Engineers at Australia’s University of New South Wales have recently invented a new type of Quantum computing based on novel ‘flip-flop qubits’. This new architecture, which scientists hope, will make it possible to manufacture a true, large-scale quantum computer.
This new design could allow a silicon quantum processor to be scaled up without the precise placement of atoms required in other approaches. Basically, it allows quantum bits to be placed on hundreds of nanometers apart and still remain coupled.
This new type of Quantum computing is a whole new way to define a ‘spin qubit’. Meanwhile, it uses both the electron and the nucleus of the atom. The spin qubit uses electric signals that are easier to distribute to monitor themselves.
Research led Andrea Morello said, “It’s a brilliant design. Like many conceptual leaps, it’s amazing no-one had thought of it before.”
The main challenge was to space these spin qubits larger and larger arrays. According to that, scientists need to space them at a distance of only 10-20 nanometers, or just 50 atoms apart. Placing them too close, or too far apart doesn’t allow to occur entanglement between them.
Morello said, “Researchers at UNSW already lead the world in making spin qubits at this scale. If we want to make an array of thousands or millions of qubits so close together, it means that all the control lines, the control electronics, and the readout devices must also be fabricated at that nanometric scale, and with that pitch and that density of electrodes. This new concept suggests another pathway.”
“Our new silicon-based approach sits right at the sweet spot. It is easier to fabricate than atomic-scale devices but still allows us to place a million qubits on a square millimeter.”
Scientists covered the silicon chip with a layer of insulating silicon oxide within the single-atom qubit. They placed it on top of which rests a pattern of metallic electrodes that operate at temperatures near absolute zero and in the presence of a very strong magnetic field.
The phosphorous atom is placed at the core, through which scientists previously built two functional qubits using an electron and the nucleus of the atom.
In other words, this conceptual breakthrough is the creation of an entirely new type of qubit. It uses both the nucleus and the electron. Here, a qubit ‘0’ state is defined when the spin of the electron is down and ‘1’ state when the electron spin is up, and the nuclear spin is down.
Co-author Guilherme Tosi said, “We call it the ‘flip-flop’ qubit. To operate this qubit, you need to pull the electron a little bit away from the nucleus, using the electrodes at the top. By doing so, you also create an electric dipole.”
Morello said, “This is the crucial point. These electric dipoles interact with each other over fairly large distances, a good fraction of a micron, or 1,000 nanometres.”
“This means we can now place the single-atom qubits much further apart than previously thought possible. So there is plenty of space to interspersed the key classical components such as interconnects, control electrodes and readout devices while retaining the precise atom-like nature of the quantum bit.”
According to him, the study suggests, the qubit has yet to be built. It’s entirely feasible.
Although, building a new type of quantum computing means a difficult and ambitious challenge with the potential to deliver revolutionary tools for tackling otherwise impossible calculations. It is a great example how scientists like many of the world’s leading research universities, sophisticating global knowledge to shape the future.