Research On Secure Delegated Quantum Computation Protocols And Verifiability

Quantum computer is a new type of computing device that follows the basic principles of quantum mechanics.It uses microscopic quantum states as information carriers,and uses the unitary evolution of quantum states as logical operations.Relying on the superposition principle of quantum mechanics,quantum computers have inherent parallel processing capabilities,so they are considered to be far more computing power than classical computers.Since the concept of quantum computing was proposed,quantum computing theory has developed rapidly.Many physical implementation schemes of quantum computers have been proposed one after another,such as superconductor,ion trap,linear optical,and so on.Although it is generally believed that it is still far from the advent of universal quantum computers,the current quantum computers have shown great advantages over classical computers in many application fields,such as machine learning and combinatorial optimization.However,even so,it is impractical to achieve a large-scale deployment of quantum computers in a short period of time.This is mainly because that building a quantum computer is an extremely difficult engineering challenge,and the cost of maintaining a quantum computer is also extravagant.Superconducting quantum computers,for example,must operate at temperatures close to absolute zero.Therefore,most scholars believe that quantum computers can only be mastered by a few enterprises or organizations in the foreseeable future,and quantum computers are likely to be used as a special computing device to solve specific complicated problems.In order to enable the general public to use quantum computers to solve their practical problems,the concept of delegated quantum computing came into being.Delegated quantum computation is similar to the classical cloud computing model,where clients delegate their computing tasks to servers who have quantum computers at their disposal.Obviously,how to guarantee the security of clients’ input and output during the computation is an important issue in delegated quantum computation.In addition,how to guarantee that quantum computations have been performed correctly is also a crucial issue.The research content of this dissertation is centered on secure delegated quantum computation,and has conducted in-depth research on secure delegated quantum computation protocols,universal blind quantum computation protocols,verifiability of quantum computation,and distributed secure delegated quantum computation protocols.The main research results are as follows:1.A secure delegated quantum computation protocol based on Z-rotation encryption is proposed,in which the client is only required to be able to prepare qubits |+〉 and perform the phase gate S.The new protocol greatly reduces the client’s quantum capacities while guaranteeing that even if some of the client’s input qubits are fixed and known to the server,the computation output is still unconditionally secure against the server.In addition,even if some encryption keys are exposed accidentally to the server during the computation,then the proposed protocol can still guarantee the unconditional security of the computation output.2.A kind of resource-efficient universal blind quantum computation protocols is proposed.In the existing work,the commonly used graph state resource for universal blind quantum computation protocols is the so-called Brickwork state.In view of the quantum resource overhead and structural defects of the Brickwork state,we propose three different degrees of improved Brickwork state.And by the improved Brickwork states,we propose three corresponding resource-efficient universal blind quantum computation protocol.For the scheme based on the neat brickwork state,it reduces the the number of auxiliary qubits used to realize a single-qubit gate from the previous 4 to 2; for the scheme based on the hyper brickwork state,it directly realizes a CZ gate between non-adjacent qubits,and the upper bound of resource overhead is reduced by an order of magnitude; for the scheme based on the circular brickwork state,it avoids the difficulty of constructing a hyper brickwork state on a two-dimensional plane.3.A permutation-based quantum computation self-testing system is proposed.Making use of the self-testing system,a quantum computer can directly output a verified computation result.We first define two specific quantum permutation circuits and then design two effective algorithms to generate such two permutation circuits.After that,we use these two kind of quantum permutation circuits and auxiliary qubits to concretely construct a self-testing system which satisfies our definition.Finally,a rigorous mathematical analysis on the completeness and soundness of the constructed self-testing system is fulfiled.Our work shows that any problem that can be efficiently solved by a quantum computer admits a self-testing system.4.A distributed secure delegated quantum computation protocol is proposed.First,a scheme that implements a non-local CZ gate is proposed.Compared with existing schemes,the scheme is simpler.And for servers,their operations are similar.Then,by this proposed scheme,a distributed secure delegated quantum computation protocol based on Z rotation encryption is designed,by which an almost classical client who can only prepare a specific single-qubit state can delegate a dm-qubit circuit to d servers,each of which can only process at most 2m-qubit circuit.In addition,under the premise that the entangled state is shared among the servers,there is no need for any classical communication(except for necessary synchronization)and quantum communication among all the servers during the computation,which effectively reduces the communication overhead between servers.