In 1935, Albert Einstein wrote a paper with two collegues, Boris Podolsky and Nathan Rosen, called “Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?” The spirit of the paper was to uncover the defects of quantum mechanics in the form of the wave function. I suppose Einstein had a bone to pick with quantum mechanics, a bone about probability replacing God’s will, more simply. But what the paper brought up has captivated me for the better part of two decades—the phenomenon now known as quantum entanglement.
Einstein, Podolsky, and Rosen did not refer to entanglement as such. Quantum entanglement, as it is now known, postulated the existence of particle pairs (an electron and a positron, for example) that act like a system no matter how far they are apart, even if they are separated by the entirety of the universe. If the pair acts as a system with a unity of spin, then if one particle spins one way, the other particle will always be found to spin the other way. The relationship exists no matter the distance between them, even if it is light years or the width of the galaxy or the entire breadth of spacetime.
This was the subject of my first date with my husband. And the second date. People used to ask me about how our relationship began and I used to answer that it was over the Einstein-Podolsky-Rosen thought experiment until I realized how pretentious that sounded. Then I came up with the story of how I met him the week after my rabbit died, which is true. I replaced the EPR paradox with a story about my late rabbit because I was worried about being pretentious. But it is not as pretentious as it seems. In fact, quantum entanglement has to be one of the most romantic ideas I’ve ever heard in science: two particles so attached that the laws of quantum mechanics don’t apply and the speed of light does not limit the strength of their unity. If ever the idea that “love is love is love is love is love” should apply outside living consciousness, this is it.
The EPR paradox paper refers to “physical reality” and “physical theory” but was in fact really three guys in Princeton just thinking. It was a thought experiment. The instruments didn’t exist to verify these ideas in a lab in 1935. Quantum entanglement was not observed until 1972 in an experiment performed at the Massachusetts Institute of Technology by Stuart Freedman and John Clauser. Today, quantum entanglement has crossed over to the pedestrian world of applied physics most notably in quantum computing and communications (availing of the superluminal transfer of information). I keep finding articles on the subject in magazines. They bring up an exciting new application or another new lab verification. But I find the lofty concept much more profound than its practical application. Particles so attached that they transcend the constraints of spacetime. How romantic is that? So romantic, it reminds me of my first date with the guy I eventually married.