Two-qubit Entangling Gate for Superconducting Quantum Computers

Abstract

The success of quantum computation and quantum information processing is fundamentally reliant
on the existence of entangled states. Without such states, quantum computers would not be able to
surpass classical computers in terms of computational power. In this paper, we propose a scheme for
implementing a two-qubit entangling gate, known as the DB gate, using a system that combines two
capacitively coupled Josephson superconducting phase qubits. This gate is of particular importance,
as it belongs to the canonical family, compared to the CNOT gate, the DB gate has a shorter pulse
sequence, which is important for performing as many gate operations as possible before coherence
is lost, and has the potential to enable the efficient execution of various quantum algorithms on a
solid quantum processor. In using quantum process tomography to estimate the gate fidelity, we
demonstrate a process fidelity of 0.8821.

Keywords: Entangling Gates, Superconducting Qubits, DB Gate, SQUID, Josephson Junctions