Yusuf Ahmad / Reuters

Faster, more powerful computing has the potential to revolutionize fields from drug delivery to freight transportation. But some are also worried that the computers of the future could upend what it means to be human.

Quantum computing capitalizes on the quantum-physics principle that a particle may be in two states at once, as long as it does not leave a record of either state. Unlike traditional computers, which are made of bits restrained to values of zero or one, a quantum computer would allow bits to have both values simultaneously, which would lead to much faster, more powerful processing.

According to Mordechai Segev, a professor of physics at Technion Israel Institute of Technology, a functional, accurate quantum computer would need to consist of about 2,000 quantum bits. “I think it is reasonable to assume that a quantum computer will be there in our lifetime,” he said on Friday at the Aspen Ideas Festival, which is co-hosted by the Aspen Institute and The Atlantic. Such a computer would perhaps be “a specialized machine,” Segev said, but “it would work better than any traditional computer” at solving the problems for which it is designed.

But the advent of quantum computing promises to bring more than improved problem-solving. Such an increase in processing power could spell apocalypse for current encryption methods. On a more existential level, according to Daniel Zajfman, some people are concerned that quantum computing could bring about the end of free will.

Zajfman, the president of the Weizmann Institute of Science in Israel, said on Friday that the question boils down to: “Could we create a system that would really make everything predictable?” As a physicist, Zajfman said, he believes that “there is always a cause and effect,” which would imply that, given enough processing power, a computer fed every detail of the world as we know it could bring those details to their logical conclusions, thereby predicting the future with perfect accuracy.

But, he said, physicists also believe in the theory of chaotic behavior, which, in Zajfman’s words, posits that “there’s something inherent in nature ... that creates systems that are by definition chaotic.” That complicates the straightforward system of cause and effect, he said, because “the language of the cause and effect is so much dependent on very, very tiny changes”—for example, spending a few more seconds brushing your teeth on a given morning could make the difference between whether you get into a car crash that day or not.

More in this series

This interdependence of details, commonly known as the butterfly effect, means that predicting the future with perfect accuracy is a problem that’s “almost impossible to solve,” Zajfman said. Free will, he said, is likely safe—at least from quantum computing. “But then again,” he added, “don’t believe anyone who tells you something is impossible.”