When the news broke earlier this month that the U.S. government is trying to build a superfast quantum computer, reports suggested the demise of private information as we know it. The end may not be so nigh, however. A full-fledged quantum computer is likely decades away. More important, even if a quantum code cracker can be built, it might be defeated by encryption algorithms already in the works—or by another technology, called quantum key distribution, that relies on quantum mechanics itself for security. Such countermeasures could rob a quantum computer of its widely perceived killer app before building one is even possible.