The relaxation time of a single-electron spin is an important parameter for solid-state spin qubits, as it directly limits the lifetime of the encoded information. Thanks to the low spin-orbit interaction and low hyperfine coupling, graphene and bilayer graphene (BLG) have long been considered promising platforms for spin qubits. Only recently, it has become possible to control single-electrons in BLG quantum dots (QDs) and to understand their spin-valley texture, while the relaxation dynamics have remained mostly unexplored. Here, we report spin relaxation times (T₁) of single-electron states in BLG QDs. Using pulsed-gate spectroscopy, we extract relaxation times exceeding 200 μs at a magnetic field of 1.9 T. The T₁ values show a strong dependence on the spin splitting, promising even longer T₁ at lower magnetic fields, where our measurements are limited by the signal-to-noise ratio. The relaxation times are more than two orders of magnitude larger than those previously reported for carbon-based QDs, suggesting that graphene is a potentially promising host material for scalable spin qubits.

单电子自旋的弛豫时间是固态自旋量子比特的一个重要参数，因为它直接限制了编码信息的寿命。由于低自旋轨道相互作用和低超精细耦合，石墨烯和双层石墨烯（BLG）长期以来一直被认为是自旋量子比特的有前途的平台。直到最近，才有可能控制 BLG 量子点 (QD) 中的单电子并了解它们的自旋谷纹理，而弛豫动力学大部分仍未被探索。在这里，我们报告了 BLG 量子点中单电子态的自旋弛豫时间 ( T _{1 )。}使用脉冲门光谱，我们在 1.9 T 的磁场中提取了超过 200 μs 的弛豫时间。T ₁值显示出对自旋分裂的强烈依赖性，在较低的磁场中承诺更长的T ₁，我们的测量受到信噪比的限制。弛豫时间比之前报道的碳基量子点的弛豫时间大两个数量级以上，这表明石墨烯是一种潜在的可扩展自旋量子比特的主体材料。