Researchers develop cooling system that makes them more reliable, affordable, allowing qubits to accurately reset to their ground states in just a couple of tens of nanoseconds

 

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By Heather Hamilton, contributing writer

Researchers from Aalto University in Finland have developed
a way to cool quantum computers, an ongoing issue in their development.
According to Phys.org, quantum computers differ from
regular computers in that they use quantum bits, called qubits. The bits in a
normal computer are zeros or ones and enact sequence logical, whereas qubits
exists in both states allowing calculations to take place in parallel. This
allows entire new realm of computation to take place that can delve deeper into
logistics, health screen, and even artificial intelligence. At the same time, their
versatility makes them sensitive to external factors. If they get too hot, they
are not initialized because they’re switching between different states too
frequently. 

In an interview with IFLScience, lead researcher Mikko Möttönen said, “One
of the basic criteria that a working quantum computer must satisfy is that
there has to be a way to accurately initialize its memory. In practice, this
means that we must be able to accurately take the quantum bits in their ground
state.” 

Of course, this means a temperature of absolute zero
temperature, though close will do. Enter Möttönen and his team of researchers with a refrigerator
for quantum computers. The study began with the idea that something can
be cooled down with radiation. By using quantum mega-microwave to surround
superconducting devices, which the researchers used in place of qubits, with
electrons carrying just a bit less energy than necessary to quantum phase-shift
(tunnel) through a nanoscale insulator beside their qubits.  

When the
electrons interact with the qubit stand-in, they have a variety of
interactions, which includes the natural stealing of energy. So, the energy is
stolen, the electron tunnels through the insulator and is then stranded because
it now lacks the energy to get back. Slowly, it is cooled by energy theft. 

“With our new refrigerator, we
think that is should be possible to reset qubits very accurately to their
ground states in just a couple of tens of nanoseconds,” Möttönen said.

The
nanoscale refrigerator makes quantum computers more reliable and powerful. Kuan
Yen Tan, a postdoctoral researchers in Möttönen’s group of researchers, has
worked on the cooling device for five years and is pleased that it is now functional.
“Our refrigerator keeps quanta in order,” Mikko Möttönen says.

Currently
quantum computers exist in limited availability, in part because they’re
difficult to cool. According to Inverse, D-Wave Systems cools quantum
devices with liquid helium, which is very expensive and is accompanied by a
host of additional problems. The refrigerators are complicated and costly, and
also prone to breakdowns. An efficient cooling process could reduce the price
of chips and allow engineering to include more qubits in each processor and
make quantum computers a reality for everyday users. 

Still,
there is work to be done. Möttönen’s group will now work toward cooling quantum
bits in addition to resonators. They’d also like to lower the minimum
temperature achievable with refrigerator,and make its on/off switch function
with more speed.

“Thus far we have also only shown that we can turn the
cooling on and off but not how fast,” Möttönen said. “We want to be
able to do this in nanosecond timescales for qubits. Again, we do not see any
obstacles here and are currently working on an experiment showing that the
fridge is very fast as well.”

Sources: Nature
Communications
, Phys.org, IFLScience,  Inverse
Image Source: Wikimedia