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Hybrid organic-inorganic perovskites (HOIPs) offer long carrier diffusion lengths, high absorption coefficients, tunable bandgaps and long spin lifetimes. The flexible crystal structure and ionic nature of HOIPs makes it possible to allow tune their material properties through rational design, including the incorporation of chiral organic ligands. Recently, chiral HOIPs have emerged as promising materials for chiroptoelectronics, spintronics and ferroelectricity. They exhibit high photoluminescence polarization (17% without an external magnetic field), good device performance (a circularly polarized photodetector had 100 times higher responsivity than one based on chiral metasurface) and high saturated polarization (~2 times higher than that of barium titanate). Here we review the latest advances in chiral HOIPs and investigate the specific benefits of combining chiral organic and inorganic components in perovskites. We discuss demonstrations of chiroptical and ferroelectric applications, and conclude with our perspective on the future opportunities for chiral HOIPs.

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

Entanglement has a central role in fundamental tests of quantum mechanics as well as in the burgeoning field of quantum information processing. Particularly in the context of quantum networks and communication, a main challenge is the efficient generation of entanglement between stationary (spin) and propagating (photon) quantum bits. Here we report the observation of quantum entanglement between a semiconductor quantum dot spin and the colour of a propagating optical photon. The demonstration of entanglement relies on the use of fast, single-photon detection, which allows us to project the photon into a superposition of red and blue frequency components. Our results extend the previous demonstrations of single-spin/single-photon entanglement in trapped ions, neutral atoms and nitrogen-vacancy centres to the domain of artificial atoms in semiconductor nanostructures that allow for on-chip integration of electronic and photonic elements. As a result of its fast optical transitions and favourable selection rules, the scheme we implement could in principle generate nearly deterministic entangled spin-photon pairs at a rate determined ultimately by the high spontaneous emission rate. Our observation constitutes a first step towards implementation of a quantum network with nodes consisting of semiconductor spin quantum bits.

Coherent manipulation of a large number of qubits and the generation of entangled states between them has been an important goal and benchmark in quantum information science, leading to various applications such as measurement-based quantum computing 1 and high-precision quantum metrology 2 . However, the experimental preparation of multiparticle entanglement remains challenging. Using atoms 3,4 , entangled states of up to eight qubits have been created, and up to six photons 5 have been entangled. Here, by exploiting both the photons' polarization and momentum degrees of freedom, we experimentally generate hyper-entangled six-, eight-and ten-qubit Schrödinger cat states with verified genuine multi-qubit entanglement. We also demonstrate super-resolving phase measurements enhanced by entanglement, with a precision to beat the standard quantum limit. Modifications of the experimental set-up would enable the generation of other graph states up to ten qubits. Our method offers a way of expanding the effective Hilbert space and should provide a versatile test-bed for various quantum applications.Control of single photonic qubits using linear optics has been an appealing approach to implementing quantum computing 6 . Experiments in recent years have demonstrated the photons' extremely long decoherence time 7 , fast clock speed 8 , a series of controlled quantum logic gates 9,10 and algorithms 8,11,12 and the generation of multiqubit entangled states 5 . A significant challenge, however, lies in making experimentally accessible sources of photonic multi-qubit states. This is because, on the one hand, the probabilistic nature of spontaneous parametric down-conversion 13 represents a bottleneck with regard to the attainable brightness and fidelity of multiphoton states based on it: manipulating seven photons or more seems an insurmountable challenge with present technology. On the other hand, triggered single-photon sources from independent quantum dots or other emitters still suffer from spectral and temporal distinguishability, which prevents up-scaling.There is, however, a way to experimentally control more effectively qubits, by exploiting hyper-entanglement 14 -the simultaneous entanglement in the multiple degrees of freedom that naturally exist for various physical systems. For instance, one can encode quantum information not only in the polarization of a single photon, but also in its spatial modes 15 Although the largest hyper-entangled state 15 realized so far has expanded the Hilbert space up to 144 dimensions, it is a product state of two-party entangled states and does not involve multipartite entanglement. Other schemes 20,21 for creating hyperentanglement have been limited by the technical problem of photonic subwavelength phase stability and seem infeasible to generate larger states than the two-photon four-qubit ones. Here, we will describe a method that overcomes these limitations, and the experimental generation of hyper-entangled six-, eight-and ten-qubit photonic Schrödinger cat states.The Schröding...

