[elleparismaroc 2023] New 'flip-flop' qubits emerge

Australian researchers recently demonstrated a new type of qubit operation called a "flip-flop" that combines the delicate quantum properties of individual atoms with the ease of controlling electrical signals in ordinary computer chips. The findings were published in Science Advances.

The UNSW research team has shown for the first time in the world that electron spins as well as nuclear spins of individual phosphorus atoms in silicon can be used as qubits. Both qubits work very well on their own, but they require an oscillating magnetic field to work. And the nanometer-scale magnetic fields inherent in the individual components of a quantum computer are difficult to accommodate.

The team realized that by defining a qubit as the combined up/down direction of electrons and nuclei, they could manipulate these qubits using only electric fields. This new qubit is called a "flip-flop" because it consists of two spins (electron spin and nuclear spin) belonging to the same atom that always point in opposite directions.

This theory predicts that flip-flop qubits can be programmed into arbitrary quantum states by rearranging electrons relative to the nucleus. A new study has confirmed this prediction with complete accuracy.

Most importantly, instead of illuminating the chip with an oscillating magnetic field, this electron displacement is achieved by applying a voltage to tiny metal electrodes. It more closely resembles the electronic signal type chips that are common in traditional silicon computers.

Electrically controlling flip-flop qubits by moving electrons in atomic nuclei is accompanied by very important phenomena. When a negative charge (electron) moves away from a positive charge (nucleus), an electric dipole is formed. It combines two or more electric dipoles located close to each other to create a strong electrical connection. It can be modulated to perform multiqubit logic operations.

These electric dipoles do not have to touch each other, but they do influence each other. Theoretical studies have shown that 200 nanometers is the optimal distance for fast and accurate quantum work. Researchers say this could be a game changer. Various control and readout devices can be embedded between the qubits, making the processor easier to connect and operate.