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Entanglement-enhanced quantum lock-in detection achieving Heisenberg scaling
J-W Zhang1, M Zhuang2, B Wang3,4
1School of Physics and Astronomy & Guangdong Provincial Key Laboratory of Quantum Metrology and Sensing, Sun Yat-Sen University (Zhuhai Campus), Zhuhai, China.
Nature Communications
|December 6, 2025
Summary
This study demonstrates entanglement-enhanced quantum lock-in detection (QLID) for the first time using trapped ions. This breakthrough achieves measurement precision nearing the Heisenberg limit, surpassing the standard quantum limit for weak signal detection.
Area of Science:
- Quantum Information Science
- Quantum Sensing
- Atomic Physics
Background:
- Quantum lock-in detection (QLID) extracts weak oscillating signals from noise.
- Entanglement promises enhanced measurement precision beyond the standard quantum limit (SQL).
- Integrating entanglement with QLID presents experimental challenges.
Purpose of the Study:
- To experimentally realize entanglement-enhanced QLID.
- To demonstrate measurement precision approaching the Heisenberg limit using entangled states.
- To investigate the temporal scaling of QLID with and without entanglement.
Main Methods:
- Utilized two trapped 40Ca+ ions.
- Prepared a Greenberger-Horne-Zeilinger (GHZ) state via a Mølmer-Sørensen gate.
- Applied periodic multipulse sequences for QLID and optimized pulse sequences for error robustness.
Main Results:
- Achieved measurement precision approaching the Heisenberg limit (Δω ∝ N⁻¹) using the GHZ state, surpassing the SQL (Δω ∝ N⁻¹/²).
- QLID demonstrated superior inverse-quadratic temporal scaling (Δω ∝ T⁻²), exceeding conventional inverse-linear scaling (Δω ∝ T⁻¹).
- Enhanced robustness against experimental errors was achieved through optimized pulse sequences.
Conclusions:
- First experimental realization of entanglement-enhanced QLID.
- Demonstrated a pathway to Heisenberg-limited quantum sensing of weak oscillating signals.
- Established QLID's inherent advantage in temporal scaling, independent of entanglement.
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