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Quantum Oblivious Transfer: Difference between revisions
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→Computation phase
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===Computation phase=== | ===Computation phase=== | ||
The sender sends a random sequence of | The sender sends a random sequence of highly attenuated coherent pulses of the four canonical polarizations from the standard basis and the Hadamard basis. | ||
The receiver randomly decides for each pulse whether to measure it in the standard or the Hadamard basis, and records the basis and measurement | The receiver randomly decides for each pulse whether to measure it in the standard or the Hadamard basis, and records the basis and measurement results. The receiver then reports the arrival times of all pulses he received to the sender, but not the bases or the measurement results. | ||
The sender then | The sender then conveys to the receiver the bases measurement she used for each of the pulses received by the receiver. | ||
The receiver partitions his pulses into two sets: a “good” set consisting of pulses he received in the correct basis, and a “bad” set consisting of pulses he received in the | The receiver partitions his pulses into two sets: a “good” set consisting of pulses he received in the correct basis, and a “bad” set consisting of pulses he received in the incorrect basis. | ||
He tells the sender the addresses of the two sets without telling which is the good and which is the bad one. | He tells the sender the addresses of the two sets without telling which is the good and which is the bad one. | ||
Now, the receiver shares with the sender a word corresponding to his good set of measurements; he shares nothing with her with respect to his bad set of measurements. | Now, the receiver shares with the sender a word corresponding to his good set of measurements; he shares nothing with her with respect to his bad set of measurements. | ||
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Using the error-correcting code, sender computes the syndromes of the words corresponding to each set, and she sends them to the receiver over an error free channel. | Using the error-correcting code, sender computes the syndromes of the words corresponding to each set, and she sends them to the receiver over an error free channel. | ||
Given this data, the receiver | Given this data, the receiver is able to recover the original word corresponding to his good set but not that corresponding to his bad set. | ||
Furthermore, the sender computes the parity of a random subset of each set, and tells the receiver the addresses defining these random subsets, but not the resulting parities. | Furthermore, the sender computes the parity of a random subset of each set, and tells the receiver the addresses defining these random subsets, but not the resulting parities. | ||
At this point, the receiver knows one of these parities exactly, and nothing about the other parity, and he knows which parity he knows. | At this point, the receiver knows one of these parities exactly, and nothing about the other parity, and he knows which parity he knows. | ||