Quantum computing

Quantum bits are fussy and fragile. Useful quantum computers will need to use an error-correction technique like the one that was recently demonstrated on a real machine.

So-called topological quantum computing would avoid many of the problems that stand in the way of full-scale quantum computers. But high-profile missteps have led some experts to question whether the field is fooling itself.

Like a perpetual motion machine, a time crystal forever cycles between states without consuming energy. Physicists claim to have built this new phase of matter inside a quantum computer.

To understand what quantum computers can do — and what they can’t — avoid falling for overly simple explanations.

The secret to making a qubit for future quantum computers might depend on knowing how to tie knots in unusual materials, argues the physicist Charlie Marcus.

Two teams found different ways for quantum computers to process nonlinear systems by first disguising them as linear ones.

The result highlights a fundamental tension: Either the rules of quantum mechanics don’t always apply, or at least one basic assumption about reality must be wrong.

Can we test speculations about how quantum physics affects black holes and the Big Bang?

A landmark proof in computer science has also solved an important problem called the Connes embedding conjecture. Mathematicians are working to understand it.