Google’s new ‘time crystals’ could be a breakthrough for long-awaited quantum computers
Google’s new ‘time crystals’ could be a breakthrough for long-awaited quantum computers
Dalvin Brown August 12, 2021
Time crystals sound like majestic objects
from science fiction movies that unlock passageways to alternative universes.
In the Marvel universe, the “time stone” gives wielders control over the past,
present and future.
While that remains a fantasy, scientists have successfully created micro-scale time crystals for years — not for powering intergalactic spaceships but for energizing ultrapowerful computers. “Time crystals are like a rest stop on the road to building a quantum computer,” said Norman Yao, a molecular physicist at the University of California at Berkeley.
It’s an area of interest for Google, which, along
with physicists at Stanford and Princeton universities, claim to have developed
a “scalable approach” to time crystal creation using the company’s Sycamore quantum computer.
In a paper published last month on the research-sharing platform Arxiv.org, a team
of over 100 scientists describe how they set up an array of 20 quantum particles, or qubits, to serve as a time
crystal. During experiments, they applied algorithms that spun the qubits
upward and downward, generating a controllable reaction that could be sustained
“for infinitely long times,” according to the paper.
Time crystals are scientific oddities made of atoms arranged in
a repeating pattern in space. This design enables them to shift shape over time
without losing energy or overheating. Since time crystals continuously evolve
and don’t seem to require much energy input, they may be useful for quantum
computers, which rely on extremely fragile qubits that are prone to decay.
Quantum computing is weighed down
by hard-to-control qubits, which are error prone and often die. Time crystals
might introduce a better method for sustaining quantum computing, according to
Yao, who published a blueprint for making time crystals in 2017.
“Time crystals are a weighted benchmark, showing that your
system has the requisite level of control,” Yao said.
The scientists involved in Google’s research say they can’t
discuss their findings as they undergo peer review.
However, the work tackles an area where physicists have long
hoped for a breakthrough.
“The consequence is amazing: You evade the second law of
thermodynamics,” Roderich Moessner, a co-author of the Google paper, told Quanta Magazine.
The time crystal concept was first proposed in 2012 by Nobel
Prize-winning physicist Frank Wilczek, who wondered whether atoms could be
arranged in time similar to their arrangement in ordinary crystals.
Essentially, he wondered whether a closed system could spin,
oscillate or move in a repetitious manner. What followed was a healthy dose of
scrutiny from the broader physics community, years of university experiments
with and without Wilczek, and testing to see whether his vision was possible.
The definition expanded to include objects that would be
activated by an external influence such as a shake, stir or a laser strike.
“The definition is somewhat fluid. But if you want to call it a
new state of matter, you want it to be autonomous and not have stirring,”
Wilczek said.
Early experiments pumped ions with lasers so they would
artificially pulsate. It was useful but difficult to scale, Wilczek added.
By 2017, scientists from Harvard University and the University
of Maryland revealed they created micro-scale time crystals at frigid
temperatures in a lab. Both passed peer review. More recently, a team from the
Delft University of Technology in the Netherlands published findings in
July on its approach to building a time crystal inside a diamond. (Those
findings haven’t undergone peer review.)
Time crystals are a tough concept to grasp, but scientists say
you can think of them like a perpetual motion machine, adding a caveat to the
second law of thermodynamics, which states that any isolated system will
degenerate into a more disordered state or entropy. Their existence also
undermines Newton’s first law of motion, detailing how an object must react to
motion.
Time crystals are the first objects created that spontaneously
break “time-translation symmetry” or the idea that a stable object, such as
solids, liquids, gases and plasma, will remain the same throughout time.
Google’s work produced a time crystal that functioned for
milliseconds, but the research looks promising, Wilczek said. The assumption is
that once the hardware is more advanced, the resulting time crystals would last
longer, he added.
“Nothing lasts forever, not even diamonds, their protons will eventually decay,” Wilczek said. “If you can make something that has time crystal behavior that lasts millions of cycles, or thousands of cycles, it can support sensitive technologies. You can do a lot even if it’s not perfect.”
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