New Quantum Phase Discovery Could Help Correct Quantum Computers' Errors

 

Quantum Computing Is Particularly Susceptible To Mistakes, Making Error Correction Essential. Image Credit: Zelenov IURII

Exotic states of matter emerge when known physics breaks down under severe cold, just as it occurs on extremely small scales. Despite the strangeness we've seen in these circumstances, theory has often been well ahead of practice. Quantum phases are states of matter that can be predicted long before they occur. Two groups independently revealed a previously unknown kind of quantum entanglement, both in the same issue of Science, decades after theoreticians anticipated its presence. The research was made feasible by breakthroughs in quantum information programming, and it could pave the way for more dependable and practical quantum computers.

Quantum computers have the potential to be significantly more powerful than ordinary computers, with the ability to solve search problems and execute cryptography millions of times quicker. Despite the fact that quantum computing advances is currently disclosed on a nearly weekly basis, fundamental issues remain. Quantum computing, in particular, is particularly prone to errors, necessitating error correction. Time-reversal symmetry, defined as functioning the same way if time flowed backward, is one technique to detect flaws.

Dr. Kevin Satzinger of Google Quantum AI led a team to create a two-dimensional lattice suitable for quantum error correction using Google's Sycamore quantum processor, which was said to be the first quantum device capable of outperforming the most powerful supercomputers in 2019.

The study of Satzinger and co-authors is based on quantum entanglement, which occurs when the physical properties of subatomic particles become so intertwined that they can't be described separately. Although Einstein famously rejected and criticized entanglement as one of the great shocks of twentieth-century physics, progressively complex entangled states have been developed, involving more particles or bigger distances.

Professor Stephen Bartlett of the University of Sydney defines the class of quantum phases known as "topologically organized" in a perspective following Satzinger's research. These, according to Bartlett, have "unchanged under constant local deformations" long-range entanglement between their components. Because topologically ordered phases are not vulnerable to local effects, they should be error-resistant. However, investigating the properties of topologically ordered phases has only been achievable in non-time-symmetric phases until recently.

Sycamore, according to Satzinger and co-authors, ran a quantum programme that was both error-proof and reversible, demonstrating that it is both reproducible and time-symmetric.

Dr. Giulia Semeghini of Harvard University presents a different way to a similar conclusion, using "optical tweezers" (lasers that prod atoms into position) to arrange 219 rubidium atoms in a two-dimensional lattice to create a quantum spin liquid, in the same edition. Five years ago, the first quantum spin liquid, a phase of matter within a magnetic substance with interacting quantum spins but no ordinary magnetic ordering, was generated, yet these exotic states of matter have resisted our efforts to investigate their properties. In a statement, Semeghin referred to the version she and her co-authors developed as "a fantasy in quantum computation."

Professor Mikhail Lukin, senior author, remarked, "You can truly touch, poke, and prod at this strange state and alter it to learn its features." "It's a brand-new condition of matter that no one has ever seen before."

"Neither experiment was achieved by using novel materials, as is normally the case," Bartlett says. Instead, quantum processors were used to achieve the goal virtually." These processors track how structure components entangle with parts that aren't next to them, resulting in topological order.

Despite the fact that the error correction in both tests fell well short of what is required for practical usage of quantum computers, Bartlett points out that each represents a significant step toward that goal.