Fig. 5: Measurement setting for two-qubit states. | Nature Communications

Fig. 5: Measurement setting for two-qubit states.

From: Device-independent quantum key distribution with random key basis

Fig. 5

Alice has two projective measurement that are described by projectors \(({{{\Pi }}}_{0}^{{A}_{0}},{{{\Pi }}}_{1}^{{A}_{0}})\) and \(({{{\Pi }}}_{0}^{{A}_{1}},{{{\Pi }}}_{1}^{{A}_{1}})\) with relative angle φ. Bob has in total four measurements: for key generation, ideally he should perform measurements B0 and B1 which are aligned with Alice’s measurements A0 and A1 to minimise the quantum bit error rates. The security analysis only depends on Bob’s measurements B2 and B3, which are w.l.o.g. specified by a relative angle ω.

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