Experimental quantum state compression from two identical qubits to a qutrit

In the realm of modern information technology, data compression technology occupies a pivotal position. With advancements in quantum information technology, the need to compress large-scale qubits ensembles has become urgent, aiming to reduce the demand on quantum storage resources. However, existing quantum state compression schemes generally face a limitation: the particles before and after compression must reside in the same dimensional space. In specific scenarios, compressing qubits into particles of higher dimensions not only enhances the efficiency of quantum state compression but also further reduces the usage of quantum storage resources. Here we experimentally demonstrated a quantum state compression between particles of different dimensions, successfully compressing two qubits into a single qutrit. The average fidelity of the resulting qutrit with the ideal quantum state is 0.8835. Our study may have potential applications in future quantum information, such as increasing quantum communication bandwidth and reducing storage resource consumption in quantum computing.