Physics researchers created an "extra" dimension of time by exposing quantum computer qubits to quasi-rhythmic laser pulses based on the Fibonacci sequence.
A Fibonacci laser pulse fired at atoms inside a quantum computer has created a strange, two-dimensional phase of matter that does not obey normal laws of physics: it behaves as if having two dimensions of time.
Physicists have created a previously unknown phase of matter using a laser pulse sequence inspired by Fibonacci numbers. Physicists report in Nature on July 20, 2022. that the phase has two time dimensions despite only having one singular flow of time.
Comparatively to other quantum computer setups, this mind-bending property makes the information stored in the phase more error-resistant.
Its result makes quantum computing viable by extending information’s lifespan without affecting its quality, according to study lead author Philipp Dumitrescu.
Using an “extra” time dimension changes the way we think about phases of matter, says Dumitrescu, a research fellow at the Flatiron Institute.
“I’ve been working on these theory ideas for over five years, and seeing them come actually to be realized in experiments is exciting.”
Ajesh Kumar of the University of Texas at Austin and Andrew Potter of the University of British Columbia at Vancouver collaborated on the study’s theoretical component. Brian Neyenhuis led the team at Quantinuum in Broomfield, Colorado, that conducted the experiments on a quantum computer.
An element called ytterbium is the workhorse of the team’s quantum computer. Laser pulses can be used to manipulate or measure individual ions held by electric fields produced by an ion trap.
The atomic ions serve as quantum bits, which scientists call qubits. While conventional computers store information in bits (each representing a 0 or a 1), quantum computers store even more information using the strangeness of quantum mechanics.
A qubit can be either 0 or 1 in the same way Schrödinger’s cat can be both dead and alive. Because of that extra information density and the way qubits interact, quantum computers are capable of solving computational problems that conventional computers are unable to solve.
Interacting with a qubit has the same consequence as peeking into Schrödinger’s box: It seals the cat’s fate.
Even if it isn’t deliberate, the interaction can still occur. Dumitrescu says even if you keep the atoms under tight control, they can lose their quantumness by communicating with their environment, heating up, or interacting with things in unexpected ways.
“In practice, experimental devices have many sources of error that can degrade coherence after just a few laser pulses.”
Thus, making qubits more robust is the challenge. In order to achieve this, physicists can use symmetries, which are properties that are resistant to change. An example of rotational symmetry is a snowflake, which looks the same at 60 degrees.
One method involves blasting atoms with rhythmic laser pulses to add time symmetry. Aiming to make this approach more effective, Dumitrescu and his collaborators explored ways to make it more effective. By using ordered but not repeating laser pulses, they aimed to add two-time symmetry instead of just one.
An easy way to understand their approach would be to consider something else that is repeatable yet not well-ordered: quasicrystals. Most crystals are made up of regular, repeating shapes, such as hexagons in honeycombs.
Despite its order, a quasicrystal’s patterns never repeat.
This can be seen in Penrose tiling. A quasicrystal is a crystal from higher dimensions projected into a lower dimension.
These higher dimensions can extend beyond the three dimensions of physical space: Penrose tiles could be considered slices of five-dimensional lattices.
According to Dumitrescu, Vasseur, and Potter, qubits could be modeled as quasicrystals in time rather than space in 2018.
The researchers created a quasi-periodic laser pulsing regimen based on the Fibonacci sequence instead of alternating periodic pulses (A, B, A, B, A, B, etc.).
Every part of such a sequence is a combination of its two preceding parts (A, AB, ABA, ABAAB, ABAABABA, etc.).
Exactly like a quasicrystal, this arrangement is ordered without repetition. Similar to a quasicrystal, it’s a single-dimensional representation of a 2-dimensional pattern. As a consequence of the flattening of dimensions, the system is given two time symmetries instead of just one: the system is given another dimension of time that does not exist.
Nevertheless, quantum computers remain extremely complex experimental systems, so it is not yet known whether the benefits of the theory will hold true in actual qubits.
The experientialists tested the theory using Quantinuum’s quantum computer. Periodically and using Fibonacci sequences, laser light was pulsed at the computer’s qubits.
At either end of the 10-atom lineup, the new phase of matter was expected to experience two-time symmetries simultaneously.
Due to the strong interactions between the edge qubits, the edge qubits remained quantum for about 1.5 seconds in the periodic test.
As a result of the quasi-periodic pattern, the qubits remained quantum for about 5.5 seconds of the experiment. According to Dumitrescu, the extra time symmetry provided more protection.
In this quasi-periodic sequence, all the errors on the edge are canceled out by a complicated evolution.
“Because of that, the edge stays quantum-mechanically coherent much, much longer than you’d expect,” the researcher revealed.
It was found that the new phase of matter can store quantum information for a long time, but researchers still need to integrate it with quantum computing’s computational side.
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