Synthetic gauge field and chiral physics on two-leg superconducting circuits

The gauge field is essential for exploring novel phenomena in modern physics. However, it has not been realized in the recent breakthrough experiment on two-leg superconducting circuits with transmon qubits [Y. Ye et al., Phys. Rev. Lett. 123, 050502 (2019)]. Here we present an experimentally feasible method to achieve the synthetic gauge field by introducing ac microwave driving in each qubit. In particular, the effective magnetic flux per plaquette achieved can be tuned independently by properly choosing the driving phases. Moreover, the ground-state chiral currents for single- and two-qubit excitations are obtained and the Meissner-vortex phase transition is found. In the Meissner phase, the ground-state chiral current increases as the magnetic flux increases, while it decreases in the vortex phase. In addition, chiral dynamics, which depends crucially on the initial state of the system, is also revealed. Finally, the possible experimental observations of the chiral current and dynamics are addressed. Our results provide a new route to explore novel many-body properties induced by the interplay of the gauge field, two-leg hoppings, and interaction of photons on superconducting circuits.