![]() ![]() ![]() Many-body localization (MBL) describes a quantum phase where an isolated interacting system subject to sufficient disorder displays non-ergodic behaviour, evading thermal equilibrium that occurs under its own dynamics. ![]() We focus our analysis on three particular examples: a single atom exciting two photons, frequency conversion, and a single photon exciting two atoms. By shifting the paradigm from simulating a particular model to simulating a particular process, we are able to implement a much wider family of nonlinear coherent protocols than in previous simulation approaches, doing so with fewer resources and constraints. Here, we show that these parity-nonconserving processes can be simulated and that this can be done in an even simpler setup: a Jaynes-Cummings-type system with the addition of a single classical drive. However, parity is still a conserved quantity in the quantum Rabi Hamiltonian, which forbids a wide family of processes involving virtual transitions that break this conservation. This allows one to implement nonlinear processes that do not conserve the total number of excitations. Recent theory and experiments have shown that the quantum Rabi Hamiltonian can be simulated by a Jaynes-Cummings system with the addition of two classical drives. We propose the effective simulation of light-matter ultrastrong-coupling phenomena with strong-coupling systems. The measured relaxation (T1=1.6 ms) and dephasing (TR=9μs, T2E=25μs) times demonstrate that the soft 0–π circuit not only broadens the family of superconducting qubits but also constitutes an important step toward quantum computing with intrinsically protected superconducting qubits. Using a Raman-type protocol, we exploit a higher-lying charge-insensitive energy level of the device to realize coherent population transfer and logical operations. We name the resultant device the “soft 0–π qubit.” Multitone spectroscopy measurements reveal the energy-level structure of the system, which can be precisely described by a simple two-mode Hamiltonian. More precisely, the logical states of this qubit feature disjoint support and are exponentially protected against relaxation and exponentially (first order) protected against dephasing due to charge (flux) noise. Here we realize the proposed circuit topology in an experimentally obtainable parameter regime, where the ground-state degeneracy is lifted but the qubit is still largely noise protected. One of the most promising candidates for such a fully protected superconducting qubit is the 0–π circuit. Our proposal can be readily realized in experiment and may pave the way towards the investigation of topological quantum phases and topologically protected quantum information processing.Įncoding a qubit in logical quantum states with wave functions characterized by disjoint support and robust energies can offer simultaneous protection against relaxation and pure dephasing. Finally, we also demonstrate the stable Bloch-like-oscillation of multiple interface states induced by the interference of them. Moreover, we explore the appearance and detection of the topological protected edge states in such multiband qubit system. Specifically, by considering a quadrimeric superlattice, we show that the topological invariant (winding number) can be effectively characterized by the dynamics of the single-excitation quantum state through a time-dependent quantities. Here, we extend such dimer lattice to superlattice with arbitrary number of qubits in each unit cell in superconducting circuits, which exhibit rich topological properties. In that study, a dimerized qubit chain was realized. The recent experimental observation of topological magnon insulator states in a superconducting circuit chain marks a breakthrough for topological physics with qubits. ![]()
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