However, it makes no sense to assume being able to convert a planetary mass into energy without having increased control of technology and information and increased economy. It is like assuming a group of cavemen get the designs for a supersonic plane but only have the economy of their tribe of six to fund it. The assumptions would also be that they need to transport their rock caves and the woolly mammoths and buffalo herds that they hunt.
A civilization able to convert Jupiter into energy would have near the physical limits of computing and all other technologies. Getting towards the ultimate limits of computing with slow atomic ballistic cooled computronium. (theoretical 1 m/s coolant) flux 10 ** 26 bits/s cm**2. 100 trillion trillion operations per second in a sugar cube. Full blown diamondoid nanotechnology would be developed, which was recently had experiments funded.
Having a smaller sized cube for the faster than light system would also reduce the power requirements by one million to one billion times (instead of 1000 cubic meters).
The engineering of the casimir force and the control of virtual particles in the vacuum.
A recent antimatter powered rocket design by Robert Frisbee would still take nearly 40 years to travel the 4.3 light years to Earth's nearest neighbor, Alpha Centuri.
Frisbee presented a theoretical design for a ship using antimatter to propel its way to nearby stars. Frisbee's design calls for a long, needle-like spaceship with each component stacked in line to keep radiation from the engines from harming sensitive equipment or people.
At the rocket end, a large superconducting magnet would direct the stream of particles created by annihilating hydrogen and antihydrogen. A regular nozzle could not be used, even if made of exotic materials, because it could not withstand exposure to the high-energy particles, Frisbee said. A heavy shield would protect the rest of the ship from the radiation produced by the reaction.
A large radiator would be placed next in line to dissipate all the heat produced by the engine, followed by the storage compartments for the hydrogen and antihydrogen. Because antihydrogen would be annihilated if it touched the walls of any vessel, Frisbee's design stores the two components as ice at one degree above absolute zero.
The systems needed to run the spacecraft come after the propellant tanks, followed by the payload. In its entirety, the spaceship would resemble a large needle massing 80 million metric tons with another 40 million metric tons each of hydrogen and antihydrogen. In contrast, the Space Shuttle weighs in at a mere 2,000 metric tons.
Even for a civilization with mature antimatter propulsion technology. The lifespan of humans would have been drastically extended. 40 years on a space ship would be nothing to being who do not age and especially if it was artificial intelligences operating the computronium.
There is also better and faster space propulsion designs using beamed power. Photonic laser propulsion using laser arrays and mirrors to bounce the beam and economize on power.