  We report charge detection studies of a lateral double quantum dot with
controllable charge states and tunable tunnel coupling. Using an integrated
electrometer, we characterize the equilibrium state of a single electron
trapped in the doubled-dot (artificial H2+ molecule) by measuring the average
occupation of one dot. We present a model where the electrostatic coupling
between the molecule and the sensor is taken into account explicitly. From the
measurements, we extract the temperature of the isolated electron and the
tunnel coupling energy. It is found that this coupling can be tuned between 0
and 60 micro electron-volt in our device.
