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Directly Measuring the Degree of Quantum Coherence using Interference Fringes
Yi-Tao Wang1,2, Jian-Shun Tang1,2, Zhi-Yuan Wei1,2
1CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, People's Republic of China.
Physical Review Letters
|January 28, 2017
Summary
Researchers developed a direct method to measure quantum coherence by observing interference fringes. This technique offers a robust alternative to state tomography for quantifying this key quantum resource.
Area of Science:
- Quantum Mechanics
- Quantum Information Science
Background:
- Quantum coherence is a fundamental concept in quantum mechanics and a key resource for quantum information technologies.
- While theoretical frameworks for coherence are developing, experimental measurement often relies on state tomography.
Purpose of the Study:
- To develop and present novel, direct experimental methods for quantifying quantum coherence.
- To provide alternatives to traditional state tomography for coherence measurement.
Main Methods:
- A novel method involving mixing ancilla states into the target state and observing the vanishing point of interference fringes.
- Utilizing a witness observable, where the optimal witness provides a direct measure of coherence.
Main Results:
- The minimal ancilla ratio causing fringe disappearance quantifies coherence, aligning with witness-based measurements.
- Both new methods were validated against the l1 norm of coherence derived from state tomography, showing agreement.
Conclusions:
- The developed methods offer explicit and robust direct measurements of quantum coherence.
- These techniques provide a valuable alternative to state tomography in experimental quantum mechanics.
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