New phase transitions in quantum circuits with many symmetries
February 4, 2025 - Cole Kelson-Packer and Akimasa Miyake
Entanglement is one of the keys to quantum computing’s unique powers. It is a distinctly quantum phenomenon that disappears when measurements convert information to the bits of ordinary computers. In the future, quantum computers will carry out entanglement-degrading measurements not only at the termination of their operations, but also during them for a variety of purposes. Disturbances from the environment similarly reduce this essential quantum property. Recent discoveries have shown that entanglement dramatically transforms from existing in abundance to repletion depending on measurement and noise rates, like how ice changes phase and melts into water as the temperature increases. Better understanding of this surprising phenomena yields valuable insights into the role of this precarious resource in quantum
computational tasks.
Kelson-Packer and Miyake’s work combines this theme with models of computation employing quantum resources with special symmetries. Such resources have special entanglement structures intrinsically tied to their ability to carry out computational tasks. The authors have found that matching quantum circuits to such symmetries changes the essential nature of the entanglement phase transition, greatly diminishing the “phase of matter” with excess quantum entanglement. They have also observed a novel third “phase,” featuring symmetries associated with useful quantum resources. This publication sheds light on the mysterious interplay of quantum symmetries and entanglement, which
are sometimes at odds inhibiting–and yet other times cooperate facilitating–the power of quantum computers.
Read the paper here: https://doi.org/10.1103/PhysRevB.111.075109
