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June 08, 2006

other tech: Error Checking for superconducting quantum computing

Scientist at the University of California in Santa Barbra, US, have discovered a new way to check how much the information stored inside a superconducting quantum computer has decayed. This is an impressive feat since measuring the state of a qubit normally destroys its quantum properties.

There are several competing approaches to quantum computing, the most advanced of which involves using ions trapped in an electromagnetic field. An error-checking method for this approach already exists but some researchers doubt it will ever successfully scale up to make a practical device

The error-checking method developed by the University of California team involves a competing approach, which experts say could have far greater potential to scale up.

In their set-up, a qubit is created using two superconducting metals separated by an insulating barrier. Passing a current through this component produces a qubit in the form of two energy levels in superposition, or both states simultaneously

Reducng the energy barrier used to maintain this state of superposition "collapses its quantum waveform" into one of the two energy levels. But Katz's team has found it can lower the energy barrier to a point just above the highest of the two energy levels, only partially collapsing the waveform. This is called a partial measurement

Scanning the qubit using microwave radiation then reveals its state of superposition without making it collapse. In a functional quantum computer this could be used to confirm that a qubit can still be used for a quantum computation. Past article summarizing the state of research into quantum computing

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