Australian physicists created a new type of qubit – an elementary unit for storing information in a quantum computer. And, in their opinion, we will finally be able to create truly full-scale quantum computers. In general, at the moment there are two capable of creating a quantum computer. In one case, this requires less space, but the systems themselves are incredibly difficult to produce. In the other, the systems are simpler, but you have to demolish a couple of walls to accommodate such machineries in the premises. A new discovery of scientists in this case may lead to a compromise.
Some researchers use proven methods of capturing qubit, such as the standard atomic capture model, where so-called ion traps and optical (laser) tweezers are used that can hold particles long enough to allow analysis of the quantum states of these particles. Others use circuits based on superconducting materials, determining the state of superpositions right inside the hardly perceptible electrical flows.
The advantage of such systems is that the technologies and equipment necessary for this already exist. This makes these methods relatively affordable and at the same time simple. The basic price to pay is in space. And here the technology allows you to create a relatively small number of qubits. The creation and storage of hundreds and thousands of qubits inside one compact computer now seems an impossible task.
Implementing the coding of information in both the nucleus and the electron of the atom, scientists received a new silicon qubit, which they called a "trigger qubit". Its feature is that it can be controlled by electrical signals, instead of magnetic ones. This means that such qubits can support quantum entanglement at a more remote distance than before, which makes it easier and cheaper to scale computers.
"If they are too close to or too far apart in an ordinary quantum system, then the" entanglement "between the qubits (what makes quantum computers so special) does not show up," says Guillerme Tosi, a researcher University of New South Wales, invented a new type of qubit.
The trigger qubit will be able to be between these two extremes, offering real quantum confusion at a distance of several hundred nanometers. In other words, it can be exactly what will allow to produce scalable quantum computer based on silicon materials.
To clarify: at the moment, scientists have only a diagram of such a device, they have not yet built it. But according to Andrea Morell, the head of the research group, their achievement is as important as the article by Bruce Kane published in 1998 in Nature, which initiated the development of silicon quantum computing.
"Like Kane's work, it's just a theory, a proposal. We have not yet built the qubit, "Morello notes.
"We already have some initial experimental data on hand that indicate the possibility of creating such a system, so now we are busy demonstrating this. But fundamentally, our work has the same visionary view, as was the case with Kane's original article. "
As mentioned above, the trigger qubit works by encoding information inside the electron and the nucleus of the phosphorus atom enclosed within the silicon chip and is associated with a set of electrodes. The whole system is then cooled to almost absolute zero and placed inside the magnetic field.
The value of a qubit is determined by the combination of a binary property called spin. If this spin is open to the electron and is closed to the nucleus, the qubit acquires a common value of "unity". If we are talking about the reverse order, then the qubit is a "zero". In this case, it is possible to control the qubit using an electric field instead of magnetic signals, which gives two advantages at once. First, it is much easier to integrate such a system into a conventional electronic circuit, and secondly, and more importantly, in this case, the qubits are able to interact with each other at more remote distances.
"To control the qubit, you need to place the electron a little farther from the core, using the electrodes on the chip. By doing this, you also create a dipole, "says Toshi.
"This is critically important. Since these dipoles can interact with each other at longer distances, up to 1000 nanometers, "adds Morello.
"This means that the qubits on the basis of one atom can be located much farther apart than previously thought possible. In this case, it becomes possible to integrate more classical components, such as connecting channels, control electrodes and reading devices, into the system, while at the same time preserving the exact "atomic" nature of the quantum bit. Production becomes simpler than atomic-level devices, while the technology makes it possible to fit a million qubits in an area of 1 square millimeter. "
All this in general means that the trigger qubits will allow to preserve the balance between compact and potentially available quantum computers of the future.
"The design is unique and surprising. And how many conceptual proposals make us wonder why no one before guessed it, "says Morello.
The results of the research of scientists were published in the journal Nature Communications.