Ultra-Spooky Action at a Distance: From Quantum Materials in the Lab to Black Holes

The strangest feature of quantum theory was dubbed “spooky action at a distance” by Einstein. Today, scientists have convincing evidence that two quantum particles far apart can entangle with each other such that the observation of one can instantaneously determine the state of the other.

I will describe how this quantum feature is playing a central role in many modern developments in physics. Quantum entanglement can occur on a macroscopic scale with trillions of electrons, leading to new forms of ‘ultra-quantum matter’ with properties of technological importance, such as the high-temperature superconductor, YBa2Cu3O7. Related entanglement structures arise across black hole horizons, and recent advances have shed new light on Hawking’s information paradox. I will use simple models of entanglement to describe these mutually beneficial developments across different fields of physics.

Subir Sachdev studied at the Indian Institute of Technology in Delhi, the Massachusetts Institute of Technology and Harvard University. He is now the Herchel Smith Professor of Physics and department chair of physics at Harvard University. He is a member of national academies of science in the U.S. and India, and has received several honors, including the Lars Onsager Prize and the Dirac Medal.