Room‐Temperature Long‐Coherence Quintet Qudit for Quantum Information Processing in Organic Amorphous Solids

Abstract Organic high electron spin states, such as quintet state, can be used as multiple quantum bits for implementing quantum information. However, the practical quintet state via singlet fission is generally observed in strict conditions. Achieving long‐term quantum coherence of quintets at room temperature is still challenging. Here, quantum coherence in electron quintet states up to 505 ns at room temperature is observed, enabling quantum operations up to 54 times. Detailed investigations show that two Rabi oscillations from the multiple levels of the quintet are detectable at room temperature, with frequencies of 1.69 ± 0.01 and 1.39 ± 0.01 times of that of triplet states, respectively. More importantly, this quintet derived from singlet fission process can be realized via a simple co‐melting technology with amorphous form of 6,13‐bis(triisopropylsilylethynyl)pentacene dopped 1,3,5‐tri(1‐naphthyl)benzene (TIPS‐Pn:TNB). The organic TNB host with light elements is helpful for achieving long decoherence time. This study not only proves a simple method for preparing controllable quintet state at room temperature, but also emphasizes the opportunities of organic high electron spin states in quantum information science for working at low‐cost and friendly condition.