If only we could produce anti matter. A tiny amount would provide a fuel source viable for deep space exploration.
The problem is not production of it but the economy of producing it. It's still very costly to produce and then to build and engine around it which uses the energy efficiently is still at least 10-15 years. But do believe that the time to start actively looking into it is NOW.
You won't be able to store large amounts of it since quantum tunneling will become a statistical problem.
The probability of quantum tunneling is exponential so adding a little more separation or reducing the energy can change the probability from 10^-1 to 10^-100.
I found this overview, discussing a bit about the antimatter research:
http://www.enthea.org/docs/Forward-Emerging-Technologies-Fut...