Coherent control of tunnelling dynamics in functionalized semiconductor nanostructures: a quantum-control scenario based on stochastic unitary pulses

Abstract

The feasibility of achieving coherent control of tunnelling dynamics, associated with electronic excitations in functionalized semiconductor nanostructures, is investigated. The coherent control scenario is based on the application of frequent stochastic unitary pulses, affecting the interference phenomena between electronic wave-packet components and consequently the overall electronic tunnelling dynamics without collapsing the coherent quantum evolution of the system. It is shown that tunnelling can be inhibited and eventually halted by sufficiently frequent pulse fields that exchange energy with the system but do not affect the potential energy tunnelling barriers. Further, the proposed stochastic quantum-control scenario is demonstrated more generally as applied to an archetype model, a particle tunnelling in a quartic double-well potential.

Coherent Control of Quantum Dynamics with Sequences of Unitary Phase-Kick Pulses

“…Figure 1 (c) shows that the decay of the metastable initial state can be strongly suppressed by a sequence of sufficiently frequent 2 pulses, or otherwise accelerated by less frequent sequences, without changing the potential energy surface responsible for the evolution of quantum dynamics [6]. These results are consistent with several other studies of coherent control based on sequences of 2 pulses that were successfully applied to inhibit unwanted transitions [96,98,99,[4][5][6], accelerate decay into a continuum [95], control dynamics of orientation of molecules [100,101]. .…”

“…5 correspond to deterministic sequences of 2 pulses, similar coherent control over relaxation dynamics can be achieved with stochastic 2pulses, where is a random phase. The intervals between pulses can also be varied stochastically so long as the pulses are applied sufficiently frequently [5]. These results suggest the feasibility of applying currently available femtosecond laser technology to achieve coherent optical manipulation of electronic excitations in functionalized TiO 2 surfaces, under a wide range of experimental conditions.…”

“…with  = 1/2 2 and  = 1/2 5 . In the absence of an external perturbation, the initial non-stationary state  0 (x) =  1/4 exp[-(x-x 0 ) 2 /2] (with x 0 = -4) evolves in time, tunneling back and forth through the potential energy barrier.…”

“…As a result, a variety of coherent control methods based on sequences of ultrafast laser pulses have been proposed [41][42][43][44], including the suppression of quantum tunneling by affecting the relative phases of interfering dynamical pathways [4][5][6]. The ultimate goal of these developments has been to provide fundamental understanding on how to manipulate quantum mechanical interferences in order to control the dynamics of quantum systems ranging from single atoms and molecules to quantum reaction dynamics and processes in nanoscale devices, including control over quantum superpositions of macroscopically distinct states which can be realized in REGO▪SANTOS▪BATISTA COHERENT CONTROL OF QUANTUM DYNAMICS _____________________________________________________________________________________________ 5 Josephson junction based devices and nanomechanical resonators.…”

“…The development of practical methods for controlling quantum dynamics with electromagnetic fields has a long history and remains an outstanding challenge of great technological interest [1][2][3][4][5][6]. In this chapter we focus on coherent control scenarios based on sequences of unitary pulses that can significantly influence quantum dynamics (e.g., suppress tunneling) by changing the relative phases of interfering dynamical pathways, without necessarily changing the potential energy surfaces responsible for reaction dynamics in kinetic control [7,8], or collapsing the coherent unitary evolution of the system as in control schemes based on the quantum Zeno effect [9][10][11][12][13].…”