Tag Archives: quantum computer

Quantum computers are among us: update

In July, I wrote a post on the basics of quantum computation and the current state of the art. This field offers the promise of drastic improvements over our current computers, particularly in the ways they can factor large numbers. (That sounds dull, but it’s critical to modern cryptography, among other things.) Though quantum computers are not yet close to being cost-effective, their future is rapidly evolving from science fiction to science fact.

The development of real-world quantum computers relies on overcoming two challenges. The first is scientific: given the limitations of physics, is quantum computation possible? What sorts of calculations can be done with it, and how can the technique best be applied?

The second challenge is from the engineering standpoint; true quantum computers require atom-level precision and accuracy in the creation of the qubits. While current transistors in silicon-based chips are just reaching 22 nm in size, atoms themselves are a hundred times smaller. Truly controlling the positions of individual atoms on a surface might have, at one time, seemed an enormous hurdle to manufacturing quantum computers.
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Are quantum computers among us?

http://en.wikipedia.org/wiki/File:DWave_128chip.jpgMoore’s Law describes an observed trend in the number of transistors on a chip over time; over several decades, this number has doubled roughly every two years. The influence of this phenomenon has had a profound effect on virtually all aspects of modern life: everything from your phone to your microwave exhibits the results.

The problem facing scientists and engineers is this: Moore’s Law is not a law. Nothing guarantees that this doubling trend will continue; computers as you and I know them are approaching a dead end. The basis of modern computer is the doped silicon semiconductor, but in order to increase the number of silicon transistors on a chip, the size of the transistors needs to be decreased. The approach of making smaller transistors has worked for decades, but will eventually run up against the limits of solid state physics. Fundamentally, a different material is needed to fulfill the projections of Moore’s Law.

Over the coming decades, a host of new technologies will supplement and (perhaps) replace the ubiquitous silicon chip. New materials like graphene seem like they may offer at least incremental improvements over silicon, but is there hope for really continuing this exponential growth in the face of the very limits of physics?
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