## Primitive quantum computer outperforming the current machines find researchers

Researchers from the University of Bristol and the University of Western Australia have demonstrated that even primitive quantum processors of only a few quantum bits (qubits) can perform important computations that can outperform the capabilities of classical computing for very specific tasks. In other words, they have developed how to capably simulate a “quantum walk” on a new design for a primitive quantum computer.

Basically, the quantum walk is the quantum world’s version of the classic random walk in mathematics—a path made up of a series of random steps. In the quantum version, the walker exists in a state of superposition.

The results of this research were recently published in the journal Nature Communications. Dr Ashley Montanaro, Lecturer in Applied Mathematics and EPSRC Fellow from the University of Bristol’s School of Mathematics, said: “A quantum computer is a machine designed to use quantum mechanics to solve problems more efficiently than any possible classical computer.

“We know some algorithms that can run on such machines and it’s an open and exciting challenge to find more. But most of the quantum algorithms we know need to be run on a large-scale quantum computer to see a speed up.”

A quantum computer uses superposition and entanglement to perform operations on data, unlike traditional computers, which are based on transistors. While classical computing utilises binary bits (ones and zeroes) to encode information, quantum computing uses ‘qubits’ – that can be both one and zero. Or probably one but maybe zero. Or a 50-50 chance of being one and zero.

Quantum computers almost sound too good to be true – and in a way, they are. But, one of the biggest engineering challenges today is to build a large-scale quantum computer. It’s very difficult to scale up the technology. While it is easy to built computers from a few qubits, but as soon as you try to scale it up, it breaks down. As a result, everyone is working on it right now, but even very small computers can work wonders.

“An exciting outcome of our work is that we may have found a new example of quantum walk physics that we can observe with a primitive quantum computer, that otherwise a classical computer could not see,” said Dr. Jonathan Matthews EPSRC Early Career Fellow and Lecturer in the School of Physics and the Centre for Quantum Photonics. “These otherwise hidden properties have practical use, perhaps in helping to design more sophisticated quantum computers.”

The “Quantum walk” he is mentioning is the quantum alternative of the Brownian motion, which defines the chaotic movement of particles in a suspension – the “drunken sailor’s random walk” of particles. This means that quantum processors are very good at randomness, which in turn means it can be very effective for some algorithms.

Scientists are already using small, two-qubit computers for some calculations, and the results are already promising. They think their study could help point the way to designs for more sophisticated quantum computers. Also, it may give rise to a new class of quantum algorithms.

“It’s like the particle can explore space in parallel,” said Xiaogang Qiang, a PhD student in Bristol’s School of Physics. “This parallelism is key to quantum algorithms based on quantum walks that search huge databases more efficiently than we can currently.”