Loophole-Free Test of Local Realism via Hardy's Violation

Area of Science:

• Quantum Physics
• Quantum Information Science

Background:

• Bell's theorem challenges local realistic theories, underpinning quantum information.
• Hardy's paradox offers a simple "All versus Nothing" test of local realism.
• Previous tests were limited by experimental imperfections (loopholes).

Purpose of the Study:

• To experimentally demonstrate Hardy's nonlocality in a loophole-free manner.
• To provide affirmative evidence against local realistic theories.
• To establish a benchmark for quantum information applications.

Main Methods:

• Utilized a photonic entanglement source.
• Achieved high detection efficiency (82.2%) and quantum state fidelity (99.10%).
• Employed high-speed quantum random number generators for measurement setting switching.

Main Results:

• Observed a strong violation of Hardy's paradox (P_Hardy=4.646×10^{-4}, 5 std dev) over 6 hours and 4.32×10^9 trials.
• Demonstrated loophole-free testing against local realism.
• Null hypothesis test yielded an extremely low probability (10^{-16348}) for local realistic explanations.

Conclusions:

• The experiment provides conclusive evidence refuting local realism.
• The findings set a new standard for quantum information applications.
• This work strengthens the foundation for quantum technologies.