THIS summer, physicists celebrated a triumph that many consider
fundamental to our understanding of the physical world: the discovery,
after a multibillion-dollar effort, of the Higgs boson.
Given its importance, many of us in the physics community expected the event to earn this year’s Nobel Prize in Physics. Instead, the award went to achievements in a field far less well known and vastly less expensive: quantum information.
It may not catch as many headlines as the hunt for elusive particles,
but the field of quantum information may soon answer questions even more
fundamental — and upsetting — than the ones that drove the search for
the Higgs. It could well usher in a radical new era of technology, one
that makes today’s fastest computers look like hand-cranked adding
machines.
The basis for both the work behind the Higgs search and quantum
information theory is quantum physics, the most accurate and powerful
theory in all of science. With it we created remarkable technologies
like the transistor and the laser, which, in time, were transformed into
devices — computers and iPhones — that reshaped human culture.
But the very usefulness of quantum physics masked a disturbing
dissonance at its core. There are mysteries — summed up neatly in Werner
Heisenberg’s famous adage “atoms are not things” — lurking at the heart
of quantum physics suggesting that our everyday assumptions about
reality are no more than illusions.
Take the “principle of superposition,” which holds that things at the
subatomic level can be literally two places at once. Worse, it means
they can be two things at once. This superposition animates the famous
parable of Schrödinger’s cat, whereby a wee kitty is left both living
and dead at the same time because its fate depends on a superposed
quantum particle.
For decades such mysteries were debated but never pushed toward
resolution, in part because no resolution seemed possible and, in part,
because useful work could go on without resolving them (an attitude
sometimes called “shut up and calculate”). Scientists could attract
money and press with ever larger supercolliders while ignoring such
pesky questions.
But as this year’s Nobel recognizes, that’s starting to change.
Increasingly clever experiments are exploiting advances in cheap,
high-precision lasers and atomic-scale transistors. Quantum information
studies often require nothing more than some equipment on a table and a
few graduate students. In this way, quantum information’s progress has
come not by bludgeoning nature into submission but by subtly tricking it
to step into the light.
Take the superposition debate. One camp claims that a deeper level of
reality lies hidden beneath all the quantum weirdness. Once the
so-called hidden variables controlling reality are exposed, they say,
the strangeness of superposition will evaporate.
Another camp claims that superposition shows us that potential realities
matter just as much as the single, fully manifested one we experience.
But what collapses the potential electrons in their two locations into
the one electron we actually see? According to this interpretation, it
is the very act of looking; the measurement process collapses an
ethereal world of potentials into the one real world we experience.
And a third major camp argues that particles can be two places at once
only because the universe itself splits into parallel realities at the
moment of measurement, one universe for each particle location — and
thus an infinite number of ever splitting parallel versions of the
universe (and us) are all evolving alongside one another.
These fundamental questions might have lived forever at the intersection
of physics and philosophy. Then, in the 1980s, a steady advance of
low-cost, high-precision lasers and other “quantum optical” technologies
began to appear. With these new devices, researchers, including this
year’s Nobel laureates, David J. Wineland and Serge Haroche, could trap
and subtly manipulate individual atoms or light particles. Such
exquisite control of the nano-world allowed them to design subtle
experiments probing the meaning of quantum weirdness.
Soon at least one interpretation, the most common sense version of hidden variables, was completely ruled out.
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