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One try | QC Explained

An “eigenvector-free” explanation to phase kickback

Circuit representation of CNOT: q0 as the control, and q1 as the target
On notation, q1 comes first followed by q0 (this notation will apply for the rest of the article)
Notice how the last step has a negative sign in front of the whole quantum state, this can be disregarded as a global phase. If you have no idea what that is, check the last section of this article out.
Notice how this is the exact same quantum state as before except there’s now a negative phase on |1 (q0) but as mentioned above this can be factored out to result in the same quantum state we started with.
Applying the CNOT on q1 has kicked the relative phase of q1 up to q0
An eigenstate of the unitary X gate

The easy part — Bernstein Vazirani algorithm

How may qubits though?

Don’t we need to know the answer to make the oracle? Feel like cheating…

Full circuit diagram of our circuit that solves for 1010





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Pavan Jayasinha

Pavan Jayasinha | Invested in QC + ML | Intern @IQC | EECS @UWaterloo | Seeker of rigorous truth

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