Electron spin relaxation due to charge noise

We study decoherence of an electron spin qubit in a quantum dot due to charge noise. We find that at the lowest order in spin-orbit interaction, the pure dephasing channel is suppressed for both 1/f charge noise and Johnson noise, so that charge noise leads to a pure relaxation channel of decoherence. Because of the weaker magnetic field dependence, the spin relaxation rate due to charge noise could dominate over phonon noise at low magnetic fields in a gate-defined GaAs or Si quantum dot or an InAs self-assembled quantum dot. Furthermore, in a large InAs self-assembled quantum dot, spin relaxation due to phonon noise could be suppressed in high magnetic fields due to the suppression of the coupling matrix element, so that the spin relaxation due to charge noise could dominate in both low and high magnetic fields. Numerically, in a 1 T magnetic field, the spin relaxation time due to typical charge noise is about 100 s in Si, 0.1 s in GaAs for a gate-defined quantum dot with a 1 meV confinement, and 10 μs (or 1 s) in InAs self-assembled quantum dot with a 4 meV (or 30 meV) confinement.