Scaling quantum computing chips to include multiple qubits increases the physical space occupied by the chip to a size that supports electromagnetic modes having frequencies comparable with the operating frequencies of the quantum computing circuit on the chip. Such spurious EM chip-like modes may interfere with the operation of a quantum computing circuit resulting in a detrimental lack of coherence in the qubits. As will now be described, an embodiment of the present invention provides a superconducting quantum computing circuit package in which these spurious modes, as well as cross-talk, are suppressed.

FIG. 1 shows a superconducting quantum computing circuit package 1 according to an embodiment of the present invention. The package 1 includes a substrate 2, a holder 3 for the substrate 2 and a cover 4. The package 1 is shown in FIG. 1 in an expanded configuration, e.g. prior to assembly.

FIG. 2 shows the substrate 2 of the superconducting quantum computing circuit package 1 shown in FIG. 1. The substrate is typically made from silicon or sapphire. A quantum computing circuit 5 is formed on the surface of the substrate 2 (a similar circuit may also be formed on the opposite face of the substrate 2).

The quantum computing circuit 5 includes multiple qubits 6 arranged in a regular geometric grid. The qubits 6 are connected together by respective interconnections 7. The qubits 6 are addressed by respective control lines and readout elements, e.g. as disclosed in the Applicant's previous application published as WO 2017/021714 A1.