1
$\begingroup$

Sender (Alice) wants to exchange private encryption key with Bob using BB84 protocol. She generate a binary string (1010100010010111),and encode using Hadamard gate and identity gate (HHHIIHIHHIIIHIIH).

What is the quantum state she transmits to reciever (Bob)?

$\endgroup$
  • 1
    $\begingroup$ Does the Description section of en.wikipedia.org/wiki/BB84 answer your question? $\endgroup$ – Victory Omole Feb 28 at 16:46
  • 1
    $\begingroup$ Hi @ba. taj, this sounds like a homework problem. Can you talk about what you've tried so far? $\endgroup$ – Mohammad Athar Feb 28 at 17:30
4
$\begingroup$

Application of Hadamard gates changes states $|0\rangle$ and $|1\rangle$ followingly:

  • $\mathrm{H}|0\rangle = \frac{1}{\sqrt{2}}(|0\rangle + |1\rangle)$
  • $\mathrm{H}|1\rangle = \frac{1}{\sqrt{2}}(|0\rangle - |1\rangle)$

Identity operator does not change the state in any way, i.e. $\mathrm{I}|0\rangle = |0\rangle$ and $\mathrm{I}|1\rangle = |1\rangle$.

Hence if gates $\mathrm{HHHII}\dots$ are applied on input string of qubits $|10101\dots\rangle$, the result is state $|-+-01\dots\rangle$.

| improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.