Quantum computers inch closer to reality thanks to entangled qubits in silicon

Nov 16, 2015

By Dario Borghino

Practical quantum computers are still years away, but lately the pace of research seems to have picked up. After building the basic blocks of a quantum computer in silicon and storing quantum information for up to 30 seconds, scientists at the University of New South Wales (UNSW) have now violated a principle of classical physics to demo for the first time a pair of entangled, high-fidelity quantum bits (qubits) in silicon. The advance could help unleash the power of a new kind of computation that would affect everything from data cryptography to drug design, overnight deliveries and subatomic particle experiments.

A mathematical relationship known as Bell’s inequality places a limit on how strongly two particles can correlate without violating two intuitive principles that govern classical physics – locality, meaning what happens in one place can only be influenced by nearby objects; and realism, meaning physical objects exist whether or not they are observed.

But when two quantum particles commune, or entangle, their correlation can be strong enough to break this principle, giving rise to what Einstein famously dismissed as spooky action at a distance. While it is possible to achieve entanglement without violating the inequality, in the context of quantum computing a violation is desirable as it means qubit operations are more reliable and have access to more “spooky” – and useful – behavior for faster number-crunching.

Professor Andrea Morello and team have now, for the first time, demonstrated a violation of Bell’s inequality in silicon, paving the way for quantum computers that are reliable and highly scalable.

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