Research from UNSW Sydney demonstrates a new type of silicon quantum bit, called the ‘flip-flop’ qubit, which could make it easier to build large-scale computers.
The team led by Professor Andrea Morello has demonstrated the functionality of a new type of quantum bit, the so-called “flip-flop” qubit, which combines a good number of single atoms, with simple control using electrical signals, such as those used on a normal computer page.
Intended Purpose: Single-Atom Quantum Bit Electrical Control
“Sometimes, new qubits, or new types of work, are discovered by accident. But this is quite the purpose,” explains the professor. Nightshade. “Our team has had large qubits for ten years, but we wanted something that could be electrically controlled, for ease of use. So we have to create something completely new.
A Professor Morello was the first in the world to show that using the spiel of electrons and the nuclear repulsion of a single phosphorus atom in silicon can be used with “qubits” – units of information used in mathematical calculations. He explains that although the two qubits work well on their own, they need a rotating magnetic field for their operation.
“Magnetic fields are difficult to detect at the nanometer scale, which is the size of the individual components of a quantum computer. This is why the original silicon quantum bit design proposed that all the qubits be placed in a single oscillating magnetic field, applied to the entire chip, and then use the local electric field to select which qubits to mine.
A few years ago, Professor Morello’s team had an insight: defining a qubit as an up-down/down combination of electrons in the nucleus of an atom would make it possible to control electricity alone. Today’s results are an experimental demonstration of this new idea.
“This new qubit is called a ‘flip-flop’ because it is a pair of spins of the same atom – electron and nuclear spin – as long as they point in opposite directions,” said Dr Rostyslav Savytskyy explains, one of the leaders. researchers of the paper, published in Science Advances.
“For example, if the ‘0’ state is ‘small electron / up nucleus’ and the ‘1’ state is ‘up electron / down nucleus’, going from ‘0’ to ‘1’ means that the electron’ ‘turn ‘up and the head ‘leans’ down. Hence the name!”
The theory predicts that by moving an electron in space, one can tune the quantum state of a qubit flip-flop.
“Our experiments fully support this prediction,” said Dr. Tim Botzem, another research writer.
“More importantly, the movement of such electrons is achieved simply by applying a voltage to a small metal electrode, instead of using a magnetic field to move the chip. It is a process similar to the type of electrical signal that is commonly carried in silicon computer chips like we use every day in our computers and smartphones.
The scheme promises to scale up to the largest quantum producers
The electrical control of the qubit “flip-flop” by moving the electron from the nucleus is accompanied by a very important effect. When a negative charge (electron) is removed from a positive charge (nucleus), an electric dipole is created. Placing two (or more) electric dipoles in close proximity to each other creates a strong electrical coupling between them, which can enable multi-qubit quantum logic operations of the type required to perform practical quantum computing.
“The standard way to connect spin qubits to silicon is to keep the electrons so close to each other that they effectively ‘touch’ each other,” explains the professor Nightshade.
“This requires the qubits to be placed in a grid of a few tens of nanometers in pitch. The engineering challenge to do this is very difficult. Electric dipoles, on the other hand, do not need to “touch” each other – they affect each other from a distance. Our theory shows that 200 nanometers is the best place for fast, high-reliability performance.
“It could be a game changer, because 200 nanometers is enough to allow different controls and playback devices to be placed between the qubits, making the design easier to wire and use .”
