Quantum-computing companies are trading higher after Amazon Web Services launched Quantum Embark, an advisory program aiming to prepare users for society's shift toward quantum computing. The emerging field harnesses qualities of quantum mechanics to solve problems that are beyond the ability of the most powerful classical computers, according to the Amazon.com unit. In after-hours trading, shares of Quantum Computing rise 4.6%, to $6.38. Shares of Arqit Quantum gained 8.1%, to $13.96. Shares of D-Wave Quantum jumped 11%, to $3.24. Defiance Quantum, an exchange-traded fund, or basket of stocks that can be purchased all at once, rises 7.4% to $73.50.