Phonon-induced decoherence for a quantum-dot spin qubit operated by Raman passage

Abstract

We study single-qubit gates performed via stimulated Raman adiabatic passage (STIRAP) on a spin qubit implemented in a quantum dot system in the presence of phonons. We analyze the interplay of various kinds of errors resulting from the carrier-phonon interaction (including also the effects of spin-orbit coupling) as well as from quantum jumps related to nonadiabaticity and calculate the fidelity as a function of the pulse parameters. We give quantitative estimates for an InAs/GaAs system and identify the parameter values for which the error is considerably minimized, even to values below 10 −4 per operation.

Phonon-Induced Pure Dephasing of Two-Electron Spin States in Vertical Quantum Dot Molecules

“…Material parameters used may be found in Ref. [1,7]. The pure dephasing rates corresponding to the two--phonon virtual transition as a function of temperature are shown in the left part of Fig.…”

“…The carrier-phonon interaction leads to pure dephasing of charge-state superpositions on picosecond timescales. One of the possible solutions to this problem is to use the electron spin degrees of freedom for information storage [1] or as the qubit itself [2][3][4]. Phonon influence on spin states is much weaker than on charge states due to the lack of a direct spin-phonon coupling (an interaction is mediated by the spin-orbit coupling which is weak in QDs and strongly dependent on the magnitude of the magnetic field).…”

Two-Photon Coherent Polarization Flipping of Confined Excitons

“…While the curves describing the two processes at the two-photon resonance (symmetric detuning) are the same, they become very different out of resonance. This additional freedom of control may be useful for optimizing experimental parameters against phonon--induced dephasing [11,12].…”

Phonon-Induced Dephasing of Optically Driven Exciton States in Quantum Dots: Spectral Interpretation

“…As discussed in detail in Refs. [8,10], one then arrives at closed formulae for the diagonal elements of the reduced density matrix, i.e., the occupations of exciton states…”