* Astronomy

Blobrana · L

RE: Uncollapsing of a quantum state

Blobrana · L

It's one of the most perplexing questions in physics: how does the seemingly exotic behaviour of tiny particles in the quantum realm collapse to create the classical reality observable in matter that is at least a molecule big? Now, an experiment further muddies the distinction between the two realms by demonstrating that it is possible to halt the transition from the quantum to the classical in its tracks and reverse it.

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Blobrana · L

Title: Uncollapsing of a quantum state in a superconducting phase qubit
Authors: Nadav Katz, Matthew Neeley, M. Ansmann, Radoslaw C. Bialczak, M. Hofheinz, Erik Lucero, A. O'Connell, H. Wang, A. N. Cleland, John M. Martinis, Alexander N. Korotkov

We demonstrate in a superconducting qubit the conditional recovery ("uncollapsing") of a quantum state after a partial-collapse measurement. A weak measurement extracts information and results in a non-unitary transformation of the qubit state. However, by adding a rotation and a second partial measurement with the same strength, we erase the extracted information, effectively cancelling the effect of both measurements. The fidelity of the state recovery is measured using quantum process tomography and found to be above 70% for partial-collapse strength less than 0.6.

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