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A variety of emerging applications in medical ultrasound rely on 3D volumetric imaging, calling for dense 2D transducer arrays with thousands of elements. Due to this high channel count, the traditional per-element cable interface used for 1D arrays is no longer viable. To address this issue, recent work has proven the viability of flip-chip bonding [1] or direct transducer integration [2]. This shifts the burden to a CMOS substrate, which must provide dense signal conditioning and processing before the massively parallel image data can be pushed off chip. A common approach for data reduction is to employ subarray beamforming (BF), which applies delay and sum operations within a group of pixels. To implement such functionality within the tight pixel pitch, prior works have implemented the delays using simple S/H circuits [2] or analog filters [3], and typically suffer from a combination of issues related to limited delay, coarse delay resolution and limited SNR.

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 three-terminal 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., 4 figures