Charge qubit in a double dot
= Charge qubit in a double dot
{title2=$H=(\varepsilon\sigma_z+2t_c\sigma_x)/2$}
A single <electron> shared by two dots has a left/right charge basis. In that basis, a two-level model is $H=(\varepsilon\sigma_z+2t_c\sigma_x)/2$, where detuning sets the energy imbalance and tunnelling mixes the states. Electrical control and charge sensing are direct, but electric-potential fluctuations also couple strongly to the encoded information.