Electromagnetically induced transparency without control field in giant atoms

Quantum interference between different excitation pathways in a three-level system can make an otherwise opaque medium transparent. The transparency window is achieved by turning on a control field, and is therefore named electromagnetically induced transparency (EIT). Since EIT is accompanied by a drastic change in refractive index, it gives rise to highly non-linear effects, such as slow light. We have investigated the creation of EIT in systems without the need for an explicit control field: two two-level atoms coupled to a waveguide. In particular, these atoms can be giant, i.e., couple to the waveguide at two spatially separated points. By tuning the distance between the two coupling points, a giant atom can decouple from the waveguide, thus forming a dark state, a key component in EIT physics. Since our proposed system does not involve neither an explicit three-level system, nor a control field, the complexity of achieving EIT is drastically reduced. Our proposal can be realized in several experimental setups, e.g., superconducting qubits coupled to microwave photons or surface-acoustic-wave phonons.