Letters to the Editor
Still entangled?
That was a fascinating article about quantum entanglement (“Untangling Entanglement,” Fall 2019). It mentioned how a single photon could upset a delicate experiment. But if quantum gravity and gravitons are real, why don’t gravitons get entangled with experimental setups? Wouldn’t gravitons be part of the environment? A curious mind wants to know.
Bill Holland (BS ’77)
If a particle like an electron is in a superposition of two different positions, a single emitted photon could reveal the position of the particle, causing that delicate superposition to decohere. In principle, emission of a single graviton could have the same effect. In practice, however, gravity is such a weak force that we never need to worry about this source of decoherence in today’s laboratory experiments. — John Preskill, Richard P. Feynman Professor of Theoretical Physics
As part of the article on quantum entanglement, I wish you had mentioned some of the history and the role played by Caltech alumni. The first experiment to demonstrate entanglement was done by my Caltech classmate John Clauser (BS ’64). Following this original experiment, numerous more refined versions have been carried out.
The idea that spatially separated particles could be correlated, or entangled, such that a measurement of some property of one would be instantaneously reflected—faster than the speed of light—in the other had deeply troubled philosophically minded physicists from Einstein onward. John had already become interested in these ideas while at Caltech, but no one there, or at Columbia where he went to grad school, took any of it seriously.
After receiving his PhD in astrophysics at Columbia, John managed to get a postdoc at Lawrence Berkeley Labs with Nobel Laureate Charles Townes (PhD ’39) who found the idea of experimentally testing entanglement intriguing. So John, together with graduate student Stuart Freedman, finally did the experiment at Berkeley. This represented the beginning of quantum entanglement as an experimental science.
Frank Winkler (BS ’64)
The recent article on quantum entanglement misunderstood the nature of the perfect correlation between spin measurements of entangled particles with net zero spin (e.g., superposition of horizontal and vertical spin). If one particle is measured to have horizontal polarization when the polarizer is at angle alpha, its twin will instantly adopt vertical polarization if measured at the same angle. If the twin also adopted horizontal polarization, angular momentum would not be conserved.
Jerre Levy (PhD ’70)
Nice job!
Great to see these colorful jobs, especially those of my friends Garnett Pessel and Bernie Schweitzer. To add to your list, I was (1) a roustabout in a Wisconsin carnival and (2), not to be outdone by the prominent foot model Bridget Landry, a New York hand model, shaking maracas for Gunther Beer.
Sam Phillips (BS ’56, MS ’57)
Mulling the myths
When I got to “Myth #7: Genetically modified food is unsafe” (“Humans Have Landed on Mars,” Fall 2019), I was surprised to read the following: “In order for any of the resulting GMOs to go to market, they first have to be tested extensively by the USDA, the FDA, and the EPA.”
Until I read Jane Goodall’s book, Seeds of Hope, in 2015, I would have sworn on a stack of Feynman Lectures that the FDA did extensive testing on every GMO plant before it went to market. Ms. Goodall disabused me of that notion in chapter 14.
FDA does no independent testing. Neither does it require any testing by the developer. The FDA encourages developers to consult, but the consultation is entirely voluntary. And if a developer agrees to a consultation, the data that are used are generated by the developer.
D. J. Krajnovich
Regarding Myth #7, it is worth noting that the most prevalent genetic modification is resistance to Roundup, promoting widespread use of this herbicide. There is significant debate about whether or not the side effects of this are serious, especially when you include non-laboratory effects like promiscuous overspray affecting nearby vegetation and the as-yet-not-understood effects on the soil biome.
John Bloom (PhD ’77)
Soaring
“Soaring” in the Fall 2019 issue brought back a fond memory from my days at Caltech. My friend Jim LaFleur was both a sailplane and power plane pilot. One time, we went out to El Mirage Dry Lake, where there was a sailplane operation. They had a 3,000-foot steel wire laying in an adjacent dirt road. We dragged that onto the dry lake and car-towed the sailplane to the dizzying height of 1,200 feet or so. It was a two-place plane so we non-pilots took turns riding with Jim and driving the tow car.
Every time we could rustle up $7 between us, we would run down to the Rosemead Airport (now the SoCal Edison headquarters) and rent a Piper Cub for an hour. Jim taught me to fly ... unofficially, of course. I earned my license later.