Anti-butterfly effect enables new benchmarking of quantum-computer performance
Bin Yan, shown here, Nikolai Sinitsyn and Joseph Harris developed a new method that determines how much information is lost from a quantum system to decoherence and how much is preserved through information scrambling. Credit: Los Alamos National Laboratory

A method for benchmarking the performance of quantum computers has been established by research using the anti-butterfly effect.

Bin Yan, a quantum theorist at Los Alamos National Laboratory, said that they can determine the degree to which quantum computers can process information using a simple, robust protocol.

The paper on benchmarking information scrambling was written byYan. He said that the protocol quantifies information scrambling in a quantum system and distinguishes it from fake positives.

All quantum information in a quantum computer can be erased by noise in the form of decoherence. Information scrambling through quantum chaos protects it and allows it to be retrieved.

The loss of a quantum state as information leaks to the surrounding environment is called coherence.

"Our method, which draws on the quantum anti-butterfly effect we discovered two years ago, evolved a system forward and backward through time in a single loop, so we can apply it to any system with time-reversing dynamics."

Simulations on IBM cloud-based quantum computers were used to demonstrate the protocol.

Experiments into the phenomenon of decoherence have been hampered by the inability to distinguish between the two. Information scrambling is relevant in a wide range of research areas, including quantum machine learning and quantum computing. Superconductors, trapped ion and cloud-based quantum computers are some of the experimental platforms used to study information scrambling.

The anti-butterfly effect can be applied in a practical way.

The paper was published in 2020 and showed that quantum processes on a quantum computer can damage information from the past. The back-and-forth time loop is ruined by a classical- physics system.

The protocol was developed by Joseph Harris, a University of Edinburgh graduate student and co-author of the current paper. It prepares a quantum system and subsystem, evolves the full system forward in time, causes a change in a different subsystem, then evolution the system backwards for the same amount of time. The overlap of information shows how much information has been scrambled and how little has been lost.

More information: Joseph Harris et al, Benchmarking Information Scrambling, Physical Review Letters (2022). DOI: 10.1103/PhysRevLett.129.050602 Journal information: Physical Review Letters