Construction of controlled-NOT gate based on microwave-activated phase (MAP) gate in two transmon system

Taewan Noh,Gwanyeol Park,Yonuk Chong,Woon Song,Soon-Gul Lee

doi:10.1038/s41598-018-31896-3

Abstract

We experimentally constructed an all-microwave scheme for the controlled-NOT (cNOT) gate between two superconducting transmon qubits in a three dimensional cavity. Our cNOT gate is based on the microwave-activated phase (MAP) gate, which requires an additional procedure to compensate the accumulated phases during the operation of the MAP gate. We applied Z-axis phase gates using microwave hyperbolic secant pulse on both qubits with adequate rotation angles systematically calibrated by separate measurements. We evaluated the gate performance of the constructed cNOT gate by performing two-qubit quantum process tomography (QPT). Finally, we present the experimental implementation of the Deutsch-Jozsa algorithm using the cNOT gate.

Highlights

During the last decades, superconducting qubits coupled to a microwave cavity has been the key building block for realizing a scalable quantum processor
We constructed the cNOT gate between two fixed-frequency transmon qubits embedded in a three dimensional microwave cavity
The cNOT gate is based on the microwave-activated phase (MAP) gate which is an all-microwave entangling gate scheme

Summary

Introduction

During the last decades, superconducting qubits coupled to a microwave cavity has been the key building block for realizing a scalable quantum processor. Remarkable improvements in qubit coherence, fidelity of qubit operation and microwave control[1,2,3,4,5,6], have enabled many demonstrations of quantum algorithms[7,8,9] in superconducting qubit systems. By studying the microwave-activated phase (MAP) gate[17] in more detail and constructing the controlled-NOT (cNOT) gate in a more efficient way, we hope that this study will be helpful for a realizing small-scale quantum processor in circuit QED system based on three dimensional microwave cavity. The cNOT gate consists of the MAP gate followed by the Z-axis phase gate on each qubit with systematically calibrated phases This combination for the realization of the cNOT has advantage over the previous refocusing scheme[16] in that the total gate time can be reduced and the coherence-time limited gate infidelity can be mitigated. We applied the cNOT gate to demonstrate the two-qubit version of the Deutsch-Josza algorithm

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Conclusion