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Quantum computing

Conventional computers are becoming faster and faster and the chips that power them smaller and smaller. For decades Moore’s law has correctly forecast the increasing speed of conventional computers as well as the constant reduction in size on the chips that power them. Despite these constant improvements in computational power scientists are looking at quantum computing as a way to fundamentally change the way that computers work, making them millions of times more powerful than a normal PC.

Recently a key barrier in producing a quantum computer was overcome by an international team led by Mike Thewalt of Simon Fraser University, Canada. The team managed to hold a fragile quantum memory state stable at room temperature for a "world record" 39 minutes. The issue of stability of quantum states like entanglement is very important for a practical quantum computer since these states can be very easily disrupted by outside influences.

The importance of quantum computing was reflected when the 2012 Nobel prize for physics was awarded to Serge Haroche of France and David Wineland for their work on quantum optics. Their work allowed the direct observation of individual quantum systems without destroying the very fragile quantum states which have applications for quantum computing and communication.

Quantum computers would allow complex simulations to be performed more quickly than is currently possible. This could benefit research into many areas including molecular biophysics (DNA), drug testing, engineering problems, cosmological models and weather forecasting and climatology. Quantum computing could also cause problems in areas such as internet security, as the processes required to break encryption codes would also be much faster. Fortunately, quantum encryption also presents new ways of checking for eavesdroppers, since the very act of probing quantum data would disrupt the information itself.

A conventional computer uses bits which are either 1 or 0 to perform calculations. In quantum computers, a qubit (made from photons or trapped atoms) can be both 1 and 0 at the same time, a so-called superposition of states. A quantum computer performs calculations on all superpositions at once. This property allows quantum computers to perform many parallel operations, speeding up the time it takes to do calculations.

Current quantum computers are small-scale laboratory-based devices that can solve simple problems. Although large scale “desktop” quantum computers are theoretically possible, there are many practical challenges in actually building one. These challenges arise from keeping the computer stable and dealing with decoherence: when a qubit changes from a 1 to a 0 due to interference from other parts of the computer.

This is not so much of a challenge with the current small-scale quantum computers but does become a problem when scaling up. Some people also believe that quantum computers will only really improve upon normal computers in the field of code breaking and simulations of quantum mechanics systems. Although research is proceeding at a rapid rate with big companies such as IBM becoming involved in research, a desktop quantum computer may still be some way off from reality.

Inspec covers all aspects of quantum computing:

Control terms include:

  • quantum communication
  • quantum computing
  • quantum cryptography
  • quantum entanglement
  • quantum interference phenomena
  • quantum optics
  • quantum theory

Classifications include:

  • a0365 Quantum theory; quantum mechanics
  • a0365B Foundations, theory of quantum measurement, miscellaneous quantum theories
  • a0367 Quantum information
  • a0367D Quantum cryptography
  • a0367H Quantum communication
  • a0367L Quantum computation
  • a4230Q Optical communication
  • a4250 Quantum optics
  • b6110 Information theory
  • b6120D Cryptography
  • b6150 Communication system theory
  • b6260 Optical communication
  • c1260 Information theory
  • c1260C Cryptography theory
  • c4270 Quantum computing theory
  • c5295 Quantum computing techniques

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