By aiming a Fibonacci laser beam at atoms within a quantum computer, scientists have created a brand-new, peculiar phase of matter that behaves as though it has two dimensions of time.
Researchers can now store information in a way that is significantly more error-protected, opening the door for quantum computers that can retain data for a very long time without becoming jumbled. The new phase of matter was created by rhythmically jiggling a strand of 10 ytterbium ions with lasers. The scientists detailed their results in an article that was released on July 20 in the journal Nature.
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, said 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 actually implemented in trials.
The goal of the scientists was not to develop a phase with a fictitious additional time dimension or to enhance quantum data storage. As opposed to this, they aimed to create a brand-new phase of matter that went beyond the usual solid, liquid, gas, and plasma phases.
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 calculations are based on bits, or 0s and 1s. Qubits, which can 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 process Albert Einstein named "spooky action at a distance"—is made possible by this peculiar behaviour, which is the secret to the power of quantum computing. Even if two or more qubits are separated by great distances, entanglement connects their properties so that any change in one will result in a change in the others. This allows quantum computers to carry out several 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 physicists 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 motions and interactions of the entire system—in the very structure, or topology, of the material's entangled states—rather than just encoding it across the singular, static positions of qubits. This results in a "topological" qubit, which is far less likely to lose its information because 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 preferred spots in space to occupy, 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 specific 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 time 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 preceded it (A, AB, ABA, ABAAB, ABAABABA, etc.).
This Fibonacci pulse produced a time symmetry that was organised 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 time symmetries are flattened into a single physical one while examining the Fibonacci pulse rhythm.
According to the researchers, the system "basically receives a bonus symmetry from an extra temporal dimension that does not exist. Even though it might be physically impossible in reality, the system looks to be a material 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 entire 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 evolution with this quasi-periodic pattern, which cancels 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 calculations before it can be used as a tool by quantum programmers.
Dumitrescu stated, "We have this direct, tantalising application, but we need to figure out how to plug it into the computations. That is an ongoing issue that we are addressing.
Reference: Nature
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