|q⟩ Bad Qubits

← Question Bank

Multiple choice
Magic-state injection teleports a T gate onto ψ=a0+b1|\psi\rangle = a|0\rangle + b|1\rangle with the target Tψ=a0+beiπ/41T|\psi\rangle = a|0\rangle + b e^{i\pi/4}|1\rangle. Both measurement branches are corrected: outcome 0 needs no fix, and outcome 1 is repaired by applying the S=diag(1,i)S = \mathrm{diag}(1, i) gate. After correction, what is the gate fidelity F=Tψcorrected2F = |\langle T\psi | \text{corrected}\rangle|^2 of the worse of the two branches?