The core component of modern computers is the semiconductor chip (CPU) with full electronic control. Semiconductor quantum chip compatible with modern semiconductor technology is an important research direction of quantum computers. A research group led by Academician GUO Guangcan from Key Laboratory of Quantum Information and Synergetic Innovation Center of Quantum Information & Quantum Physics of USTC makes great progress in quantum computing based on solid quantum chip. Professor GUO Guoping and Professor XIAO Ming with collaborators realized the controlled-Not quantum logic gate in two-charge-qubit system of semiconductor quantum dot. Their research was published on 17 July on the Nature Communications with “Conditional rotation of two strongly coupled semiconductor charge qubits” as its title (Nature Communications 6, 7681(2015)).
The quantum chip group of Prof. GUO Guoping is always dedicated to the development of semiconductor quantum chip supported by the National Fundamental Research Program "solid-state quantum chip" project.
Ultrafast universal quantum control of a quantum-dot charge qubit was realized in 2013 (Nature Communications 4, 1401(2013)). Furthermore,related experiments are performed on multiple qubits. Strong two-qubit coupling and precise pulse-timing are two key advances to realize two-qubit manipulation. They preparedavariety of strong couplingelectricsemiconductorquantumdot structure, using standardsemiconductormicro- and nano-fabrication processes. The couplingstrengthbetweenthe twoqubits exceeds100 microelectronics-volts. Also, precise control of high frequencypulses with picosecond level is applied on quantum logic gate. And finally they accomplished the goal of two-charge-qubit controlled-Not logic gate with the shortest manipulation time less than 200 picoseconds.
The highest current level ofthe semiconductor two-qubitwas realized with electron spins.The new chargetwo-qubit system achieved a fidelity as high as the spin counterparts. Although the coherence time of charge qubit is two orders of magnitude shorter than spin quantum qubit, the operation speed of charge qubit logic gate is more than two orders of magnitude faster. On the other hand, charge qubit has the important advantages of all-electronic-manipulation method and compatibility to conventional semiconductor technology.
In the standard circuit model, arbitrary single-qubit rotations together with two-qubit controlled-NOT gate, provide a universal set of quantum logic gates. This work is a solid foundation for further development of semiconductor quantum computing.
Schematic of two-qubit controlled NOT gate
The work was supported by the Ministry of Science, the National Natural Science Foundation of China, Chinese Academy of Sciences and the Ministry of Education.
(LI Haiou, Quantum Information and Synergetic Innovation Center of Quantum Information & Quantum Physics)
