High quality-factor excitonic quibit operation in quantum dots

Si Xiao

The Rabi oscillations of the exciton of the excited state in single semiconductor quantum dots were investigated by using the photoluminesence and nano-spectroscopy technique. The population on the excited state oscillated as a function of phase angle of the qubit were recorded, in which pulse-pairs with the adjustable time delay were used as the excitation. The quality factors of free rotation is about 9.8×104, and that of the dynamic rotation is about 18 for the single quantum dot excitonic qubit based on the experimental observations, The decoherece mechanism of Rabi oscillation stem from the capture processes from wetting layer to quantum dot is also analyzed. The exciton coherent control and the statistic characteristics of single photon emission in single semiconductor quantum dot are discussed as well.

T. Takagahara

T. Takagahara

Shruti Puri, Na Young Kim, Y. Yamamoto

We describe a design to implement a two-qubit geometric phase gate, by which a pair of electrons confined in adjacent quantum dots are entangled. The entanglement is a result of the Coulomb exchange interaction between the optically excited exciton polaritons and the localized spins. This optical coupling, resembling the electron-electron Ruderman-Kittel-Kasuya-Yosida interactions, offers high speed, high fidelity two-qubit gate operation with moderate cavity quality factor Q. The errors due to the finite lifetime of the polaritons can be minimized by optimizing the optical pulse parameters (duration and energy). The proposed design, using electrostatic quantum dots, maximizes entanglement and ensures scalability.

Qu‐Quan Wang, Andreas Müller, Pablo Bianucci +2 more

The quality factors of quantum bit (qubit) rotations in single self-assembled quantum dots were investigated using photoluminescence spectroscopy. Rotations with azimuthal angle ϕ along the equator of the qubit sphere were implemented by varying the time delay between two π∕2 pulses, resulting in a “free rotation” quality factor Q0=9.8×104. Qubit rotations with polar angle θ as large as 10π along the meridian of the qubit sphere (Rabi oscillations with zero detuning) were realized with a quality factor QR∼18, in experiments probing an excited excitonic state.

Alistair J. Brash, Feng Liu, A. M. Fox