Qutech speeds up readout of quantum dot qubits

Paul van Gerven
Leestijd: 2 minuten

Researchers at Qutech have shown that qubits can simultaneously be read out quickly, reliably and scalably. Being able to do these three things simultaneously is a prerequisite for building an effective quantum computer.

The research at the group led by Lieven Vandersypen focuses on quantum dots, ie individual electrons, confined in silicon. A single electron spin signal is very weak, so the spin state is read out via its charge. In one of the spin states, the electron can escape from the quantum dot, changing the charge on the quantum dot. In the other state, it cannot escape.

The change in charge is measured by an electrometer, but these are located next to the dot, and therefore obstruct any physical expansion of the number of dots and scaling up to more qubits. “That’s why, for a number of years, research has been conducted into an alternative readout method in which a resonator is connected to an electrode – which anyway is already present to make the dot. The significant advantage of this approach is that scaling up is a lot easier, provided that the readout method functions properly,” explains Qutech researcher Guoji Zheng.

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