QIQT 2022: Breakthroughs in Quantum Cryptography Using Measurement Inputs 🔐

Dr. Ramij Rahaman, ISI

Title: Quantum cryptography based on measurement inputs

Abstract: Many quantum communication protocols have been proposed over the years and their security are mostly based on the fact that correlations used in the protocols have non-local- realistic feature. Checking violation of Bell-type inequalities are usually used to grantee the non-local-realistic nature of the correlations and the unrevealed local measurement outcomes authorize the integrity of the key for the scheme. But, this is only one possible way. Another option is to verify with some non-inequality type arguments for quantum non-locality e.g., Hardy’s argument, which uses a set of conditions impossible for classical systems, but satisfied by predictions for a unique quantum two-particle state. Here, we extend this idea and proposed tests for detecting genuine multipartite entanglement. If the dimensions of the local Hilbert spaces are all two then not only genuine, but a specific entangled state can pass our test for a given set of local observables pairs. This uniqueness feature of the correlation allow us to propose secure quantum protocols for various communication and information processing tasks such as quantum key distribution, quantum oblivious transfer, quantum digital signatures, quantum liar detection, etc. Also, in our schemes, the bits used for the protocols do not come from the results of the measurements on an entangled state but from the choices of settings unlike most of the existing quantum protocols based on Bell-type inequalities.