The only way I know of to insta kill anyone in Quantum Armor is sadly a nuke related. Make a big, about 200 nukes high column and place redwire in a way so that every nuke will be activated at the same time at the flick of a switch. Then, activate them all and start counting. Right when they're about to explode, try starting to jump for better results. Also, be sure to be placed right over them. After the explosion, you'll have to wait a minute or two until your comp finishes processing all the explosions (Mine didn't, but it might crash some computers). Then, when the game resumes, you'll be about 30 kilometers high (I will mention that the nukes weren't even close to killing me) and falling. While you're becoming a living meteorite, you should have the time to read a few pages of a book. Then, the contact with the ground should kill you, sprawling the items of your inventory dozen of meters away in all directions. Congratulations! You managed to die in a quantum suit!
P.S. This is all experimental data. ;D