Physics Colloquium– “Cosmic Bell Test: Measurement Settings from Milky Way Stars,” Jason Gallicchio

February 21, 2017 Add to Calendar

4:15–5:30 p.m.

Location

Shanahan Center, B460
320 E. Foothill Blvd.
Claremont, CA 91711

Contact

Kathy Morrison
kmorrison@hmc.edu

Details

Bell's theorem states that some predictions of quantum mechanics cannot be reproduced by a local-realist theory. That conflict is expressed by Bell's inequality, which is usually derived under the assumption that there are no statistical correlations between the choices of measurement settings and anything else that can causally affect the measurement outcomes. In previous experiments, this "freedom of choice" was addressed by ensuring that selection of measurement settings via conventional "quantum random number generators" was space-like separated from the entangled particle creation. This, however, left open the possibility that an unknown cause affected both the setting choices and measurement outcomes as recently as mere microseconds before each experimental trial. I'll talk about a new experimental test of Bell's inequality that, for the first time, uses distant astronomical sources as "cosmic setting generators." In our tests with polarization-entangled photons, measurement settings were chosen using real-time observations of Milky Way stars while simultaneously ensuring locality. This pushes back by ~600 years the most recent time by which any local-realist influences could have engineered the observed Bell violation.

Jason Gallichio is assistant professor of physics at Harvey Mudd College. Besides his work on the cosmic microwave background, Gallicchio aims to close a loophole in tests of Bell’s inequalities—which confirm the  “spooky action at a distance” between quantum entangled particles—by using telescopes that look at widely separated quasars to generate the random settings in delayed choice experiments.

4:15 p.m. - Refreshments
4:30 p.m. - Lecture
Shanahan B460 (Tiered Classroom)