“If you think you understand quantum mechanics, you don’t understand
quantum mechanics,” said the late Nobel laureate Richard Feynman, who is
widely regarded as the pioneer in quantum computing. Here’s how it works, in theory: While a classical computer, however
fast, must do one calculation at a time, a quantum computer can
sometimes avoid having to make calculations that are unnecessary to
solving a problem. That allows it to home in on the correct answer much
more quickly and efficiently. Quantum computing is difficult to attain because of the fragile nature
of such computers. In theory, the building blocks of such a computer
might include individual atoms, photons or electrons. To maintain the
quantum nature of the computer, these particles would need to be
carefully isolated from their external environments. “Quantum computers are extremely delicate, so if you don’t protect them
from their environment, then the computation will be useless,” said
Daniel Lidar, a professor of electrical engineering and the director of
the Center for Quantum Information Science and Technology at the
University of Southern California. A working quantum computer would open the door to easily breaking the
strongest encryption tools in use today, including a standard known as
RSA, named for the initials of its creators. RSA scrambles
communications, making them unreadable to anyone but the intended
recipient, without requiring the use of a shared password. It is
commonly used in Web browsers to secure financial transactions and in
encrypted e-mails. RSA is used because of the difficulty of factoring
the product of two large prime numbers. Breaking the encryption involves
finding those two numbers. This cannot be done in a reasonable amount of
time on a classical computer. In 2009, computer scientists using classical methods were able to
discover the primes within a 768-bit number, but it took almost two
years and hundreds of computers to factor it. The scientists estimated
that it would take 1,000 times longer to break a 1,024-bit encryption
key, which is commonly used for online transactions. A large-scale quantum computer, however, could theoretically break a
1,024-bit encryption much faster. Some leading Internet companies are
moving to 2,048-bit keys, but even those are thought to be vulnerable to
rapid decryption with a quantum computer. Quantum computers have many applications for today’s scientific
community, including the creation of artificial intelligence. But the
NSA fears the implications for national security. “The application of quantum technologies to encryption algorithms
threatens to dramatically impact the US government’s ability to both
protect its communications and eavesdrop on the communications of
foreign governments,” according to an internal document provided by
Snowden. Experts are not sure how soon a quantum computer would be feasible. A
decade ago, some experts said that developing a large quantum computer
was likely 10 to 100 years in the future. Five years ago, Lloyd said the
goal was at least 10 years away. Last year, Jeff Forshaw, a professor at the University of Manchester,
told Britain’s Guardian newspaper, “It is probably too soon to speculate
on when the first full-scale quantum computer will be built but recent
progress indicates that there is every reason to be optimistic.” “I don’t think we’re likely to have the type of quantum computer the NSA
wants within at least five years, in the absence of a significant
breakthrough maybe much longer,” Lloyd told The Washington Post in a
recent interview.
