A team of researchers from the University of Manchester announced Monday they had taken a significant step forward in the creation of viable quantum computers. In a study published in the latest edition of the journal Chem, the researchers provided evidence that large molecules made of nickel and chromium could be used as qubits — the quantum computing equivalent of the bits used to store and process information in conventional computers.
According to the study, it is possible, at least in theory, to use molecular chemistry to connect these molecules, thereby creating several stable qubits that can then be used to create two-qubit logic gates.
“We have shown that the chemistry is achievable for bringing together two-qubit gates — the molecules can be made and the gates can be assembled,” lead author Richard Winpenny said in a statement. “The next step is to show that they work.”
Unlike conventional computers, which utilize bits that can exist in one of the two states — 0 or 1 — quantum computers utilize quantum bits, or “qubits,” that can exist in a state of superposition. This phenomenon, which allows qubits to exist in both states at the same time, coupled with quantum entanglement, is what gives quantum computers a significant advantage over conventional computers.
The development of quantum computers has been a goal of computer scientists and physicists ever since the idea was first floated in the early 1980s. However, one of the key hurdles researchers have faced in realizing this goal is scalability — increasing the number of qubits from a mere handful to an order of millions or billions, depending on the complexity of the task the computer needs to perform.
Another key hurdle is increasing the duration of quantum “coherence,” which refers to the state wherein subatomic particles exist in two or more states simultaneously. As things stand now, “coherence” lasts for only a fraction of a second before the whole system decoheres — a phenomenon that marks the transition from the realm of quantum to classical mechanics.
“Say you’re in a pub and you’re trying to bring two pints of beer back to your friends, but the pub is filled with customers who are singing, jumping around, and dancing — the coherence time is a measure of how far you can get the beer without spilling it,” Winpenny said in the statement. “You want the bar to be very well behaved and very stationary so you can walk through the pub and get back to the table, just like we want the qubits to be stable long enough so we can store and manipulate information.”
While the latest study does not detail a method to overcome this hurdle, it suggests that connecting individual qubits does not change coherence time.
“If it’s achievable to create multi-qubit gates, we’re hoping it inspires more scientists to move in that direction,” Winpenny said.