Tunable phonon-induced steady-state coherence in a double-quantum-dot charge qubit

Archak Purkayastha,Radim Filip,Giacomo Guarnieri,Mark T Mitchison,John Goold

doi:10.1038/s41534-020-0256-6

Archak Purkayastha, Radim Filip + Show 3 more

Open Access

https://doi.org/10.1038/s41534-020-0256-6

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Abstract

Charge qubits can be created and manipulated in solid-state double-quantum-dot (DQD) platforms. Typically, these systems are strongly affected by quantum noise stemming from coupling to substrate phonons. This is usually assumed to lead to decoherence towards steady states that are diagonal in the energy eigenbasis. In this article, we show, to the contrary, that due to the presence of phonons the equilibrium steady state of the DQD charge qubit spontaneously exhibits coherence in the energy eigenbasis with high purity. The magnitude and phase of the coherence can be controlled by tuning the Hamiltonian parameters of the qubit. The coherence is also robust to the presence of fermionic leads. In addition, we show that this steady-state coherence can be used to drive an auxiliary cavity mode coupled to the DQD.

Highlights

Preparation and coherent control of qubit states is at the heart of many quantum technologies[1]
We model the dynamical evolution of these platforms and focus on their steady-state properties
We find that the presence of phonons autonomously drives the DQD charge qubit to a steady state that has coherence in the energy eigenbasis while retaining a significant degree of purity

Summary

Introduction

Preparation and coherent control of qubit states is at the heart of many quantum technologies[1]. It is no surprise that a plethora of strategies to preserve coherence have been conceived, such as quantum error correction[5], dynamical decoupling[6] or feedback control[7] All of these schemes are to some degree an inevitable battle against decoherence. We find that the presence of phonons autonomously drives the DQD charge qubit to a steady state that has coherence in the energy eigenbasis while retaining a significant degree of purity. This surprising result finds its explanation in the particular structure of the system–bath interaction[17]. We show that the coherence is robust to the presence of fermionic leads

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