Quantum computers are cool, and I mean that
in a very literal sense.
In order to make use of quantum phenomena
and avoid calculation errors, the most advanced
versions need to be kept as near as possible
to absolute zero, aka zero kelvin, aka -273.15
degrees celcius, aka the coldest temperature
there is.
Now though, researchers claim they’ve demonstrated
“hot qubits,” which could be key to overcoming
a major obstacle to scaling this technology
up.
The quantum computer is built around the quantum
bit, or qubit.
Like a classical bit in the computers you’re
used to seeing every day, a quantum bit can
be used to represent a one or a zero in logical
operations.
But unlike a classical bit, a single qubit
can also be any combination of one and zero
simultaneously thanks to the quantum phenomenon
of superposition.
Qubits can also take advantage of quantum
entanglement.
This allows a quantum computer composed of
dozens of qubits to tackle certain problems
in minutes, while ordinary supercomputers
would take millenia.
For quantum computers the enemy is decoherence,
when qubits interact with the environment
and lose information.
The colder and more isolated the qubit is,
the less likely it is to flip to another quantum
state when it’s not supposed to.
But well-isolated qubits are also difficult
to keep cold, and the more qubits a computer
has, the more heat the system generates.
When you consider the fact that quantum computers
that will tackle our biggest challenges like
precision drug making will require millions
of qubits, the problem becomes clear: we have
to figure out how to keep these large quantum
computers operating at an optimal temperature.
There are two ways of approaching the problem.
One is to improve cooling systems.
The most sophisticated quantum computers we
have now are based on superconductors and
are kept cool with dilution refrigerators.
Imagine basically a hideous steampunk chandelier
and you’re halfway there.
Most that exist right now can keep fewer than
100 qubits cold enough to operate.
So scaling up a dilution refrigerator to keep
millions of qubits cold would be incredibly
expensive, and still may not be capable of
maintaining sufficient temperatures.
The other approach is to make qubits that
can operate at warmer temperatures, and this
is where two separate groups of researchers
believe they’ve made a breakthrough.
Rather than basing their qubits off superconductors,
the scientists used nanoscale metal electrodes
to confine electrons in silicon, in devices
known as quantum dots.
This allowed them to operate at significantly
hotter temperatures.
How hot, you ask?
A scorching 1.5 kelvin.
So… not exactly flip-flops weather, but
at the atomic level it's a huge difference.
That’s 15 times warmer than superconductor-based
qubits can operate.
A silicon basis has a few other advantages.
We are already very experienced at making
things out of silicon; it’s the basis for
all conventional computer chips, after all.
So the researchers claim silicon based qubits
can be manufactured with foundries we have
today.
And get this: hot silicon qubits allow for
the integration of conventional chips that
can control the operations of the qubit.
Normally these conventional chips would get
too hot to have them next to superconducting
qubits, meaning they would have to be kept
separate with long wires connecting them.
But if the qubits can operate at higher temperatures,
a silicon chip can be placed right next to
them and the overall size of the computer
can be greatly reduced.
Is this the breakthrough quantum computers
need to push them from curious doohickies
to world-changing number crunchers?
We’ll only know when this two-qubit proof-of-concept
is scaled up.
Until then, we’ll keep tabs on all the other
quantum computing breakthroughs until one
of them finally establishes the quantum age.
Another group of researchers recently discovered
a more precise way of controlling qubits in
silicon, all it took was a series of fortunate
accidents.
Check out my other video on that story here.
If you had a quantum computer, what would
you use it for?
Let us know in the comments, be sure to subscribe,
and I'll see you next time on Seeker!
