Thermal spin writing in a quantum-dot qubit via spin accumulation

We theoretically propose a device scheme for a quantum-dot qubit written by a temperature gradient. The device consists of a Si-based quantum dot (QD) weakly coupled to two nonmagnetic reservoirs, with spin accumulation established in each reservoir via ferromagnetic tunnel contacts. A thermal bias ΔT across the two reservoirs broadens the Fermi distributions asymmetrically, allowing non-target-spin electrons in the hotter reservoir to escape, which traps the opposite spin in the QD. For antiparallel spin accumulations, the sign of ΔT writes either a spin-up or a spin-down state into the QD, while tuning ΔT to a compensating value erases it—all by purely thermal means. With realistic parameters, error rates below 0.01 are achievable at liquid-helium temperature. These results show that thermal effects, often viewed as detrimental to spin qubits, can be harnessed for both deterministic writing and erasure of spin states.