Active control of probability amplitudes in a mesoscale system via feedback-induced suppression of dissipation and noise

Abstract

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:

Quantum Tunneling Currents in a Nanoengineered Electrochemical System

“…For coherent polarization states, the uncertainty in the polarization state is given by , where the time dependence in eq occurs over the slower time scales associated with the ensemble-averaged parameters like γ. The rationale for assuming coherence in the polarization states presupposes a classical trajectory for the heavier nuclear modes under the influence of an external biasing field Figure A) that “contains” the polarization mode in eq .…”

“…The fluctuations in the bath field, when referred to the input of the biasing feedback network, describe the equivalent thermal noise source for the electrochemical system as demonstrated in Gupta et al where G (ω) is the frequency-dependent closed loop gain of the feedback. Equation presupposes an ideal noiseless feedback action applied on the physical interface by the accompanying electronics, which is modified by additional additive noise sources in the case there are added fluctuation sources from the feedback instrumentation . The gain also attenuates the damping forces acting on the reaction coordinate polarization density as where and Re­[ G (ω)] is the real part of G (ω).…”

“…Mismatch between the junction field effect transistor (JFET) devices and the biasing 33 Ω resistors introduces a <10 mV difference between V ref and V meas , which is accounted for during instrument calibration. Noise from the active components and resistances in the circuit contribute to the dissipative coupling of the redox state’s vibronic energies; however, these noise contributions can be minimized by design. The reference electrode itself should also have a small source resistance to minimize the dissipative coupling in the measurement of the redox state’s vibronic energies .…”

“…Noise from the active components and resistances in the circuit contribute to the dissipative coupling of the redox state’s vibronic energies; however, these noise contributions can be minimized by design. The reference electrode itself should also have a small source resistance to minimize the dissipative coupling in the measurement of the redox state’s vibronic energies . Similarly, the counter electrode that applies the corrective signal V x ′ should have minimal source impedance as well.…”

“…The influence of the accompanying electronics on the evolution of the transition event is described in this section, including the mitigation of the resulting disturbances that arise from a coupling with an external measurement system. In this context, the use of potentiostatic feedback for the application of a low voltage-noise excitation bias and for the measurement of the resulting current between the "source" and "drain" of a molecular-scale charge-transfer system has been characterized in Gupta et al 28 The source and drain in this context refer to the entities participating in the energy exchange interaction that accompanies the physical transition of the system from donor to acceptor state, with the energy flow occurring from source to drain. For the chargetransfer interface, the source and drain elements of the system are, interchangeably, the vibration-dressed electronic (vibronic) energy levels associated with the redox species and the vibrational modes of the participant reaction coordinates.…”