Physicists ‘uncollapse’ a partially collapsed qubit

Quantum quality control: By peeking at a qubit, physicists can make sure that the qubit hasn’t decayed, though without finding out the qubit’s state. However, the act of peeking often alters the qubit’s state, causing partial qubit collapse. A recovery method like the one demonstrated in the new paper can be used to reverse the effects of the peek on the qubit. As a result, the peek ensures the qubit is OK without changing the qubit’s state. Credit: J. A. Sherman

Quantum quality control: By peeking at a qubit, physicists can make sure that the qubit hasn’t decayed, though without finding out the qubit’s state. However, the act of peeking often alters the qubit’s state, causing partial qubit collapse. A recovery method like the one demonstrated in the new paper can be used to reverse the effects of the peek on the qubit. As a result, the peek ensures the qubit is OK without changing the qubit’s state. Credit: J. A. Sherman

One of the striking features of a qubit is that, unlike a classical bit, it can be in two states at the same time. That is, until a measurement is made on the qubit, causing it to collapse into a single state. This measurement process and the resulting collapse may at first seem irreversible. (Once you open the box to find a dead cat, there’s no going back, right?) But recently physicists have been investigating the possibility of “uncollapsing,” or recovering the state of, a qubit that has been partially collapsed due to a weak measurement. The results could be used for implementing quality control in quantum systems.

In a new paper published in Physical Review Letters, physicists J. A. Sherman, et al., at the University of Oxford, have experimentally demonstrated a recovery method that can restore the state of a single qubit, in principle perfectly, after it has partially collapsed…..

…. Read more at: http://phys.org/news/2013-11-physicists-uncollapse-partially-collapsed-qubit.html#jCp

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