| Abstrakt: |
Analog quantum simulations offer rich opportunities for exploring complex quantum systems and phenomena through the use of specially engineered, well-controlled quantum systems. A critical element, increasing the scope and flexibility of such experimental platforms, is the ability to access and tune in situ different interaction regimes. Here, we present a superconducting circuit building block of two highly coherent transmons featuring in situ tuneable photon hopping and nonlinear cross-Kerr couplings. The interactions are mediated via a nonlinear coupler, consisting of a large capacitor in parallel with a tuneable superconducting quantum interference device (SQUID). We demonstrate the working principle by experimentally characterising the system in the single-excitation and two-excitation manifolds, and derive a full theoretical model that accurately describes our measurements. Both qubits have high coherence properties, with typical relaxation times in the range of 15 to 40 μs at all bias points of the coupler. Our device could be used as a scalable building block in analog quantum simulators of extended Bose-Hubbard and Heisenberg XXZ models, and may also have applications in quantum computing such as realising fast two-qubit gates and perfect state transfer protocols. Analogue Quantum Simulators: scalable building block with tuneable capabilities A superconducting circuit composed of two transmons can be devised to have tuneable photon hopping and nonlinear couplings with adjustable ratios, giving access to previously unexplored interaction regimes, while maintaining high qubit coherence. The realisation comes from a team of researchers from Delft University of Technology and University of Technology Sydney, led by Marios Kounalakis, and relies on the addition of a capacitor and a tuneable nonlinear inductor: analogously to LC filtering, photon hopping can be tuned and suppressed at the filtering condition, while the Josephson nonlinearity of the circuit can be used to implement tuneable cross-Kerr interactions. This design allows changing the ratio between the two coupling strengths. Such a device could constitute a fundamental unit to build large quantum devices able to simulate condensed matter models which are not efficiently computable with classical computers. [ABSTRACT FROM AUTHOR] |
