  There has been considerable progress in electro-statically emptying, and
re-filling, quantum dots with individual electrons. Typically the quantum dot
is defined by electrostatic gates on a GaAs/AlGaAs modulation doped
heterostructure. We report the filling of such a quantum dot by a single
photo-electron, originating from an individual photon. The electrostatic dot
can be emptied and reset in a controlled fashion before the arrival of each
photon. The trapped photo-electron is detected by a point contact transistor
integrated adjacent to the electrostatic potential trap. Each stored
photo-electron causes a persistent negative step in the transistor channel
current. Such a controllable, benign, single photo-electron detector could
allow for information transfer between flying photon qubits and stored electron
qubits.
