We present results for the binding energies for He and ^3He nuclei calculated
in quenched lattice QCD at the lattice spacing of a = 0.128 fm with a heavy
quark mass corresponding to m_pi = 0.8 GeV. Enormous computational cost for the
nucleus correlation functions is reduced by avoiding redundancy of equivalent
contractions stemming from permutation symmetry of protons or neutrons in the
nucleus and various other symmetries. To distinguish a bound state from an
attractive scattering state, we investigate the volume dependence of the energy
difference between the nucleus and the free multi-nucleon states by changing
the spatial extent of the lattice from 3.1 fm to 12.3 fm. A finite energy
difference left in the infinite spatial volume limit leads to the conclusion
that the measured ground states are bounded. It is also encouraging that the
measured binding energies and the experimental ones show the same order of
magnitude.Comment: 4 pages, 3 figure
