Time molecules with periodically driven interacting qubits

TL;DR

This paper numerically demonstrates the existence of time molecules in periodically driven interacting qubits, revealing stable, long-duration entangled states with potential for experimental observation in superconducting qubit arrays.

Contribution

It introduces the concept of time molecules in quantum systems, showing their formation via Floquet eigenstates and their stability under parameter variations.

Findings

Time molecules appear periodically with large duration compared to driving period.

Time molecules exhibit near-zero polarization and maximal entanglement entropy.

They are stable against detuning and system size increases.

Abstract

We provide numerical evidence for a temporal quantum-mechanical interference phenomenon: time molecules (TM). A variety of such stroboscopic states are observed in the dynamics of two interacting qubits subject to a periodic sequence of $\pi$-pulses with the period $T$. The TMs appear periodically in time and have a large duration, $\delta t_\mathrm{TM} \gg T$. All TMs demonstrate an almost zero value of the total polarization and a strong enhancement of the entanglement entropy $S$ up to the maximum value $S=\ln 2$ of a corresponding Bell state. The TMs are generated by the commensurability of the Floquet eigenvalues and the presence of maximally entangled Floquet eigenstates. The TMs remain stable with detuned system parameters and with an increased number of qubits. The TMs can be observed in microwave experiments with an array of superconducting qubits.