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2017/Nov Experimentally demonstrated quantum coherent dynamics of a tunable triple-dot-based hybrid qubit

Experimentally demonstrated quantum coherent dynamics of a tunable triple-dot-based hybrid qubit[TOP]

A new progress in semiconductor quantum dot hybrid qubit had been achieved by Key Laboratory of Quantum Information and Synergetic Innovation Center of Quantum Information & Quantum Physics of USTC. The jointed group of Professor GUO Guo-Ping and researchers from UCLA and University at Buffalo experimentally demonstrated quantum coherent dynamics of a tunable triple-dot-based hybrid qubit. The results was published on 29 December as 'Tunable Hybrid Qubit in a Triple Quantum Dot' (Physical Review Applied8, 064035 (2017)).
Developing the scalable semiconductor quantum chip that is compatible with modern semiconductor-technics is an important research area. However, in solid-state system, there are varies of dephasing mechanisms such as charge noise and nuclear spin. It is highly desired to get an encoding method which can both be manipulated fast and have long coherence.Hybrid qubit is one of the proposals to address this issue. In the early experiments, using the anharmonicity of quantum dot, Professor Guo's grouphad experimentally demonstrated a hybrid qubit with fast operation and long coherence time in a GaAs double quantum dot in 2016(Phys. Rev. Lett. 116, 086801 (2016)).
To further improve the tunability of hybrid qubit, taking the advantage of asymmetry andextending the double quantum dot toa linearly coupled triple quantum dot device, the researchers realized a controllable hybrid qubit with asymmetric tunnel couplings in the multi-electron region.Thetriple dot system could be conveniently initialized, controlled, measured electrically, and had good ratio Q ~ 29 between the coherence time and gate time. More importantly, the qubit evaluated between the left and middle dot, while the energy splitting of this hybrid qubit could be continuously adjusted in a wide range, from 2 to 15 GHz, by conveniently tuning the gate voltage of right dot.
Improving the tunability of electron energy levels in semiconductor quantum dot system is an important issue. The demonstration of the high tunability in a triple dot system could be potentially useful for future quantum control.The results could potentially lead to various applications, including a new encoding scheme that can be exploited on the triplet dot structure.
This work was supported by the Ministry of Science, the National Natural Science Foundation of China, Chinese Academy of Sciences and the Ministry of Education.

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