# Tunable quantum entanglement of three qubits in a non-stationary cavity

## TL;DR

This paper explores how the dynamical Lamb effect in a non-stationary cavity can be used to control and enhance quantum entanglement among three superconducting qubits, with practical methods for increasing entanglement levels.

## Contribution

It introduces a method to evaluate and control three-qubit entanglement via cavity boundary condition changes, providing a physical realization with superconducting qubits.

## Key findings

- Entanglement can be tuned by controlling cavity photon frequency.
- Probabilities of qubit excitation are calculated for the dynamical Lamb effect.
- A practical setup with superconducting qubits is proposed.

## Abstract

We investigate the tunable quantum entanglement and the probabilities of excitations in a system of three qubits in a non-stationary cavity due to the dynamical Lamb effect, caused by non-adiabatic fast change of the boundary conditions of the cavity. The transition amplitudes and the probabilities of excitation of qubits due to the dynamical Lamb effect have been evaluated. The conditional concurrence and the conditional residual tangle for each fixed amount of created photons are introduced and calculated as measures of the pairwise or three-way dynamical quantum entanglement of the qubits. We also give a prescription on how to increase the values of those quantities by controlling the frequency of the cavity photons. A physical realization of the system with three superconducting qubits, coupled to a coplanar waveguide entangled due to the non-adiabatic fast change of boundary conditions of the cavity is proposed.