Configuration interaction calculations of the controlled phase gate in double quantum dot qubits

TL;DR

This paper uses full configuration interaction calculations to analyze the capacitive coupling in double quantum dot qubits, revealing new operational points for entangling gates that balance coupling strength and stability.

Contribution

It demonstrates the importance of full CI over common approximations in understanding qubit coupling behavior in the (0,2) charge sector.

Findings

Multiple detuning points enable entangling gates.

Operating in the (0,2) regime offers advantageous trade-offs.

Full CI uncovers behaviors not seen with simpler models.

Abstract

We consider qubit coupling resulting from the capacitive coupling between two double quantum dot (DQD) single-triplet qubits. Calculations of the coupling when the two DQDs are detuned symmetrically or asymmetrically are performed using a full configuration interaction (CI). The full CI reveals behavior that is not observed by more commonly used approximations such as Heitler London or Hund Mulliken, particularly related to the operation of both DQDs in the (0,2) charge sector. We find that there are multiple points in detuning-space where a two-qubit entangling gate can be realized, and that trade-offs between coupling magnitude and sensitivity to fluctuations in detuning make a case for operating the gate in the (0,2) regime not commonly considered.