Nowadays, most qubits are built on a single quantum state. Most often, the spin of an electron, photon or atom is used for this, as the most convenient phenomenon for control and manipulation. But over time, scaling problems will force us to think about densifying qubits, which will force us to find other quantum states in qubits and learn to control them. As scientists have found, antimony is well suited for increasing the density of qubits and here’s why.
Researchers from the University of New South Wales (UNSW) in Sydney have shown that an antimony (Sb) atom can have 16 quantum states simultaneously. The atom itself has 8 unique quantum states, two more are provided by its electrons. The combination of each of the quantum states of the atom with one and another quantum state of the electrons gives a total of 16 unique quantum states. This is like the 3D NAND of the future, in which each cell can write 16 bits of data.
Moreover, scientists have determined that the quantum states of antimony atoms and electrons can be controlled in four different ways. This will improve work with qubits and bring closer the emergence of quantum universal computers. In the journal Nature Communications, the researchers published an article in which they reported on the results achieved. So, the quantum states of electrons could be controlled by oscillations of the magnetic field. They controlled the rotation of the atomic nucleus using magnetic resonance, as happens in MRI scanners. They also used an electric field to control the state of the nucleus. And finally, using an electric field, you can control the so-called trigger qubits, proposed by UNSW scientists in 2017 (above in the video).
“We are investing in a technology that is more complex, slower, but for very good reasons, one of which is extreme information density, it can handle it,” said Professor Andrea Morello, lead author of the study. “Having 25 million atoms per square millimeter is very good, but you have to control them one by one. The ability to do this using magnetic fields, electric fields, or any combination of the two will give us many possibilities to exploit [всех их] when scaling the system.”
The team next plans to use these atoms to encode logical qubits, which could ultimately pave the way to more practical quantum computers.
Let us add that Russian scientists have advanced the furthest in the creation of multi-level qubits. They were able to not only create, but also test logical structures on five-level qubits. But that's another story.
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