Focusing RKKY interaction by graphene P-N junction

The carrier-mediated RKKY interaction between local spins plays an important role for the application of magnetically doped graphene in spintronics and quantum computation. Previous studies largely concentrate on the influence of electronic states of uniform systems on the RKKY interaction. Here we reveal a very different way to manipulate the RKKY interaction by showing that the anomalous focusing - a well-known electron optics phenomenon in graphene P-N junctions - can be utilized to refocus the massless Dirac electrons emanating from one local spin to the other local spin. This gives rise to rich spatial interference patterns and symmetry-protected non-oscillatory RKKY interaction with a strongly enhanced magnitude. It may provide a new way to engineer the long-range spin-spin interaction in graphene.Comment: 9 pages, 4 figure

Proof-of-randomness protocol for blockchain consensus: the white paper version 1.0

A proof-of-randomness (PoR) protocol could be a fair and low energy-cost consensus mechanism for blockchains. Each network node of a blockchain could use a true random number generator (TRNG) and hash algorism to fulfil the PoR protocol. In this whitepaper, we give the consensus mechanism of the PoR protocol, and show how it could make the random numbers unforgeable. The PoR protocol could generate a blockchain without any competition of computing power or stake of cryptocurrency. Besides, we give some advantages of integrating quantum random number generator (QRNG) chips in hardware wallets, and also discuss the route to cooperate with quantum key distribution (QKD) technology.Comment: 7 pages, 1 figur