Long-time readers to this site know that we try to keep abreast of developments in quantum computing because of its potential to transform computing as we know it. Indeed, if researchers can solve the many hurdles, quantum computing will be a first-degree game changer, with quantum processors capable of performing calculations magnitudes faster than any transistor-based computer.

The technology was first theorized in the 1970s and early 1980s. Jacob West of Caltech's Computer Science department presents a concise history:

The idea emerged when scientists were pondering the fundamental limits of computation. They understood that if technology continued to abide by Moore's Law, then the continually shrinking size of circuitry packed onto silicon chips would eventually reach a point where individual elements would be no larger than a few atoms. Here a problem arose because at the atomic scale the physical laws that govern the behavior and properties of the circuit are inherently quantum mechanical in nature, not classical. This then raised the question of whether a new kind of computer could be devised based on the principles of quantum physics.

While conventional, transistor-based computing follows the laws of classical physics, quantum computing adheres to the laws of quantum mechanics, which are radically different, and often counter-intuitive. In a quantum computer, the fundamental unit of information is the quantum bit, or qubit. Qubits can exist in the two binary states that we're all familiar with, but can also exist in a superposition of those two states, allowing for the representation of an unlimited number of states simultaneously. Quantum computing is naturally parallel, similar to running many serial computing machines at the exact same time.

Even though a practical working quantum computer is not yet a reality, there is already a killer app: encryption/decryption. For this reason, the federal government is one of the biggest backers of quantum computing research. Quantum computers are considered critical to national security and the feds are eager to wrangle the computational edge for strategic advantage. The benefits of being able to create and crack codes faster than your opponent are too great to ignore. This is the premise for a recent article at SignalOnline.

In that article, Barry Barker, NSA technical director for quantum computing, states that "because NSA is responsible for the protection of national security systems, the computer systems of the Department of Defense and intelligence community, we must understand the likelihood of development of -- and the threat posed by -- quantum computers so that we can help to protect against that."

In January of this year, the National Institute of Standards and Technology (NIST) awarded the Joint Quantum Institute $10.3 million to build the Laboratory for Advanced Quantum Science at the University of Maryland. The facility is being constructed underground with cutting-edge environmental controls designed to eliminate even minute vibrations or temperature changes. Research in quantum science demands such exacting specifications. The project is expected to be completed by spring 2013.

We don't know what the future quantum computer will look like, but it's not likely to fit on a desk. Barker explains:

"In general, it's going to be fairly large. It will be one of the most complex devices ever built. It's going to be the size of a room, or at least a large fraction of a room, and it will probably have some sort of vacuum chamber, so it will have vacuum pumps attached to it, and it may have cryogenic operation, meaning temperatures 400 degrees below zero, for example."

Despite the many advancements in quantum computing, a fully functioning quantum computer is still a ways a way, if indeed it's even possible. Says Barker:

"There are so many fundamental scientific challenges that have to be overcome, we can't predict when, or if, the scientific community is going to overcome these problems, but most guesses are -- and calling it a 'guess' is a more accurate term than calling it an 'estimate' -- the guess is that a practical quantum computer is still many decades away. If you think about the timeline from building an individual transistor in the 1940s or early 1950s to modern-day computers, we're talking about 50 years."

Best guesses also say that Moore's Law, which states that transistor density on integrated circuits doubles about every two years, is only going to last another decade or two. That leaves about three decades between the two technologies. If history is any indicator, technological progress doesn't just stop. Something will come along to fulfill the gap...it's just a question of what.