Researchers develop new way to manipulate qubits

Researchers at an Australian university have found and developed a new way to manipulate qubits. According to them, the new method makes it possible to produce quantum computers with ‘billions of qubits’.

The discovery was made as early as 2020 by an employee of the UNSW University of Sydney. Postdoc researcher Tuomo Tanttu discovered then during experiments that he could manipulate the spin of electrons in quantum dots with electric fields. Until now, the laboratory has used magnetic fields for this. Since 2020, the research team, which in addition to Dr. Tanttu includes Dr. Gilbert and Professor Dzurak, has refined the technique.

Illustration intrinsic spin orbit EDSR

Tanttu made the discovery more or less by chance. He experimented with different geometries of the microwave antennas with which he influences the electron spin with a magnetic field. However, one of the experimental antennas produced a much stronger electric field than the magnetic field, to which the spin responded much more strongly than it did to magnetic fields. With this, a third way has been developed to manipulate electron spin in qubits, in addition to ESR and EDSR. Microwave antennas are used for ESR, or electron spin resonance, and magnetic fields are used for EDSR, or electric dipole spin resonance. The new third method, the so-called intrinsic spin-orbit EDSR, no longer requires magnets to manipulate the qubits, which greatly simplifies their ‘control’. The technique uses electric fields to manipulate the spin and would make it possible to change the electron spin without affecting nearby qubits. This does not require micromagnets or antennas right next to the gates. The researchers have their work in Nature published.

Tanttu’s research group collaborates with UNSW spinoff Diraq, a quantum technology company founded by Dzurak. That applicable the aforementioned company wants to make quantum computers based on cmos quantum dots using existing chip production techniques. Using those known production methods, quantum chips with millions or even billions of logic gates could be made; the more qubits a quantum computer has, the more powerful it is. The researchers build these logic gates with qubits that consist of quantum dots with ‘captured’ electrons. Without relying on micromagnets to change the spin of those electrons, the qubits can potentially be packed closer together in the silicon substrate.