# Quantum based lottery using W-State and spatial separation

I'm thinking of a use case of building a quantum based lottery. Using a W-state with spatial separation (see this question) the circuit is build at one location and afterwards the n qubits are distributed to n locations. Once one qubit is measured the winner (qubit with value 1) should be fixed. At each location it can be measured independently if the qubit at this location is the winner.

Questions:

• Are my considerations correct?
• How far are we from such feasibility?
• What does it need at each location?
• Working initially with the three-qubit state $\vert W_3\rangle$, and calling the qubits Alice, Bob, and Charlie, if Alice measures $\vert 1\rangle$ in your scheme how do you envision each of Bob and Charlie to agree that she was the one who won the lottery? The $\vert W_n\rangle$ state is highly entangled; seeing as quantum computers nowadays have a couple dozen qubits in total, all within the same chip, I don't imagine you getting much more than a such a lottery of more than a handful of players anytime soon. May 31, 2021 at 15:49
• If Alice measures $\vert 1 \rangle$, Bob and Charlie have to measure $\vert 0 \rangle$ and they "have to trust" that only one qubit can measure $\vert 1 \rangle$. I'm thinking of a consensus protocol.
– TimW
May 31, 2021 at 16:02