Qutech demonstrates 6-qubit silicon quantum processor

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Researchers at Qutech have engineered a record number of six silicon-based spin qubits in a fully interoperable array. Importantly, the qubits can be operated with a low error-rate that is achieved with a new chip design, an automated calibration procedure, and new methods for qubit initialization and readout. These advances will contribute to a scalable quantum computer based on silicon, the researchers say.

“The quantum computing challenge today consists of two parts,” explains Qutech researcher Stephan Philips. “Developing qubits that are of good enough quality, and developing an architecture that allows one to build large systems of qubits. Our work fits into both categories. And since the overall goal of building a quantum computer is an enormous effort, I think it is fair to say we have made a contribution in the right direction.”

The qubits (labeled 1-6) are created by tuning the voltage on the red, blue and green wires on the chip. Credit: Qutech

To make the qubits, individual electrons were placed in a linear array of six quantum dots spaced 90 nanometers apart. The array of quantum dots is made in a silicon chip with structures that closely resemble the transistor. The Delft-based team used finely-tuned microwave radiation, magnetic fields, and electric potentials to control and measure the spin of individual electrons and make them interact with each other.

Silicon qubits lag behind superconducting qubits, of which arrays with over 50 qubits have been built. Researchers are counting on the industry’s decades-long industrial experience with silicon processing to speed up the industrialization phase.