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Decay of Loschmidt echo enhanced by quantum criticality
1Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100080, China.
Physical Review Letters
|May 23, 2006
Summary
Quantum criticality in a surrounding system drives a quantum system's transition from pure to mixed states. This quantum phase transition significantly enhances the decay of the Loschmidt echo (LE).
Area of Science:
- Quantum Information Science
- Condensed Matter Physics
- Quantum Measurement
Background:
- Quantum systems can transition from pure to mixed states due to environmental interactions.
- Quantum criticality describes unique behaviors of systems near a quantum phase transition.
- The Loschmidt echo (LE) quantifies the stability of a quantum state under perturbation.
Purpose of the Study:
- To investigate how quantum criticality of an environment influences a coupled quantum system's decoherence.
- To quantitatively characterize the pure-to-mixed state transition using the Loschmidt echo.
- To explore the role of a quantum critical environment as a measurement apparatus.
Main Methods:
- Modeling the environment (E) as an Ising model in a transverse field.
- Analyzing the behavior of the Loschmidt echo (LE) of the system (S).
- Examining the off-diagonal elements of the reduced density matrix for system S.
Main Results:
- Quantum criticality of the environment (E) strongly enhances the decay rate of the Loschmidt echo (LE).
- Near the critical transverse field value, the off-diagonal elements of S's reduced density matrix vanish sharply.
- The quantum critical environment acts as an effective measuring apparatus, accelerating decoherence.
Conclusions:
- Quantum phase transitions in coupled systems can drive rapid decoherence.
- The Loschmidt echo is a sensitive probe of quantum criticality and environmental influence.
- Understanding these transitions is crucial for quantum information processing and quantum measurement.
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