Fast entanglement of two charge-phase qubits through nonadiabatic coupling to a large junction

TL;DR

This paper presents a fast, efficient protocol for entangling two charge-phase qubits via a large junction acting as a quantum data bus, without requiring adiabatic conditions, enabling broader operational regimes.

Contribution

It introduces a nonadiabatic coupling protocol for entangling Josephson charge-phase qubits through a large junction acting as a harmonic oscillator mode.

Findings

Protocol enables rapid entanglement of qubits.

Does not require adiabatic evolution of the data bus.

Operates effectively over a wide parameter range.

Abstract

We propose a theoretical protocol for quantum logic gates between two Josephson junction charge-phase qubits through the control of their coupling to a large junction. In the low excitation limit of the large junction when $E_{J}\gg E_{c}$, it behaves effectively as a quantum data-bus mode of a harmonic oscillator. Our protocol is efficient and fast. In addition, it does not require the data-bus to stay adiabatically in its ground state, as such it can be implemented over a wide parameter regime independent of the data-bus quantum state.