According to new research, if you use four different methods to store data on a single atom, you can cram more quantum processing power into a given space. This approach could unlock more powerful, easier-to-control quantum computers.
Traditional computers can process and store information in the form of 0 or 1, while quantum computers can process and store information in the form of 0 or 1, and simultaneously process and store the superposition of the two. As the number of quantum bits (qubits) increases, the processing power of quantum computers will increase exponentially, allowing them to solve problems that are too complex for ordinary computers.
The problem is, manipulating these qubits can be tricky, especially as quantum computers start using more and more qubits. But now scientists at the University of New South Wales (UNSW) in Sydney have shown how to write data into qubits (in this case, individual atoms) in four different ways, depending on what is needed each time.
The atom is an element called antimony, which can be implanted into a silicon chip, replacing one of the silicon atoms in it. This heavy atom was chosen because its nucleus already contains eight independent quantum states that can be used to encode quantum data. In addition, its electron itself has two quantum states, doubling the total number of quantum states in the antimony atom to 16 (each of the original eight quantum states is paired in turn with two quantum states of the electron). Using other materials to create a quantum computer with 16 states would require four qubits coupled together.
The real breakthrough in this study, though, was how the team used four different methods to manipulate the data on the atoms. Electrons can be controlled by oscillating magnetic fields. Magnetic resonance methods, such as those used in MRI machines, can manipulate the spin of atomic nuclei. Electric fields can also be used to control atomic nuclei. Finally, a technique called "flipping bits" can control nuclei and electrons with the help of electric fields.
The research team said this research will help make quantum computers more "dense", containing more qubits in a smaller space.
Professor Andrea Morello, first author of the study, said: "We are investing in a technology that is harder and slower, but for very good reasons, one of which is the extremely high density of information it can handle. 25 million atoms in 1 square millimeter is great, but they have to be controlled one by one. We have the flexibility to control the atoms using magnetic fields, electric fields or any combination of them, which will give us a lot of options when scaling up the system."
Next, the team plans to use these atoms to encode logical qubits, ultimately paving the way for more practical quantum computers.
The research was published in the journal Nature Communications.