In this paper and this paper, the "Noise Stability of Qubits" (the stability of qubits to external noise) has been discussed. In the first one, Gil Kalai states that it is difficult to create a quantum computer since the noise produced in creating a few qubits is enough to reach the threshold for corrupting the entire system of qubits. What can be done to reduce the noise and increase stability of the qubits?
EDIT: To clarify the doubts mentioned in the comments, I want to add that IBM, Rigetti and some other companies have already started manufacturing Quantum Computers with 4-6 qubits. How have they overcome or what are they working on to face this problem of noise sensitivity?