Graph states are special kinds of multipartite entangled states that correspond to mathematical graphs where the vertices take the role of quantum spin systems and the edges represent interactions. They not only provide an efficient model to study multiparticle entanglement, but also find wide applications in quantum error correction, multi-party quantum communication and most prominently, serve as the central resource in one-way quantum computation. Here we report the creation of two special instances of graph states, the six-photon Greenberger-Horne-Zeilinger states -- the largest photonic Schr\"{o}dinger cat, and the six-photon cluster states-- a state-of-the-art one-way quantum computer. Flexibly, slight modifications of our method allow creation of many other graph states. Thus we have demonstrated the ability of entangling six photons and engineering multiqubit graph states, and created a test-bed for investigations of one-way quantum computation and studies of multiparticle entanglement as well as foundational issues such as nonlocality and decoherence

Here, we report a proof-of-principle demonstration of five-photon entanglement and open-destination teleportation. In the experiment, we use two entangled photon pairs to generate a four-photon entangled state, which is then combined with a single photon state to achieve the experimental goals. The methods developed in our experiment would

We report an experimental demonstration of a complied version of Shor's algorithm using four photonic qubits. We choose the simplest instance of this algorithm, that is, factorization of N = 15 in the case that the period r = 2 and exploit a simplified linear optical network to coherently implement the quantum circuits of the modular exponential execution and semi-classical quantum Fourier transformation. During this computation, genuine multiparticle entanglement is observed which well supports its quantum nature. This experiment represents a step toward full realization of Shor's algorithm and scalable linear optics quantum computation.Shor's algorithm [1,2] for factoring large numbers is arguably the most prominent quantum algorithm to date. It provides a way of factorizing large integers in polynomial time using a quantum computer, a task for which no efficient classical method is known. Such a capacity would be able to break widely used cryptographic codes, such as the RSA public key system [3,4]. Experimental realization of Shor's algorithm has been a central goal in quantum information science. Owing to its high experimental demands, however, this algorithm has so far only been demonstrated in a nuclear magnetic resonance (NMR) experiment [5]. Since the NMR experiments cannot prepare pure quantum states and exhibits no entanglement during computation, concerns have been arisen on its quantum nature [6]. In particular, it has been proved that the presence of entanglement is a necessary condition for quantum computational speed-up over classical computation [6].The approach of using photons to implement quantum algorithms is appealing due to the long decoherence times and precise single-qubit operations [7,8,9]. Along this line, the Deutsch-Josza algorithm and Grover algorithm have been realized (see e.g. [10,11,12,13,14]). In this Letter, we use the photonic qubits to demonstrate the easiest meaningful instance of Shor's algorithm, that is, factorization of N = 15 in the case that the period r = 2. A simplified linear optics network is designed to implement the quantum circuit. We have observed genuine multiparticle entanglement and multipath interference during computation, which thus for the first time prove the quantum nature of the implementation of Shor's algorithm [6].Suppose we wish to find a non-trivial prime factor of an l-digit integer N . Even using the best known classical algorithm, prime factorization takes exponentially many operations, which quickly becomes intractable as l increases. Shor's algorithm, in contrast, offers a new powerful way to solve this problem in only polynomial time [1,2]. The strategy for the quantum factoring of a composite number N = p q, with both p and q being odd primes, is as follows. First we pick a random number a (0 < a < N ) with no factor in common with N . Then we quantum compute the period r of the modular exponential function (MEF): f (x) = a x modN , which is the smallest positive satisfying a r modN = 1. From this period r, at least one nontrivial factor...

We report an experimental realization of entanglement concentration using two polarizationentangled photon pairs produced by pulsed parametric down-conversion. In the meantime, our setup also provides a proof-in-principle demonstration of a quantum repeater. The quality of our procedure is verified by observing a violation of Bell's inequality by more than 5 standard deviations. The high experimental accuracy achieved in the experiment implies that the requirement of tolerable error rate in multi-stage realization of quantum repeaters can be fulfilled, hence providing a practical toolbox for quantum communication over large distances.

Halide double perovskites have recently bloomed as the green candidates for optoelectronic applications, such as X‐ray detection. Despite great efforts, the exploration of promising organic–inorganic hybrid double perovskites toward X‐ray detection remains unsuccessful. Now, single crystals of the lead‐free hybrid double perovskite, (BA)2CsAgBiBr7 (BA+ is n‐butylammonium), featuring the unique 2D multilayered quantum‐confined motif, enable quite large μτ (mobility‐lifetime) product up to 1.21×10−3 cm2 V−1. This figure‐of‐merit realized in 2D hybrid double perovskites is unprecedented and comparable with that of CH3NH3PbI3 wafers. (BA)2CsAgBiBr7 crystals also exhibit other intriguing attributes for X‐ray detection, including high bulk resistivity, low density of defects and traps, and large X‐ray attenuation coefficient. Consequently, a vertical‐structure crystal device under X‐ray source yields a superior sensitivity of 4.2 μC Gyair−1 cm−2.