In a groundbreaking advancement in quantum physics, researchers from the University of Science and Technology of China (USTC) have successfully maintained a Schrödinger-cat state—a quantum superposition of two opposite spin states—for over 20 minutes.

In a groundbreaking advancement in quantum physics, researchers from the University of Science and Technology of China (USTC) have successfully maintained a Schrödinger-cat state—a quantum superposition of two opposite spin states—for over 20 minutes. 

Schrödinger's cat is a famous thought experiment illustrating quantum superposition, where a system can exist in multiple states simultaneously until observed. In this study, the USTC team trapped ytterbium (^173Yb) atoms with a spin of 5/2 in an optical lattice. By precisely controlling laser pulses to induce nonlinear light shifts, they prepared a superposition state consisting of two spin projections, +5/2 and -5/2. This state, known as the Schrödinger-cat state, exhibited enhanced magnetic field sensitivity and resided within a decoherence-free subspace, making it immune to certain environmental interferences. 

The researchers achieved a coherence time exceeding 20 minutes, a significant improvement over previous experiments where such states lasted only seconds or milliseconds. This extended duration was made possible by cooling the ytterbium atoms to near absolute zero and trapping them with laser light, allowing precise control over their quantum states. 

This achievement has profound implications for quantum metrology, quantum information processing, and the exploration of new physics beyond the Standard Model. The long-lived Schrödinger-cat state enhances the sensitivity of quantum measurements and could lead to more stable quantum computers capable of performing complex calculations while resisting environmental interference. 

The study was published in Nature Photonics on November 16, 2024.