|q⟩
Bad Qubits
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A two-qubit state is
(
1
/
10
)
(
∣
00
⟩
+
2
∣
01
⟩
+
2
∣
10
⟩
+
∣
11
⟩
)
(1/\sqrt{10})(|00\rangle + 2|01\rangle + 2|10\rangle + |11\rangle)
(
1/
10
)
(
∣00
⟩
+
2∣01
⟩
+
2∣10
⟩
+
∣11
⟩)
, with amplitudes labeled
c
q
0
q
1
c_{q0 q1}
c
q
0
q
1
. Qubit 0 is measured and gives 0. In the collapsed (renormalized) state, what is the probability that qubit 1 = 1?
1/5 = 0.2
4/5 = 0.8
1/2 = 0.5
2/5 = 0.4 (not renormalizing)
Check answer