14 November 2016

Researchers from The University of Manchester have taken a significant step closer to demonstrate that it is possible to create miniscule - but very powerful - computers that could work at atomic scale.

Scientists have been working on the developing the theory of quantum computing for decades - that is, highly efficient and powerful computing created at atomic scale. Such computing would perform some computational tasks far more efficiently than the computers we currently use.

Now The University of Manchester has revealed breakthrough evidence that large molecules made of nickel and chromium could store and process information in the same way bytes do for everyday digital computers.

The researchers have shown in the science journal Chem that it is possible to use supramolecular 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.”

Traditional computers organize and store information in the form of bits, which are written out in long chains of 0s and 1s, whereas quantum computers use qubits, which can be 1, 0, or any superposition between those numbers at the same time - 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 address 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.

Professor Winpenny explained. “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.”

“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."

Professor Winpenny added: “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.”

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