The ground state of charge neutral graphene under perpendicular magnetic field was predicted to be a quantum Hall topological insulator with a ferromagnetic order and spin-filtered, helical edge channels. In most experiments, however, an otherwise insulating state is observed and is accounted for by lattice-scale interactions that promote a broken-symmetry state with gapped bulk and edge excitations. We tuned the ground state of the graphene zeroth Landau level to the topological phase via a suitable screening of the Coulomb interaction with a SrTiO3 high-k dielectric substrate. We observed robust helical edge transport emerging at a magnetic field as low as 1 tesla and withstanding temperatures up to 110 kelvins over micron-long distances. This new and versatile graphene platform opens new avenues for spintronics and topological quantum computation.There is a variety of topological phases that are classified by their dimensionality, symmetries and topological invariants [1,2]. They all share the remarkable property that the topological bulk gap closes at every interfaces with vacuum or a trivial insulator, forming conductive edge states with peculiar transport and spin properties. The quantum Hall effect that arises in two-dimensional (2D) electron systems subjected to a perpendicular magnetic field, B, stands out as a paradigmatic example characterized by the Chern number that quantizes the Hall conductivity and counts the number of chiral, onedimensional edge channels. The singular aspect of quantum Hall systems compared to time-reversal symmetric topological insulators (TIs) lies in the pivotal role of Coulomb interaction between electrons that can induce a wealth of strongly correlated, symmetry or topologicallyprotected phases, ubiquitously observed in various experimental systems [3][4][5][6][7][8][9][10][11][12].In graphene the immediate consequence of the Coulomb interaction is an instability towards quantum Hall ferromagnetism. Due to exchange interaction, a spontaneous breaking of the SU(4) symmetry splinters the Landau levels into quartets of broken-symmetry states that are polarized in one, or a combination of the spin and valley (pseudospin) degrees of freedom [15][16][17].Central to this phenomenon is the fate of the zeroth Landau level and its quantum Hall ground states. It was early predicted that if the Zeeman spin-splitting (enhanced by exchange interaction) overcomes the valley splitting, a topological inversion between the lowest electron-type and highest hole-type sub-levels should occur [13,18]. At charge neutrality, the ensuing ground state is a quantum Hall ferromagnet with two filled states of identical spin polarization, and an edge dispersion that exhibits two counter-propagating, spin-filtered helical edge channels ( Fig. 1A and B), similar to those of the quantum spin Hall (QSH) effect in 2D TIs [19][20][21][22][23]. Such a spin-polarized ferromagnetic (F) phase belongs to the recently identified new class of interaction-induced TIs with zero Chern number, termed quantum Hall topolog...

The hybridization of distinct quantum systems is now seen as an effective way to engineer the properties of an entire system leading to applications in quantum metamaterials, quantum simulation, and quantum metrology. One well known example is superconducting circuits coupled to ensembles of microscopic natural atoms. In such cases, the properties of the individual atom are intrinsic, and so are unchangeable. However, current technology allows us to fabricate large ensembles of macroscopic artificial atoms such as superconducting flux qubits, where we can really tailor and control the properties of individual qubits. Here, we demonstrate coherent coupling between a microwave resonator and several thousand superconducting flux qubits, where we observe a large dispersive frequency shift in the spectrum of 250 MHz induced by collective behavior. These results represent the largest number of coupled superconducting qubits realized so far. Our approach shows that it is now possible to engineer the properties of the ensemble, opening up the way for the controlled exploration of the quantum many-body system.Quantum science and technology have reached a very interesting stage in their development where we are now beginning to engineer the properties that we require of our quantum systems [1,2]. Hybridization is a core technique in achieving this. An additional (or ancilla) system can be used to greatly change not only the properties of the overall system, but also its environment [3][4][5].Specifically, a hybrid system composed of many qubits and a common field such as cavity quantum electrodynamics [6,7] may provide an excellent way of realizing such quantum engineering, leading to an interesting investigation of many-body phenomena including quantum simulations [8,9], superradiant phase transitions [10][11][12][13][14][15], spin squeezing [16][17][18], and quantum metamaterials [19][20][21][22][23][24][25]. In this regard, one of the ways to realize such a system is to employ superconducting circuits coupled to electron spin ensembles where basic quantum control such as memory operations have been demonstrated [26][27][28][29][30]. If we are to investigate quantum many-body phenomena, we will need control over the ensemble. In most typical superconducting circuit-ensemble hybrid experiments, the ensemble has been formed from a collection of either atoms or molecules with examples including nitrogen vacancy centers [26][27][28]31], ferromagnetic magnons [32], and bismuth donor spins in silicon [33]. In these cases, the properties of the atomic ensemble system are basically defined as the ensemble is formed, and are difficult to change. However, our ensembles could be composed of artificial atoms such as superconducting qubits.Superconducting qubits are macroscopic two-level systems with a significant degree of design freedom [34,35]. Josephson junctions provide the superconducting circuit with non-linearity, and we can tailor the qubit properties by changing the design of the circuit. Moreover, in contrast to natural a...