 RIKEN Center for Quantum Computing
Three RIKEN researchers have demonstrated a way to stop problematic 'dark modes' from squelching intriguing effects in quantum systems1. This advance could help with the development of more versatile quantum devices that can be used to control the storage and transmission of quantum information.
Manipulations that alter the topology of certain quantum systems known as non-Hermitian systems are attracting increasing attention, since they offer novel possibilities for manipulating particles of sound (phonons) and light (photons) as well as other excitations.
"Topological operations allow for various weird and fascinating phenomena, such as the buildup of chiral phases and the movement of phonons in one direction," notes Franco Nori of the RIKEN Center for Quantum Computing (RQC).
However, several challenges must be addressed before these quantum effects can be used in practical applications.
Chief among these challenges are dark modes, which are completely decoupled from certain external fields. "Dark modes are so-called because they are 'invisible' to the environment or to the driving field that couples to a system's other modes, which are bright modes," explains Nori.
Dark modes are problematic because they can entirely suppress the topological responses of a non-Hermitian system.
"When dark modes are present, both conversion between different modes and the topological transfer of phonons break down," says Nori. "These effects can't be restored by the usual measures."
Now, Nori, Deng-Gao Lai and Adam Miranowicz, all of the RQC, have discovered a way to counter dark modes-they have demonstrated how to engineer dark modes so that they temporarily become bright modes (in other words, non-dark modes).
"By using dark-mode engineering, our method allows precise topological control over phonons," says Lai. "It completely avoids the problems usually caused by dark modes."
The team were able to engineer dark modes by introducing artificial quantum information to the system.
The method turned out to be surprisingly robust, even surpassing the team's expectations. "We were thrilled," says Lai. "Such engineered transitions make topological operations possible-something which was previously inaccessible due to dark modes."
The trio anticipates that the demonstration will help to develop new devices and find new effects. "Our work paves the way for constructing scalable quantum devices and discovering novel topological phenomena," says Lai.
The researchers are now exploring how the effect could be applied to the processing of quantum information.
Franco Nori (left) and Deng-Gao Lai (right) have found a way to overcome the problem of dark modes in non-Hermitian systems. © 2026 RIKEN
