Along with applying blockchain technology in the health care service system (HSS), many distributed solutions have been proposed to solve the centralized, data island problems. Although blockchain-enabled HSS has significantly changed the traditional management mode of medical Big Data [e.g., electronic medical records (EMRs)], some new problems such as ledger corpulence, data searchable security, and quantum attack threat are exposed. In this article, we first introduce an efficient EMRs management model called on-chain ledger and off-chain storage (OLOS), in which the indexes of EMRs are uploaded on public blockchain and the real EMRs data are stored in native server. This model can relieve the public ledger and save the public cloud space. Meanwhile, it can protect data security by keeping off the direct operation on real EMRs data. Then, to protect the cross-institutional EMRs sharing security and improve the quantum-resist ability, we proposed a secure keyword-searchable attribute-based encryption (KS-ABE) scheme based on lattice cryptography. Moreover, the scheme can prove to be secure against adaptive chosen-keyword attack and adaptive chosen-policy attack in the random oracle model. Besides, comparison analysis and experimental results show that our KS-ABE scheme has fewer communication costs and smaller key sizes than similar literary works.

Electronic medical records (EMRs) are the most critical data in human health management. As in traditional centralized healthcare service systems (HSSs), user privacy security, EMRs data leakage, tampering, and island are some significant problems. However, blockchain is a promising technology to protect the privacy and realize cross-institutional data sharing for solving these problems. In this paper, a novel peer-to-peer EMRs data management and trading system called healthchain has been proposed based on consortium blockchain technology. Through this distributed system, the patient can access their EMRs in different institutions freely, and the EMRs can be traded among different users conveniently. Then, to balance EMRs data supply and demand, we establish a Stackelberg pricing model to evaluate EMRs data providers and consumers’ interactions. The optimal unit price and data amounts can be found by applying the backward induction method, and the maximizing benefits of the participants can be obtained by achieving the Nash equilibrium in the proposed game. Moreover, security analysis shows the healthchain can provide secure EMRs management and trading, and the simulation results show that the proposed pricing model can help the healthchain achieve social welfare maximization.

The circuit complexity of quantum qubit system evolution as a primitive problem in quantum computation has been discussed widely. We investigate this problem in terms of qudit system. Using the Riemannian geometry the optimal quantum circuits are equivalent to the geodetic evolutions in specially curved parametrization of SU(dn). And the quantum circuit complexity is explicitly dependent of controllable approximation error bound.

In this paper, our concern is to design some criteria for deterministic remote state preparation for preparing an arbitrary three-particle state via a genuinely entangled six-qubit state. First, we put forward two schemes in both the real and complex Hilbert space, respectively. Using an appropriate set of eight-qubit measurement basis, the remote three-qubit preparation is completed with unit success probability. Departing from previous research, our protocol has a salient feature in that the serviceable measurement basis only contains the initial coefficients and their conjugate values. By utilizing the permutation group, it is convenient to provide the permutation relationship between coefficients. Second, our ideas and methods can also be generalized to the situation of preparing an arbitrary N-particle state in complex case by taking advantage of Bell states as quantum resources. More importantly, criteria satisfied conditions for preparation with 100% success probability in complex Hilbert space is summarized. Third, the classical communication costs of our scheme are calculated to determine the classical recourses required. It is also worth mentioning that our protocol has higher efficiency and lower resource costs compared with the other papers.