New Protocol Inverts the Evolution of a Qubit

Technique could one day lead to more accurate quantum computers

Researchers at the Institute for Quantum Optics and Quantum Information (IQOQI) in Vienna have developed a universal mechanism to invert the evolution of a qubit in an uncontrolled setting. This protocol is based on a previous technique published by the same group in 2020, but the latest version is thought to increase accuracy to a “high probability” or success.

"Our newly developed protocol inverts the unitary evolution of a qubit," David Trillo, one of the researchers who carried out the study together with Benjamin Dive and Miguel Navascués, told "A qubit (or quantum bit) is a two-level quantum system that serves as the quantum equivalent of bits used in quantum computers. Any quantum system has some natural evolution in time that needs to be controlled or at least accounted for when designing physical processes around them (e.g., when building a quantum computer). Our protocol takes a qubit and outputs the same system, but in the state that it would be in if it had evolved backwards in time."

According to the article at, other protocols exist for rewinding a qubit exist for controlled settings, but the new universal protocol developed at IQOQI can work in an uncontrolled setting and with a high probability of success.