Mobile spin qubits demonstrated in quantum dot arrays by Delft University of Technology and QuTech
Researchers have achieved a 99 per cent success rate for two-qubit gates and 87 per cent for quantum teleportation, suggesting a path toward scalable, reconfigurable quantum computing hardware.
A collaboration between Delft University of Technology and the startup QuTech has successfully demonstrated the movement of spin qubits between quantum dots on a single chip without losing quantum information. The team shifted electron spins across a linear array of six quantum dots, enabling two-qubit gates and entanglement. This achievement combines the bulk-manufacturing benefits of electronic quantum dots with the flexible connectivity typically associated with atomic or ion-based systems.
Traditional electronic quantum dot systems are wired during manufacturing, forcing a commitment to specific error-correction schemes that cannot be changed later. In contrast, systems using atoms or ions offer flexibility but require complex hardware to manage. The new work addresses this trade-off by showing that it is possible to move these spin qubits from one quantum dot to another without losing quantum coherence.
The experiment achieved a 99 per cent success rate for two-qubit gates and an 87 per cent success rate for quantum teleportation. These operations are essential for building error-corrected logical qubits and performing calculations. The ability to move qubits around could potentially enable the sort of any-to-any connectivity seen with atoms and ions, allowing for dynamic reconfiguration of connections rather than being locked into a static manufacturing layout.
In the proposed architecture, there are dedicated storage zones where qubits reside until they are moved to interaction zones for manipulation. This approach envisions a system similar to neutral atom setups but with integrated control hardware that leverages standard chipmaking processes. The current device consists of a linear array of only six quantum dots, indicating this is a proof-of-concept rather than a fully optimised system.
While electron-based qubits are fragile, quantum dots provide sufficient isolation from the environment to maintain performance. Competitors like Google and IBM utilise transmons, whereas companies like Intel are actively developing quantum dot technologies. The researchers envision connectors allowing qubits to move onto different tracks to enable longer-distance interactions, though the current device has a way to go before performance reaches the point where it can be relied upon for complex error-correction schemes.
The findings, published in Nature, suggest that further improvements are likely possible as quantum dot technology develops to the same level of sophistication as current market leaders. Whether this approach will ultimately boost over competing technologies may take a number of years to become clear, but it represents a significant step toward scalable hardware.
