Source-linked AI summary
A strong loophole-free test of local realism
Lynden K. Shalm, Evan Meyer-Scott, Bradley G. Christensen, Peter Bierhorst, Michael A. Wayne, Martin J. Stevens, Thomas Gerrits, Scott Glancy, Deny R. Hamel, Michael S. Allman, Kevin J. Coakley, Shellee D. Dyer, Carson Hodge, Adriana E. Lita, Varun B. Verma, Camilla Lambrocco, Edward Tortorici, Alan L. Migdall, Yanbao Zhang, Daniel R. Kumor, William H. Farr, Francesco Marsili, Matthew D. Shaw, Jeffrey A. Stern, Carlos Abellán, Waldimar Amaya, Valerio Pruneri, Thomas Jennewein, Morgan W. Mitchell, Paul G. Kwiat, Joshua C. Bienfang, Richard P. Mirin, Emanuel Knill, Sae Woo Nam
TL;DR
The paper addresses whether local realism can be tested without loopholes caused by experimental assumptions. It performs a Bell test with spacelike-separated measurements, high-efficiency detection, and quantified setting predictability, obtaining a strong violation and rejecting local realism.
Problem
Earlier Bell tests required additional assumptions because technological constraints left loopholes, including locality and fair sampling.
Method
The experiment combines entangled photons, spacelike-separated high-speed measurements, efficient single-photon detection, and an analysis that accounts for predictability in the random settings.
Results
2.3 × 10^-7 was the smallest p-value reported after accounting for the bound on excess predictability.
Takeaways & Limitations
The experiment reports a strong loophole-free Bell-inequality violation and identifies the system as suitable for high-rate randomness generation in cryptographic applications.
Takeaways & Limitations
Excess predictability cannot be ruled out through statistical tests alone, and greater predictability lowers confidence in rejecting local realism.
Abstract
from arXiv · showhide
We present a loophole-free violation of local realism using entangled photon pairs. We ensure that all relevant events in our Bell test are spacelike separated by placing the parties far enough apart and by using fast random number generators and high-speed polarization measurements. A high-quality polarization-entangled source of photons, combined with high-efficiency, low-noise, single-photon detectors, allows us to make measurements without requiring any fair-sampling assumptions. Using a hypothesis test, we compute p-values as small as $5.9\times 10^{-9}$ for our Bell violation while maintaining the spacelike separation of our events. We estimate the degree to which a local realistic system could predict our measurement choices. Accounting for this predictability, our smallest adjusted p-value is $2.3 \times 10^{-7}$. We therefore reject the hypothesis that local realism governs our experiment.