Editing Quantum Weak Coin Flipping (section)

==Protocol Description==

[https://arxiv.org/abs/quant-ph/0202118 The QWCF protocol by Spekkens and Rudolph] consists of the following steps:
# Alice and Bob agree on two orthogonal single-qubit states, ψ(0) and ψ(1), that have equal probability distribution in the computational basis, and an angle θ between them, which determines the bias of the protocol. For simplicity, we assume that they choose ψ(0)=cos(θ/2)∣0⟩+sin(θ/2)∣1⟩ and ψ(1)=sin(θ/2)∣0⟩−cos(θ/2)∣1⟩, where θ∈[0,π/2].
# Alice and Bob each choose a secret bit, a,b∈{0,1}, that represents their preferred outcome, and a random bit, x,y∈{0,1}, that is used to encode their qubits. They keep their bits secret from the other party.
# Alice and Bob each send two qubits to the other party, one in the state ψ(x) and the other in the state ψ(x⊕a), and a classical bit, z=x⊕a and w=y⊕b, respectively.
# Alice and Bob each return one of the qubits they received from the other party, depending on the value of the classical bit they received. If the classical bit is 0, they return the first qubit; if the classical bit is 1, they return the second qubit.
# Alice and Bob each measure the qubit they kept from the other party in the basis {ψ(0),ψ(1)}, and the qubit they returned to the other party in the same basis. If any of the measurements fails, they abort the protocol. They obtain the results m,n∈{0,1} for the qubits they kept, and m′,n′∈{0,1} for the qubits they returned, respectively.
# Alice and Bob each announce their secret bit, a and b, and their measurement result, m and n, respectively. The outcome of the coin flip is c=a⊕m=b⊕n.