We introduce a classical potentiostatic feedback mechanism that attenuates the dissipation in a quantum system arising from coupling to the surrounding thermodynamic bath, preserving the inter-state interference in an electronic excitation transfer (EET) process. A threeterminal potentiostat device applies a low-noise voltage bias to the terminals of the EET system and reduces the physical coupling between the quantum system and its environment. We introduce a classical equivalent circuit to model the environment-coupled excitation transfer in an elementary two-state system. This model provides qualitative insight into how classical feedback action affects the transition probabilities between the states and selectively reduces the dissipative coupling for one of the vibronic energy levels of the transfer system. Furthermore, we show that negative feedback results in persistent spectral coherence between the energy level of the decoupled state and the vibronic levels of the complementary state, making the decoupled vibronic channel a probe for characterizing the vibronic structure of the complementary channel of the EET system. DOI:PACS numbers:

We propose an architecture for the control system of BETTII, 1 a far-infrared, balloon-borne interferometer with a baseline of 8 meters. This system involves multiple synchronized control loops for real-time pointing control and precise attitude knowledge. This will enable accurate phase estimation and control, a necessity for successful interferometry. We present the overall control strategy and describe our flight hardware in detail. We also show our current test setup and the first results of our coarse pointing loop.

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