Tunneling-noise-induced spin dephasing of two electrons in an arbitrarily detuned double quantum dot

Recent progress enables operations of a two-qubit gate for two electron spin qubits in a double quantum dot (DQD), which is an important step towards scalable semiconducting quantum computing. In an asymmetric DQD, it has been shown that 1/f charge-noise-induced tunneling noise can dominate spin decoherence under condition relevant in a two-qubit experiment. Here, we study spin decoherence due to 1/f charge noise for two electrons in a DQD with arbitrary detuning. We show that, in a symmetric DQD, charge-noise-induced tunneling noise can have a profound contribution compare to detuning noise, where the contribution of detuning noise is vanished due to the destructive interference while the contribution of tunneling noise remains finite. We study the spin decoherence for various detuning and tunneling and discuss its consequence on the figure of merit of a two-qubit gate.