L’Chaim! Yale Scientists Multiply Qubit’s Lifetime — And Validate ‘Foundation of Quantum Computing’

Insider Summary

• Yale researchers have substantially extended the lifetime of quantum bits using error correction.
• The team managed to double the lifetime of quantum information by making the qubits active for 1.8 milliseconds.
• According to the researchers, the experiment proves that quantum error correction works in practice.
• Image: Yale News

PRESS RELEASE — Researchers at Yale are using a process known as quantum error correction for the first time, substantially extending the lifetime of a quantum bit — a long-sought goal and one of the most difficult challenges in the field of quantum physics.

Led by Michel Devoret of Yale, the experiment proved — decades after its proposed theoretical foundation — that quantum error correction works in practice. Quantum error correction is a process designed to keep quantum information intact for a longer period of time than if the same information were stored in a hardware component without any correction.

The results are published in Nature.

Information in classical computing comes in the form of bits that correspond to ones or zeros. In quantum computing, information is stored in special devices with quantum properties known as quantum bits, or “qubits”. In Devoret’s lab, Frederick W. Beinecke Professor of Applied Physics, these qubits are built with superconducting circuits that are cooled to temperatures 100 times lower than those in outer space. Qubits can represent either one or zero, or — confusingly — both one And zero at once. This “quantum parallelism” is one of the properties that allows quantum computers to make calculations potentially many orders of magnitude faster than are possible on classical supercomputers, and changed many industries.

Quantum systems, however, are fragile. They are puzzled by the fundamental phenomenon of decoherence, a process in which information stored in qubits rapidly loses its quantum properties as a result of its interactions with its surroundings.

Quantum error correction, which was theoretically discovered in 1995, offers a means of combating this decoherence. Employing redundancy, it protects bits of quantum information by encoding them in a larger system than what would, in principle, be needed to represent a single qubit.

This larger system, however, makes ambient environmental effects more invasive and the encoded qubits more fragile. Because of this effect, and the complications of the additional components required to perform error correction, this process can never definitively extend the life of a quantum bit in practice. In fact, breaking even with an uncorrected qubit is a rare occurrence, the researchers said. Contrary to theoretical promises, in most experiments, error correction accelerates the decoherence of quantum information.

“For the first time, we have shown that making systems more redundant and actively detecting and correcting quantum errors confers an advantage in the robustness of quantum information,” said Devoret. “Our experiments show that quantum error correction is a real practical tool. This is more than just a proof-of-principle demonstration.”

The Devoret group has succeeded in doubling the quantum information age. Their error-corrected qubits live for 1.8 milliseconds — things happen fast in the quantum realm.

They achieved their result using an error-correcting code invented in 2001. “This gives you a sense of the delay between a theoretical proposal and its practical realization in our field,” says Devoret.

Volodymyr Sivak, lead author of the paper, said this performance was achieved in part by using machine learning agents that tweak the error correction process to improve results.

“None of the breakthroughs made this result possible,” said Sivak, a former Ph.D. student in Devoret’s lab and now a research scientist at Google. “It’s actually a combination of a large number of different technologies developed in the last few years, which we combined in this experiment.”

The practical success of quantum computing will depend on being able to generate very high quality quantum bits using quantum error correction. “Our experiment validates the foundational assumptions of quantum computing, and it makes me very excited about the future of this field,” said Sivak.

Other authors on the paper include Alec Eickbusch, Baptiste Royer, Shraddha Singh, Ioannis Tsioutsios, Suhas Ganjam, Alessandro Miano, Benjamin Brock, Andy Ding, Luigi Frunzio, Steven GirvinAnd Robert Schoolkopf.

Source: Yale News