Figure 2

Implementations of \(\left| {GHZ_{3} } \right\rangle\) and \(\left| {GHZ_{4} } \right\rangle\): (a) original version of \(\left| {GHZ_{3} } \right\rangle\) in terms of one H and two CNOT gates, (b) \(\left| {GHZ_{3} } \right\rangle\) thanks to one QFT₂¹_×2¹ and four flipped QFT₂²_×2², (c) \(\left| {GHZ_{3} } \right\rangle\) based on one QFT₂¹_×2¹ and two flipped QFT₂³_×2³, (d) original version of \(\left| {GHZ_{4} } \right\rangle\) in terms of one H and three CNOT gates, (e) \(\left| {GHZ_{4} } \right\rangle\) thanks to one QFT₂¹_×2¹ and six flipped QFT₂²_×2², (f) \(\left| {GHZ_{4} } \right\rangle\) based on one QFT₂¹_×2¹ and two flipped QFT₂⁴_×2⁴.