Prime numbers are the keys to encrypting sensitive information (see the Reference Frame by N. David Mermin, Physics Today, April 2007, page 8). If an adversary wanted to decipher a message protected by today’s most often-used encoding method, known as RSA encryption, they would need to identify the prime factors of numbers with thousands or tens of thousands of digits. That feat is beyond the capability of classical computers, although not for quantum-based ones.1
In a quantum computer, the information stored as zeroes and ones in classical bits can be encoded as a superposition of quantum states in various physical systems, such as trapped ions and large groups of cold, neutral atoms (see the article by Ignacio Cirac and Peter Zoller, Physics Today, March 2004, page 38). A qubit stores more information than a classically equivalent bit, and a unitary transformation of a qubit can...
