Unconditional and Robust Quantum Metrological Advantage beyond N00N States

Area of Science:

• Quantum physics
• Metrology
• Quantum information science

Background:

• Quantum metrology leverages quantum phenomena to surpass classical measurement limits.
• N00N states offer theoretical Heisenberg limit scaling but are difficult to prepare and sensitive to photon loss.
• Existing quantum metrology methods face challenges in scalability and robustness.

Purpose of the Study:

• To propose and realize a scalable, unconditional, and robust quantum metrological advantage.
• To overcome the limitations of N00N states in practical quantum metrology.
• To achieve enhanced measurement sensitivity using unconventional quantum resources.

Main Methods:

• Combining unconventional nonlinear interferometers with stimulated emission of squeezed light.
• Utilizing principles from the photonic quantum computer Jiuzhang.
• Implementing a scheme robust to photon loss and imperfections.

Main Results:

• Observed a 5.8(1)-fold enhancement in Fisher information per photon above the shot-noise limit.
• Demonstrated unconditional quantum metrological advantage without discounting photon loss.
• Outperformed ideal 5-N00N states in terms of metrological enhancement.
• Showcased Heisenberg-limited scaling and robustness to photon loss.

Conclusions:

• The developed scheme offers a practical and scalable approach to quantum metrology.
• This method provides a robust quantum advantage even at low photon flux.
• The technique is applicable for real-world quantum sensing applications.