So let’s look at what is possible in experiments with antimatter today, leaving the speculation to aficionados of sci-fi and NASA. If you wanted to take antimatter to the offices of your national funding agency, you might consider taking some antiprotons, since most of the mass-energy of an antihydrogen atom is in the nucleus. This might be tempting, since our charged-particle traps are certainly deeper than those for neutral matter or antimatter. ATRAP and ALPHA initially capture antiprotons in traps with depths of a few kilo-electron-volts, corresponding to tens of millions of kelvin. But, density is an issue. A good charged-particle trap for cold positrons has a particle density of about 10[super]9[/super] cm[super]–3[/super]. Antiproton density is much smaller, but we’ll be optimistic and use this number. So to transport a milligram of antiprotons – of the order of 10[super]21[/super] particles – you would need a trap volume of 10[super]12[/super] cm[super]3[/super], or 10[super]6[/super] m[super]3[/super]. That means a cube 100 m wide, which will not fit in your luggage. Incidentally, a milligram of antimatter, annihilating on matter, would yield an energy equivalent to about 50 tonnes of TNT.
So, what about transporting some neutral antimatter? Neutral atom traps certainly have higher densities. The first BEC result for hydrogen at MIT reported a density in the order of 10[super]15[/super] cm[super]–3[/super] for about 10[super]9[/super] atoms in the condensate. This is better, but still far less than a milligram, even if you can get the atoms from a gas bottle. The size of the trap is now down to 10[super]5[/super] cm[super]3[/super], which is more manageable. Note, however, that the BEC transition in this experiment was at 50 μK – far below the 4.2 K that we hope to achieve with antihydrogen. Unfortunately, to get really cold and dense atomic hydrogen requires using evaporative cooling – throwing hot atoms away to cool the remaining ones in the trap. This implies damaging your lab before you send the surviving, trapped anti-atoms to their final, cataclysmic fate. And don’t forget that the total history of antiproton production here on Earth amounts to perhaps a few tens of nanograms in the past 25 years or so. Unfortunately, the antiproton production cross-section is unlikely to change.