"Anyone who claims to understand quantum theory is either lying or crazy," physicist Richard Feynman once said, according to legend.
That situation hasn't changed much in the roughly 90 years since quantum mechanics was first introduced, as evidenced by a new poll, detailed online this month, showing that physicists are still divided over the theory's meaning.
The 16-question poll was given to 33 physicists, philosophers and mathematicians at a conference on "Quantum Physics and the Nature of Reality" in Austria in July 2011. The poll probed the experts' thoughts on fundamental tenets of the theory, such as the randomness of nature and the impact of outside measurements on quantum systems.
Though the pollsters admit the sample size is small and the test not completely scientific, they found a striking divide among the experts on some of the most basic principles of quantum mechanics.
"Nearly 90 years after the theory's development, there is still no consensus in the scientific community regarding the interpretation of the theory's foundational building blocks," the authors of the poll, led by physicist Maximilian Schlosshauer of the University of Portland, wrote in a paper describing the results posted on Jan. 6 on the preprint site arXiv.org. "Our poll is an urgent reminder of this peculiar situation."
For example, experts were nearly split over the question: "Do you believe that physical objects have their properties well defined prior to and independent of measurement?"
While slightly more answered "yes, in some cases" (52 percent), just under half responded "no" (48 percent). (Respondents were allowed to check multiple answers and write in responses; 3 percent said "yes, in all cases," while 9 percent were "undecided.")
Bohr vs. Einstein
Quantum mechanics, first formulated in the early 20th century, is physicists' best way of describing the behavior of the universe's smallest things, such as the atoms that make up our bodies. Yet much of it is esoteric and counterintuitive.
[ Wacky Physics: The Coolest Little Particles in Nature ]
For example, the theory suggests that particles don't exist in a particular place at a particular time, but rather float around in a haze of probability, with a certain chance of being in point A, and another chance of being in point B. In his "Copenhagen interpretation," physicist Niels Bohr took this to mean that the physical universe is indeterminate and fundamentally probabilistic.
Yet Albert Einstein never believed this, famously saying "God does not play dice with the universe." He preferred to think that underneath it all, the universe is deterministic, meaning the future state of, say, a particle, is completely determined by its prior states. In other words, all effects have causes.
In the poll, 42 percent of respondents said Bohr's Copenhagen interpretation was their favorite interpretation of quantum mechanics — no other interpretation received more than 24 percent of the votes.
Meanwhile, 64 percent of those polled said that Einstein's view of quantum mechanics "is wrong," while 6 percent said it would "ultimately turn out to be correct." Another 12 percent said Einstein's view would "ultimately turn out to be wrong," while the same percentage said "we'll have to wait and see."
Quantum computers
Participants were equally divided over the possibilities for quantum computers, machines that would utilize the quantum properties of particles, such as their ability to be in multiple states at the same time, to achieve superfast calculation speeds.
The largest share of poll respondents, 42 percent, said a working and useful quantum computer would be achieved within 10 to 25 years, while another 30 percent predicted quantum computers within 25 to 50 years. An especially optimistic 9 percent said the technology would be realized in the next 10 years, while 15 percent said "never."
Ultimately, those polled were so divided they couldn't even agree on whether similar conferences on quantum foundations would take place 50 years in the future. "Probably yes" was the answer of 48 percent, while 15 percent said "probably no," and 24 percent said "who knows?" An enterprising 12 percent, though, said, "I'll organize one no matter what."
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