Figure 1: False-colored scanning electron microscope image of the quantum dot device. The red dots indicate the locations of the quantum dots. © 2026 RIKEN Center for Quantum Computing
Devices that can confine individual electrons are potential building blocks for quantum information systems. But the electrons must be protected from external disturbances.
RIKEN researchers have now shown how quantum information encoded into a so-called quantum dot can be negatively affected by nearby quantum dots1. This has implications for developing quantum information devices based on quantum dots.
Quantum computers process information using so-called qubits: physical systems whose behavior is governed by the laws of quantum mechanics. An electron, if it can be isolated and controlled, is one example of a qubit platform with great potential.
One way of controlling an electron is to use a quantum dot. These tiny structures trap charged particles using electric fields at the tips of metal electrodes separated by just a few tens of nanometers.
To be useful, quantum dots have to be able to store quantum information for a long time. But quantum states are very fragile and can be easily destroyed by interference from the outside world.
As Takashi Kobayashi of the RIKEN Center for Quantum Computing and co-workers have now shown, this problem is exacerbated when many quantum dots are placed close together, which will necessarily be the case in a fully functioning quantum computer.
"Our experimental results let the silicon quantum computing community recognize the impact of electron rearrangements in quantum circuits," says Kobayashi. "This insight paves the way toward realizing a large-scale silicon quantum computer with an appropriate quantum error correcting code."
The qubits constructed by the RIKEN team incorporated a micromagnet that made the electrons highly sensitive to electric fields. This meant the electron could be controlled by making only small changes to the voltage applied across the quantum-dot electrodes (Fig. 1).
But this sensitivity had a downside: as the electrons in neighboring quantum dots move through the micromagnet's magnetic field, they generate an electric field that alters the energy of the qubit and disturbs the quantum information.
Kobayashi and co-workers have now directly measured this shift for the first time. They found that it is large enough to cause a considerable qubit error rate unless it is properly dealt with.
"Our next step is to develop methods to cancel or avoid the impact of this charge-induced energy shift," says Kobayashi. "We are also seeking to harness the energy shift as a resource for a new class of qubit operations, which might give silicon spin qubits a distinctive advantage against other qubit platforms."
Takashi Kobayashi (third from right) and co-workers have measured the energy shift of an electron-spin qubit induced by neighboring quantum dots. © 2026 RIKEN