The discovery of monolayer superconductors bears consequences for both fundamental physics and device applications. Currently, the growth of superconducting monolayers can only occur under ultrahigh vacuum and on specific lattice-matched or dangling bond-free substrates, to minimize environment- and substrate-induced disorders/defects. Such severe growth requirements limit the exploration of novel two-dimensional superconductivity and related nanodevices. Here we demonstrate the experimental realization of superconductivity in a chemical vapour deposition grown monolayer material—NbSe2. Atomic-resolution scanning transmission electron microscope imaging reveals the atomic structure of the intrinsic point defects and grain boundaries in monolayer NbSe2, and confirms the low defect concentration in our high-quality film, which is the key to two-dimensional superconductivity. By using monolayer chemical vapour deposited graphene as a protective capping layer, thickness-dependent superconducting properties are observed in as-grown NbSe2 with a transition temperature increasing from 1.0 K in monolayer to 4.56 K in 10-layer.

Diamond photonics is an ever-growing field of research driven by the prospects of harnessing diamond and its colour centres as suitable hardware for solid-state quantum applications. The last two decades have seen the field shaped by the nitrogen-vacancy (NV) centre with both breakthrough fundamental physics demonstrations and practical realizations. Recently however, an entire suite of other diamond defects has emerged—group IV colour centres—namely the Si-, Ge-, Sn- and Pb-vacancies. In this perspective, we highlight the leading techniques for engineering and characterizing these diamond defects, discuss the current state-of-the-art group IV-based devices and provide an outlook of the future directions the field is taking towards the realisation of solid-state quantum photonics with diamond.

Atomically thin magnets are the key element to build up spintronics based on twodimensional materials. The surface nature of two-dimensional ferromagnet opens up opportunities to improve the device performance efficiently. Here, we report the intrinsic ferromagnetism in atomically thin monolayer CrBr3, directly probed by polarization resolved magnetophotoluminescence. The spontaneous magnetization persists in monolayer CrBr3 with a Curie temperature of 34 K. The development of magnons by the thermal excitation is in line with the spin-wave theory. We attribute the layer-number dependent hysteresis loops in thick layers to the 2 magnetic domain structures. As a stable monolayer material in air, CrBr3 provides a convenient platform for fundamental physics and pushes the potential applications of the two-dimensional ferromagnetism.Ferromagnetism in atomically thin magnet has been studied in a variety of van der Waals materials 1, 2 , including metallic Fe3GeTe2 3, 4 , semiconducting Cr2Ge2Te6 5 and insulating CrI3 6 .Even though the long-range magnetic order is highly suppressed by the thermal excitation of magnons in a two-dimensional (2D) magnet at finite temperature 7 , the magnetic anisotropy opens an energy gap in the magnon spectra and therefore, protects the ferromagnetism in two dimensions.The magnon-magnon interaction in such van der Waals ferromagnets also provides a platform to study the fundamental topological spin excitation, for example, Dirac magnon 8 and topological magnon surface state 9 . Moreover, in contrast to the three-dimensional ferromagnet, magnetic 2D materials show tunable magnetic properties due to their surface nature 1-3, 10-13 . Particularly the layer-number dependent 4, 6, 14 and gate-tunable magnetism 3, 10-13 opens a new way to build spintronic devices with high accuracy and efficiency 15-20 .Among various van der Waals ferromagnets, CrBr3 is an interesting platform to study the magnetism in low dimensions and light matter interactions in magnetic materials. The neutron scattering has revealed the Dirac points in bulk CrBr3 21, 22 , formed by acoustic and optical spinwave modes, where both intralayer and interlayer exchange interactions play an important role.On the other hand, optical absorption spectra in CrBr3 have shown the out-of-plane magnetic field dependence 23 , suggesting potential applications in optoelectronics. However, magnetism in atomically thin CrBr3, especially in monolayer limit, is still unknown.