Among the many people in San Francisco taking drugs in the early 1970s were members of a maverick group of Berkeley physicists who called themselves the Fundamental Fysiks Group. The young scientists dabbled in mind-altering drugs as they searched for a quantum-physics-based explanation for such phenomena as telepathy and extrasensory perception. The scientific basis for this quest was the experimental confirmation that once two quantum entities (such as electrons) have interacted with one another, they remain connected by what Einstein called "spooky action at a distance." The connection is technically known as entanglement; if one of the entities is prodded, the other one jumps.

As David Kaiser deftly spells out in "How the Hippies Saved Physics," these physicists based their work on good science, however drug-fogged were their aims. Entanglement is at the heart of today's uncrackable quantum encryption; it makes the "teleporting" of particles over distances of several miles feasible; and entanglement may soon be employed in the production of quantum computers that will make the best contemporary computer look like an abacus.

The effort to harness entanglement is in itself a story worth telling, and Mr. Kaiser tells it very well. But the science is almost secondary to the book's main focus, a romantic tale of these hippie physicists' role in the quantum revolution. No wonder Mr. Kaiser was drawn to the story: It's rare to find quantum physics mentioned in the same breath with sex, drugs and rock 'n' roll, plus religion (of a sort), shady (but strictly speaking, legal) financial dealings involving a research foundation that spent most of its money on fees for its officers, and a fugitive murderer (a leading member of the group who killed his girlfriend, went on the lam and was convicted in absentia).

'Countercultural' physicists Jack Sarfatti, Saul-Paul Sirag, Nick Herbert and Fred Alan Wolf (kneeling), circa 1975. Courtesy Fred Alan Wolf

How the Hippies Saved Physics By David Kaiser

Norton, 372 pages, $26.95

I heartily enjoyed "How the Hippies Saved Physics," even if readers should take some of its assertions with a pinch of salt. Why? Because, alas, the countercultural scientists' influence on mainstream physics was not as great as Mr. Kaiser would have us believe. The key developments in what has been described as the "quantum revival" were made by sober scientists working in conventional laboratories far removed in both space and time from the psychedelia of early-1970s Berkeley. But the hippie-physicists did play two important roles that are not always appreciated as they should be.

First, the young scientists reached a huge popular audience in the 1970s with books such as Jack Sarfatti's "Space-Time and Beyond," Fritjof Capra's "The Tao of Physics" and Gary Zukav's "The Dancing Wu Li Masters." Linking physics with Eastern mysticism and parapsychology, these books struck a chord and introduced a whole generation to the mysteries of quantum mechanics. Particularly in the United States, universities in the second half of the decade found students clamoring for courses on topics such as "The Zen of Physics," and even if some of the courses (and books) were more flaky than others, physics students did learn about fundamental developments at the cutting edge of research.

But the hippie physicists played an even more important role by taking a maverick approach to the one question that everyone asks upon first encountering the idea of entanglement: Can it be used to send signals faster than light? According to Einstein's theories of relativity, the answer must be no—useful information simply cannot be transmitted faster than light. By the 1970s, the matter was settled in the minds of most physicists, who knew that experimental data backed up Einstein. But the hippie group looked for loopholes. The physicists wrote scientific papers with cunning schemes describing how such "superluminal signaling" might work. Mainstream physicists, irritated but intrigued, had to find the flaws in their scruffy colleagues' arguments, refining their own ideas about quantum reality along the way. This process bounced backward and forward for years. Every possibility for superluminal signaling proposed by the mavericks was knocked down—eventually. But the improved understanding of quantum mechanics that resulted led directly to the development of quantum cryptography. By eliminating what was not possible, physicists had been left, like Sherlock Holmes, with a kernel of what was possible, however improbable it seemed.

Mr. Kaiser makes a neat analogy with the way, in the 19th century, people would try to invent perpetual-motion machines. In trying to explain why perpetual-motion machines could not work, physicists were led to a deeper understanding of physics, one that became a foundation of thermodynamics. The moral is that it is always useful to have a few mavericks prodding away at the fringes of science to keep folks on their toes.

As for quantum cryptography, it has been making steady advances since the day in 2004 when it was employed for a secure communications channel in a financial transaction between a major bank and the Viennese City Hall. Similar signals have been tested using wireless transmissions over a distance of about 100 miles, sufficient for them to be bounced off Earth-orbiting communications satellites in the future. Before long, the Internet is likely to be using quantum cryptography, making it impossible for hackers to intercept your credit-card details when you make a purchase. Articles about quantum physics now appear on newspaper business pages as well is in Scientific American.

But spare a thought for the poor hippies. Their dream of explaining parapsychology by quantum mechanics has not come true, not least because experiments they initiated have found no evidence for ESP. Bummer.

—Mr. Gribbin is a visiting fellow in astronomy at the University of Sussex and the author of "In Search of Schrödinger's Cat" (Bantam).