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 nonunitary transformation of the qubit state. However, by adding a rotation and a second partial measurement with the same strength, we erase the extracted information, canceling 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.
%0 Journal Article
%1 Katz2008Reversal
%A Katz, Nadav
%A Neeley, Matthew
%A Ansmann, M.
%A Bialczak, Radoslaw
%A Hofheinz, M.
%A Lucero, Erik
%A O'Connell, A.
%A Wang, H.
%A Cleland, A.
%A Martinis, John
%A Korotkov, Alexander
%D 2008
%I American Physical Society
%J Physical Review Letters
%K measurementproblem, weak\_measurement
%N 20
%P 200401+
%R 10.1103/physrevlett.101.200401
%T Reversal of the Weak Measurement of a Quantum State in a Superconducting Phase Qubit
%U http://dx.doi.org/10.1103/physrevlett.101.200401
%V 101
%X 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 nonunitary transformation of the qubit state. However, by adding a rotation and a second partial measurement with the same strength, we erase the extracted information, canceling 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.
@article{Katz2008Reversal,
abstract = {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 nonunitary transformation of the qubit state. However, by adding a rotation and a second partial measurement with the same strength, we erase the extracted information, canceling 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.},
added-at = {2014-01-09T15:14:33.000+0100},
author = {Katz, Nadav and Neeley, Matthew and Ansmann, M. and Bialczak, Radoslaw and Hofheinz, M. and Lucero, Erik and O'Connell, A. and Wang, H. and Cleland, A. and Martinis, John and Korotkov, Alexander},
biburl = {https://www.bibsonomy.org/bibtex/2657c69816e5a0a400fba5c3d5b2888b0/jaspervh},
citeulike-article-id = {7148887},
citeulike-linkout-0 = {http://dx.doi.org/10.1103/physrevlett.101.200401},
doi = {10.1103/physrevlett.101.200401},
interhash = {1a226021ddea70d505164de83ed7c3cb},
intrahash = {657c69816e5a0a400fba5c3d5b2888b0},
issn = {0031-9007},
journal = {Physical Review Letters},
keywords = {measurementproblem, weak\_measurement},
month = nov,
number = 20,
pages = {200401+},
posted-at = {2013-11-26 13:53:17},
priority = {2},
publisher = {American Physical Society},
timestamp = {2014-01-09T15:14:33.000+0100},
title = {Reversal of the Weak Measurement of a Quantum State in a Superconducting Phase Qubit},
url = {http://dx.doi.org/10.1103/physrevlett.101.200401},
volume = 101,
year = 2008
}