Loophole-free Bell inequality violation with superconducting circuits

Area of Science:

• Quantum Physics
• Quantum Information Science

Background:

• Quantum mechanics exhibits superposition, entanglement, and non-locality, fundamental features diverging from classical local causality.
• Bell tests experimentally verify quantum non-locality using entangled particle pairs, with recent advances achieving loophole-free demonstrations.

Purpose of the Study:

• To demonstrate a loophole-free violation of Bell's inequality using superconducting circuits.
• To explore the potential of superconducting circuits as a platform for quantum information technologies.

Main Methods:

• Deterministic entanglement of a pair of superconducting qubits.
• Fast, high-fidelity measurements on entangled qubits over a 30-meter cryogenic link.
• Evaluation of a Clauser-Horne-Shimony-Holt type Bell inequality over one million trials.

Main Results:

• A statistically significant violation of Bell's inequality was observed, with an average S value of 2.0747 ± 0.0033.
• The P value was less than 10^-108, providing extremely strong evidence against local realism.
• Successful demonstration of non-locality in a superconducting circuit system.

Conclusions:

• Superconducting circuits can exhibit and utilize quantum non-locality.
• This work validates superconducting circuits as a promising platform for quantum computing and communication.
• Non-locality is established as a potential resource for advanced quantum information applications.