Related Experiment Videos
Leggett-Garg inequality with a kicked quantum pump.
Andrew N Jordan1, Alexander N Korotkov, Markus Büttiker
1Department of Physics and Astronomy, University of Rochester, New York 14627, USA.
Physical Review Letters
|August 16, 2006
Summary
A new kicked quantum nondemolition measurement technique was developed. This method allows for weak qubit measurements, leading to violations of the Leggett-Garg inequality due to detector backaction.
Area of Science:
- Quantum physics
- Quantum information science
- Mesoscopic physics
Background:
- Quantum nondemolition (QND) measurements are crucial for quantum information processing.
- Weak measurements allow for minimal disturbance of quantum states.
- The Leggett-Garg inequality provides a test for macroscopic realism.
Purpose of the Study:
- To introduce a novel kicked quantum nondemolition measurement scheme.
- To investigate measurement statistics for weak measurements combined with single-qubit unitary operations.
- To explore the violation of a generalized Leggett-Garg inequality.
Main Methods:
- Development of a kicked quantum nondemolition measurement protocol.
- Derivation of measurement statistics for combined weak measurements and unitary operations.
- Application of results to test a generalized Leggett-Garg inequality.
Main Results:
- Successfully derived measurement statistics for the proposed scheme.
- Demonstrated a violation of a generalized Leggett-Garg inequality.
- Interpreted the violation in terms of noninvasive detector failure, detector backaction, or qubit-detector entanglement.
Conclusions:
- The introduced kicked QND measurement provides a new tool for quantum state characterization.
- The violation of the Leggett-Garg inequality highlights limitations of the noninvasive detector assumption in quantum measurements.
- The findings offer insights into the interplay between quantum systems and their measurement apparatus, particularly in systems like quantum point contacts measuring double quantum dots.