The method might be used to shield data from faults in quantum
computers.
Scientists have produced a brand-new, bizarre phase of matter that acts as
like it had two dimensions of time by directing a Fibonacci laser beam at
atoms within a quantum computer.
The new phase of matter, which was produced by rhythmically jiggling a
strand of 10 ytterbium ions with lasers, allows researchers to store
information in a way that is significantly more error-protected, paving the
way for quantum computers that can retain data for a very long time without
becoming jumbled. The researchers published an article outlining their
findings in the journal Nature on July 20. (opens in new tab).
In a statement, the study's principal author Philipp Dumitrescu, a
researcher at the Flatiron Institute's Center for Computational Quantum
Physics in New York City, stated that the introduction of a hypothetical
"extra" time dimension "is a whole different way of thinking about phases of
matter." I've been working on these theory concepts for more than five
years, so it's thrilling to see them really implemented in trials.
The scientists weren't trying to invent a phase with a hypothetical
additional time dimension, and they weren't seeking for a way to improve
quantum data storage either. Instead, they sought to develop a new phase of
matter, one that went beyond the conventional solid, liquid, gas, and plasma
states.
The H1 quantum processor, developed by Quantinuum, consists of 10 ytterbium
ions in a vacuum chamber that are precisely controlled by a device known as
an ion trap. They started construction on the new phase of this
processor.
In typical computers, all computations are based on bits, or 0s and 1s.
Qubits, which may also exist in a state of 0 or 1, are used in quantum
computers. But the parallels stop there, pretty much. Until they are
measured, when they randomly collapse into either a 0 or a 1, qubits can
live in a combination, or superposition, of both the 0 and 1 states, thanks
to the strange principles of the quantum realm.
The ability of qubits to connect with one another through quantum
entanglement—a phenomenon Albert Einstein named "spooky action at a
distance"—is made possible by this peculiar behavior, which is the secret to
the power of quantum computing. Even if two or more qubits are separated by
great distances, entanglement connects their characteristics so that any
change in one will result in a change in the others. This allows quantum
computers to carry out many calculations at once, dramatically increasing
their processing capability in comparison to classical machines.
However, a significant flaw prevents the development of quantum computers:
qubits interact and become entangled with one another as well as with the
environment outside the quantum computer because this environment cannot be
completely isolated from the quantum computer. This interaction causes
qubits to lose their quantum properties and the information they contain, a
process known as decoherence.
Dumitrescu remarked, "Even if you tightly regulate all the atoms, they can
lose their 'quantumness' by conversing with their surroundings, heating up,
or interacting with objects in ways you didn't expect.
The scientists turned to a certain category of phases known as topological
phases to circumvent these annoying decoherence effects and produce a
brand-new, stable phase. Quantum entanglement makes it possible for quantum
devices to weave information into the dynamic movements and interactions of
the whole system—in the very structure, or topology, of the material's
entangled states—rather than merely encoding it across the solitary, static
locations of qubits. This results in a "topological" qubit, which is far
less likely to lose its information since it encodes information in the
shape produced by numerous pieces rather than just one.
Breaking physical symmetry, the notion that the rules of physics are the
same for an item at any point in time or space, is a significant indicator
of transitioning from one phase to another. Water molecules behave like a
liquid, obeying the same physical principles everywhere in space and in
every direction. However, when water is sufficiently cooled to turn into
ice, its molecules will choose predictable locations along a crystal
structure, or lattice, to arrange themselves across. The spatial symmetry of
the water has suddenly been shattered; the water molecules have selected
spots in space to inhabit, leaving the other points unoccupied.
In a quantum computer, symmetry breaking is similarly necessary to produce
a new topological phase, but in this case, the symmetry is broken over time
rather than space.
The goal of the researchers was to break the continuous time symmetry of
the at-rest ions and impose their own time symmetry, where the qubits stay
the same over certain time periods, which would produce a rhythmic
topological phase across the material.
However, the test was a failure. Regular laser pulses increased the noise
from outside the system instead of producing a topological phase that was
resistant to decoherence effects, causing the system to be destroyed less
than 1.5 seconds after it was turned on.
After reevaluating the experiment, the scientists concluded that in order
to produce a more stable topological phase, they would need to incorporate
more than one temporal symmetry into the ion strand in order to reduce the
likelihood that the system would become chaotic. To do this, they decided to
look for a pulse pattern that exhibited increased temporal symmetry while
not repeating simply and consistently.
This introduced them to the Fibonacci sequence, in which the following
number is obtained by adding the two preceding ones. Instead of simply
switching between two laser sources (A, B, A, B, A, B, and so on) as in a
typical periodic laser pulse, each new pulse train operated by merging the
two pulses that before it (A, AB, ABA, ABAAB, ABAABABA, etc.).
This Fibonacci pulse produced a temporal symmetry that was organized
without ever repeating, much like a quasicrystal in space. The Fibonacci
pulses also compress a higher dimensional pattern into a smaller dimensional
surface, much like a quasicrystal does. A slice of a five-dimensional
lattice is projected onto a two-dimensional surface in the case of a spatial
quasicrystal like Penrose tiling. Two hypothetical temporal symmetries are
flattened into a single actual one while examining the Fibonacci pulse
rhythm.
According to the researchers, the system "basically obtains an additional
symmetry from a non-existent extra temporal dimension." Even though it could
be physically impossible in reality, the system looks to be a substance that
exists in some higher level with two dimensions of time.
The new quasiperiodic Fibonacci pulse produced a topographic phase during
testing that shielded the system from data loss for the whole 5.5 seconds.
In fact, they had produced a phase that, unlike others, had a significantly
longer immunity to decoherence.
According to Dumitrescu, "there is a sophisticated development with this
quasi-periodic pattern, which balances out all the flaws that exist on the
edge." As a result, the edge maintains quantum-mechanical coherence for a
lot longer than you might anticipate.
Although the researchers succeeded in their goal, there is still one
obstacle to integrate their phase with the computational side of quantum
computing so that it can be entered with computations before it can be used
as a tool by quantum programmers.
Dumitrescu stated, "We have this direct, tantalizing application, but we
need to figure out how to plug it into the computations. That is an ongoing
issue that we are addressing.
