A team of scientists at the University of Chicago announced the discovery of a simple
modification that allows quantum systems to stay operational—or “coherent”—10,000
times longer than before.
Though the scientists tested their technique on a particular class of quantum systems called
solid-state qubits, they think it should be applicable to many other kinds of quantum
systems and could thus revolutionize quantum communication, computing and sensing.
The study was published in the journal Science.
This breakthrough lays the groundwork for exciting new avenues of research in quantum
science.
The broad applicability of this discovery, coupled with a remarkably simple implementation,
allows this robust coherence to impact many aspects of quantum engineering.
It enables new research opportunities previously thought impractical.
Down at the level of atoms, the world operates according to the rules of quantum mechanics—very
different from what we see around us in our daily lives.
These different rules could translate into technology like virtually unhackable networks
or extremely powerful computers.
But fundamental engineering challenges remain: Quantum states need an extremely quiet, stable
space to operate, as they are easily disturbed by background noise coming from vibrations,
temperature changes or stray electromagnetic fields.
Thus, scientists try to find ways to keep the system coherent as long as possible.
One common approach is physically isolating the system from the noisy surroundings, but
this can be unwieldy and complex.
Another technique involves making all of the materials as pure as possible, which can be
costly.
The scientists at UChicago took a different tack.
With their approach, the researchers don’t try to eliminate noise in the surroundings;
instead, they “trick” the system into thinking it doesn’t experience the noise.
In tandem with the usual electromagnetic pulses used to control quantum systems, the team
applied an additional continuous alternating magnetic field.
By precisely tuning this field, the scientists could rapidly rotate the electron spins and
allow the system to “tune out” the rest of the noise.
To get a sense of the principle, it’s like sitting on a merry-go-round with people yelling
all around you.
When the ride is still, you can hear them perfectly, but if you’re rapidly spinning,
the noise blurs into a background.
This small change allowed the system to stay coherent up to 22 milliseconds, four orders
of magnitude higher than without the modification—and far longer than any previously reported electron
spin system.
The system is able to almost completely tune out some forms of temperature fluctuations,
physical vibrations, and electromagnetic noise, all of which usually destroy quantum coherence.
The simple fix could unlock discoveries in virtually every area of quantum technology.
This approach creates a pathway to scalability.
It should make storing quantum information in electron spin practical.
Extended storage times will enable more complex operations in quantum computers and allow
quantum information transmitted from spin-based devices to travel longer distances in networks.
Though their tests were run in a solid-state quantum system using silicon carbide, the
scientists believe the technique should have similar effects in other types of quantum
systems, such as superconducting quantum bits and molecular quantum systems.
This level of versatility is unusual for such an engineering breakthrough.
There are a lot of candidates for quantum technology that were pushed aside because
they couldn’t maintain quantum coherence for long periods of time.
Those could be re-evaluated now.
The best part is, it’s incredibly easy to do.
The science behind it is intricate, but the logistics of adding an alternating magnetic
field are very straightforward.