Abstract
AbstractWe implement resonant single qubit operations on a semiconductor hybrid qubit hosted in a three-electron Si/SiGe double quantum dot structure. By resonantly modulating the double dot energy detuning and employing electron tunnelling-based readout, we achieve fast (>100 MHz) Rabi oscillations and purely electrical manipulations of the three-electron spin states. We demonstrate universal single qubit gates using a Ramsey pulse sequence as well as microwave phase control, the latter of which shows control of an arbitrary rotation axis on the X–Y plane of the Bloch sphere. Quantum process tomography yields π rotation gate fidelities higher than 93 (96)% around the X (Z) axis of the Bloch sphere. We further show that the implementation of dynamic decoupling sequences on the hybrid qubit enables coherence times longer than 150 ns.
Highlights
A quantum dot hybrid qubit formed by three electrons in a double quantum dot was proposed,[16,17] and non-adiabatic pulsed-gate operation was implemented experimentally,[18] demonstrating simple and fast electrical manipulations of spin states with a promising ratio of coherence time to manipulation time
The two states in the right quantum dot that are separated by δE most likely correspond to two combinations of the z-valleys, which are weakly mixed by the step in potential at the quantum well interface.[32]
The improvement in overall fidelity of the alternating current (AC)-gated quantum dot hybrid qubit demonstrated here compared with DC-pulsed gating stems mainly from (1) elimination of the need to enter the regime in which the qubit is sensitive to charge noise by using resonant manipulation and tunnelling-based readout, and (2) reduced
Summary
Isolated spins in semiconductors provide a promising platform to explore quantum mechanical coherence and develop engineered quantum systems.[1,2,3,4,5,6,7,8,9,10,11,12,13] Silicon has attracted great interest as a host material for developing spin qubits because of its weak spin-orbit coupling and hyperfine interaction, and several architectures based on gate defined quantum dots have been proposed and demonstrated experimentally.[14,15] Recently, a quantum dot hybrid qubit formed by three electrons in a double quantum dot was proposed,[16,17] and non-adiabatic pulsed-gate operation was implemented experimentally,[18] demonstrating simple and fast electrical manipulations of spin states with a promising ratio of coherence time to manipulation time. The overall gate fidelity of the pulse-gated hybrid qubit is limited by relatively fast dephasing due to charge noise during one of the two required gate operations. We perform the first microwave-driven gate operations of a quantum dot hybrid qubit, avoiding entirely the regime in which it is most sensitive to charge noise. Resonant detuning modulation along with phase control of the microwaves enables a π rotation time of o 5 ns (50 ps) around X (Z) axis with high fidelities 493 (96)%. We further discuss a pathway to improve gate fidelity to above 99%, exceeding the threshold for surface code based quantum error correction.[23]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
