Quantum computing creeps closer with molecular chromium breakthrough

The quest for quantum computing has received a boost, following a discovery by researchers at the University of Manchester that large molecules made of nickel and chromium could store and process information in the same way that bytes do for current digital computers.

Publishing their research in the science journal Chem, the scientists showed that it is possible to use supra-molecular chemistry to connect “qubits” - the basic units for quantum information processing. This approach would generate several kinds of stable qubits that could be connected together into structures called “two-qubit 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," explained senior author Professor Richard Winpenny, an inorganic chemist at the University of Manchester. "The next step is to show that they work."

Scientists have been working on developing the theory of quantum computing for decades, with each incremental discovery inching the field forward. Quantum computing is expected to enable the creation of highly efficient and powerful computing power created at an atomic scale.  Such computing would perform computational tasks far more efficiently than the computers we use every day.

Traditional computers organize and store information in the form of bits, which are written out in long chains of 0s and 1s. Quantum computers use qubits, which can be 1, 0, or any superposition between those numbers at the same time, thus allowing researchers to do much more powerful computations.

However, large assemblies of qubits that are stable enough to be applied to perform useful algorithms do not yet exist.

Professor Winpenny and his collaborators addressed this problem in their algorithm designs, which combine large molecules to create both two qubits and a bridge between the units, called a “quantum gate”. These gates are held together through supramolecular chemistry.

Studies of the gates show that the quantum information stored in the individual qubits is stored long enough to allow manipulations of the information and hence algorithms. The time information that can be stored is called the coherence time.

“Say you’re in a pub and you’re trying to bring two pints of beer back to your friends without spilling it. 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,” Professor Winpenny explains.

“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.

“The real problem seems to be whether we could put these qubits together at all. But we showed that connecting these individual qubits doesn’t change the coherence times, so that part of the problem is solvable.

“If it’s achievable to create multi-qubit gates we’re hoping it inspires more scientists to move in that direction.”

The research work was primarily supported by the Engineering and Physical Sciences Research Council and the European Commission. 

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