Charge-Qubit Operation of an Isolated Double Quantum Dot

We have investigated coherent time evolution of pseudomolecular states of an isolated (leadless) silicon double quantum dot, where operations are carried out via capacitively coupled elements. Manipulation is performed by short pulses applied to a nearby gate, and measurement is performed by a single-electron transistor. The electrical isolation of this qubit results in a significantly longer coherence time than previous reports for semiconductor charge qubits realized in artificial molecules.