A quantum computing system can include one or more classical processors. The quantum computing system can include quantum hardware including one or more qubits. The quantum computing system can include a chamber mount configured to support the quantum hardware. The quantum computing system can include a vacuum chamber configured to receive the chamber mount and dispose the quantum hardware in a vacuum. The vacuum chamber can form a cooling gradient from an end of the vacuum chamber to the quantum hardware. The quantum computing system can include a plurality of flex circuit boards including one or more signal lines. Each of the plurality of flex circuit boards can be configured to transmit signals by the one or more signal lines through the vacuum chamber to couple the one or more classical processors to the quantum hardware.