Voltage control method brings large-scale quantum computers within reach
Large-scale, practical quantum computers always seem to be just around the corner, with small research steps edging them tantalizingly closer. Now a large leap towards their practical realization. Scientists at the University of Sussex claim to have produced a method to use voltage control over ions instead of lasers in quantum logic gates, thereby removing one of the largest stumbling blocks to producing a workable, full-sized system.
Simple quantum computers have been around for a while now. IBM, for example, made a small quantum processor with a few quantum bits (qubit) available online, while Bristol University came up with a basic two-qubit system that was even able to do some useful work. But these tiny machines are difficult to scale up practically because each of the trapped ions used as quantum bits in the system are aligned using a separate laser beam for each one, so building a full-size computer with billions of qubits would potentially take just as many individual lasers to control them.
The scientists working at Sussex University, however, eschewed the idea of using lasers to align the trapped ions, instead they came up with a system that uses controlling voltages on a quantum computer microchip to produce the same results. And, according to the researchers, they did so with an exceptionally low error rate that was on par with similar, laser-controlled quantum systems.
"Developing this step-changing new technology has been a great adventure and it is absolutely amazing observing it actually work in the laboratory," said Doctor Seb Weidt, of the Ion Quantum Technology Group at the University of Sussex.
Though not the first quantum processor on a microchip to achieve multiple entangled photon qubit states (an international effort, including a team from the University of Sussex, managed to use a number of techniques to split incoming laser beams to create four photon entangled states), the University of Sussex version does so without the need for complex manipulation of external laser beams and their associated hardware.
In effect, using individual voltages, the researchers controlled quantum gates (the building blocks of quantum circuits, similar in operation to classic logic gates used by conventional digital computers) and generated an entangled state on two quantum-engineered qubits.
"This development is a game changer for quantum computing making it accessible for industrial and government use," said Winfried Hensinger, Professor of Quantum Technologies at the University of Sussex. "We will construct a large-scale quantum computer at Sussex making full use of this exciting new technology."
The results of this research were recently published in the journal Physical Review Letters.
The video below shows Professor Hensinger explaining more about quantum computing.