rp1 = RegionPlot3D[j1, {Q1, 0, 1/2}, {Q2, 0, 1/3}, {Q3, 0, 1/4}];
rp2 = RegionPlot3D[j0 && MUB, {Q1, 0, 1/2}, {Q2, 0, 1/3}, {Q3, 0, 1/4}];
rp3 = RegionPlot3D[j0 && Choi, {Q1, 0, 1/2}, {Q2, 0, 1/3}, {Q3, 0, 1/4}];
coords = Cases[#, GraphicsComplex[x_, __] :> MaximalBy[x, Last, 1],
All][[1Median/@Transpose[x], 1]] &All][[1]]& /@ {rp1, rp2, rp3};
labels = {"PPT", "MUB", "CHOI"};
texts3d = Graphics3D[MapThread[Text, {labels, coords}], Axes -> True];
Show[rp1, rp2, rp3, texts3d,
AxesLabel -> {Subscript[Q, 1], Subscript[Q, 2], Subscript[Q, 3]}]