TALES OF ENTANGLEMENT
“Spooky Action,” by Ronald Hanson and Krister Shalm, discusses quantum entanglement, in which two particles exhibit a “spooky” connection regardless of distance.
The authors do not explain why something as nonspooky as the following can't be going on: Suppose I hide a pair of gloves in two different envelopes and send one (without knowing which) to my friend on Mars, with a note to open it on receipt. The envelopes are now “entangled” because if my friend finds a left glove, then I will find a right glove, and vice versa—before a light signal has had time to travel to Earth.
GORDON B. HAZEN Professor emeritus of industrial engineering and management sciences, Northwestern University
The article made this old sci-fi fan's imagination run wild. Do we know that entangled particles are “monogamous”? If an electron can be entangled with one partner, why not multiple partners simultaneously? Could entanglement be a relationship among a large number of particles independent of location? And if so, could manipulating allow for truly instant messaging across interstellar distances?
BOB MORRISON Asheboro, N.C.
THE AUTHORS REPLY: Regarding Hazen's suggestion: Just as “correlation does not imply causation,” it does not always imply entanglement. The nonspooky correlation of the two gloves is determined the moment they are placed in their envelopes and is an example of a “hidden variable theory.” John Bell showed that any such theory will not have correlations that are as rich as those allowed by quantum entanglement. In our experiments, once our particles are sent to their distant locations, they are randomly measured in one of two ways. Because the particles do not know in advance how we are measuring them, they cannot agree ahead of time how to correlate their outcomes. It appears as if measuring one particle randomly and instantaneously influences its distant partner, which is the spookiness that Albert Einstein referred to.
In answer to Morrison: It is possible to entangle many different particles with one another, and this is an active area of research—for instance, for building quantum computers. But if two particles are maximally entangled, there can be no entanglement with any other particles at the same time. In that sense, entanglement is indeed monogamous, which ensures a level of privacy that is unmatched in classical physics and is at the heart of quantum applications in secure communication.
Alas, faster-than-light communication must remain science fiction. With entanglement, the outcome is random but correlated. Let's say you and a distant friend share entangled electrons and have agreed that if they are measured to be “up,” that means “yes,” whereas “down” means “no.” Your partner will get the same result as you, so the electrons appear to have somehow influenced one another faster than the speed of light. But there is no way to force your electron to be “up” to send a “yes” response. When it is measured, the electron, not you, will “choose” with a 50 percent probability of whether it will be up or down. It is no better than flipping a coin.
In “Sacred Groves,” Madhav Gadgil discusses the ecological benefits of areas of primeval forest in India protected as the homes of deities. Gadgil illustrates how the sacred in traditional cultures can transmit practical wisdom distilled from bitter experience, which we need to help save our planet. Such perspectives make me less sanguine about the technologies Scientific American often features. I appreciate the lure of discovery, having had a 40-year career in the physics of the earth, but not everything we might create ought to be created. All technologies must be evaluated in the current reality that anything that can be exploited for a profit probably will, regardless of the dangers.
The greatest service to humanity at the moment would be rendered not by implementing technical innovations of uncertain benefit but by gaining the emotional maturity to appreciate and act on the kind of wisdom portrayed in “Sacred Groves.”
GEOFF DAVIES Retired senior fellow, Australian National University
In “The Last of the Ocean Wilderness” [Forum], Kendall Jones and James Watson raise the point that we have depleted about “90 percent of formerly important coastal species” and that any conservation agreements should set wilderness-retention targets. But their recommendation does not go far enough. I think to be successful over the short and the long term, we must also spearhead public campaigns that identify overexploited ocean species, explain what classifies as pollution and how it can affect ocean life, and make a list of recommended actions geared toward the average consumer. And we should monitor overfishing or illegal fishing by enforcing existing legislation; using nontransferable unique numbers to tag fishing vessels; encouraging seafood traceability through documentation; and monitoring vessels via inspection stations, drones and satellites.
VASILIOS VASILOUNIS Brooklyn, N.Y.
Please refrain from misattributing popular sayings to celebrities. “Rethinking the ‘Anthropocene,’” by the Editors [Science Agenda], quotes Albert Einstein as asserting, “We cannot solve our problems with the same thinking we used when we created them.” There is no evidence that Einstein said or wrote those words. The nearest we come seems to be a passage in a 1948 essay in which he argued that a “supranational organization” should be given sole authority over atomic weapons: “Our situation is not comparable to anything in the past. It is impossible, therefore, to apply methods and measures which at an earlier age might have been sufficient. We must revolutionize our thinking, revolutionize our actions, and must have the courage to revolutionize relations among nations of the world. Clichés of yesterday will no longer do today, and will, no doubt, be hopelessly out of date tomorrow.”
STEVEN WENNER Cohasset, Mass.
THE EDITORS REPLY: We would like to thank Wenner for pointing out that this quote is most likely apocryphal, as is indicated by the seeming elusiveness of a primary source and the existence of several variations. In the future, we will not allow for the inclusion of any quotes commonly attributed to famous figures unless they can be fully substantiated.
“A Meditation on Keyboard Shortcuts,” by David Pogue [TechnoFiles], should not have implied that Apple was the first to use keyboard shortcuts by referring to them as “Apple's brilliant innovation.” The company was an early adopter of shortcuts.
“Hidden Inferno,” by Shannon Hall, should have described winds blowing potential volcanic ash from the Laguna del Maule region in Chile to Argentina as westerly, not easterly. Further, it should not have described 1,200 degrees Celsius as 50 percent hotter than 800 degrees C, because such comparisons break down at different scales of temperature: in kelvins, the former temperature would be 37 percent hotter than the latter.