  Coherent coupling between a large number of qubits is the goal for scalable
approaches to solid state quantum information processing. Prototype systems can
be characterized by spectroscopic techniques. Here, we use pulsed-continuous
wave microwave spectroscopy to study the behavior of electrons trapped at
defects within the gate dielectric of a sol-gel-based high-k silicon MOSFET.
Disorder leads to a wide distribution in trap properties, allowing more than
1000 traps to be individually addressed in a single transistor within the
accessible frequency domain. Their dynamical behavior is explored by pulsing
the microwave excitation over a range of times comparable to the phase
coherence time and the lifetime of the electron in the trap. Trap occupancy is
limited to a single electron, which can be manipulated by resonant microwave
excitation and the resulting change in trap occupancy is detected by the change
in the channel current of the transistor. The trap behavior is described by a
classical damped driven simple harmonic oscillator model, with the phase
coherence, lifetime and coupling strength parameters derived from a continuous
wave (CW) measurement only. For pulse times shorter than the phase coherence
time, the energy exchange between traps, due to the coupling, strongly
modulates the observed drain current change. This effect could be exploited for
2-qubit gate operation. The very large number of resonances observed in this
system would allow a complex multi-qubit quantum mechanical circuit to be
realized by this mechanism using only a single transistor.
