Quantum Key Distribution - Counterfactual Quantum Key Distribution

Counterfactual Quantum Key Distribution

The task of distributing a secret key could be achieved even when the particle (on which the secret information, e.g. polarization, has been encoded) does not traverse through the quantum channel. A protocol developed by Tae-Gon Noh. Here Alice generates a photon which randomly takes either path (a) or path (b). Path (a) stays inside Alice's secure device and path (b) goes to Bob. By rejecting the photons that Bob receives and only accepting the ones he doesn't receive, Bob & Alice can set up a secure channel, i.e. Eve's attempts to read the counterfactual photons would still be detected. This protocol uses the quantum phenomenon whereby the possibility that a photon can be sent has an effect even when it isn't sent. So-called Interaction-free measurement also uses this quantum effect, as for example in the bomb testing problem, whereby you can determine which bombs are not duds without setting them off, except in a counterfactual sense.

Read more about this topic:  Quantum Key Distribution

Famous quotes containing the words quantum, key and/or distribution:

    A personality is an indefinite quantum of traits which is subject to constant flux, change, and growth from the birth of the individual in the world to his death. A character, on the other hand, is a fixed and definite quantum of traits which, though it may be interpreted with slight differences from age to age and actor to actor, is nevertheless in its essentials forever fixed.
    Hubert C. Heffner (1901–1985)

    You have many choices. You can choose forgiveness over revenge, joy over despair. You can choose action over apathy.... You hold the key to how well you make the emotional adjustment to your divorce and consequently how well your children will adapt.
    Stephanie Marston (20th century)

    The question for the country now is how to secure a more equal distribution of property among the people. There can be no republican institutions with vast masses of property permanently in a few hands, and large masses of voters without property.... Let no man get by inheritance, or by will, more than will produce at four per cent interest an income ... of fifteen thousand dollars] per year, or an estate of five hundred thousand dollars.
    Rutherford Birchard Hayes (1822–1893)