ur, from top to bottom, we easily obtain the definition of 1x): 4 + |00) (18.25) + [11)1: 000)34+|11)12011)34) Note the factor 1/2, which was introduced to ensure proper normalization of the resulting tensor state. The subsequent application of the CNOT gate C32 with qubit 3 as control, and qubit 2 as target finally yields: (18.26) + |0111) + |1100) + [1011))1234. It is seen from the above definition that 1x) is a 4-qubit entangled state, which cannot be expressed as any tensor product of the form |a); x |bcd) jkl or |ab)ij x |cd> kl, with any permutations of the indices i, j, k, l = 1, 2, 3, 4. It is a rather involved and tedious task to check that the circuit in Fig. 18.10, together with the communication to Bob of Alice's measured cbits n, m, n', m', actually results in the simultaneous teleportation of the two qubits /q'), lq). However, this represents an excellent test case to apply all that we have learnt in this chapter, and the previous ones as well, in terms of Pauli gates, tensor states, entangled states, measurements in the Bell-state basis and quantum teleportation. For this specific reason, the full details of the demonstration have been outlined in Appendix P. Going through this appendix, it is observed that the 6-qubit pre-measurement state, ), involves no less than 64 terms! But the twin measurement executed thereupon from Alice results in the instant collapse of |") into a single state of the form |nmn'm' 1256 x 10) 34. After hearing from Alice what the four cbits n, m, n', m' are, it is just a routine for Bob to set up his gate circuit according to the sequence X3 X3 Zm' Zm Zm, as indicated in Fig. 18.10. If the whole exercise shows that teleporting a number of qubits greater than one is possible, it certainly Qubit measurements, coding, and teleportation illustrates that the corresponding quantum circuits become increasingly complex as this number increases. Superdense quantum teleportation is about maximizing the information contents that can be communicated through a quantum channel, along wi