Interconnections for connecting flex circuit boards in classical and/or quantum computing systems can include a first flex circuit board having a removed portion that exposes one or more signal lines and a second flex circuit board having a removed portion that exposes one or more other signal lines. The flex circuit boards can be aligned at the removed portions to form a signal trace gap near the exposed signal lines. Exposed signal lines of the first flex circuit board can be coupled with exposed signal lines of the second flex circuit board. A ground support layer can be coupled to the first flex circuit board and the second flex circuit board along the same side. An isolation plate at least partially covering the signal trace gap can be coupled to the first flex circuit board and/or the second flex circuit board on a side opposite of the ground support layer.