Demonstration of universal time-reversal for quantum processes

• DOI: 10.48550/arxiv.2205.01122
• Publication Date: 2023-01-26
• Authors: Schiansky, Peter; Strömberg, Teodor; Trillo, David; Saggio, Valeria; Dive, Benjamin; Navascués, Miguel; Walther, Philip
• Keywords: 103026 Quantum optics; Quantum Physics; 103025 Quantenmechanik; 103026 Quantenoptik; 103025 Quantum mechanics; FOS: Physical sciences; Quantum Physics (quant-ph); Atomic and Molecular Physics, and Optics; Electronic, Optical and Magnetic Materials

In quantum mechanics, the unitary nature of time evolution makes it intrinsically reversible, given control over the system in question. Remarkably, there have been several recent demonstrations of protocols for reverting unknown unitaries in scenarios where even the interactions with the target system are unknown. These protocols are limited by their probabilistic nature, raising the fundamental question of whether time-reversal could be performed deterministically. Here we show that quantum physics indeed allows for this by exploiting the non-commuting nature of quantum operators, and demonstrate a recursive protocol for two-level quantum systems with an arbitrarily high probability of success. Using a photonic platform, we achieve an average rewinding fidelity of over 95%. Our protocol, requiring no knowledge of the quantum process to be rewound, is optimal in its running time, and brings quantum rewinding into a regime of practical relevance.