Non-Markovian dynamics of double quantum dot charge qubits due to acoustic phonons

TL;DR

This paper studies how acoustic phonons cause non-Markovian behavior in double quantum dot charge qubits, revealing that phonon-induced decoherence is less significant than previously thought, with implications for quantum computing.

Contribution

It provides a numerically exact analysis of phonon effects on charge qubit dynamics, avoiding common approximations and offering detailed dependence on system parameters.

Findings

Q-factor is two orders of magnitude larger than experimental measurements.

Phonon-induced decoherence is a subordinate mechanism.

Non-Markovian effects are significant at low temperatures.

Abstract

We investigate the dynamics of a double quantum dot charge qubit which is coupled to piezoelectric acoustic phonons, appropriate for GaAs heterostructures. At low temperatures, the phonon bath induces a non-Markovian dynamical behavior of the oscillations between the two charge states of the double quantum dot. Upon applying the numerically exact quasiadiabatic propagator path-integral scheme, the reduced density matrix of the charge qubit is calculated, thereby avoiding the Born-Markov approximation. This allows a systematic study of the dependence of the Q-factor on the lattice temperature, on the size of the quantum dots, as well as on the interdot coupling. We calculate the Q-factor for a recently realized experimental setup and find that it is two orders of magnitudes larger than the measured value, indicating that the decoherence due to phonons is a subordinate mechanism.