本文介绍了基于测量的量子计算（MBQC）的原理，详细比较了利用连续变量和离散变量物理实现 cluster states 的多种方法，并报告了光子与超导量子比特的最新成果。
摘要：
利用量子力学特性，量子计算机在许多应用中有望超越经典计算机，并被设想为影响我们社会的各个方面。目前人们正在探索构建此类计算机的不同方法。其中一种潜在的方法是由 Raussendorf 和 Briegel 于 2001 年提出的基于测量的量子计算（MBQC）。在 MBQC 中，大量量子比特被制备在高度纠缠的簇态中，称为 cluster states。随后，通过一系列测量来执行所需的量子计算。人们正在使用连续变量（CV）和离散变量（DV）方法对 cluster states 进行物理实现。基于 CV 的方法可进一步分为频域复用（FDM）、时域复用（TDM）、空域复用（SDM）和混合复用。我们详细讨论并比较了这些方法。我们还讨论了 DV 中 cluster states 的生成，并报告了一些使用光子和超导量子比特的最新成果。
英文摘要：
Harnessing quantum mechanics properties, quantum computers have the potential to outperform classical computers in many applications and are envisioned to affect various aspects of our society. Different approaches are being explored for building such computers. One of such potential approaches is Measurement based quantum computation (MBQC), introduced by Raussendorf and Briegel in 2001. In MBQC a large number of qubits are prepared in a highly entangled clusters, called cluster states. The required quantum computation is then performed by a sequence of measurements. Cluster states are being physically realized using continuous variables (CV) and discrete variables (DV) approaches. CV-based approaches can be further categorized as Frequency domain multiplexing (FDM), Time domain multiplexing (TDM), Spatial domain multiplexing (SDM) and hybrid. We discuss and compare these approaches in detail. We also discuss cluster states generation in DV and report some recent results where photons and superconducting qubits are used.
A fundamental requirement of quantum information processing is the protection from the adverse effects of decoherence and noise. Decoherence-free subspaces and geometric processing are important steps of quantum information protection. Here, we provide a new experimentally feasible scheme to combine decoherence-free subspaces with nonadiabatic geometric manipulations to attain a universal quantum computation. The proposed scheme is different from previous proposals and is based on the typical XY interaction coupling, which can be set up in various nano-engineered systems and therefore open up …
The Measurement Based Quantum Computation (MBQC) model achieves universal quantum computation by employing projective single qubit measurements with classical feedforward on a highly entangled multipartite cluster state. Rapid advances in improving scalability of quantum computing systems have enabled the generation of large cluster states for implementing MBQC on various platforms. This review focuses on three such efforts, each utilizing a different quantum computing technology viz., superconducting qubits, trapped ion qubits and squeezed photon states. MBQC is being increasingly employed on…
We describe a physical implementation of a quantum finite automaton recognizing a well known family of periodic languages. The realization exploits the polarization degree of freedom of single photons and their manipulation through linear optical elements. We use techniques of confidence amplification to reduce the acceptance error probability of the automaton. It is worth remarking that the quantum finite automaton we physically realize is not only interesting per se, but it turns out to be a crucial building block in many quantum finite automaton design frameworks theoretically settled in th…
Disordered photonic structures are promising materials for the realization of physical unclonable functions (PUF), physical objects that can overcome the limitations of conventional digital security methods and that enable cryptographic protocols immune against attacks by future quantum computers. One PUF limitation, so far, has been that their physical configuration is either fixed or can only be permanently modified, and hence allowing only one token per device. We show that it is possible to overcome this limitation by creating a reconfigurable structure made by light-transformable polymers…
Nonadiabatic holonomic quantum computation as one of the key steps to achieve fault tolerant quantum information processing has so far been realized in a number of physical settings. However, in some physical systems particularly in spin qubit systems, which are actively considered for realization of quantum computers, experimental challenges are undeniable and the lack of a practically feasible and scalable scheme that supports universal holonomic quantum computation all in a single well defined setup is still an issue. Here, we propose and discuss a scalable star-shape architecture with prom…
Realization of the quantum Toffoli gate with trapped ions
用于量子信息处理的算法通常被分解为量子门操作的序列，最常使用单量子比特门和双量子比特门来实现[1]。虽然这样的操作构成了量子计算的通用集合，但作用于两个以上量子比特的门可以简化复杂量子算法的实现[2]。因此，单个三量子位操作可以取代复杂的两量子位门序列，这反过来又保证了更快的执行速度和更高的保真度。一个重要的三量子位操作是量子Toffoli门，它根据两个控制量子位的状态对目标量子位执行NOT操作。在这里，我们提出了第一个实验实现的量子Toffoli门的离子阱量子计算机。我们的实现是特别有效的，因为我们直接编码的相关逻辑信息的离子串的运动。[1]Diplenenzo，D.两位门是量子计算的通用门。Cond-mat/9407022，Phys.Rev. A 51，1015-1022（1995）。[2]Chiaverini，J. et al.实现量子纠错. Nature 432，602-605（2004）.
