Harmonic mixing in two coupled qubits: quantum synchronization via ac drives

TL;DR

This paper demonstrates quantum synchronization in two coupled qubits driven by ac signals, showing control over state probabilities and coherence, with potential implications for quantum information processing.

Contribution

It reveals a novel quantum synchronization mechanism via harmonic mixing in coupled qubits driven by bi-harmonic signals, distinct from classical nonlinear mixing.

Findings

Control of qubit state probabilities via ac drive

Enhancement of quantum coherence through bi-harmonic signals

Quantum synchronization arising from multiplicative coupling

Abstract

Simulating a system of two driven coupled qubits, we show that the time-averaged probability to find one driven qubit in its ground or excited state can be controlled by an ac drive in the second qubit. Moreover, off-diagonal elements of the density matrix responsible for quantum coherence can also be controlled via driving the second qubit, i.e., quantum coherence can be enhanced by appropriate choice of the bi-harmonic signal. Such a dynamic synchronization of two differently driven qubits has an analogy with harmonic mixing of Brownian particles forced by two signals through a substrate. Nevertheless, the quantum synchronization in two qubits occurs due to multiplicative coupling of signals in the qubits rather than via a nonlinear harmonic mixing for a classical nano-particle.