1. Entanglement is at the heart of quantum physics and future quantum technologies. The phenomenon of entanglement reveals itself when two particles, such as a pair of photons or electrons, become entangled, they remain connected even when separated by vast distances. When hundreds of particles become entangled, they still act as one unified object. Like a flock of birds, the particles become a whole entity unto itself without being in direct contact with one another. Some scientists, including Albert Einstein in the 1930s, argued against the mind-boggling aspect of entanglement. Thanks to theoretical work by John Stewart Bell in the 1960s,“local hidden-variable theories” have been ruled out.

2. Nonlocality describes the apparent ability of objects to instantaneously know about each other’s state, even when separated by large distances, almost as if the universe instantaneously arranges its particles in anticipation of future events. Bell’s Theorem, published in 1964, and referred by some as one of the most profound discoveries in all of physics, effectively showed that the results predicted by quantum mechanics could not be explained by any theory which preserved locality. Instantaneous action or transfer of information does appear to be possible.

3. Bell inequalities. At the time that Bell formulated his theorem, it was an open question whether the Bell inequality-violating correlations predicted by quantum mechanics were realized in nature. Beginning in the 1970s, there has been a series of experiments to test whether the Bell inequalities are satisfied. With few exceptions, the results of these experiments have confirmed the quantum mechanical predictions, violating the relevant Bell Inequalities.


4. The EPR Paradox. In a 1935 paper, Einstein, Boris Podolsky and Nathan Rosen, argued that quantum mechanics was not a complete physical theory. Known today as the “EPR paradox,” it said that the result of a measurement on one particle of an entangled quantum system can have an instantaneous effect on another particle, regardless of the distance of the two parts. Ranked by impact, EPR is among the top ten of all papers ever published in Physical Review journals.

5. Spooky Action at a Distance. Albert Einstein colorfully dismissed quantum entanglement—the ability of separated objects to share a condition or state—as “spooky action at a distance.”

6. Local Hidden Variables. The local hidden variable theory was an attempt made by some of the earlier physicists (most notably Einstein, Podolsky and Rosen) to explain certain counter-intuitive features of quantum mechanics. It assumes that all natural processes are local and the hidden aspect ascribes to the uncontrollable parameters of the model. It was not until John Bell, that an experimentally testable way to settle this question. But much to the surprise of some, all real tests done on entangled quantum systems fails the Bell's inequality test thereby establishing that reality cannot be described by a model which is both local and realistic. There are many LHV theories that bypass Bell's inequality due to loopholes in the measurement process. The most well known loophole is that of detection efficiency.

7. Detection Loophole. The problem with photons experiments is that they close the locality loophole, but they open a new one. The new problem comes from the measurement process and it is called the Detection Loophole. If the detection efficiencies are not perfect, one might observe a violation of a Bell inequality. Imagine that there are unknown states of the photon, that are easily lost or that cannot be detected, and they have specific properties that reduce the value of the inequality violation. If you cannot detect them you cannot assure that the violation you observe is legitimate. Finally, in 2015, experiments were performed that demonstrated violation of Bell inequalities with these loopholes blocked.

8. Everybody Rides the Carousel. As a bonus track to sum up the human understanding of our connection to the physical world, Everybody Rides the Carousel is a 1975 animated film about the eight stages of life and the peculiar conflicts that shape an individual’s behaviors. Birth, death, alpha, omega, are all one continuous cyclic samsara with no beginning and no end. Based on Erik Erikson’s theories of human social development, this landmark film was written, produced and directed by John Hubley and his wife Faith. One of my favorite parts is the teenage stage, Mirrorland, featuring an amazing score by Dizzy Gillespie. Also noted is the voice work from from the Hubleys’ children to Meryl Streep.