Abstract
The on-demand preparation of higher-order Fock states is of fundamental importance in quantum information sciences. We propose and compare different protocols to generate higher-order Fock states in solid state quantum-dot--cavity systems. The protocols make use of a series of laser pulses to excite the quantum dot exciton and off-resonant pulses to control the detuning between dot and cavity. Our theoretical studies include dot and cavity loss processes as well as the pure-dephasing type coupling to longitudinal acoustic phonons in a numerically complete fashion. By going beyond the two-level approximation for quantum dots, we study the impact of a finite exchange splitting, the impact of a higher energetic exciton state, and an excitation with linearly polarized laser pulses leading to detrimental occupations of the biexciton state. We predict that under realistic conditions, a protocol which keeps the cavity at resonance with the quantum dot until the desired target state is reached is able to deliver fidelities to the Fock state $| 5\rangle$ well above $40\,\%$.
Highlights
Semiconductor quantum-dot–cavity (QDC) systems are widely discussed as candidates for highly integrable ondemand emitters of nonclassical states of light
The basic ingredients of this scheme are a series of π -pulse excitations and effective energy shifts induced by AC-Stark pulses that effectively interrupt the coupling between the quantum dots (QDs) and the cavity
That a protocol where the coupling is uninterrupted until the final target state is reached outperforms this standard scheme both in terms of duration and in terms of fidelity as long as it is justified to treat the system as a two-level system
Summary
Semiconductor quantum-dot–cavity (QDC) systems are widely discussed as candidates for highly integrable ondemand emitters of nonclassical states of light. While schemes to prepare higher-order Fock states have been known in atomic cavity systems for decades [24,25,26], these protocols rely on properties specific to atoms, such as the finite time of flight through a resonator, which cannot be translated straightforwardly to a locally fixed solid state qubit as encountered in quantum dots (QDs). This protocol has been applied to a superconducting qubit coupled to a microwave cavity [27]. We start our analysis with a simple twolevel QD-model and subsequently shift our focus to more complex situations by taking into account levels present in a QD that might have adverse effects on the preparation fidelity of higher-order Fock states
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