QuTech Study Tracks Performance of Growing Quantum Circuits in Silicon

Researchers at QuTech have successfully demonstrated programmable quantum circuits using up to six silicon spin qubits, providing critical insight into the challenges of scaling up this promising semiconductor technology. Published in PRX Quantum, the study moves beyond previous three-qubit demonstrations, tracking performance as circuits grew to include three, four, five, and six qubits and revealing key physical bottlenecks. The team ran circuits on the linear array, comparing measured outputs to expected quantum behavior to assess processor evolution; Irene Fernández de Fuentes, first author of the paper, says that this type of experiment allows researchers to follow how behavior changes as circuit size increases. Lieven Vandersypen, professor at TU Delft and lead investigator, emphasizes the significance of building on established microelectronics techniques, noting that spin qubits are interesting because they are built in a semiconductor environment. Six-Qubit Circuits Demonstrate Silicon Spin Qubit Scalability This work extends beyond previous demonstrations of three-qubit algorithms in silicon quantum dots, representing a significant progression toward more extensive, programmable processors capable of complex calculations. The team employed a linear array of six qubits and executed circuits on groupings ranging from three to six. By monitoring the processor’s evolution through sequences of single and two-qubit operations, they validated the observed output against predicted quantum behavior. Measurements revealed that as circuits expand, qubits experience increasing idle periods while awaiting operations on others, leading to a gradual loss of phase coherence and diminished final result quality; the team directly identified idling and dephasing as key limitations in the current device by comparing performance across different system sizes. Fernández de Fuentes adds that extracting this level of detail from these experiments is valuable, as it allows for understanding dominant physical effects during scaling. Researchers at QuTech have begun to quantify the impact of idling and dephasing on silicon spin qubit performance as circuit complexity increases, revealing critical bottlenecks in scaling quantum processors. “What makes spin qubits so interesting is that they are built in a semiconductor environment, with single electrons confined and controlled using techniques that connect naturally to the world of microelectronics,” Lieven Vandersypen, professor at TU Delft and lead investigator Source: https://qutech.nl/2026/04/02/programmable-quantum-circuits-put-silicon-qubits-to-the-test/ QUANTUM CIRCUITS QUANTUM COMPUTING QUTECH SILICON QUBITS SPIN QUBITS