# Tunable phonon induced steady state coherence in a double quantum dot

## TL;DR

This paper demonstrates that phonons can induce and control high-purity steady-state coherence in a double quantum dot charge qubit, challenging the usual decoherence assumption and enabling new quantum control methods.

## Contribution

It reveals that phonons can generate and tune steady-state coherence in DQD charge qubits, which is robust and can be used to manipulate auxiliary cavity modes.

## Key findings

- Phonons induce high-purity steady-state coherence in DQD charge qubits.
- The coherence magnitude and phase are tunable via Hamiltonian parameters.
- Steady-state coherence remains robust in the presence of fermionic leads.

## 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 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.