Slowing down when we get home would either require another magnetic brake, or use of a fuel launcher at earth. Internally fueled Fusion Rocket. A fusion powered rocket could cross interstellar distances, and is a near term enough technology to be considered likely for the mid 21st century. Possibly weighing hundreds to thousands of times as much as the rest of the ship. The following table gives a breakdown of the fuel to ship mass ratios given fusion rockets of various specific impulses.
Specific impulse is a standard way of measuring the performance of a rocket engine.
A specific impulse of 1,000,000 has long been a standard fusion engine performance number. Current designs might exceed 1,500,000, possibly more than 2,000,000. So we would need to assume that fusion engines are developed, and advanced quite a bit before we could use them. For example for a fusion rocket with a specific impulse of 1,000,000. The ship would need to carry 147 times its dry weight in fuel and reaction mass.