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One day, perhaps, quantum computers will tackle problems that our current machines cannot solve. Among the serious candidates to achieve this are spin qubits in silicon: electrons trapped in a silicon transistor, whose magnetization carries quantum information. These electrons are confined in silicon “quantum dots,” nanometric structures similar to transistors, manufactured using microelectronics production tools.

But when trying to assemble a large number of these boxes, two major problems arise:
1. Electrons have too many different ways to occupy these boxes.
2. The sensors used to read the state of each electron are too bulky and too slow.

Researchers from CNRS, CEA, and the start-up Quobly have developed a new approach in this study:

• Isolate the network from the outside world: this way, electrons have fewer possibilities to enter and exit, making them easier to control.
• Measure without bulky sensors: they use the reflection of a microwave signal on the boxes, a technique that detects electron movements by observing very slight changes in the signal’s phase.
• Probe the entire network at once: thanks to multiplexing, several measurement circuits can be combined on a single chip.

Result: they successfully controlled a network of four quantum boxes, each containing exactly one electron. Additionally, the information carried by each electron can be extracted in a single measurement.

In summary: this method could pave the way for the creation of larger qubit networks, which may form the basis of future quantum computers, while remaining compatible with the industrial processes of microelectronics

Pierre Hamonic, Martin Nurizzo, Jayshankar Nath, Matthieu C. Dartiailh, Victor Elhomsy, Mathis Fragnol, Biel Martinez, Pierre-Louis Julliard, Bruna Cardoso Paz, Mathilde Ouvrier-Buffet, Jean-Baptiste Filippini, Benoit Bertrand, Heimanu Niebojewski, Christopher Bäuerle, Maud Vinet, Franck Balestro, Tristan Meunier & Matias Urdampilleta

Nature Communications volume 16, Article number: 6323 (2025)

Journal here

Artist’s view of a network of four interacting quantum boxes. T
he microwave signal represented by the red wave queries the presence and spin
of the electrons trapped under the electrodes. . (crédit : © Maxime Diard)